M.tech thesis

STUDY ON THE STRESS-STRAIN BEHAVIOUR OF HIGH STRENGTH GLASS FIBRE REINFORCED

SELF-COMPACTING CONCRETE UNDER AXIAL COMPRESSION WITH & WITHOUT

CONFINEMENT

A DISSERTATION SUBMITTD IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF

Master of Technology in

Structural Engineering

By B.VENKATARAJU

(06014D2023)

DEPARTMENT OF CIVIL ENGINEERING JNTUH COLLEGE OF ENGINEERING, KUKATPALLY

HYDERABAD – 500085, AP, INDIA (AUTONOMOUS)

MARCH – 2011

STUDY ON THE STRESS-STRAIN BEHAVIOUR OF HIGH STRENGTH GLASS FIBRE REINFORCED

SELF-COMPACTING CONCRETE UNDER AXIAL COMPRESSION WITH & WITHOUT

CONFINEMENT

A DISSERTATION SUBMITTD IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF

Master of Technology in

Structural Engineering

By B.VENKATARAJU

(06014D2023)

Under the guidance of

Dr.M.V.SESHAGIRI RAO

DEPARTMENT OF CIVIL ENGINEERING JNTUH COLLEGE OF ENGINEERING, KUKATPALLY

HYDERABAD – 500085, AP, INDIA (AUTONOMOUS)

MARCH – 2011

DEPARTMENT OF CIVIL ENGINEERING

JNTUH COLLEGE OF ENGINEERING, KUKATPALLY HYDERABAD– 500085, AP, INDIA.

CERTIFIACTE

This is to certify that the dissertation work entitled “Study On The Stress-

Strain Behaviour Of High Strength Glass Fibre Reinforced Self-Compacting

Concrete Under Axial Compression With & Without Confinement” that is

being submitted by B.VenkataRaju, HT No: 06014D2023 in partial fulfillment for

the award of M.Tech in “Structural Engineering” to the Department of Civil

Engineering, JNTUH College of Engineering, KUKATPALLY, Hyderabad, is a

record of bonafide work carried out by him under my guidance and supervision.

Signature of Head Project Guide

Dr. P.SRINIVASA RAO Dr.M.V.SESHAGIRI RAO,

Professor and Head of the Proffesor of Civil Engineering

Deparment of Civil Engineering Dept. of Civil Engineering

JNTUHCE, Hyderabad-85 JNTUHCE, Hyderabad-85

i

DECLARATION BY THE CANDIDATE

I, B.VenkataRaju, bearing HT. No: 06014D2023 hereby declare that the

report of the Post Graduate Thesis work entitled “Study On The Stress-Strain

Behaviour Of High Strength Glass Fibre Reinforced Self-Compacting

Concrete Under Axial Compression With & Without Confinement”, which is

being submitted to the JNTUH College of Engineering, Kukatpally, in partial

fulfillment of the requirements for the award of the Degree of Master of

Technology in Structural Engineering., Department of Civil Engineering, is a

bonafide report of the work carried out by me. The material contained in this

report has not been submitted to any university or Institution for the award of any

degree or diploma.

Place: JNTUHCE, Kukatpally, Hyderabad

Date:

ii

B.VENKATARAJU

H.T.No: 06014D2023

Ph: +919177263599

Ph: +919440904158

e-mail: [email protected]

Department of Civil Engineering,

JNTUHCE, Hyderabad.

Dedicated to DEAR and NEAR ONES

iii

ACKNOWLEDGEMENT

I sincerely thank my advisor Dr. M.V.SESHAGIRI RAO, Professor in Civil

Engineering for his guidance, suggestions, and continuous support throughout my Project. I

greatly appreciate all the support that he has been given to me, both on this thesis and during

the entire period in which I have been working for him.

My profound thanks to Dr. P.SRINIVASA RAO, Professor and Head of the

Department of the Civil Engineering, JNTU College of Engineering from for his valuable

suggestions and help is carryout this dissertation work. For the assistance and help he

provided as being my co-advisor here at JNT University and also during my Project work.

I express my sincere gratitude to Dr. N.V.RAMANA RAO, Principal & professor,

JNTUH College of Engineering for his constant encouragement during the project work. The

support and help provided by him good self during this work is invaluable.

I would like to thank Smt. P.SRI LAKSHMI, Assistant professor of Civil

Engineering, JNTUH College of Engineering, for sparing her valuable time in clarifying my

doubts during my project work.

I would like to thank M/s Grasim Industries Limited, manufactures of Ultra tech

cement for extended co-operation in free supply of cement for research purpose to conduct

this project work.

I also acknowledge the sincere and untiring efforts of Engr.Devaraj who assisted me

during all stages of my experiments and also helped me in preparing the experimental set-up

utilized in this study. Thanks are due to the laboratory personnel for their substantial

assistance in the experimental work

Finally, my special thanks to all my professors & friends, who rendered valuable help.

I had taken, which helped me complete my Master’s Degree in Technology.

(B.VENKATA RAJU) M.Tech (Structural Engineering) Department of Civil Engineering

JNTUHCE, Hyderabad-85

iv

ABSTRACT

A self-compacting concrete (SCC) is the one that can be placed in the form and can

go through obstructions by its own weight and without the need of vibration. Since its

first development in Japan in 1988, SCC has gained wider acceptance in Japan, Europe

and USA due to its inherent distinct advantages. Although there are visible signs of its

gradual acceptance in the Middle East through its limited use in construction, Saudi

Arabia has yet to explore the feasibility and applicability of SCC in new construction.

The contributing factors to this reluctance appear to be lack of any supportive evidence of

its suitability with local marginal aggregates and the harsh environmental conditions.

Concrete is a vital ingredient in infrastructure development with its versatile and

extensive applications. It is the most widely used construction material because of its

mouldability into any required structural form and shape due to its fluid behaviour at

early ages. However, there is a limit to the fluid behaviour of normal fresh concrete.

Thorough compaction, using vibration, is normally essential for achieving the required

strength and durability of concrete. Inadequate compaction of concrete results in large

number of voids, affecting performance and long-term durability of structures. Self-

compacting concrete (SCC) provides a solution to these problems. As the use of concrete

becomes more widespread the specifications of concrete like durability, quality, and

compactness of concrete becomes more important. Self -Compacting Concrete is recently

developed concept in which the ingredients of the concrete mix are proportioned in such a

way that it can flow under its own weight to completely fill the formwork and passes

through the congested reinforcement without segregation and self consolidate without any

mechanical vibration. Self – Compacting Concrete (SCC) is a very fluid concreter and a

homogeneous mixture that solves most of the problems related to ordinary concrete. This

specification helps the execution of construction components under high compression of

reinforcement.

In this work an attempt has been made to study Stress – Strain behaviour of Glass

fibre Self–Compacting Concrete under confined and unconfined states with different

percentages of confinement (in the form of hoops). Since the confinement provided by

lateral circular-hoop reinforcement, is a reaction to the lateral expansion of concrete,

lateral reinforcement becomes effective only after considerable deformation in the axial

v

direction. Complete Stress – Strain behaviour has been presented and an empirical

equation based on rational polynomial is proposed to predict the stress – strain behaviour

of such concrete under compression. The proposed empirical equation shows good

correlation with the experimental results. There is an improvement in the Compressive

Strength, Secant modulus and this is due to the addition of the glass – fibres to the Self-

Compacting concrete and also confinement in the form of hoops in Self-Compacting

Concrete mix.

Key words: Glass-fibre, Reinforced Self – Compacting Concrete, 6mm diameter Mild

steel, admixtures, Stress – Strain behaviour, A single Polynomial empirical equation.

vi

TABLE OF CONTENTS

Certificate ……...………………………………….…………………………………….. i

Declaration by the Candidate …………….…………………………………………….. ii

Acknowledgement …………………………………………………………………..…. iv

Abstract ………………………………………………...………………………………...v

Table of Contents …......................................................................................................... vii

List of Figures …………………………………………………………………………. xvi

List of Tables ……………………………………………………………………...…….xix

Notations and Abbreviations ………………………………………………………........xxi

CHAPTER 1: INTRODUCTION………………………………………………….1-37

1.0 . Introduction to Self-Compacting Concrete ......………………..…………………….1

1.0.1. Advantages and disadvantages of Self-Compacting Concrete……………1

1.0.2.Definition and Properties of Self-Compacting Concrete…………………....3

1.1. Historical Development of Self-Compacting Concrete……………….…..………....4

1.2. World-wide Current Situation of Self-Compacting Concrete …………………...…...5

1.2.1. Japan………………………………………………………………………...6

1.2.2. Europe ……………………………………………………………………...8

1.2.3. European Development …………………………………….……….….....10

1.2.4. Scandinavia ………………………………………………….…………….12

1.2.5. France ……………………………………………………………………..12

1.2.6. Germany …………………………………………………………………..13

1.2.7. Belgium …………………………………………………………………...13

1.2.8. Spain ………………………………………………………………………14

1.2.9. Holland ……………………………………………………………………14

1.2.10. Switzer Land …………………………………………………………….14

1.2.11. Italy ………………………………………………………………………14

1.2.12. Other European countries ………………………………………………..15

1.2.13. UK Development ………………………………………………………...15

1.2.14. Academic Institutions ……………………………………………………16

vii

1.2.15. Concrete Producers ……………………………………………………...16

1.2.16. Admixture suppliers ……………………………………………………..17

1.2.17. Consultants ………………………………………………………………17

1.2.18. Contractors ………………………………………………………………18

1.2.19. UK Precasters ……………………………………………………………18

1.2.20. Seminars and events ……………………………………………………..18

1.2.21. The Future ……………………………………………………………….17

1.3. Motive for Development of Self-Compacting Concrete ……………………………21

1.4. Construction Issues …………………………………………………………………22

1.5. Applications of Self-Compacting Concrete ………………………………………...22

1.6. Existing Tests for Fresh SCC Mixes ………………………………………………..25

1.6.1. Filling ability..…………….……………………………………………....25

1.6.2. Passing ability.………….…….….………………………………….....…25

1.6.3. Resistance to segregation...……………………………………………….25

1.6.4. U-type test...……………………………………………………………....25

1.6.5. Slump Flow test...………………………………………………………....26

1.6.6. L-Box test ………..…………………………………………………….…26

1.6.7. Orimet test...……………………………………………………………....27

1.6.8. V-funnel test...……………………………………………………….……27

1.6.9. Slump Flow/J-Ring combination test………………………………...…...28

1.6.10. Orimet/J-Ring combination test.……...……………………………...….28

1.6.11. GTM Segregation test...……………………………………………..…..29

1.7. Development of Prototype ……………………………………………………….....29

1.8. Scope and Objectives of Investigation …………………...…………...…………….30

1.8.1. Models of the Specimens ……………….………………..……………….32

1.8.2. Advantages of Reinforced Structures …………… ……………………….33

1.8.3. Investigations on Self-Compacting Concrete……………………………...34

1.8.4. Mix-design method ……………………….………………………..…......34

1.8.5. Evaluation method for materials ……………………………………….…34

1.9. Acceptance Test at Job Site ………………………………………………………....35

1.10. New structural design and construction systems …………………………………..36

viii

CHAPTER 2: LITERATURE REVIEW…………………….................................38-86

2.0 General …………………………………...………………….……………………...38

2.1 Previous Research Work on Self-Compacting Concrete ……….…...………………38

2.1.1 Hajime Okamura ……………………………………..….………………39

2.1.2 Kazumasa Ozawa ……………………………………..…………………41

2.1.3 Subramanian and Chattopadhyay ………………………..………………41

2.1.4. Khayat et al ……………………………………………….……………..43

2.1.5. Dehn et al. ……………………….……………………….……………...44

2.1.6. Kuroiwa ………………………………………………….………………45

2.1.7 Ferraris et al………………………………………………...…………….46

2.1.8 Anirwan Senu Guptha et al[2006] ……………………………………….49

2.1.9. ACI committee report No.226 [1987]…………………………..……......49

2.1.10. Gibbs, [1999] ………………………………………………….…………50

2.1.11. Manu Santhanam,[2008] ……………………………………..……...50

2.1.12. Hemant Sood[3] Et Al, [2009] …………………………………..………50

2.1.13. Kazim Turk[3] Et Al, [2007] ……………………………………...……..50

2.1.14. Srinivasa Rao.P, [2008] ……………………………………………...…..51

2.2 Constituent Materials for SCC ………………………………………………………51

2.2.1. Powder (Mixture of Portland cement and Filler)………………………...51

2.2.1.1 Cement …………………………………………………………..51

2.2.1.2 Filler ……………………………………………………………..52

2.2.2 Aggregates …………………………………………………………………54

2.2.3 Admixtures ………………………………………………………………...56

2.2.4 Ranges of the quantities of the Constituent Materials for SCC …………...57

2.3 Hardened Properties of SCC ………………………………………………………...58

2.3.1 Compressive, Tensile, and Bond Strength ………………………………...58

2.3.2 Modulus of Elasticity ……………………………………………………...59

2.3.3 Shrinkage and Creep ………………………………………………………59 2.3.4. Durability…………………………………………………………………...60

2.3.5 Water Absorption and Initial Surface Absorption ………………………...63

2.3.6 Water Permeability ………………………………………………………..63

2.3.7 Rapid Chloride Permeability ………………………………………………64

ix

2.4. Influence of Admixtures on Concrete Properties …………………………………...65

2.5. Mineral Admixtures ………………………………………………………………...65

2.6 Blast Furnace Slag ………………………...……………………………………..…..65

2.7 Fly Ash …………………………………………...………………………………….67

2.8 Silica Fume …………………………………...………………………………….…..69

2.9 Chemical Admixtures ……………………………………………………………..…71

2.10 Superplasticizers ..…………………………………...……………………………...72

2.11 Viscosity Modifiers ..……………………………………………………………….75

2.12 Bonding between Aggregate and Cement Paste ………………….………………..78

2.13 Examples of Self-Compacting Concrete Applications ………………………….….80

2.14 Criteria………………………………………………………………………………..82

2.14.1 Guidelines in Japan…………………………………………………………82

2.14.2 Guidelines in Europe……………………………………………………......83

CHAPTER 3: SELF-COMPACTING CONCRETE COMPOSITION…..........87-103

3.0 Introduction….…………………………………………………....………………….87

3.1 Portland Cement ………………………………………………………..……………88

3.2 Aggregates ……………………………………………………………….…………..92

3.3 Blast Furnace Slag ………………………………………………………..………….92

3.4 Fly Ash ………………………………………………………………………………93

3.5 Silica Fume ……………………………………………………………….………….96

3.6 Superplasticizers …………………………………………………………..…………97

3.7 Viscosity-Modifying Admixtures ……………………………………...…...……….99

3.8 Fibres …………………...……………………………………………….………….100

3.8.1. The effect of fibres on workability………………………………………101

3.8.2. Maximum fibre content…………………………………………………..101

3.9 Concrete Mix and Tests ………………………………………………………...….102

CHAPTER 4: DESIGN OF A SUITABLE SCC MIX…….…………………104-121

4.0. Materials for Self-Compacting Concrete ………………………………………….104

4.0.1. Cement ………………………………..…………………………..……..104

4.0.2. Aggregates ………………………………………………..……………..104

x

4.0.2.1. Fine aggregate .......……………………………………….……104

4.0.2.2. Coarse aggregate ………………………………………………104

4.0.3. Admixtures ………………………………………………………….…...104

4.0.3.1. Mineral Admixtures ………………………………………..….104

4.0.3.2. Fly ash …………………………………………………………………106

4.0.3.2.1. Advantages of Fly ash ……………………………….106

4.0.3.2.2 Environmental Protection …………………………….107

4.0.3.2.3. Areas of usage of Fly ash ……………………………107

4.0.3.2.4. Chemical Admixtures ………………………………..108

4.0.4. Superplasticizer ………………………………………………………...109

4.0.4.1. Advantages of Superplasticizer ………………………………..109

4.0.4.2. Dosage ………………………………………………………..109

4.0.5. Viscosity modifying Agent (VMA) ………………………………….….109

4.0.5.1. Advantages ………………………………………………….…111

4.0.5.2. Dosage …………………………………………………………111

4.0.6. Water ……………………………………………………….……………111

4.1. Mix Design ……………………………………………………………….………..112

4.1.1. Mix Design Principles.…...……………………………..…..…..………..113

4.1.2. General requirements in the Mix Design ……………………………..…114

4.1.2.1. A high volume of paste ………………………….…….…..…..114

4.1.2.2. A high volume of fine particles (<80m) ………………..…..…114

4.1.2.3. A high dosage of super plasticizer ………………………….…114

4.1.2.4. The possible use of viscous agent (water retainer) ……….…...114

4.1.2.5. A low volume of core segregate ………………………….…...115

4.1.3. Mix Design ………………………………………………………..……..115

4.1.4. Various procedures for Mix Design …………………………………..…117

4.2. By EFNARC Guidelines …………………………………………………………..119

4.2.1. Guidelines to find reasons of Faulty mixes ……………………..……….119

4.2.2. Mix Design and Trial Proportion …………………………………..……120

CHAPTER 5: QUALITY ASPECTS OF SELF -COMPACTING

CONCRETE ……………………………………………………. 122-143

5.0. Test Methods ………………………………………………………………....……122 xi

5.0.1. Introduction …….……………………………………………..…………122

5.0.2. Slump Flow Test / and T50 cm test ……………………………………...123

5.0.2.1. Assessment of test ………………………………………….….123

5.0.2.2. Equipment ………………………………………………...…...123

5.0.2.3. Procedure …………………………………………………....…124

5.0.2.4. Interpretation of results ……………………………………......125

5.0.3. V funnel test ……………………………………………………………..125

5.0.3.1. Introduction ….…………… ………………………………......125

5.0.3.2. Assessment of test …..………………………… ……….…..…125

5.0.3.3. Equipment ………………………………………… ….……....126

5.0.3.4. Procedure of flow time ………………………………..…….....126

5.0.3.5. Procedure for flow time at T 5 minutes ……………..…………127

5.0.3.6. Interpretation of results …………………………….....……….127

5.0.4. L –Box test method ……………………………………………...………128

5.0.4.1. Introduction ………….……….………………...………..…….128

5.0.4.2. Assessment of test ………………………….……………..…...128

5.0.4.3. Equipments …………………………………..………………...129

5.0.4.4. Procedure …………………………….………..…………….…130

5.0.4.5. Interpretation of results ………………………...…………..….130

5.1. Case Studies Overseas ………………………………………………..……..……..130

5.1.1. Shark and Pengium Aquariums at the Oceanopole

MarineParkinBrest. …………………………………………...…..……..130

5.1.1.1 Main project description ……………………………….....…….130

5.1.1.2. Why SCC was used …………………………………..….…….131

5.1.1.3. Project requirements …………………………………..…...…..131

5.1.2.Basement for Research and Development building in Tokyo, Japan ….....131

5.1.2.1. Main project description ……………………………………...131

5.1.2.2. Why SCC was used ……………………………………………131

5.1.3. Pipe screen for a Tail Tunnel at the Meinrad Leinert

Square,Zurich, Switzerland...…………………………………………...131

5.1.3.1. Main project requirements ……………………………….....…131

5.1.3.2. Why SCC was used ……………………………………………132

xii

5.1.4. Modular hotel room units by old castle Precast

Rehoboth, MA (USA) ………………………………………………….132

5.1.4.1. Main project description………………………………...……...132

5.1.4.2. Why SCC was used ……………………………………….…...132

5.1.5. Case study in land ……………………………………………...…….….132

5.2. Requirements of Self-Compacting Concrete ...…………………………...……….133

5.2.1.Application area …………………………………………………..……………...133

5.2.2. Requirements ……………………………………………………..….…133

5.2.2.1. Filling Ability …………………………………………….……133

5.2.2.2. Passing Ability ………………………………………….……..134

5.2.2.3. Resistance to Segregation ………………………………...……134

5.3. Workability criteria for the fresh SCC ………………………………………….....136

5.4. Complexities Involved In Making SCC ………………………………………...…137

5.5. Limitations of SCC ……………………………………………………...………...138

5.6. Advantages of SCC ………………………………………………………………..138

5.6.1. Some Architectural Advantages of SCC Include ……………………....139

5.7. Economic Impact of Self-Compacting Concrete In Precast …………..…………...140

5.7.1. Applications ………………………………………………..……..…...142

5.8. Perfomance …………………………….…………………………………………..142

CHAPTER 6: EXPERIMENTAL PROCEDURES..……………………..........144-181

6.0. General……………………………………………………………………………..144

6.1. Introduction ………………………………………………………………………..144

6.2. Research Significance ……………………………………………………………..145

6.3. Experimental Program ……………………………………………………………..145

6.4. Materials Used …………………………………………………………..…………145

6.4.1. Cement …………………………………………………...…….………..145

6.4.2. Fine aggregate ………………………………………………….………..146

6.4.3. Coarse aggregate ………………………………………………..……….146

6.4.4. Mineral Admixtures ……………………………………………..………147

6.1.4.1. Fly ash …………………………………………………………147

xiii

6.4.5. Chemical Admixture ……………………………………………..……...147

6.4.6. Viscosity Modifying Agent ……………………………………….……..148

6.4.7. Glass Fibres ……………………………………………………….……..148

6.1.7.1. Effect of Glass fibre on Bleeding ………………………………...148

6.1.8. Water ……………………………………………………………….……149

6.5. Mix Proportion ………………………………………………………………..…...149

6.5.1. Trail Mixes ………………………………………………………….…...149

6.6. Development of Glass Fiber Reinforced Self Compacting Concrete(GFRSCC)….150

6.7. Workability…………………………………………………………………………151

6.8. Testing of SCC in Fresh State.………………………………………………….….151

6.9. Specimen Preparation …………………………………………………………...…151

6.10.Casting ...……………………………………………………………………….….152

6.11.Curing ………………………………………………………………………....…..152

6.12.Compressive Strength ………………………………………………...………..…152

6.13. Tests of GFRSCC With and Without Confinement in Hardened State …….……153

6.14. Failure mode of Test Specimen in Compression …………………………..…….154

6.15. Comparison with Conventional Concrete to GFRSCC ...………………………...156

6.15.1. Conventional Concrete ………………………………………………....156

6.15.2. Glass Fibre Reinforced Self Compacting Concrete (GFRSCC) ….........156

6.16. Development of Analytical Stress-Strain models for GFRSCC with & without

Confinement ……………………………………………………………………157

6.16.1. Effect of fiber on Ultimate strength and strain …………………………157

6.16.2. Relationship between Fiber Index, stress ratio and strain ratio ………...158

6.16.3. Ductility factor Vs Fiber Index ………………………………………...160

6.16.4. Non Dimensionalised stress – strain curve …………………………….161

6.16.5. Model caluculations for Normalised stress – Normalised Strain curve of

GFRSCC (0.798% Confinement)………………………………………162

6.17. Experimental Results ……………………………………………………………..165

6.17.1. Stress-Strain values of Cylinder without confinement (M50 grade

GFRSCC)…………………………………………………………….…165

6.17.2. Stress-Strain values of Cylinder with 0.798% confinement (M50 grade

GFRSCC)……………………………………………………….………168

xiv


GFRSCC)………………………………………………………….……171


GFRSCC)………………………………………………………….……174


GFRSCC)………………………………………………………….……177

CHAPTER 7: DISCUSSIONS OF THE TEST RESULTS...…..……………....182-188

7.0. Discussions ………………………………………………………………………...182

7.1. Characteristics of GFRSCC Mixes in Hardened State …………………………….183

7.1.1. Compressive Strength ……………………………………………...……183

7.1.2. Modulus of elasticity ……………….……………………………………183

7.1.3. Secant Modulus ………………………………………………………….183

7.1.4. Stress-Strain behaviour with & without confinement……………………184

7.1.5. Energy absorption capacity (Toughness) ………………………………..185

7.1.6. Ductility ………………………………………………………………….186

7.1.7. Analytical expressions.…………………………………………………...186

CHAPTER 8: CONCLUSIONS AND RECOMMENDATIONS……………..189-205

8.0. Conclusions ………………………………………………………………………..189

8.1 Recommendations for Future Research ………………………………………….192

BIBLIOGRAPHY ………………………………………………………………194

APPENDIX A …………………………………………………………………..200

VITA ……………………………………………………………………………205

xv

LIST OF FIGURES

Figure No. Title. Page No.

1.0 Excellent finish of a neat cement SCC…………………………………………………..2 1.1. Necessity of Self-Compacting Concrete (Ouchi and Hibino, 2000) ………………..21

1.2. Rational construction system proposed by Ozawa (Ouchi et al., 1996) ………..….22

1.3 Annual production of SCC in Japan Total production of ready-mixed concrete in

Japan in 19997 is 67,620×1,000 m ………………………………………………..…23

1.4 Anchorage 4A of Akashi-Kaikyo Bridge …………………………………………...24

1.5 U-type test (Ouchi and Hibino, 2000) ……………………………………………….26

1.6 V-funnel (Dietz and Ma, 2000) ……………………………………………………...27

1.7 Slump Flow/J-Ring combination test (Kosmatka et al., 2002) ……………………...28

1.8. Cylinder without any confinement …………………...……………………………..32

1.9. Cylinder with confinement ………………………………………………………….32

1.10 Rational acceptance test at job site for self-compacting concrete (Ouchi and

Hibino, 2000) .......……………………………………………..………………..36

1.11 Anchorage of Akashi-Kaikyo Bridge, Japan (Ouchi and Hibino, 2000) …………..37 2.1. Small pipes used as obstacles in formwork (Okamura, 1997) ...……………………39

2.2 Effect of super plasticizer on viscosity (Okamura, 1997)……………………………40

2.3 Compressive strength of SCC with and without HPMC (Subramanian and

Chattopadhyay, 2002) ……………………………………………………………..43

2.4 Pullout specimen (Dehn et al., 2000) ………………………………………………..45

2.5 Viscosity –Yield stress and the workability box (Ferraris et al., 1999) ……………..48

2.6 Rational mix-design method for self-compacting concrete (Ouchi et al., 1996) ……74

2.7 Anchorage of Akashi-Kaikyo Bridge, Japan (Ouchi and Hibino, 2000) ……………81

2.8 Sandwich structure applied to immersed tunnel in Kobe, Japan (Ozawa, 1989) ……82

3.1 Materials used in regular concrete and self-compacting concrete

by absolute volume (Kosmatka et al., 2002) …………………………...…………..88

3.2. Microstructural development in Portland cement pastes (Mindess et al., 2003) …...90

3.3 SEM micrograph of fly ash particles (Kosmatka et al., 2002) ………………………94

xvi

Figure No. Title. Page No.

3.4 Effect of microsilica in densifying the concrete mix - comparison between

conventional and microsilica concretes (St John, 1998) …………………………….97

3.5 Effect of superplasticizer on cement: (a) Cement and water; (b) Cement,

water, and superplasticizer (Ramachandran, 1984) ………………………...……….98

3.6 Dispersing action of water-reducing admixtures: (a) flocculated paste;

(b) dispersed paste (Mindess et al., 2003) …………………………………………...99

4.1. Mix design flow chart ……………………………..……………………………...114

5.1. Showing the apparatus of Slump Flow and slump flow in (a) & (b) respectively....123

5.2. Showing the apparatus of V-funnel test ……………...………………...………….126

5.3. L-Box Apparatus …………………………………………………………………..129

5.4. Showing the performance of Conventional Concrete & SCC in (a) and (b)

respectively …………………………………………………………………………143

6.1 Casted cylinder specimen tested UTM …………………………………………….155

6.2 Casted cube specimen under tested under Compression testing machine………….155

6.3. Cracks being visible on the test specimen ………………………………………....156

6.4. Typical Stress-Strain behaviour of (M50 grade GFRSCC) with and without

confinement at 28 days………………………………………………………....157

6.5. Stress ratio (fu/f') Vs Fiber Index…………………………………………………..159

6.6. Strain ratio (єu/є) Vs Fiber Index …………………………………………………159

6.7. Fiber Index Vs Ductility Factor …………………………………………………...160

6.8. Normalised Stress – Normalised Strain…………………………………………….161

6.9. Stress-Strain behaviour of GFRSCC without confinement………………………..167

6.10. Normalized Stress-Strain Curve of GFRSCC without Confinement……………..167

6.11. Stress-Strain behaviour of GFRSCC (0.798% Confinement)………………….....170

6.12. Normalized Stress-Strain Curve of GFRSCC (0.798% Confinement)………..….170

6.13. Stress-Strain behaviour of GFRSCC (1.062% Confinement) ………………..…..173

6.14. Normalized Stress-Strain Curve of GFRSCC (1.062% Confinement)………..….173

6.15. Stress-Strain behaviour of GFRSCC (1.327% Confinement) ……………..176

6.16. Normalized Stress-Strain Curve of GFRSCC (1.327% Confinement)…………...176

xvii

6.17 Stress-Strain behaviour of GFRSCC (1.591% Confinement) …………………….179

6.18. Normalized Stress-Strain Curve of GFRSCC (1.591% Confinement)………….. 179

6.19. % of Different confinements Vs % of Improvement of compressive Strength…..180

7.1. Typical Stress-strain behavior of GFRSCC with and without confinement ………182

7.2 Graphical representation of increase in strength, Specific Toughness

with different confinements …………………………………………..…………...187

7.3 Graphical representation of increase in strength, Energy Absorption

(% increase) with different confinements ………………………………………….188

7.4 Graphical representation of increase in strength, ductility

(% increase) with different confinements ………………………………………….188

xviii

LIST OF TABLES

Table No. Title. Page No. 1.1. SCC Guide line and specification development in Europe as of

September 2001 (Based up on a paper by Dingenouts ………………………………9

2.1. Chemical composition and Physical characteristics of Super-pozz®

(SeedatandDijkema, 2000)…………………………………………….……………..52

2.2 Assessment of Concrete Permeability according to Water Penetration

Depth(TheConcreteSociety, 1987)……………………………………………….….63

2.3 Relationship between charge passed and chloride permeability

(ASTM C-1202-94)………………………………………………………………….65 3.1 Typical composition of ordinary Portland cement (Mindess et al., 2003) …………..88

3.2: Concrete composition, dry materials……………………………………………….103

4.1. Typical Properties of Glenium-2 ………………………………………………..…119

4.2. Mix composition as per EFNARC guidelines ……………………………………..110

5.1. List of methods for workable properties of SCC ………………………………….135

5.2 Workability properties of SCC and alternative methods …………………………..136

5.3 Acceptance criteria for SCC as per EFNARC guide lines …………………………136

6.1. Physical properties of Cement ……………………………………………………..146

6.2. Chemical compositions of Cement as per manufacturers test report ...……………146

6.3 Physical characteristics of VTPS fly ash …………………………………………...147

6.4 Chemical composition of VTPS fly ash ……………………………………………147

6.5. Properties of Selected Glass Fibres ………………………………………………..148

6.6. Details of Mix proportion for SCC M50 grade ……………………………………150

6.7 Quantities per m3 of the final mix arrived for GFRSCC M50 grade …………….…150

6.8. Fresh properties of GFRSCC ……………………………………………………...151

6.9. Hardened properties of GFRSCC with & without Confinement

at 28days (Cylinder) ……………………………………………………………….153

6.10 Compressive strength of Cubes tested at 28 days (without Confinement) ……….154

6.11. Peak Stress and Peak Strain values of M50 grade GFRSCC with different

confinement variation …………………………………………………………..158

xix

Table No. Title. Page No.

6.12 Stress-Strain values of Cylinder without confinement

(M50 gradeGFRSCC) ………………………….................................................165

6.13 Stress-Strain values of Cylinder with 0.798% confinement

(M50 gradeGFRSCC) ………………………………. ……………………...168


(M50 gradeGFRSCC) ………………………………………………………....171


(M50 gradeGFRSCC) …………………..………………………………………174


(M50 gradeGFRSCC) …………………..……………………………………....177

6.17. Peak stress values and strain values corresponding to peak stress ……………….180

6.18 Stress Strain Equations for Different Confinements

of M50 Grade GFRSCC..……………………………………………….............181

7.1 Secant Modulus of GFRSCC ……………………………………………….…….184

7.2 Constants A1, B1 values for Ascending & Descending Portions ……………...…..185

7.3 Young’s Modulus of Elasticity, Energy absorption and ductility values

For GFRSCC with and without confinement reinforcement ………………………185

8.1. Peak stress and Peak strain for Different confinements of GFRSCC ...…………...192

xx

NOTATIONS AND ABBREVIATIONS

EASEC East-Asia Structural Engineering Construction

ECC Engineering Construction and Contracts

ITZ Transition Zone Interfacial

LNG Liquid Nitrogen Gas

µm Micrometer (micron)

RILEM International Union of Laboratories and Experts in Construction

Materials, Systems and Structures

SEM Scanning Electron Microscope

TC Technical Committee

W/C Water to Cement Ratio

WSM Workability of Fresh Special Concrete Mixes

Fi Fibre Index

cE Young’s Modulus, N/mm²

antEsec Secant Modulus, N/mm²

Strain

f Stress in N/mm²

fu Ultimate Stress, N/mm²

u Strain corresponding to ultimate stress

fu/f’ Stress Ratio ; єu/є’ Strain Ratio

GF pSCC GFSCC without confinement

GFR 798.0SCC GFRSCC with 0.798% confinement




3R Three rings, 6mm diameter

4R Four rings, 6mm diameter

5R Five rings, 6mm diameter

6R Six rings, 6mm diameter

xxi

CHAPTER 1

Introduction

CHAPTER 1 Introduction

1.0. Introduction to Self-Compacting Concrete Development of self-compacting concrete (SCC) is a desirable achievement in the

construction industry in order to overcome problems associated with cast-in-place

concrete. Self-compacting concrete is not affected by the skills of workers, the shape and

amount of reinforcing bars or the arrangement of a structure and, due to its high-fluidity

and resistance to segregation it can be pumped longer distances (Bartos, 2000). The

concept of self-compacting concrete was proposed in 1986 by professor Hajime Okamura

(1997), but the prototype was first developed in 1988 in Japan, by professor Ozawa

(1989) at the University of Tokyo. Self-compacting concrete was developed at that time

to improve the durability of concrete structures. Since then, various investigations have

been carried out and SCC has been used in practical structures in Japan, mainly by large

construction companies. Investigations for establishing a rational mix-design method and

self-compactability testing methods have been carried out from the viewpoint of making

it a standard concrete. Self-compacting concrete is cast so that no additional inner or outer

vibration is necessary for the compaction. It flows like “honey” and has a very smooth

surface level after placing. With regard to its composition, self-compacting concrete

consists of the same components as conventionally vibrated concrete, which are cement,

aggregates, and water, with the addition of chemical and mineral admixtures in different

proportions (see Chapter 3). Usually, the chemical admixtures used are high-range water

reducers (superplasticizers) and viscosity-modifying agents, which change the rheological

properties of concrete. Mineral admixtures are used as an extra fine material, besides

cement, and in some cases, they replace cement. In this study, the cement content was

partially replaced with mineral admixtures, e.g. fly ash, slag cement, and silica fume,

admixtures that improve the flowing and strengthening characteristics of the concrete.

1.0.1 Advantages and disadvantages of Self-Compacting Concrete

Compared to NVC, SCC possesses enhanced qualities, and its use improves

productivity and working conditions (De Schutter et al., 2008; The Concrete Society and

BRE, 2005).

1

Because compaction is eliminated, the internal segregation between solid

particles and the surrounding liquid is avoided which results in less porous transition

zones between paste and aggregate and a more even colour of the concrete (RILEM TC

174 SCC, 2000). Improved strength, durability and finish of SCC can therefore be

anticipated. Very good finish effect is shown in Figure 1.0, a pure cement SCC placed in a

steel mould, demoulded 24hours after casting. The surface is so smooth and dense that it

can reflect light.

Figure 1.0 Excellent finish of a neat cement SCC

For much concrete construction, the structural performance is improved by

increasing reinforcement volumes, limiting cracking by using smaller bar

diameters and using complex formwork, all of which increase the difficulty of

compaction (Okamura and Ouchi, 2003a; RILEM TC 174 SCC, 2000). SCC meets the

above developments by making casting homogeneous concrete in congested structures

possible; it also improves efficiency and effectiveness on site by reducing the construction

time and labour cost.

SCC also improves the workplace environment by reducing noise pollution and eliminating the health problems related to the use of vibration equipment such as ‘white fingers’ and deafness (RILEM TC 174 SCC, 2000). SCC is therefore called ‘the quiet revolution in concrete construction’ (The Concrete Society and BRE, 2005). As a result, the precast concrete products industry has become the biggest user of SCC in Europe (Skarendahl, 2003).

SCC requires higher powder and admixture (particularly superplasticisers) contents than

NVC and so the material cost is higher (The Concrete Society and BRE, 2005). It was

reported that in most cases, the cost increase ranged from 20% to 60% compared to similar

2

grade NVC (Nehdi et al., 2004; Ozawa, 2001). However, in very large structures, increased

material cost by using SCC was outweighed by savings in labour costs and construction

time (Billberg, 1999). The benefits of SCC were fully displayed in a composite

sandwich system, which involves casting SCC and NVC in layers within the same

structural elements (Okamura and Ouchi, 2003a; Ouchi, 2001; Ozawa, 2001).

The increased content of powder and admixture also leads to higher sensitivity (i.e.

reduced robustness) of SCC to material variation than that of NVC; thus greater care with

quality control is required (Walraven, 1998).

1.0.2 Definition and Properties of Self-Compacting Concrete

It is important at this stage to define SCC and its characteristics. Literally, self-

compacting characteristics are related to the fresh properties. The definitions of SCC given

in the literature vary, a most common one is that‘ a concrete that is able to flow under its

own weight and completely fill the form work, whilemaintaining homogeneity even in

the presence of congested reinforcement, and then consolidating without the need for

vibrating compaction’ (The Concrete Society and BRE, 2005).

SCC has three essential fresh properties: filling ability, passing ability and

segregation resistance Testing-SCC, 2005; The Concrete Society and BRE,

2005). Filling ability is the characteristic of SCC to flow under its own weight

and to completely fill the formwork. Passing ability is the characteristic of SCC

to flow through and around obstacles such as reinforcement and narrow spaces

without blocking. Segregation resistance is the characteristic of SCC to remain

homogeneous during and after transporting and placing. It is passing ability that

distinguishes SCC from other high consistence concrete (Domone, 2000).

Additional properties, such as robustness and consistence retention, are also

important in applications of SCC. Robustness refers to the ability of SCC to retain its

fresh property when the quality and quantity of constituent materials and the

environmental conditions change. Consistence retention refers to the period of duration of

the fresh properties.

3

A number of commonly used tests are subsequently described for evaluating the fresh

properties. There is no difference in test methods for hardened properties (strength,

stiffness, and durability etc.) between SCC and NVC. Both fresh and hardened properties are

key to the successful application of SCC. SCC therefore can be designed by fresh or

hardened requirements.

1.1 Historical Development of Self-Compacting Concrete Self-compacting concrete, in principle, is not new. Special applications such as

underwater concreting have always required concrete, which could be placed without the

need for compaction (Bartos, 2000). In such circumstances vibration was simply

impossible. Early self-compacting concretes relied on very high contents of cement paste

and, once superplasticizers became available, they were added in the concrete mixes. The

mixes required specialized and well-controlled placing methods in order to avoid

segregation, and the high contents of cement paste made them prone to shrinkage. The

overall costs were very high and applications remained very limited.

The introduction of “modern” self-leveling concrete or self-compacting concrete

(SCC) is associated with the drive towards better quality concrete pursued in Japan

around 1983, where the lack of uniform and complete compaction had been identified as

the primary factor responsible for poor performance of concrete structures (Dehn et al.,

2000). Due to the fact that there were no practical means by which full compaction of

concrete on a site was ever to be fully guaranteed, the focus therefore turned onto the

elimination of the need to compact, by vibration or any other means. This led to the

development of the first practicable SCC by researchers Okamura and Ozawa, around

1986, at the University of Tokyo and the large Japanese contractors (e.g. Kajima Co.,

Maeda Co., Taisei Group Co., etc.) quickly took up the idea. The contractors used their

large in-house research and development facilities to develop their own SCC

technologies. Each company developed their own mix designs and trained their own staff

to act as technicians for testing on sites their SCC mixes. A very important aspect was

that each of the large contractors also developed their own testing devices and test

methods (Bartos, 2000). In the early 1990’s there was only a limited public knowledge

about SCC, mainly in the Japanese language. The fundamental and practical know-how

was kept secret by the large corporations to maintain commercial advantage.

4

The SCCs were used under trade names, such as the NVC (Non-vibrated concrete) of

Kajima Co., SQC (Super quality concrete) of Maeda Co. or the Biocrete (Taisei Co.).

Simultaneously with the Japanese developments in the SCC area, research and

development continued in mix-design and placing of underwater concrete where new

admixtures were producing SCC mixes with performance matching that of the Japanese

SCC concrete (e.g. University of Paisley / Scotland, University of Sherbrooke / Canada)

(Ferraris, 1999).

1.2. World-wide Current Situation of Self-Compacting Concrete

Self-compacting concrete has already been used in several countries. In Japan,

major construction projects included the use of SCC in the late ’90s. Today, in Japan,

efforts are being made to free SCC of the “special concrete” label and integrate it into

day-to-day concrete industry production (Okamura, 1997). Currently, the percentage of

self-compacting concrete in annual product of ready-mixed concrete (RMC), as well as

precast concrete (PC), in Japan is around 1.2% and 0.5% of concrete products.

In the United States, the precast industry is also leading SCC technology

implementation through the Precast/Prestressed Concrete Institute (PCI) which has done

some research on the use of SCC in precast/prestressed concretes starting with 1999

(Bartos, 2000). It is estimated that the daily production of SCC in the precast/prestressed

industry in the United States will be 128000 m3 in the first quarter of 2011 (around 1% of

the annual ready-mix concrete). Furthermore, several state departments of transportation

in the United States (23 according to a recent survey) (Bartos, 2000)are already involved

in the study of SCC. With such a high level of interest from the construction industry, as

well as manufacturers of this new concrete, the use of SCC should grow at a tremendous

rate in the next few years in the United States. However, even if it is made from the same

constituents the industry has used for years, the whole process, from mix design to

placing practices, including quality control procedures, needs to be reviewed and adapted

in order for this new technology to be applied properly.

Research regarding the self-compacting concrete was also carried out in Canada,

few years after the concept was introduced in Japan. Institute for Research in

Construction, Canadian Precast/Prestressed Concrete Institute, CONMET-ICON, and

ISIS are some of the bodies which studied various aspects of the new technology.

5

The introduction of the SCC in Europe is largely connected with the activities of

the international association RILEM, France, particularly of its Technical Committee

TC145-WSM on “Workability of Fresh Special Concrete Mixes” (Dhir and Dyer, 1999).

The TC145-WSM was founded in 1992 and immediately attracted expert memberships

from all over the world.

The aim was to look at the production stage of a number of “special” concretes

and identify workability parameters and other characteristics of the mixes in their fresh

state that governed the reliable and economical achievement of the “special” or “high-

performance” parameters the concretes offered. As the importance of the SCC became

widely recognized, other European countries, Germany, Sweden, UK, Denmark,

Netherlands, Norway, Finland, etc., have decided to keep up with the developments in

this area. For example, in Sweden, the SCC market share was at five percent in RMC and

PC in 2010, and was expected to double in 2012. Housing and tunneling, as well as

bridge construction for the Swedish National Road Administration were the main areas of

use for SCC. In the Netherlands and Germany, the precast industry is mainly driving the

development of SCC, with an expected eight percent of market share in 2012 in

Netherlands.

Today, self-compacting concrete is being studied worldwide, with papers

presented at almost every concrete-related conference, but until now - year 2003 - there is

no universally adopted standardized test method for evaluation of self-compactability of

this concrete. Currently, the use of self-compacting concrete is being rapidly adopted in

many countries. The use of self-compacting concrete should overcome concrete

placement problems associated with the concrete construction industry. However, there

still is a need for conducting more research and development work for the measurement

and standardization of the methods for the evaluation of the self-compacting

characteristics of SCC.

1.2.1. Japan

SCC was first developed in Japan in 1988 in order to achieve more durable

concrete structures by improving the quality achieved in the construction process and the

placed material. The removal of the need for compaction of the concrete reduced the

potential for durability defects due to inadequate compaction (e.g. honeycombing).

6

The use of SCC was also found to offer economic, social and environmental

benefits over traditional vibrated concrete construction. These benefits included faster

construction and the elimination of noise due to vibration. One of the main drivers for the

development of the technology was the reduction in the number of skilled site operatives

that the Japanese construction industry was experiencing in the 1980s. The use of SCC

meant that less skilled labour was required for the placing and finishing of the concrete.

SCC was developed from the existing technology used for high workability and

underwater concretes, where additional cohesiveness is required. The first research

publications that looked into the principles required for SCC were from Japan around

1989 to 1991. These studies concentrated upon high-performance and super-workable

concretes and their fresh properties such as filling capacity, flowability and resistance to

segregation.

The first significant publication in which ‘modern’ SCC was identified is thought

to be a paper from the University of Tokyo by Ozawa et al. in 1992. The term ‘self-

compacting concrete’ is not used within the paper, although a high-performance concrete

was produced which possessed all the essential properties of a self-compacting concrete

mix.

In the following few years many research papers were published on concretes

such as super-workable, self-consolidating, highly-workable, self-placeable and highly-

fluidised concretes, all of which had similar properties to what we now know as SCC.

These were mainly papers on work into the mix design of what would become ‘SCC’ and

its associated fresh properties. In 1993, research papers were beginning to be published of

case studies on the use of these early forms of ‘SCC’ in actual applications. One of the

first published references utilising the term ‘self-compacting’ was in Japan in 1995.

After the development of this prototype SCC, intensive research began in many

places in Japan, especially within the research institutes of large construction companies,

and as a result, SCC has now been used in many practical applications.

The first significant international workshop dedicated to the material was held at

Kochi University of Technology, Japan in August 1998. The majority of these papers

7

focused upon the development of SCC in different countries, including research and

development into mix design models, mix constituents and rheology.

In April 1997, the Japanese Society of Civil Engineers (JSCE) set up a research

subcommittee with the aim of establishing recommendations for the practical application

of SCC. This was subsequently published in English in August 1999.

The 2nd International Symposium on SCC was organized by the University of

Tokyo in October 2001. A total of 74 papers plus two keynote and four invited speakers

from 20 countries were included. Since the 1st International Workshop had concentrated

mainly upon mix design and rheology, the 2nd International Symposium concentrated

more on the long-term durability and life-cycle cost of SCC.

A conference was recently held in Japan in October 2002 on Concrete Structures

in the 21st Century, which contained six papers on SCC, including four from Japan.

These papers illustrated that the basic technology of the material in Japan is relatively

well understood and that the majority of current efforts in research and development are

concentrated on taking this knowledge further into new applications such as composite

structures and sheet piling

1.2.2. Europe

In the second half of the 1990s, interest and use of SCC spread from Japan to

other countries, including Europe. Some of the first research work to be published from

Europe was at an International RILEM (International Union of Testing and Research

Laboratories of Materials and Structures) Conference in London in 1996. Papers were

presented on the design of SCC by University College London, and a mix-design model

by the Swedish Cement and Concrete Research Institute (CBI).

A Technical Committee (TC 174-SCC) was set up by RILEM in 1997 with the

objective of gathering, analysing and presenting a review of the technology of SCC, as

well as looking for unified views on testing and evaluation. Seventeen full members and

three corresponding members covering ten countries on four continents took part in the

work and a state-of-the-art report was published in 2000.

8

Sweden was the first country in Europe to begin development of SCC, and in 1993

the CBI organised a seminar in Sweden for contractors and producers, leading to a project

aimed at studying SCC for housing. As part of this project, large numbers of half-scale

house walls were cast using SCCs which were made with different filler materials. The

work from this project contributed to the first European project on SCC which began in

January 1997 and was completed in 2000. The main goal of this Brite-EuRam project

(BRPR-CT96-0366) was to develop a new vibration-free production system to lower the

overall cost of in-situ-cast concrete construction. The first part concerned the

development of SCC with or without steel fibres and the second part dealt with full-scale

experiments in civil engineering and housing. This project included partners from several

European countries, including the UK.

Parallel to this Brite-EuRam project, CBI continued work together with the

Swedish National Roads Authority (SNRA) into SCC for bridge casting. Laboratory

investigations, pre-qualifying tests, half-scale trials and finally full-scale trials were all

completed. The first of three bridges wholly cast in SCC was completed in January 1998

and is thought to be the first bridge cast with this material outside of Japan. This work

also showed that the hardened properties of SCC are superior to conventional concrete,

including compressive strength, frost resistance, permeability and reinforcement bond

strength. This is thought to be mainly due to both the increased cementitious content

generally used and the denser interfacial transition zone between the aggregate and the

paste of SCCs.

Studies also showed that total bridge building costs can be reduced by as much as

5–15% when using SCC compared with conventional concrete. An earlier report on the

same work was also published by the SNRA. This report concluded that as well as

reducing overall bridge costs, using SCC has the potential to reduce the energy

consumption and emission of greenhouse gases by 20–30% due to the reduced resources

required in the construction process and the enhanced durability of the resultant concrete.

However, it does not take into account the likely increased cement content used to make

the SCC and the additional energy required for its production.

9

The first major event dedicated to SCC in Europe was the 1st International RILEM

Symposium on SCC in Stockholm in 1999. The papers included 23 from Asia, 38 from

Europe, five from North America and one from Australia. The symposium attracted 340

participants from 35 countries, which is a ratio of 5 to 1 of participants to papers,

indicating the increasing interest in the material in Europe.

1.2.3. European Development

Development and use of SCC began to quickly spread from Sweden to other

Scandinavian countries at the end of the 1990s. The concrete industry in countries such as

France and the Netherlands have also recently been developing and using the material,

with countries such as Germany and the UK progressing closely behind. All of these

countries have now used SCC in both in situ and precast applications. Countries such as

Greece and the Eastern European countries are still mainly conducting research and

development or are at the initial site trial stage.

Two European-wide research projects are currently under way in the field of SCC.

1. Following the completion of the European-wide SCC Brite- EuRam project in

2000, it was clear that the remaining fundamental obstacle to the material’s wider

use in Europe was the absence of suitable test methods to identify its three key

properties (i.e. passing ability, filling ability and resistance to segregation). The

EU therefore agreed to support an additional three-year project from 2001 to 2004

through its Growth programme (Growth Project GRD2- 2000-30024) to develop

test methods for SCC and to prepare the way for European standardisation. The

project involves twelve European partners and is led by the University of Paisley,

Scotland.

2. A RILEM committee was also formed in September 2000 to focus on assembling

relevant existing knowledge on various aspects on the casting of SCC. The

committee aims to build further on the work of RILEM TC 174-SCC mentioned

in the previous section and the objective is to find links between the fundamental

basic mechanisms of SCC and the current practical experience regarding SCC.

The knowledge will be further developed through technical discussions and a

workshop and will result in a report on the existing available knowledge on the

casting of SCC.

10

A specification and guideline document has recently been produced by EFNARC

(European Federation of Producers and Contractors of Specialist Products for Structures)

which aims to provide a framework for the design and use of high-quality SCC in Europe

based on the latest research findings combined with field experience. It is probably the

first European guidance document to be universally available, and is freely available on

the internet. It is intended that the document be updated as SCC technology evolves and

advances.

Most of the major European countries are currently in the process of developing

guidelines or specifications for the use of SCC. Table 1 shows a snapshot of the current

stage in the development of SCC guidelines or specifications for each of the European

countries listed.

Table 1.0 SCC Guide line and specification development in Europe as of

September 2001 (Based up on a paper by Dingenouts

Country Guideline Organization

Acceptance Phase

Publication Date

Austria n/a Draft 2002

Denmark n/a Draft in preparation n/a

Europe EFNARC Guideline 2002

Finland n/a Draft 2003

France AFGC Industry recommendation 2000

Germany Annex to DIN 1045 For comment 2003

For comment 2003 Italy Annex to EN 206

In preparation 2002

BRL1801 Approval n/a Netherlands

TC73/04 Accepted 2001

Norway Norwegian Concrete Society Accepted 2002

Sweden Swedish Concrete Assoc. (SCA) Accepted 2002

11

1.2.4. Scandinavia

As described earlier, Sweden was at the forefront of the development of SCC

outside Japan and it is estimated that SCC now accounts for approximately 7–10% of the

Swedish ready-mix market, up from approximately 3% in 2000. Currently, the CBI, four

universities and the government in Sweden are all conducting research into SCC.

SCC is often used in Sweden today by contractors such as NCC on a commercial

basis. NCC and other Swedish contractors are also conducting research into SCC, both

internally and with other companies and universities/institutes. The Swedish Concrete

Association (SCA) has also recently published recommendations for the use of SCC.

The volume of SCC produced in Norway has increased from approximately 0·5%

(or 12 000 m3) of total concrete volume in 2000 to approximately 1·2% (or 29 500 m3) in

2001. A Norwegian guideline for the production and use of the material was issued in late

2001 and an English translation has recently been completed.

SCC is used in Finland only to a limited degree, although companies such as

Lohja Rudus and Parma Betonila each have experience from approximately 10–20

construction sites. There is also a national project on the practical aspects of SCC led by

the Technical University of Helsinki (HUT) and VTT which began in 2001 and will finish

in 2003. No SCC standardisation as yet exists. Universities in Denmark, such as the DTU

(Technical University of Denmark), have also recently undertaken research into SCC, as

well as holding training courses on SCC.

The first project investigating SCC in Iceland was from 1996 to 1999 and was a

collaboration between the Icelandic Building Research Institute (IBRI) and an Icelandic

ready-mix concrete company, Steypusto¨ UNKNOWN SYMBOL 240 FONT¼Times

New Roman in H. F., which showed that it was possible to cast SCC in Iceland with

Icelandic materials. IBRI continue to conduct research into SCC and they are hosting the

3rd International Symposium on SCC in August 2003.

1.2.5. France France is quite active in the research and development of SCC. A national

research project on SCC called BAP (Be´tons auto-plac¸ants) is currently ongoing. French

recommendations for the use of the material were established in July 2000 and are used as

reference on construction sites.

12

The Lafarge Group have conducted a large amount of research and development

at their Laboratoire Central de Recherches (LCR) at L’Isle d’Abeau, near Lyon. Their

progress in the development of SCC is approximately two years ahead of the position in

the UK. They have spent approximately £2 million on researching and developing the

material internationally and currently produce approximately 50,000 m3/annum of SCC,

with this volume increasing almost exponentially at present.

The Lafarge Group wanted to validate the assumption that using SCC generates an

overall cost saving. They therefore worked with a contractor to simultaneously construct

two identical apartment buildings in Nanterre, France. Conventional concrete methods

were used for one building and for the second building the construction process was

adapted to utilize SCC materials and processes. The building constructed using SCC

materials and processes was completed 2·5 months before the conventionally constructed

building and with an overall project cost saving of 21·4%.

1.2.6.. Germany In Germany, SCC requires technical approval before it can be used on site. The

current DIN standards do not allow this type of concrete to be used because the

consistency and the fines content do not comply with the standard. Therefore, the DIBt

(German Institute of Technical Approvals in Berlin) requires suitability tests from a third-

party laboratory, usually universities, who then issue an official approval. Many

contractors have obtained approvals and are constructing with SCC.

At least six different universities and research establishments in Germany are also

conducting research into SCC. The University of Stuttgart is also involved with the

current European-wide SCC test methods project (Growth GRD2-2000- 30024).

1.2.7. Belgium A Belgian national contact group on SCC exists chaired by Professor De Schutter

of the University of Ghent. This group of universities, contractors, suppliers and other

interested parties meet several times a year to discuss SCC development in Belgium.

Several national research projects on SCC are also currently under way, funded

mainly by the National Fund for Scientific Research, Flanders, and other interested

parties. These projects are investigating the transport of potentially aggressive media in

SCC, the spalling behaviour of SCC and the integration of SCC into the building industry.

13

1.2.8. Spain

SCC production is just beginning in Spain, but the first structures have already

been constructed in Malaga, Valencia and Madrid. The current problem is that SCC is not

included in the basic Spanish regulations for concrete, and so care has to taken and its use

fully justified. Instituto Eduardo Torroja de Ciencias de la Construccio´n (CSIC) is

leading the standardisation group for SCC in the Spanish National Standardisation

Agency (AENOR). The target is to issue some Spanish standards on SCC by the end of

2002. They are also collaborating with other Spanish research groups such as UPC

(Universitat Polite`cnica de Catalunya) in Barcelona

1.2.9. Holland

The precast concrete industry in the Netherlands first became interested in SCC in

1998. A project was begun to develop SCC precast applications by the Belton Group, an

association of 24 precasters, which is a subsidiary of BFBN (Association of the Dutch

Concrete and Precasting Industry). Although the Belton project was formally completed

in December 1999, intensive collaboration in SCC is still continuing. In 2002 a total

volume of 2,50,000 m3of precast SCC is expected to be produced and approximately 30

companies have been certified for the production of SCC pre-cast elements.

Guidelines for ready-mix SCC are finished and are expected to be approved by the

end of 2002, at which point the certification of ready-mix plants can begin. Currently,

ready-mix SCC is being used, but mainly for demonstration projects. 1.2.10. Switzerland

SCC currently accounts for approximately 1% of the ready-mix concrete market

in Switzerland and the material has largely been developed by trial and error. The use of

SCC is currently not limited by Swiss standards because the standards apply to

performance and not the composition of concrete. Research into SCC has been conducted

at the Swiss Federal Institute of Technology (ETH) in Zurich and at the EMPA (Swiss

Federal Institute for Materials Testing and Research) in Du¨bendorf.

1.2.11. Italy

In Italy the majority of SCC applications are in the precast market, although SCC

has been used for in situ applications. The Italian Standards Institute has just completed a

14

document on SCC, which is now being considered as a Standard (as an annex to EN 206-

1). The Italian Ready-Mixed Concrete Producers Association is also preparing guidelines

on SCC. 1.2.12. Other European countries

Other countries in Europe such as the Czech Republic and Greece are also

beginning to research and construct with SCC. A bridge abutment and an experimental

tunnel lining have both been cast with SCC in Prague and a trial was held for the use of

SCC in the 2·5 km cable-stayed bridge over the Corinthian Gulf in Greece.

1.2.13. UK Development

Until about four years ago, interest in SCC in the UK was largely confined to

research studies at Paisley University and University College London (UCL). There has,

however, been a rapid increase in interest from UK industry in the last three years. Two

of the first site applications were in 2000 for the Midsummer Place shopping centre

extension in Milton Keynes and the Millennium Point project in Birmingham.

The Concrete Society in the UK formed a working party early in 1999 consisting

of 18 experts from universities, suppliers, producers, designers and contractors with the

aim to maintain a watching brief on the impact and uptake of SCC in the UK. They have

recently produced both an information sheet and Part 1 of a Current Practice Sheet. The

Part 1 report deals with materials, properties, production and placing of SCC. At the time

of writing, Part 2, which will cover production, placing and optimisation of the

construction process, was 90% complete.

A three-year research project into SCC in the UK is also currently being

conducted by the Building Research Establishment’s (BRE) Centre for Concrete

Construction. This work is funded by the UK Department of Trade and Industry’s (DTI’s)

Construction Industry Directorate. The aim of the project is to encourage the wider use of

SCC by the UK construction industry, and to demonstrate the economic, social and

environmental advantages it offers over traditional vibrated concrete construction. The

work involves consulting with UK industry on its perceptions of SCC, researching the

production of SCC mixes suited to industry needs and disseminating this and additional

information through demonstration events and the publication of case studies and

guidance material.

15

1.2.14. Academic institutions

The leading academic institution in the UK with regard to SCC is the Advanced

Concrete and Masonry Centre at the University of Paisley. This team is led by Professor

Bartos and also includes John Gibbs and Dr Mohammed Sonebi. They were key members

of the original Brite-EuRam project (BRPR-CT96- 0366) mentioned in the previous

section and are leading the current European-wide project on test methods. In addition,

Professor Bartos is Chairman and John Gibbs the Secretary of the Concrete Society

Working Party on SCC. Paisley University also began an 18-month Government-funded

research project in December 2001 aimed at reducing the cost of SCC and encouraging its

use in general construction.

As mentioned earlier, the other academic institution in the UK with a history of

research into SCC is University College London (UCL). The work into SCC is being

coordinated by Dr Peter Domone, who is also a member of the Concrete Society Working

Party on SCC. UCL is also involved with the European-wide project on the testing of

SCC.

Dundee University’s Concrete Technology Unit has also recently begun a three-

year research project investigating the formwork pressures generated by SCCs and other

specialist concretes. This project will determine if the current CIRIA formwork pressure

recommendations are applicable to current new materials and types of concrete such as

SCC, and if not, safe design pressures will be established.

1.2.15. Concrete producers

RMC Ready-mix Ltd is the UK’s leading supplier of ready-mixed concrete. The

company has been undertaking development work on SCC since 1998 with the aim of

producing mix design criteria for materials local to any of their 325 batching plants

throughout the UK. It was originally thought that the material would be a niche product,

but RMC is now concentrating upon developing more economical mixes to enable the

material to be more universally used. This development is targeted at customer needs in

terms of the application, strength requirement and other technical factors that may be

specified.

16

Lafarge Aggregates Ltd have been conducting research and development into SCC in

France for several years, and it is now available at each of their plants in the UK. Lafarge

produce their own family of admixtures especially for the production of SCC, called

Agilia. These products are fully developed and are all currently available and Lafarge see

the next step as getting these existing products accepted and used by the market.

Tarmac Topmix Ltd first began researching and developing SCC in 1998 and first

started using it at their precast factory at Tallington in 1999. The first ready-mixed SCC

was supplied in 2000 and the eventual aim is to make it available at all plants in the

country.

1.2.16. Admixture suppliers

Sika Ltd launched Sika ViscoCrete in the UK in 1998, which was the first

admixture on the UK market specifically for producing SCC. Six different types are

available and it can be used with either retarders or accelerators. Other admixture

manufactures have now followed this lead. MBT and Grace.

Construction Products both produce admixtures for the UK SCC market,

including superplasticisers, viscosity-modifying admixtures and specialist admixtures for

precast applications. The ready-mix companies RMC and Lafarge produce their own

admixtures for SCC. 1.2.17. Consultants

Consultants in the UK do not generally undertake any concrete research or

development directly, but do sometimes sponsor or collaborate in research projects at

universities and research organisations. Mott MacDonald have an established track record

with the development of specifications and guidance notes for SCC and are a member of

the Concrete Society Working Party on SCC. They have also worked closely with ready-

mix suppliers and contractors to use the material on a variety of projects throughout the

UK. However, many UK consultants are cautious when specifying SCC due to the lack of

existing guidance, standards and test methods and the lack of an established track record

for the material.

17

1.2.18. Contractors

Contractors in the UK generally rely upon the ready-mix supplier for any

expertise in SCC mix design. However, knowledge and appreciation of the material

among contractors is slowly increasing as the use of SCC becomes more widespread.

John Doyle Construction are probably the leading contractor in the UK in the use

of SCC and are involved in several research and development projects such as the

European SCC test methods project and the project on formwork pressures at Dundee

University. They have used the material several times in the UK in actual applications

such as column encasement and basements, although its use is still job-specific. Site trials

are always conducted before SCC is used in the intended structure.

Other contractors have used SCC in the UK but its use is still job-specific, often to

solve a problem during construction such as congested reinforcement.

1.2.19. UK precasters

Aarsleff Piling’s Balderton premises claim to be the UK’s first user of SCC in

precast pile production. An SCC mix was developed in partnership with RMC with a

compressive strength of 26–28 MPa at only 16 hours. At nine days the 50 MPa mark had

been passed and the piles could be driven. Aarsleff have also won a £4·25 million

contract to supply and install approximately 3000 precast concrete piles for the Channel

Tunnel Rail Link. SCC was used for these piles and casting began in June 2002 with

installation beginning the following month.

Tarmac Precast Concrete Ltd are also now using SCC at their three UK precast

plants. SCC currently accounts for approximately 65% of bespoke production at their

Tallington plant and their long-term objective is to convert fully to SCC when economics

and practicalities allow Current contracts are for prison units, double-T beams and

columns. Trent Concrete Ltd in Nottingham has been experimenting with SCC for the last

two years and production using the material first began in August 2002. 1.2.20. Seminars and events

The SCI (Society of Chemical Industry) held a seminar on SCC in January 2001 in

London. Approximately 60 delegates attended and the speakers were the main

18

practitioners of SCC in the UK from the areas of research (Professor P. Bartos), design

(Dr N. Henderson), ready-mix (R. Gaimster) and contracting (P. Goring). This meeting

was one of the first events in the UK to begin to introduce the material to members of the

construction industry who had no experience or knowledge of SCC.

A demonstration and international workshop on SCC, lasting a total of two and a

half days, was held at the Advanced Concrete and Masonry Centre at Paisley University

in May/ June, 2001. The event was attended by 70 delegates from eleven countries and

helped raise the awareness and knowledge of the material in Scotland and the rest of the

UK.Four demonstration events on SCC around the UK have also recently been held by

BRE’s Centre for Concrete Construction as part of their DTI-funded project on SCC,

which combined practical demonstrations with presentations by industry experts on SCC.

The events were aimed at people in the industry with little or no knowledge of the

material, with more than 140 people attending the four events

1.2.21. The Future

From its origins in Japan in the late 1980s, research, development and use of SCC

has spread steadily throughout the world. Approximately 7–10% of the Swedish ready-

mix market is now SCC and research is being conducted in virtually every country in

Europe. National working groups on the material now exist in some form in most

countries in Europe, with the majority of them working towards producing some form of

guidance on the use of SCC.

Large amounts of research and development are now also being conducted in

Canada and the USA at places such as the University of Sherbrooke and the University´

Laval. The first North American conference on SCC was held in November 2002 by

Northwestern University. American concrete organisations such as the American

Concrete Institute (ACI), American Society for Testing and Materials (ASTM) and PCI

(Precast/Prestressed Concrete Institute) have all recently formed committees to produce

guidelines, standards and specifications for SCC.

The material is slowly gaining acceptance in this huge market and already it is

estimated that approximately 4,000–5,000 m3 is used per day in precast applications in

19

North America. Nearly 1,00,000 m3 of ready-mixed SCC has also so far been used in

North America.

Countries such as Argentina, Australia and New Zealand are also all now

beginning to conduct research and development work into SCC, with more countries sure

to follow. A third International Symposium on SCC is being held in Iceland in August

2003, where much of the research and development work presently under way will be

presented.

The main barrier to the increased use of SCC in the UK and Europe seems to be

the lack of experience of the process, and the lack of published guidance, codes and

specifications. This situation will improve, however, as experience and knowledge

increases and each country begins to produce its own guidance and specifications.

Precasters are currently the overwhelming users of SCC in the UK, in Europe and

in the USA. This is partly due to them owning and operating the on-site batching plant,

and so they are able to take full advantage of all the potential benefits of SCC. They can

also minimise or control the potential disadvantages of the material (such as inconsistency

of supply and site acceptance). In the countries where SCC has been adopted relatively

quickly, such as Japan and Sweden, the ready-mix concrete producers are owned or

operated by the contractors, therefore the increased material costs can be directly offset

by savings in the construction process, in a similar way to precast production.

Although SCC is not expected to ever completely replace conventionally vibrated

concrete, the use of the material in both the precast and ready-mix markets in the UK,

Europe and the rest of the world is expected to continue to increase. The main drivers for

this increase in use are expected to include

1. An increase in the experience of both producers, contractors, designers and

clients.

2. An increase in available guidance on the production, design and use of SCC.

3. A decrease in the unit cost of the material as technology and experience

improves.

4. The demand from clients for a higher-quality finished product.

5. The decrease in skilled labour available in many countries for both the

placing and finishing of concrete.

20

1.3 Motive for Development of Self-Compacting Concrete The motive for development of self-compacting concrete was the social problem

on durability of concrete structures that arose around 1983 in Japan. Due to a gradual

reduction in the number of skilled workers in Japan's construction industry, a similar

reduction in the quality of construction work took place. As a result of this fact, one

solution for the achievement of durable concrete structures independent of the quality of

construction work was the employment of self-compacting concrete, which could be

compacted into every corner of a formwork, purely by means of its own weight (Figure

1.1). Studies to develop self-compacting concrete, including a fundamental study on the

workability of concrete, were carried out by researchers Ozawa and Maekawa (Bartos,

2000) at the University of Tokyo.

Figure 1.1 Necessity of Self-Compacting Concrete (Ouchi and Hibino, 2000).

During their studies, they found that the main cause of the poor durability

performances of Japanese concrete in structures was the inadequate consolidation of the

concrete in the casting operations. By developing concrete that self-consolidates, they

eliminated the main cause for the poor durability performance of the concrete. By 1988,

the concept was developed and ready for the first real-scale tests and at the same time the

first prototype of self-compacting concrete was completed using materials already on the

market. The prototype performed satisfactorily with regard to drying and hardening

shrinkage, heat of hydration, denseness after hardening, and other properties and was

named “High Performance Concrete.”

At almost the same time, “High Performance Concrete” was defined as a concrete

with high durability due to low water-cement ratio by professor Aitcin (Ouchi et al.,

21

Skill of workers

Self-Compacting Concrete

Durable concrete structures

Decreasing in the future

1996). Since then, the term high performance concrete has been used around the world to

refer to high durability concrete. Therefore, Okamura (1997) has changed the term for the

proposed concrete to “Self-Compacting High Performance Concrete.”

1.4 Construction Issues

By employing self-compacting concrete, the cost of chemical and mineral

admixtures is compensated by the elimination of vibrating compaction and work done to

level the surface of the normal concrete (Khayat et al., 1997). However, the total cost for

a certain construction cannot always be reduced, because conventional concrete is used in

a greater percentage than self-compacting concrete. SCC can greatly improve

construction systems previously based on conventional concrete requiring vibrating

compaction. Vibration compaction, which can easily cause segregation, has been an

obstacle to the rationalization of construction work. Once this obstacle has been

eliminated, concrete construction could be rationalized and a new construction system,

including formwork, reinforcement, support and structural design, could be developed

(Figure 1.2).

1.2 Rational construction system proposed by Ozawa (Ouchi et al., 1996).

1.5 Applications of Self-Compacting Concrete

Since the development of the prototype of self-compacting concrete in 1988, the

use of self-compacting concrete in actual structures has gradually increased. The main

reasons for the employment of self-compacting concrete can be summarized as follows:

22

1. To shorten construction period

2. To assure compaction in the structure: especially in confined zones where

vibrating Compaction is difficult

3. To eliminate noise due to vibration: effective especially at concrete products

plants

300

200

100

0

1990 91 92 93 94 95 96 97

Fig. 1.3 Annual production of SCC in Japan Total production of ready-mixed

concrete in Japan in 1997 is 67,620×1,000 m That means the current condition of self-compacting concrete is a “special concrete”

rather than standard concrete. Currently, the percentage of self-compacting concrete in

annual product of ready-mixed concrete in Japan is around 0.1% (Fig. 1.3).

A typical application example of Self-compacting concrete is the two anchorages

of Akashi-Kaikyo (Straits) Bridge opened in April 1998, a suspension bridge with the

longest span in the world (1,991 meters) (Fig. 1.4). The volume of the cast concrete in the

two anchorages amounted to 2,90,000 m³. A new construction system, which makes full

use of the performance of self-compacting concrete, was introduced for this. The concrete

was mixed at the batcher plant beside the site, and was the pumped out of the plant. It was

transported 200 meters through pipes to the casting site, where the pipes were arranged in

rows 3 to 5 meters apart. The concrete was cast from gate valves located at 5 meter

intervals along the pipes. These valves were automatically controlled so that a surface

23

level of the cast concrete could be maintained. In the final analysis, the use of self-

compacting concrete shortened the anchorage construction period by 20%, from 2.5 to 2

years.

Fig. 1.4 Anchorage 4A of Akashi-Kaikyo Bridge

Self-compacting concrete was used for the wall of a large LNG tank belonging to

the Osaka Gas Company, whose concrete casting was completed in June 1998.The

volume of the self-compacting concrete used in the tank amounted to 12,000 m³. The

adoption of self-compacting concrete means that

1. The number of lots decreases from 14 to 10, as the height of one lot of concrete

casting was increased.

2. The number of concrete workers was reduced from 150 to 50.

3. The construction period of the structure decreased from 22 months to18 months.

Self-compacting concrete is often employed in concrete products to eliminate the

noise of vibration. This improves the working environment at plants and makes it possible

for concrete product plants to be located in the urban area. The annual production of

concrete products using self-compacting concrete exceeded 2,00,000 tons in 1996.

24

1.6 Existing Tests for Fresh SCC Mixes

Fresh SCC must possess at required levels the following key properties:

1.6.1. Filling ability: This is the ability of the SCC to flow into all spaces within the

formwork under its own weight.

1.6.2. Passing ability: This is the ability of the SCC to flow through tight openings such

as spaces between steel reinforcing bars, under its own weight.

1.6.3. Resistance to segregation: The SCC must meet the required levels of properties

A & B whilst its composition remains uniform throughout the process of transport and

placing. Many tests have been used in successful applications of SCC. However, in all the

projects the SCC was produced and placed by an experienced contractor whose staff has

been trained and acquired experience with interpretation of a different group of tests. In

other cases, the construction was preceded by full-scale trials in which a number, often

excessive, of specific tests was used (Ouchi et al., 1996). The same tests were later used

on the site itself.

Below is a brief summary of the more common tests currently used for assessment

of fresh SCC.

1.6.4 U-type test:

Of the many testing methods used for evaluating self-compactability, the U-type

test (Figure 1.5) proposed by the Taisei group is the most appropriate, due to the small

amount of concrete used, compared to others (Ferraris, 1999). In this test, the degree of

compactability can be indicated by the height that the concrete reaches after flowing

through obstacles. Concrete with the filling height of over 300 mm can be judged as self-

compacting. Some companies consider the concrete self-compacting if the filling height is

more than 85% of the maximum height possible.

25

>300mm

Figure 1.5 U-type test (Ouchi and Hibino, 2000).

1.6.5. Slump Flow test:

The basic equipment used is the same as for the conventional Slump test. The test

method differs from the conventional one by the fact that the concrete sample placed into

the mold is not rodded and when the slump cone is removed the sample collapses

(Ferraris, 1999). The diameter of the spread of the sample is measured, i.e. a horizontal

distance is determined as opposed to the vertical distance in the conventional Slump test.

The Slump Flow test can give an indication as to the consistency, filling ability and

workability of SCC. The SCC is assumed of having a good filling ability and consistency

if the diameter of the spread reaches values between 650mm to 800mm.

1.6.6. L-Box test:

This method uses a test apparatus comprising of a vertical section and a horizontal

trough into which the concrete is allowed to flow on the release of a trap door from the

vertical section passing through reinforcing bars placed at the intersection of the two

areas of the apparatus (Dietz and Ma, 2000). The time that it takes the concrete to flow a

distance of 200mm (T-20) and 400mm (T-40) into the horizontal section is measured, as

is the height of the concrete at both ends of the apparatus (H1 & H2). The L-Box test can

give an indication as to the filling ability and passing ability.

26

1.6.7. Orimet test:

The test is based on the principle of an orifice rheometer applied to fresh concrete

(Bartos, 2000). The test involves recording of time that it takes for a concrete sample to

flow out from a vertical casting pipe through an interchangeable orifice attached at its

lower end. The shorter the Flow-Time, the higher is the filling ability of the fresh mix.

The Orimet test also shows potential as a means of assessment of resistance to

segregation on a site.

1.6.8. V-funnel test:

Viscosity of the self-compacting concrete is obtained by using a V-funnel

apparatus, which has certain dimensions (Figure 1.6), in order for a given amount of

concrete to pass through an orifice (Dietz and Ma, 2000). The amount of concrete needed

is 12 liters and the maximum aggregate diameter is 20 mm. The time for the amount of

concrete to flow through the orifice is being measured. If the concrete starts moving

through the orifice, it means that the stress is higher than the yield stress; therefore, this

test measures a value that is related to the viscosity. If the concrete does not move, it

shows that the yield stress is greater than the weight of the volume used. An equivalent

test using smaller funnels (side of only 5 mm) is used for cement paste as an empirical

test to determine the effect of chemical admixtures on the flow of cement pastes.

Figure 1.6V-funnel (Dietz and Ma, 2000).

27

1.6.9. Slump Flow/J-Ring combination test:

This test (Figure 1.7) involves the slump cone being placed inside a 300mm

diameter steel ring attached to vertical reinforcing bars at appropriate spacing (the J-Ring

itself) (Kosmatka et al., 2002). The number of bars has to be adjusted depending on the

maximum size aggregate in the SCC mix. Like in the Slump Flow test, the diameter of the

spread and the T-50 time are recorded for the evaluation of SCC viscosity. The Slump

Flow/J-Ring combination test is an improvement upon the Slump Flow test on its own as

it aims to assess also the passing ability of the fresh mix. In this respect, the SCC has to

pass through the reinforcing bars without separation of paste and coarse aggregate.

Figure 1.7 Slump Flow/J-Ring combination test (Kosmatka et al., 2002).

1.6.10. Orimet/J-Ring combination test:

This is recently developed test involves the J-Ring being placed centrally below

the orifice of the Orimet apparatus, allowing the discharged mix to fall into it and flow

outwards (Bartos, 2000). The Orimet time is recorded as in the conventional Orimet test,

along with the diameter of the concrete spread and the height of the concrete within the J-

Ring. The more dynamic flow of concrete in this test simulates better the behaviour of a

SCC mix when placed in practice compared with the Slump-Flow variation. The

Orimet/J-Ring combination test will be used in the future as a method of assessing filling

ability, passing ability and resistance to segregation (Bartos, 2000).

28

1.6.11. GTM Segregation test:

This is a very recent test measuring the separation of aggregate in a sample after a

period of time and wet sieving. The test has a potential for detection of tendency to

segregate (Dehn et al., 2000). It completes the tests (Slump-Flow, L-Box, etc.) carried out

to estimate the filling ability in free or shut-in environment (i.e. with some "wall-effect")

by specifying the segregation resistance. This test can be used in laboratory when

developing a concrete mix, as well as on site, when carrying out suitability tests on the

delivered concrete.

1.7. Development of Prototype

The prototype of Self-compacting Concrete was first developed in 1988 using

materials already on the market. The prototype performed satisfactorily with regard to

drying and hardening shrinkage, heat of hydration, denseness after hardening, and other

properties. This concrete was named “High Performance Concrete”.

At almost the same time, Professor Aitcin defined “High Performance Concrete”

as a concrete with high durability due to low water-cement ratio. Since then, the term

high performance concrete has been used around the world to refer to high durability

concrete. Therefore, Okamura has changed the term for the proposed concrete to “Self-

Compacting High Performance Concrete”.

Self-compacting concrete (SCC) has been described as “The most revolutionary

development in concrete construction for several decades”. Originally developed to offset

a growing shortage of skilled labour, It has proved beneficial economically because of a

number of factors as noted below.

1. Faster construction,

2. Reduction in site manpower,

3. Easier placing,

4. Uniform and complete consolidation,

5. Better surface finishes,

6. Improved durability,

7. Increased bond strength,

29

8. Greater freedom in design,

9. Reduced noise levels, due to absence of vibration, and

10. Safe working environment.

All the engineering components undergo multi-axial Stress-Strain condition either

from particular geometry of the body or multi axial nature of the load itself. Many of

these components are prone to fatigue failure and hence much effort is spent in

understanding the response of the materials.

1.8 Scope and Objectives of Investigation Poor quality of vibration of concrete, in congested locations, has often been a

shortcoming of traditional concrete. In such situations, SCC, which follows under its own

weight and does not require any external vibration for compaction has revolutionized

concrete placement. SCC does not show segregation and bleeding. Self-compacted

ability is largely affected by the characteristics of materials and mix proportion.

In the present study, it was to achieve required properties of Self-compacting

concrete with available materials in the laboratory. Coarse aggregate with nominal size

12.5mm (70%) & 20mm (30%) was used. Also, Viscosity Modifying Admixtures (VMA)

was used to increase the suspension power of aggregates and also to eliminate possible

segregation. Fine powdered materials like fly ash is also used to eliminate possible

segregation.

In the present study, confinement in the form of hoops of 6mm diameter was used.

The mechanical properties and Stress-Strain behaviour were studied for GFRSCC with

and without confinement under compression.

A single polynomial empirical equation in the form of 21

CBDAf

is used

for both ascending and descending portion of the curve. A, B are the constants and

determined using the boundary conditions and verifying whether the experimental data is

related with the mathematically calculated data.

where, f is the stress at any level and ε is the strain at any level. To express in

Non-dimensional stress-strain curves the following form is proposed.

30

2

111

11

uu

u

uCB

DA

ff

Where uf and u are the ultimate stress and strain of the GFRSCC specimen in

compression. A single equation to predict the entire behaviour was not giving good

correlation. Hence, the constants based on the following boundary conditions were

obtained separately for ascending and descending portions.

The boundary conditions common for both ascending and descending portions of

stress – strain curve. At ;0;0 uu ff

At ;1;1

uu ff

and At 0;1

u

u

u d

ffd

Stress-Strain analysis of a material is one way to determine many of its physical

properties. With the information gained through much analysis, one can predict how a

part will react when placed under various working loads.

The major objectives are:

1. Understand the basic process of deformation due to tensile loading

2. Characterize the physical properties of various metals from their stress-strain curves

Unconfined plain concrete, exhibits a brittle failure mode, the failure may be

explosive and marks the termination of the Stress-Strain Curve and loss of load-carrying

capacity shortly after the peak load.

If there exists a lateral pressure that resists this sideway expansion, however, the

core concrete will be in a state of multi-axial compression. It is accepted that when the

concrete is experiencing multi-axial compression, both the deformation capacity and

strength are improved. The scope of this work was limited to the development of a

suitable mix design to satisfy the requirements of GFRSCC using local aggregates and

then to determine the strength and durability of such concrete. The mechanical properties

and Stress-Strain behaviour were studied for GFRSCC with and without confinement

under compression. The specific objectives were as follows.

1. To design a suitable SCC mix utilizing local aggregates, and

2. To assess the strength development and durability of GFRSCC and Stress-Strain

behaviour with and without confinement under compression.

31

1.8.1 Models of the Specimens

150 mm 300mm height

Fig.1.8. Cylinder without any confinement

130mmΦ

280mm

(a) 0.798% confinement b)1.062% confinement

(c). 1.327% confinement (d).1.591% confinement

Fig.1.9.Cylinder with confinement

32

6mmΦ @ 140mmc/c

6mmΦ @ 93mmc/c

6mmΦ @ 70mmc/c

6mmΦ @ 56mmc/c

Steel as a confining material is used in Concrete and the properties of concrete

was studied. The concrete bond strength should be sufficient to prevent bond failure. The

effectiveness of bond is affected by the position of the embedded bars and the quality of

concrete as cast. An adequate concrete cover is necessary in order to properly transfer

bond stresses between steel and concrete. The main reasons for taking steel as a

reinforcing material is

1 Its thermal coefficient of expansion is similar to that of Concrete.

2 It develops good bond with concrete.

3 It is cheaply and easily available in the market.

4 It is economical comparing to all the aspects.

1.8.2 Advantages of Reinforced Structures

1 The combination of steel and concrete is economical because compressive

forces are borne by concrete and tensile forces by steel.

2 The combination of steel land concrete provides a monolithic character

and provides much rigidity to the structure.

3 They require less cost of maintenance because these are not attacked by

termites.

4 They are durable and fire resisting.

5 They are almost impermeable to moisture.

6 Due to the plastic properties of RCC, the RCC structures can be

constructed of any desired shape.

Glass-Fiber Reinforced Concrete (GFRC) is composed of concrete, reinforced

with glass fibers to produce a thin light weight, yet strong material. Though concrete has

been used through out the ages, GFRC is still a relatively new invention. High

compressive strengths. Ability to reproduce fine surface details, low maintenance

requirements, low coefficients of thermal GFRC the ideal choice for Civil Engineers.

Considering the advantages of SCC and GFRSCC an attempt has been made to

combine these two and Stress-Strain behavior is studied.

33

1.8.3. Investigations on Self-Compacting Concrete

Various investigations have been carried out in order to make self-compacting

concrete a standard one. The items to be solved are summarized as follows:

1. Self-compactability testing method

2. Mix-design method including evaluation method for materials

3. Construction method including acceptance test at jobsite

4. New construction system to make full use of the performance of SCC

The investigations were carried out at each university, large construction company

and material maker. Committee activities were also carried out. As the result,

Architectural Institute of Japan and Japan Society of Civil Engineers established

“Recommendations for Mix Design and Construction Practice of Highly Fluidity

Concrete” in 1997 and “Recommendation for Construction of Self-Compacting Concrete”

in 1998 respectively. The national ready-mixed concrete industry association, Japan,

established “Manual for Manufacturing of Self-Compacting Concrete” in 1998.

1.8.4. Mix-design method

Self-compactability can be largely affected by the characteristics of materials and

the mix- proportion. A rational mix-design method for self-compacting concrete using a

variety of materials is necessary. Okamura and Ozawa have proposed a simple mix-

proportioning system assuming general supply from ready-mixed concrete plants. The

coarse and fine aggregate contents are fixed so that self-compactability can be achieved

easily by adjusting the water- powder ratio and superplasticizer dosage only.

1.8.5. Evaluation method for materials

Investigations on establishing evaluation method of materials, especially powder

materials and superplasticizer have been carried out from the viewpoint of establishing a

rational mix- proportioning method that is, especially adjusting method for water-powder

ratio and superplasticizer dosage and of developing suitable material for self-compacting

concrete.

34

Ouchi et. al proposed evaluation method for the effect of superplasticizer and water

independent of each other on the flowability of mortar by using flow and funnel tests.

Some general construction companies employ a segregation-inhibiting agent so

that the self- compactablity can be kept constant independent of the variation of unit

water content, especially due to the variation of surface water content in the sand. There

are various agents proposed and available in Japan. The evaluation method for the effect

was also proposed.

1.9. Acceptance Test at Job Site

Since the degree of compaction in a structure mainly depends on the self-

compactability of concrete and poor self-compactability cannot be compensated by the

construction work, self-compactability must be checked for the whole amount of concrete

just before casting at the job site. However, conventional testing methods for self-

compactability require sampling and this can be extremely laborious if the self-

compactability acceptance test is to be carried out for the whole amount of the concrete.

A suitable acceptance test method for self-compactability has been developed by Ouchi

et. al (2000), in two steps. In the first step, testing apparatus is installed between agitator

truck and pump at the job site, and the whole amount of the concrete is poured into the

apparatus. In the second step, if the concrete flows through the apparatus, the concrete is

considered as self-compactable for the structure. If the concrete is stopped by the

apparatus, the concrete is considered as having insufficient self-compactability and the

mix-proportion has to be adjusted. This apparatus was successfully used at the

construction site of the Osaka Gas LNG tank, and saved a considerable amount of

acceptance test work (Figure 1.10).

35

Figure 1.10 Rational acceptance test at job site for self-compacting concrete (Ouchi and Hibino, 2000).

1.10. New structural design and construction systems

By employing self-compacting concrete, the cost of vibrating compaction can be

saved and the compaction of the concrete in the structure can be assured. However, the

total cost for the construction cannot always be reduced, except in large scale

constructions. This is because the conventional construction system is strongly based on

the necessity of the vibrating compaction of concrete. Self-compacting concrete can

greatly improve construction systems previously based on conventional concrete

requiring vibrating compaction. This sort of compaction, which can easily cause

segregation, has been an obstacle to the rationalization of construction work. Once this

obstacle has been eliminated, concrete construction can be rationalized and a new

construction system, including formwork, reinforcement, support and structural design,

can be developed (Fig. 1.2).

36

One example of this is the so-called sandwich-structure, where concrete is filled

into a steel shell. This sort of structure has already been completed in Kobe, which could

not have been achieved without the development of self-compacting concrete (Fig. 1.11).

Figure 1.11 Anchorage of Akashi-Kaikyo Bridge, Japan (Ouchi and Hibino, 2000).

37

CHAPTER 2

Literature Review

CHAPTER 2 Literature Review

2.0 General

Present-day self-compacting concrete can be classified as an advanced

construction material. As the name suggests, it does not require to be vibrated to achieve

full compaction. This offers many benefits and advantages over conventional concrete.

These include an improved quality of concrete and reduction of on-site repairs, faster

construction times, lower overall costs, facilitation of introduction of automation into

concrete construction. An important improvement of health and safety is also achieved

through elimination of handling of vibrators and a substantial reduction of environmental

noise loading on and around a site. The composition of SCC mixes includes substantial

proportions of fine-grained inorganic materials and this gives possibilities for utilization

of mineral admixtures, which are currently waste products with no practical applications

and are costly to dispose of (St John, 1998).

2.1 Previous Research Work on Self-Compacting Concrete

Self-compacting concrete extends the possibility of use of various mineral by-

products in its manufacturing and with the densification of the matrix, mechanical

behavior, as measured by compressive, tensile and shear strength, is increased. On the

other hand, the use superplasticizers or high range water reducers, improves the

stiffening, unwanted air entrainment, and flowing ability of the concrete. Practically, all

types of structural constructions are possible with this concrete. The use of SCC not only

shortens the construction period but also ensures quality and durability of concrete. This

non-vibrated concrete allows faster placement and less finishing time, leading to

improved productivity.

In the following, a summary of the articles and papers found in the literature,

about the self-compacting concrete and some of the projects carried out with this type of

concrete, is presented.

38

2.1.1 Hajime Okamura:

A new type of concrete, which can be compacted into every corner of a formwork

purely by means of its own weight, was proposed by Okamura (1997). In 1986, he started

a research project on the flowing ability and workability of this special type of concrete,

later called self-compacting concrete. The self-compactability of this concrete can be

largely affected by the characteristics of materials and the mix proportions. In his study,

Okamura (1997) has fixed the coarse aggregate content to 50% of the solid volume and

the fine aggregate content to 40% of the mortar volume, so that self-compactability could

be achieved easily by adjusting the water to cement ratio and superplasticizer dosage

only.

A model formwork, comprised of two vertical sections (towers) at each end of a

horizontal trough, was used by professor Okamura to observe how well self-compacting

concrete could flow through obstacles. Figure 2.1 shows the ends of small pipes mounted

across the horizontal trough and used as obstacles. The concrete was placed into a right-

hand tower, flowed through the obstacles, and rose in the left-hand tower.

Figure 2.1 Small pipes used as obstacles in formwork (Okamura, 1997).

The obstacles were chosen to simulate the confined zones of an actual structure.

The concrete in the left-hand tower rose to almost the same level as in the right-hand

39

tower. Similar experiments of this type were carried out over a period of about one year

and the applicability of self- compacting concrete for practical structures was verified.

This research was started at the suggestion of professor Kokubu (Okamura, 1997) from

Kobe University, Japan, one of the advisors of Hajime Okamura. They thought that it

would be easy to create this new concrete because antiwashout underwater concrete was

already in practical use. Antiwashout underwater concrete is cast underwater and

segregation is strictly inhibited by adding a large amount of a viscous agent (antiwashout

admixture), which prevents the cement particles from dispersing in the surrounding water.

However, it was found that antiwashout underwater concrete was not applicable for

structures in open air for two reasons: first, entrapped air bubbles could not be eliminated

due to the high viscosity; and second, compaction in the confined areas of reinforcing

bars was difficult. Thus, for the achievement of self-compactability, a superplasticizer

was indispensable. With a superplasticizer, the paste can be made more flowable with

little concomitant decrease in viscosity, compared to the drastic effect of the water, when

the cohesion between the aggregate and the paste is weakened (Figure 2.2).

Figure 2.2 Effect of super plasticizer on viscosity (Okamura, 1997).

The water-cement ratio was taken between 0.4 and 0.6 depending on the

properties of the cement. The superplasticizer dosage and the final water-cement ratio

were determined so, as to ensure the self-compactability, evaluated subsequently by using

the U-type test (Ouchi and Hibino, 2000) described in the previous chapter.

40

2.1.2 Kazumasa Ozawa:

After Okamura began his research in 1986, other researchers in Japan have started

to investigate self-compacting concrete, looking to improve its characteristics. One of

those was Ozawa (1989) who has done some research independently from Okamura, and

in the summer of 1988, he succeeded in developing self-compacting concrete for the first

time. The year after that, an open experiment on the new type of concrete was held at the

University of Tokyo, in front of more than 100 researchers and engineers. As a result,

intensive research has begun in many places, especially in the research institutes of large

construction companies and at the University of Tokyo.

Ozawa (1989) completed the first prototype of self-compacting concrete using

materials already on the market. By using different types of superplasticizers, he studied

the workability of concrete and developed a concrete which was very workable. It was

suitable for rapid placement and had a very good permeability. The viscosity of the

concrete was measured using the V- funnel test (see Chapter 1 cluase 1.6.8-p25).

Other experiments carried out by Ozawa (1989) focused on the influence of

mineral admixtures, like fly ash and blast furnace slag, on the flowing ability and

segregation resistance of self-compacting concrete. He found out that the flowing ability

of the concrete improved remarkably when Portland cement was partially replaced with

fly ash and blast furnace slag. After trying different proportions of admixtures, he

concluded that 10-20% of fly ash and 25- 45% of slag cement, by mass, showed the best

flowing ability and strength characteristics.

2.1.3 Subramanian and Chattopadhyay:

Subramanian and Chattopadhyay (2002) are research and development engineers

at the ECC Division of Larsen & Toubro Ltd (L&T), Chennai, India. They have over 10

years of experience on development of self-compacting concrete, underwater concrete

with antiwashout admixtures and proportioning of special concrete mixtures. Their

research was concentrated on several trials carried out to arrive at an approximate mix

proportion of self-compacting concrete, which would give the procedure for the selection

of a viscosity modifying agent, a compatible superplasticizer and the determination of

their dosages. The Portland cement was partially replaced with fly ash and blast furnace

slag, in the same percentages as Ozawa (1989) has done before and the maximum coarse

aggregate size did not exceed 25mm.

41

The two researchers were trying to determine different coarse and fine aggregate

contents from those developed by Okamura. The coarse aggregate content was varied,

along with water-powder (cement, fly ash and slag) ratio, being 50%, 48% and 46% of

the solid volume. The U-tube trials were repeated for different water-powder ratios

ranging from 0.3 to 0.7 in steps of 0.10. On the basis of these trials, it was discovered that

self-compactability could be achieved when the coarse aggregate content was restricted to

46 percent instead of 50 percent tried by Okamura (1997). In the next series of

experiments, the coarse aggregate content was fixed at 46 percent and the sand content in

the mortar portion was varied from 36 percent to 44 percent on a solid volume basis in

steps of 2 percent. Again, the water-powder ratio was varied from 0.3 to 0.7 and based on

the U-tube trials a sand content of 42 percent was selected. In order to show the necessity

of using a viscosity-modifying agent along with a superplasticizer, to reduce the

segregation and bleeding, the mixture proportion developed by the two researchers was

used to cast a few trial specimens. In these trials, viscosity-modifying agent was not used.

The cast specimens were heavily reinforced slabs having 2400x600x80 mm and no

vibration or any other method of compaction was used. However, careful qualitative

observations revealed that the proportions needed to be delicately adjusted within narrow

limits to eliminate bleeding as well as settlement of coarse aggregate. It was difficult to

obtain a mixture that was at the same time fluid but did not bleed. This led to the

conclusion that slight changes in water content or granulometry of aggregate may result

either in a mixture with inadequate flowing ability, or alternatively one with a tendency

for coarse aggregate to segregate. Therefore, it became necessary to incorporate a

viscosity-modifying agent in the concrete mixture.

Viscosity-modifying agents can be a natural polymer such as guar gum, a semi-

synthetic polymer such as hydroxy propyl methyl cellulose, or water-soluble

polysaccharides, including those derived from a microbial source such as welan gum.

Experiments involving three types of gums were being carried out by the two researchers.

One commonly used thickener in cement- based systems, namely hydroxy propyl methyl

cellulose (HPMC), a low-priced gum known as guar gum and a special product called

welan gum were selected for studying their suitability for use in self-compacting

concrete. On a first consideration, a1l these qualified as viscosity modifying agents.

However, some of these substances, with the exception of welan gum, had shortcomings.

Guar gum had to be made into a suspension in water after heating to 60˚C and stirring for

42

about one hour. This solution lost its suspending power after twelve hours. HPMC was

not compatible with the naphthalene formaldehyde superplasticizer and entrained

excessive air, causing a reduction in strength (Figure 2.3).

Figure 2.3 Compressive strength of SCC with and without HPMC (Subramanian

and Chattopadhyay, 2002).

Welan gum is suitable for use in self-compacting concrete because it combines

with most types of superplastcizer and has superior suspending power, compare to guar

gum and hydroxyl propyl methyl cellulose (HPMC).

In order to arrive at an acceptable combination of dosages of welan gum and

superplastcizer, Subramanian and Chattopadhyay (2002) ran several tests related to the

tendency of the concrete to bleed and its ability to pass the U-tube test. They discovered

that with a combination corresponding to 0.1 percent of welan gum and 0.53 percent by

weight of water acrylic copolymer type superplasticizer, a satisfactory self-compacting

mixture could be obtained

2.1.4. Khayat et al.: The use of self-consolidating concrete can facilitate the placement of concrete in

congested members and in restricted areas. Given the highly flowable nature of such

concrete, care is required to ensure adequate stability. This is especially important in deep

structural members and wall elements where concrete can segregate and exhibit bleeding

and settlement, which can result in local structural defects that can reduce mechanical

properties.

43

The objective of Khayat’s (1997) et al. research was to evaluate the uniformity of

in situ mechanical properties of self-consolidating concrete used to cast experimental wall

elements Eight optimized SCC mixtures with slump flow values greater than 630 mm and

conventional concrete with a slump of 165 mm were investigated. The self-compacting

concrete mixtures incorporated various combinations of cementitious materials and

chemical admixtures. The water-cementitious materials ratios ranged from 0.37 to 0.42.

Experimental walls measuring 95 cm in length, 20 cm in width, and 150 cm in height

were cast. After casting, no consolidation was used for the SCC mixtures, while the

medium fluidity conventional concrete received thorough internal vibration. Several cores

were obtained in order to evaluate the uniformity of compressive strength and modulus of

elasticity along the height of each wall. Khayat (1997) et al. found out that all cores from

both types of concrete exhibited little variation in compressive strength and modulus of

elasticity in relation to height of the wall, indicating a high degree of strength uniformity.

However, compressive strength and modulus of elasticity were greater for SCC samples

than those obtained from the medium fluidity conventional concrete.

2.1.5. Dehn et al.: Dehn (2000) et al. have focused their research work on the time development of

SCC compressive and splitting tensile strength and the bond behavior between the

reinforcing bars and the self-compacting concrete compared to normal concrete.

In order to ensure a good production of SCC, a mix design should be performed,

so that the predefined properties of the fresh and hardened concrete would be reached for

sure. All the components should be coordinated so that bleeding and segregation would

be prevented. Because of these aspects, their mix design was based on experience from

Japan, Netherlands, France, and Sweden. Due to the fact that the load bearing capacity of

a reinforced concrete structure is considerably influenced by the bond behavior between

the reinforcing bars and the concrete, the following items were taken into account:

1. Anchorage of the reinforcing bars

2. Crack width control

3. Lapped reinforcing bars

For this reason, investigations on the bond behavior between the re-bars and the

SCC were necessary, especially considering the time development of the bond strength.

These investigations showed, that the main parameters which influence the bond behavior

44

are the surface of the re-bars, the number of load cycles, the mix design, the direction of

concreting, as well as the geometry of the (pull-out) test specimens (Figure 2.4). The

bond behavior was determined under uniform static loading using pullout specimens

having a uniform concrete cover around the reinforcing bar. The bar diameter for the

whole test series was 10 mm and the concrete cover around it had a diameter of 100mm

and a length of also 100mm.

Figure 2.4 Pullout specimen (Dehn et al., 2000).

To avoid an unwanted force transfer between the reinforcing bar and the concrete

in the Un bonded area, the re-bars were encased with a plastic tube and sealed with a

highly elastic silicone material. The re-bars were placed concentrically and the concrete

was cast parallel to the loading direction. The tests were carried out in an electro

mechanic testing machine where the specimens were loaded with a loading rate of 0.0008

mm/sec. The applied force of the machine was measured corresponding to the slip

displacement of the reinforcing bar on the non-loaded side. The increase of the slip path

was constantly monitored during the whole testing period.

Experimental results showed higher compressive strengths (36%) and splitting

tensile strengths (28%) of the SCC specimens compared to normal concrete specimens.

Also, the bond behavior measured at 1, 3, 7 and 28 days after concreting was better for

self-compacting concrete than that of normally vibrated concrete.

2.1.6. Kuroiwa: Kuroiwa (1993) developed a type of concrete, which contained materials normally

found in conventional concrete such as Portland cement, aggregate, water, mineral and

45

chemical admixtures. The chemical admixtures were added in order to improve the

deformability and the viscosity of the concrete. The newly developed type of concrete

was called super-workable concrete and showed excellent deformability and resistance to

segregation. It could also fill completely heavily reinforced formworks without any use of

vibrators. After the laboratory tests it was found out that the super-workable concrete had

superior properties in the fresh state and excellent durability after hardening. Because of

its properties, it was considered that it would be suitable for projects involving heavily

reinforced areas and was employed in the construction of a 20-story building. The

concrete was placed in the center-core from basement to the third floor. The building had

a design of a hybrid structure, in which the reinforced concrete core was surrounded by a

steel mantle. The greatest diameter used for the reinforcing bars was 50mm and the forms

were very congested. Ready mixed concrete plants situated near the construction site

produced approximately 2,000m³ of super-workable concrete, which was placed

successfully.

2.1.7 Ferraris et al.: The slump test is widely used to evaluate the workability of concrete, but in the

case of self-compacting concrete, it has serious drawbacks. Other flow characteristics

such as viscosity or filling capacity are needed to define the flow in self-compacting

concretes. The research objectives of Ferraris (1999) et al. were to test flow

characteristics of SCC using two concrete rheometers and the widely recognized V-flow

and U-flow tests, and to determine the correlation between the two rheometers and the

tests.

The main property that defines the self-compacting concrete is high workability in

attaining consolidation and specified hardened properties. Workability is defined either

qualitatively as the ease of placement or quantitatively by rheological parameters. The

most commonly used test to determine workability in practice is the slump cone test.

Either the vertical slump distance or the horizontal spread of the concrete can be

measured. The most common rheological parameters used to qualify workability are the

yield stress and plastic viscosity as defined by the Bingham equation.

The knowledge of the two parameters, yield stress and plastic viscosity, allows a

quantitative description of the workability. The Bingham equation is a linear relationship

46

between the shear rate, γ, and the shear stress, τ. The viscosity, η, is the slope and the

intercept is the yield stress, τ0, as shown in the equation (2.1).

τ = τ0 + η γ (2.1)

A highly flowable concrete is not necessarily self-compacting, because SCC

should not only flow under its own weight, but should also fill the entire form and

achieve uniform consolidation without segregation. This characteristic of SCC is called

filling capacity.

In their research Ferraris (1999) et al. measured the rheological properties of the

concrete mixtures using two rheometers, the IBB and the BTRHEOM instruments.

The IBB rheometer was developed in Canada and consists of a cylindrical

container holding the concrete, with an H-shaped impeller driven through the concrete in

a planetary motion. The speed of the impeller rotation was first increased to a maximum

rotation rate and then the rotation rate was decreased in six stages with each stage having

at least two complete center shaft revolutions. The torque (N·m) generated by the

resistance of the concrete specimen to the impeller rotation was recorded at each stage as

well as the impeller rotation rate (revolutions per second) measured by the shaft

tachometer.

The BTRHEOM is a parallel plate rheometer, i.e., the concrete is sheared between

two plates. The plate at the bottom is stationary and the plate at the top rotates with

variable speed, similar to the impeller of the IBB rheometer. The torque generated during

rotation is recorded while the rotation rate is first increased and then decreased in stages.

The rheological parameters can be calculated using the Bingham equation applied to the

torque and rotation rate data of the decreasing speed portion of the test. Due to the simple

geometry of the shearing area, it is possible to calculate the results in fundamental units,

i.e., Pa for yield stress and Pa·s for viscosity.

The criterion adopted by Ferraris (1999) et al. in the study, in order to evaluate the

compactability of the concrete by using the U-flow test, was that if the filling height was

more than 70% of the maximum height possible, the concrete would be considered self-

compacting. Comparisons of the yield stresses from the two rheometers indicated no

correlation. The lack of correlation might have been due to the range of yield stresses

measured, which was in the vicinity of zero and sometimes negative. This situation was

expected since all the concretes tested were highly flowable and therefore, might have

had very small yield stresses. The negative values were due to the method (Bingham or

47

Herschel-Bulkley) used to calculate the yield stress.

The comparisons of the measured viscosities showed a good correlation, which

could be approximated by:

ηB = 35 + ηI , (2.2)

where ηB is the viscosity measured with the BTRHEOM and ηI is the viscosity measured

with the IBB. The correlation was considered acceptable because of the wide range of

viscosity covered (13 values). It was also considered preliminary due to the lack of

variation in the properties of the materials used, i.e., one type of cement and one type of

aggregate.

According to Beaupre (Canada, 1994), a better method to evaluate concrete with

specified flow property is to plot the yield stress versus the viscosity as shown in Figure

2.5. Concrete mixtures, determined to have a desired property, define an area in the plot

called the “workability box”. Ferraris (1999) et al. plotted the yield stress versus the

viscosity as measured with the BTRHEOM instrument.

Figure 2.5 Viscosity –Yield stress and the workability box (Ferraris et al., 1999).

The “workability box” defines the range of viscosity and yield stress needed for a

self- compacting concrete. If these results would have been trial batches, the drawing of

the box would have allowed the operator to determine whether a mixture was self-

compacting concrete based on the rheometer results.

After studying the thirteen concrete mixes, Ferraris (1999) et al. found out that the

slump flow alone is not enough to determine whether a flowable concrete is a self-

48

compacting concrete. Due to the fact, that the values measured with the two types of

rheometers correlate relatively well on viscosity but not on yield stress, further

measurements are needed to determine if the correlation holds for other types of

aggregate and cementitious materials. Also, based on the data acquired, the viscosity and

the yield stress did not correlate with the V-funnel or the U-flow tests.

2.1.8 Anirwan Senu Guptha et al [2006]

The authors on the topic “Application based mix proportioning for self

compacting concrete” in their investigation attempted to arrive at optimum mix

proportions for various consistency class of SCC with locally available materials.

Adequate passing ability for all mixes was ensured by keeping the proportion of coarse

aggregates low as the aggregates had high degree of flakiness and elongation. Based on

the investigation they concluded that,

1. Six different consistency classes of SCC as per EFNARC-2005 were produced in

the laboratory using local available materials. All mixes satisfied the criteria set

forth by EFNARC, and showed good passing ability and segregation resistance.

2. Higher powder contents were needed to design SCC high flow combined with

stability. The high powder content mixtures also resulted in the highest

compressive strengths.

3. A good correlation was found in the initial V-Funnel flow time and the T-60 from

slump flow test.

2.1.9. ACI committee report No.226 [1987]

Has discussed the effects of Fly ash. The effect on the workability depends on the

fineness of Fly ash. The fineness and roundness of particles improve cohesion and

workability. Due to workability, there will be reduction in susceptibility of segregation

and bleeding which reduces temperature developed during curing in fresh concrete and

reduces permeability in the hardened concrete. This reduction reduces the damage of steel

corrosion, alkaline sulphite attack. The reports also discussed the specification for

material testing, quality assurance for Fly ash concrete and making use of good

proportion of Fly ash.

49

2.1.10. Gibbs,[1999] States that the following practical rules of thumb for the proportioning of self-

compacting concrete mixture exits. Coarse aggregate content should be limited to 71-81

N/mm3 (about 50% of the total volume)

1. 50% of the total volume.

2. Paste not less than 40% of the volume of the mixture.

3. Low sand content in the mortar (40-50% by volume).

4. Water/powder ratio not more than 0.5 (powder solids 0.0035 in 0.09mm).

2.1.11. Manu Santhanam,[2008] In his article “Compatability issues between Cements and Water-reducing

Chemical admixtures”, describes the current level of knowledge world wide about the

issues of incompatibility cement and water-reducing chemical admixtures. Their

mechanism of action in concrete, test methods to evaluate the effectiveness of

plasticizers. Specific issues of incompatibility namely, loss of workability, alteration of

setting behaviour,reduced rates of strength gain, and change in long term behaviour and

role of the chemistry(of cement and admixture),the presence of other mineral and

chemical admixtures, and the proportioning of concrete are explained in detail.

2.1.12. Hemant Sood[3] Et Al, [2009] In their experimental investigation “Incorporating European Standards for Testing

Self Compacting Concrete in Indian Conditions”, explained SCC using Fly ash and Rice

husk ash as mineral admixtures and testing rheological properties as per European

standards. He concluded that addition of Fly ash in SCC increases filling and passing

ability of concrete and improves overall workability, which is the prime important

characteristics of SCC.Utilisation of Fly ash and Rice husk as cement replacement avoids

the environmental and ecological damages caused by quarrying and exploitation of raw

materials like limestone for making cement.

2.1.13. Kazim Turk[3] Et Al, [2007]

In their experimental study “Capillarity water absorption of Concrete under

different Curing Conditions”, explains the influence of puzzolonic materials and curing

regimes on the mechanical properties and the Capillarity water absorption(sorptivity)

50

Characteristics of Self Compacting concrete (SCC).He concluded that the Compressive

and tensile strengths of Self Compacting concrete were higher than those of PC concrete

for all testing ages and for all curing conditions and also proper curing and using

puzzolonic admixture such as Fly ash as cement component enhanced the resistivity of

concretes under water absorption significantly..

2.1.14. Srinivasa Rao.P, [2008]

In his paper “Strength properties of Glass Fibre Self Compacting concrete”

studied the properties of GFSCC using alkali-resistant glass fibres in various proportions

and compared the properties for controlled mixes of grade M30 and M35. He concluded

that there is an improvement in the compressive strength for both grades of GFSCC and is

observed to be 15% over Self-Compacted Concrete.

2.2. Constituent Materials of SCC

The constituent materials used for the production of SCC are the same as those for

conventionally vibrated normal concrete except that SCC contains lesser aggregate and

greater powder (cement and filler particles smaller than 0.125 mm). Fly ash, glass filler,

limestone powder, silica fume, etc are used as the filler materials. To improve the self-

compactibility, without segregation, a superplasticizer along with a stabilizer is added.

2.2.1. Powder (Mixture of Portland cement and Filler)

The term 'powder' used in SCC refers to a blended mix of cement and filler

particles smaller than 0.125 mm. The filler increases the paste volume required to achieve

the desirable workability of SCC. The addition of filler in an appropriate quantity

enhances both workability and durability without sacrificing early strength (Mata, 2004).

2.2.1.1 Cement

Cement used for SCC should not contain C3A content higher than 10% to avoid

the problems of poor workability retention (EFNARC, 2002). Selection of the type of

cement depends on the overall requirements for concrete, such as strength and durability.

51

2.2.1.2 Filler

Materials, such as fly ash, blast furnace slag, ground glass, limestone powder,

silica fume, etc, are commonly used as filler for producing SCC. Savings in labor costs

might offset the increased cost related to the use of more cement and superplasticizer, but

the use of limestone powder (LSP) as a filler could increase the fluidity of the concrete,

without any increase in the cost (Sonebi, 2004).

Natural pozzolan: The use of a natural pozzolan has been found to improve the

fresh and hardened properties of SCC (Ramsburg and Neal, 2003).

Super-pozz®: Super-pozz® is a new emerging mineral admixture

containinghighly reactive alumino – silicate pozzolan, which adds strength to

cementitious mixes whilst its fineness (more surface area) and spherical particle shape

improves the workability a lot (Seedat and Dijkema, 2000). So, it can be used as a

mineral filler for SCC.

The typical chemical composition and physical characteristics of Super-pozz® are

given in Table 2.1 (Seedat and Dijkema, 2000).

Table 2.1: Chemical composition and Physical characteristics of Super-pozz®

(Seedat and Dijkema, 2000).

Chemical Constituent % Physical Properties

SiO2 53.5 Relative Density 2.25

Al2O3 34.3 Surface Area 13000 cm²/g

CaO 4.4 pH 11-12

Fe2O3 3.6 Color Grey

K2O 0.8 Particle Shape Spherical

MgO 1.0 Particle Size, D90 11 µm

TiO2 1.7 Particle size, D99 25 µm

Loss on ignition at 950 °C 0.4

The effect of Super-pozz® on fresh concrete is to improve its viscosity, and it

effect is the same as that of a viscosity agent. It does not decrease the flowability of fresh

concrete. The SCC with Super-pozz® has higher mechanical properties, excellent

impermeability and freez-thaw resistance, and lower drying shrinkage (Youjun et al.,

2001).

52

Due to its particle shape and size, Super-pozz® provides a reduced water demand

and/or a reduced admixture dosage for a given workability, even up to 20% replacement

level. Due to its ability to reduce water and/or admixture, Super-pozz® can either be used

as a high range water reducer to improve compressive strength or as a super workability

aid to improve flow (Seedat and Dijkema, 2000).

Due to the fineness, spherical shape and the highly reactive nature of Super-

pozz®, many technical benefits can be associated with its use. Super-pozz® can be

ideally used in the following applications.

1. High Performance concrete,

2. Spray Concrete, i.e. shortcreting and guniting applications,

3. Repair Mortars,

4. Specialist grout mixes,

5. Cement modified Pre-Mixed base materials, and

6. Self Leveling Floor Screeds.

Due to lower water demand required, Super-pozz® can be ideally used to:

1. Decrease the water/binder ratio,

2. Reduce the high doses of superplasticizer normally required, and

3. Or a combination of the above

Class F fly ash: Class F fly ash is a finely divided ash left after hard coal is burnt for

power. If cement is replaced by fly ash, the paste volume of the concrete will increase,

bleeding will decrease and, due to the increase of paste volume, the shrinkage may

increase. Class F fly ash is generally used to replace Portland cement in the range of 15%

to 25% of the total cementitious material in conventional mixtures. According to Khayat

et al. (2003) a 40% Class F fly ash in a SCC mixture resulted in good workability, with

acceptable strength development and frost durability.

Bouzoubaa and Lachemi (2001) have conducted a study on SCC incorporating

high volumes of class F fly ash as filler in the range of 40 to 60% by mass of powder, the

water/powder ratio in the range of 0.35 to 0.45, sulfonated naphthalene- formaldehyde

superplasticizer in the range of 0 to 3.8 l/m³, and keeping the powder content constant at

400 kg/m³. They reported that it is possible to design a SCC incorporating high volumes

of class F fly ash as a filler. They achieved a slump flow in the range of 500 to 700 mm, a

53

flow time ranging from 3 to 7 sec, a segregation index the range of 500 to 700 mm, a flow

time ranging from 3 to 7 sec, a segregation index ranging from 1.9 to 14%, and

compressive strengths from 15 to 31 MPa, and from 26 to 48 MPa, at 7 and 28 days,

respectively.

Limestone: Bosiljkov (2003) has carried out a study on SCC with poorly graded

aggregate and high volume of limestone as filler (in the range of 47 to 49% of the mass of

powder), a high paste content of (in the range of 891 to 906 kg/m³ of mix, i.e. 41.3 to

42.8 % by the volume of mix) due to the poorly graded coarse aggregates, the lower

water/powder ratio (in the range of 0.22 to 0.25 by mass), a constant optimum dosage of

superplasticizer (0.6% by mass of powder), and a viscosity agent (30 to 35% by the mass

of water). The results obtained indicated that finer and better-graded limestone dust

significantly increases the deformability of the paste and it also appeared that the addition

of filler improved the 28-day compressive strength of concrete mixes besides the required

self-compacting properties.

Silica-fume: Silica-fume, also known as condensed silica fume or microsilica

(ACI 116R), is a very fine, non-crystalline silica produced in electric arc furnaces as a by-

product of the production of elemental silicon or silico-alloys. It is basically a “Super-

pozzolan” with a very high durability and excellent strength, but creates a high water

demand, thus requiring the use of HRWR. Silica-fume is generally used in quantities of

3% to 10% of the total cementitious materials in concretes with accelerated curing.

Slag: Slag is a by-product of the iron industry, generally used to replace Portland

cement in the range of 40% to 60% of the total cementitious material in conventional

concrete mixtures. According to Lachemi et al. (2003) a 50% to 70% slag, as cement

replacement, with different viscosity modifying admixtures (VMA) for various SCC

mixtures produced good results. Mixtures containing slag as a partial replacement of

portland cement generally have lower early strengths and higher ultimate strengths than

otherwise comparable mixtures containing only Portland cement

2.2.2 Aggregates

The maximum size and grading of the aggregates depends on the particular

application. Maximum size of aggregate is usually limited to 20 mm. The coarse

54

aggregate content in SCC is kept either equal to or less than that of the fine aggregate

content. Bui et al., (2002) proposed a rheological model for SCC relating the rheology of

the paste to the average aggregate spacing and average aggregate diameter to consider the

effect of most of the factors related to aggregate properties and content. According to Bui

et al. (2002) and other researchers, a higher aggregate spacing requires a lower flow and

higher viscosity of the paste to achieve satisfactory deformability and segregation

resistance of SCC. Better results were also obtained with the same spacing and a smaller

aggregate diameter. For SCC mixtures, a coarse aggregate size of 5 mm to 14 mm and

quantities varying from 790 kg/m³ to 860 kg/m³ have been used with satisfactory results

(Khayat et al., 2004).

The sand ratio (i.e. fine aggregate volume/total aggregate volume) is an important

parameter for SCC and the rheological properties improved with an increase in the sand

ratio (Su et al., 2002).

According to Okamura (1977), if the coarse aggregate content in a SCC mixture

exceeds a certain limit, blockage would occur independently of the viscosity of the

mortar. Superplasticizer and water content are then determined to ensure desired self-

compacting characteristics. Yugi et al (1993) reported that reducing the volume of coarse

aggregates in a SCC mixture is more effective than decreasing the sand-to-paste ratio to

increase the passing ability through congested reinforcement.

The aggregate packing factor (i.e. the ratio of mass of aggregates of tightly packed

state in SCC to that of loosely packed state in air) determines the aggregate content, and

influences the strength, flowability and self-compacting ability (Su et al., 2001).

The moisture content of aggregates should be closely monitored and must be

taken into account in order to produce SCC of constant quality (EFNARC, 2000).

The coarse aggregate should not contain clay seams that may produce excessive

creep and shrinkage. Therefore, aggregates must be clean for incorporation in the mix

(Gerwick, 1993).

55

2.2.3 Admixtures Superplasticizer: Superplasticizer (SP) is an essential component of SCC to

provide the necessary workability. The superplasticizer to be selected should have:

1. High dispersing effect for low water/powder ratio (less than 1 by volume),

2. Maintenance of the dispersing effect for at least two hours after mixing, and

3. Less sensitivity to temperature changes (Okamura and Ouchi, 2003; Ouchi et al.,

2001).

The main purpose of using a super plasticizer is to produce flowing concrete with

very high slump that is to be used in heavily reinforced structures and in places where

adequate consolidation by vibration cannot be readily achieved. The other major

application is the production of high-strength concrete at w/c's ranging from 0.3 to 0.4.

The ability of a superplasticizer to increase the slump of concrete depends on such factors

as the type, dosage, and time of addition, w/c and the nature or amount of cement. It has

been found that for most types of cement, a superplasticizer improves the workability of

concrete.

Some of the benefits/features of a super plasticizer are:

1. Specified strength can be achieved at high workability,

2. Faster placing with reduced labor and equipment costs, and

3. Low permeable concrete leading to enhanced durability.

Some of the benefits of a high-range water reducer are:

1. Higher strength can be achieved at "normal" workability without the need for

additional cement,

2. Reduction in water content typically reduces bleeding,

3. Produces cohesive and workable concrete at high slump, and

4. Reduction in striking times.

Some of the applications of a superplasticizer are:

1. Incorporating the admixture during batching or on delivery at site increases

workability to a flowing or self-leveling state,

2. Heavily reinforced sections,

3. Deep sections where normal consolidation is difficult,

56

4. High quality formwork finishes,

5. Pumped concrete (long pipelines), and

6. Compatible with all types of Portland cements, including sulfate-resisting cements

and blends.

Stabilizer: Other types of admixtures may be incorporated as necessary, such as

VMA for stability, air-entraining admixture (AEA) to improve freeze-thaw resistance,

retarders for control of setting, etc. Lachemi et al. (2004) have carried out a study on the

performance of new VMAs in enhancing the rheological properties and consistency of

SCC. They found that the combined use of proper dosages of VMA and SP contribute to

securing high-performance cement pastes that is highly fluid yet cohesive enough to

reduce water dilution and enhance water retention.

2.2.4 Ranges of the quantities of the Constituent Materials for SCC

Typical ranges of proportions and quantities of the constituent materials for

producing SCC are given below:

1. Water content: 170 to 176 kg/m³ (Su et al., 2001). It should not exceed 200 kg/m³

(EFNARC, 2002).

2. Cement content: 350 to 450 kg/m³ (EFNARC, 2002),

3. Total powder content (i.e., cement + filler): 400 to 600 kg/m³ (EFNARC, 2002),

4. Dosage of superplasticizer: 1.8% of the total powder content (by mass) (Su et al.,

2001). However, the recommended dosage varies from product to product,

5. Water/powder ratio: 0.80 to 1.10 (by volume) (EFNARC, 2002). A water/powder

ratio in the range of 0.30 to 0.38 (by mass) for tropical Middle East conditions

(Munn, 2003; Kapoor et al., 2003),

6. Coarse aggregate content : 28 to 35% by volume of the mix, i.e., 700 to 900 kg/m³

of concrete (EFNARC, 2002),

7. The sand content balances the volume of other constituents. The sand content

should be greater than 50% of the total aggregate content (Munn, 2003; Kapoor et

al., 2003). Sand ratio (i.e. volume ratio of fine aggregate to total aggregate) is an

important parameter in SCC and the rheological properties increase with an

increase in sand ratio. Sand ratio should be taken in the range of 50 to 57% (Su et

al., 2001), and

8. The aggregate packing factor: 1.12 to 1.16 (Su et al., 2001).

57

2.3 Hardened Properties of SCC 2.3.1 Compressive, Tensile, and Bond Strength

SCC with a compressive strength around 60 N/mm² can easily be achieved. The

strength could be further improved by using fly ash as filler (Kapoor et al., 2003). The

characteristic compressive and tensile strengths have been reported to be around 60

N/mm² and 5 N/mm², respectively (Brameshuber and Uebachs, 2002). Patel et al. (2004)

reported 28-days compressive strength values ranging from 31 to 52 N/mm².

According to Nehdi et al. (2004) the 91-days compressive strength was in the

range of 28 and 47 N/mm². Xie et al. (2002) have reported a compressive strength of up

to 80 N/mm² with a low permeability, good freeze-thaw resistance, and low drying

shrinkage (Xie et al., 2002).

SCC mixes with a high volume of cement – limestone filler paste can develop

higher or lower 28-day compressive strength, compared to those of vibrated concrete with

the same water/cementitious material ratio and cement content, but without filler. It

appears that the strength characteristics of the SCC are related to the fineness and grading

of the limestone filler used (Bosiljkov, 2003).

SCC with water/cementitious material ratios ranging from 0.35 to 0.45, a mass

proportion of fine and coarse aggregates of 50:50 with cement replacement of 40%, 50%

and 60% by Class F fly ash and cementitious materials content of 400 kg/m³ being kept

constant, obtained good results for compressive strength ranging from 26 to 48 N/mm²,

which shows that an economical SCC could be successfully developed by incorporating

high volumes of Class F fly ash (Bouzoubaa and Lachemi, 2001). According to Kumar et

al., (2004) SCC containing more than 50% fly ash of the total powdered material

produced compressive strengths ranging from 20 to 30 N/mm² at the ages of 3 and 7 days.

The bond behavior of SCC was found to be better than that of normally vibrated

concrete (Dehn et al., 2000). The higher bond strength was attributed to the superior

interlocking of aggregates due to the uniform distribution of aggregates over the full cross

section and higher volume of cement-binder matrix (Kapoor et al., 2003).

58

2.3.2 Modulus of Elasticity

Modulus of elasticity of SCC and that of a normally vibrated concrete, produced

from the same raw materials, have been found to be almost identical. Although there is a

higher paste matrix share in SCC, the elasticity remains unchanged due to the denser

packing of the particles (Brameshuber and Uebachs, 2002).

The modulus of elasticity of concrete increases with an increase in the quantity of

aggregate of high rigidity whereas it decreases with increasing cement paste content and

porosity. A relatively small modulus of elasticity can be expected, because of the high

content of ultra fines and additives as dominating factors and, accordingly, minor

occurrence of coarse and stiff aggregates at SCC (Holschemacher and Klug, 2002).

According to Holschemacher and Klug (2002), the modulus of elasticity of SCC can be

up to 20% lower compared with normal vibrated concrete having same compressive

strength and made of same aggregates. Leemann and Hoffmann (2005) reported an

average modulus of elasticity of SCC to be 16% lower than that of normal vibrated

conventional concrete for an identical compressive strength.

Results available indicate that the relationships between the static modulus of

elasticity (E) and compressive strength (fc') were similar for SCC and normally vibrated

concrete. A relationship in the form of E = k.0.5fc, where k is a constant, has been widely

reported, and all values of this constant were close to the one recommended by ACI 318-

02 for structural calculations for normal weight traditional vibrated concrete (Guidelines

on SCC, 2000). Average 28-days modulus of elasticity of SCC has been reported to be 30

GPa corresponding to average 28-days cube strength of 55.41 N/mm² (Dehn et al., 2000).

2.3.3 Shrinkage and Creep

Shrinkage and creep of the SCC mixtures have not been found to be greater than

those of traditional vibrated concrete (Guidelines on SCC, 2000; Persson and Terrasi,

2002). Ramsburg et al. (2003) have reported the shrinkage of SCC as follows: 0.03% for

mixes with cement tested at 14 days, 0.03% to 0.04% for mixes with slag cement tested at

28 days, and 0.04 to 0.045% for mixes with calcined shale cement tested at 28 days.

Shrinkage and creep of SCC coincided well with the corresponding properties of normal

concrete when the strength was held constant (Persson, 2001). According to Kapoor et al

(2003), the drying shrinkage of SCC is similar to that of conventional concrete.

59

The shrinkage and creep rates of SCC have been found to be approximately 30%

higher at an identical compressive strength; this is because of the high amount of paste

(Leemann and Hoffmann, 2005). Since SCC is rich in powder content and poor in the

coarse aggregate fraction, addition of fiber will be effective in counteracting drying

shrinkage (Corrinaldesi and Moriconi, 2004).

The 90 days drying shrinkage value as reported by Xie et al (2002) was 383 x

10ˉ6 mm/mm. They suggested that SCC with UPFA (Ultra Pulverized Fly Ash) has

higher mechanical properties, excellent impermeability and freezing resistance, and lower

drying shrinkage.

In a study on SCC incorporating high volumes of class F fly ash, conducted by

Bouzoubaa and Lachemi (2001), 112-days drying shrinkage was found in the range of

493 to 591 × 10ˉ6 and 224-days drying shrinkage was in the range of 504 to 595 × 10ˉ6

(Bouzoubaa and Lachemi, 2001).

In another study on SCC incorporating high volumes of class F fly ash, conducted

by Patel et al (2004) 112-days drying shrinkage was found to be in the range of 330 to

667 × 10ˉ6 (Patel et al., 2004).

2.3.4. Durability

Durability is a general analysis of the service life and the performance of

concrete in an aggressive environment. Physical damage to concrete includes

wetting/drying, freeze/thaw or heating/cooling cycles. Chemical damage

consists of sulphate attack, acid attack, chloride attack and alkali-silica reaction

(ASR) in which water acts as a carrier. All are greatly related to the resistance of

the cover layer to transport mechanisms such as permeation, absorption and

diffusion of gas and liquid. Thus oxygen permeability, water sorptivity and

chloride conductivity have often been defined as three durability indexes due to

the simple and inexpensive test methods (Alexander and Magee, 1999).

A brief summary of water transport in concrete and other durability aspects of

SCC are demonstrated as follows.

60

Sorption is the water movement driven by capillary action in short-term

exposure in partially dry concrete. The rate of water uptake by a porous material is defined

as sorptivity. It has been considered as an important criterion to assess the durability of

concrete (Ho and Chirgwin, 1996). The pore system of the paste and the interfacial

zone has a great influence on sorptivity. The interfacial zone is porous but it is the

hardened paste, the only continuous phase in concrete, that controls the ingress and

transportation of water (Sabir et al., 1998). Sorptivity of SCC was only 30~40% of those

of NVC with the same strength grade C40 (Zhu and Bartos, 2003).

Diffusion is the water movement driven by a concentration gradient in long-

term exposure. For example, the durability of concrete in the sea is largely

determined by the diffusivity of the chloride solution entering and moving

through the matrix. Chloride diffusivity depends on the tortuosity of the pores

instead of the total porosity. Since fly ash particles made concrete dense,

concrete incorporating fly ash was reported to have a lower chloride diffusivity

(Zhu and Bartos, 2003). On the other hand, Tang et al (1999) reported a higher

chloride diffusivity than NVC because of the poor dispersion of powders. It is

interesting to note that the diffusivity of SCC with VMA is higher than NVC

and powder-type SCC (Zhu and Bartos, 2003). This confirms that the powders

used in SCC improve packing density leading to a denser structure. Diffusion

and capillary action are the primary mechanisms of ingress of water. Diffusion

was a very slow process and it accounted for about 30% of the overall water

intake whereas sorption accounts for about 70% (Neithalath, 2006).

Capillary porosity has a very important influence on hardened properties and is

useful for predicting the durability (Yaman et al., 2002). The capillary transport especially

near concrete surface is the dominant invasion mechanism. An increase in the porosity

of the cover concrete leads to more water and more dissolved chemical flowing

through the surface, and thus, more durability problems. The relationships between water

absorption and some durability such as the resistance of concrete to carbonation and

chloride (De Schutter and Audenaert, 2004), freezing/thawing cycling and wet/dry

cycles (Martys and Ferraris, 1997) were investigated. Capillary suction was influenced

by the moisture state of the specimen, the ambient conditions, curing conditions and

testing procedures (Hall, 1989).

61

Permeability is a process in which water is transported under a hydrostatic

pressure differential. The main influences on permeation include the paste

volume, the pore structure and the interfacial zone between the mortar and

aggregates. The overall porosity of SCC was lower than that of NVC of

equivalent strength because of the higher powder content, lower W/P ratio and

improved microstructure (Tragardh, 1999; Zhu et al., 2004; Zhu and Bartos, 2003). Zhu

and Bartos reported that the oxygen permeability for SCC was only 30~40% of that of

NVC with the same strength grade C40.

Other investigations on durability between SCC and NVC include:

1. SCC with limestone powder exhibited better internal frost resistance than NVC with the same W/C ratio and air content but there was little difference between SCC and NVC for salt (NaCl) and sulphate resistance (Persson, 2003).

2. The tests (Al-Tamimi and Sonebi, 2003) of SCC with 47% carboniferous limestone

powder (less than 100 µm) and a W/P ratio of 0.36, and a neat cement NVC with the

same strength (W/P ratio of 0.46), immersed in a sulphuric and hydrochloric acid

solution, showed that at 18 weeks, the mass loss due to sulphate attack of SCC was only half

that of NVC in a sulphuric acid solution; but in a hydrochloric acid solution, SCC incurred

about2.2% more mass loss than NVC. The author concluded that SCC performed better

than NVC in a sulphuric solution but was more susceptible to hydrochloric

acid attack. This difference between SCC and NVC might be due to the

difference in constituent materials: the higher cement content in NVC

contributed more calcium hydroxide than in SCC; the lower W/P ratio used

and the incorporation of limestone, which is finer than cement, both led to a

denser matrix of SCC than NVC.

3. SCC exhibited lower resistance to freeze-thaw than NVC (Zhu and Bartos,2003).

4. Few fire tests have been done on SCC. Cylinders with different mix proportions of

strength up to 104 MPa of SCC were tested; slight spalling occurred for SCC; the degree

of spalling also depended on the type of additions used (Vanwalleghem et al., 2003).

SCC was more susceptible to spalling than NVC with the same strength grade (Bostrom,

2003; Noumowe et al., 2006). This may be attributed to the denser microstructure of SCC.

62

2.3.4 Water Absorption and Initial Surface Absorption Kapoor et al. (2003) have reported a water absorption value of 1% for SCC

against 2% for normal vibrated concrete, obtained through the water absorption test

conducted as per BS 1881: Part 122. An initial surface absorption value of 0.01 ml/m²/sec

has been reported by Kapoor et al. (2003) for SCC against 0.02 ml/m²/sec for normal

vibrated concrete, obtained through ISAT conducted as per BS 1881: Part 208.

2.3.5 Water Permeability

SCC with high strength and low permeability can easily be produced (Ouchi et al.,

2001). Zhu and Bartos have found the permeability of SCC significantly lower as

compared to that of normally vibrated concretes of the same strength grade. Kapoor et al.

(2003) have reported a water permeability value of 5 mm for SCC against 10 mm for

normal vibrated concrete, obtained through the water penetration test conducted as per

DIN 1048.

The water permeability test, which is most commonly used to evaluate the

permeability of concrete, is the one specified by DIN 1048. This test is useful in

evaluating the relative performance of concrete made with varying mix proportions and

incorporating admixtures. The Concrete Society (1987) provided some indication of

typical and specified results for various concrete, as shown in Table 2.2.

Table 2.2: Assessment of Concrete Permeability according to Water Penetration Depth (The Concrete Society, 1987).

Depth of penetration, mm Permeability

Less than 30 Low

30 to 60 Moderate

More than 60 High

It is known that most specifications control the durability of concrete almost

exclusively by specifying certain requirements for concrete composition, strength and

permeability. Hilsdorf (1995) stated that this approach frequently yields unsatisfactory

results and there is a need to develop performance criteria that would allow more reliable

estimates of the potential durability of a given concrete mix and of the probable durability

63

of a concrete structure. It is generally accepted that the concrete’s resistance to

penetration of aggressive media governs concrete durability; therefore, a criterion that is

based upon such resistance should be a more reliable approach (Hilsdorf, 1995).

Permeability tests, particularly those involving water penetration and chloride

permeability, are increasingly used to test concrete to evaluate its conformance with the

specifications, particularly for concrete exposed to aggressive conditions.

2.3.6 Rapid Chloride Permeability

Rapid chloride permeability of concrete is determined using a standard test

method for electrical indication of concrete’s ability to resist chloride ion penetration,

covered by ASTM C 1202. The rapid chloride permeability test evaluates the

performance of various cementitious materials based on the accelerated diffusion of

chloride ions under the application of an external electric field. The chloride ion

penetrability of different SCC mixes, as reported by Ramsburg et al, (2003) are as

follows: 2,000 to 4,000 coulombs (categorized as “moderate”) for mixes with cement,

1,000 to 2,000 coulombs (categorized as “low”); for mixes with slag cement, and 100 to

1,000 coulombs (categorized as “very low”); for mixes with calcined shale cement.

Kapoor et al. (2003) have reported a rapid chloride permeability value of 620 coulombs

for SCC against 1970 coulombs for normal vibrated concrete, obtained through the rapid

chloride permeability test conducted as per ASTM C-1202-94.

According to Plante and Bilodean (1989), the incorporation of supplementary

cementing materials in concrete contributes to the reduction in the porosity of the system,

which, in turn, results into a reduction in the chloride ion permeability of concrete.

Patel et al. (2004) reported the rapid chloride permeability in the range of 772 and,

1379 Coulombs with percentage of fly ash in the range of 30% and 60%. According to

Nehdi et al. (2004) the 91 days rapid chloride penetration value was in the range of 400

and 900 Coulombs. Table 2.3 shows guidelines to evaluate the chloride ion permeability

based on the charge passed.

64

Table 2.3: Relationship between charge passed and chloride permeability

(ASTM C-1202-94).

2.4. Influence of Admixtures on Concrete Properties

In the following are presented several papers, found in the literature, on the effects

of mineral and chemical admixtures on the fresh and hardened concrete. The mineral

admixtures referred to are blast-furnace slag, fly ash, and silica fume. The chemical

admixtures considered are high range water reducer or superplasticizer and viscosity-

modifying agent.

2.5. Mineral Admixtures

Mineral admixtures are added to concrete as part of the total cementitious system.

They may be used in addition to or as a partial replacement of Portland cement in

concrete depending on the properties of the materials and the desired effect on concrete

(Mindess et al., 2003). Mineral admixtures are used to improve a particular concrete

property such as workability, strength or compactability. The optimum amount to use

should be established by testing to determine (1) whether the material is indeed

improving the property, and (2) the correct dosage rate, as an overdose or underdose can

be harmful or not achieve the desired effect, because they react differently with different

cements (Kosmatka et al., 2002).

2.6. Blast Furnace Slag

Blast furnace slag (BFS), also called slag cement, is made by rapidly quenching

molten blast-furnace slag and grinding the resulting material into a fine powder. BFS is

classified by ASTM C 989 according to its level of reactivity. Depending on the desired

properties, the amount of BFS can be as high as 50 percent by mass, of the total

cementitious materials content (Ramachandran, 1981).

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Charge Passed (Coulombs) Chloride Ion Penetrability

More than 4,000 High

2,000 to 4,000 Moderate

1,000 to 2,000 Low

100 to 1,000 Very Low

Less than 100 Negligible

In his research, Russell (1997) found out that the use of slag cement lowers

concrete permeability, thereby reducing the rate of chloride ion diffusion. Proper

proportioning of slag cement can eliminate the need to use low alkali or sulfate-resistant

Portland cements. Russell’sresults showed that BFS can be used to enhance the strength

gain at later ages than 28 days, it replaces 20 to 30 percent by mass of the Portland

cement.

Sobolev (1999) studied the effect of adding up to 50% by mass granulated blast-

furnace slag in the cementitious material that resulted in the increasing of chemical and

thermal resistance. The very low permeability of the concrete obtained, provided high

resistance to chemical attack and to freezing and thawing cycles. There was no visible

destruction of blast- furnace slag concrete samples after 140 cycles of freezing and

thawing at -50ºC, and they also demonstrated high resistance to elevated temperatures.

Ozyildirim (2001) studied three concrete mixtures placed in the jointed plain

concrete paving project in Newport News, Virginia. The main goal was to reduce the

shrinkage and improve the flexural strength of the concrete. Two of the mixtures that he

used contained ground-granulated blast furnace slag and the third contained Class F fly

ash. The content of blast-furnace slag in the two mixtures was 30% by mass of the total

cementitious material and the maximum water-cement ratio was 0.50.

Flexural strengths at 28 days were similar for fly ash and blast-furnace slag

concretes, but after 60 days they were greater for those which contained slag. The

shrinkage values of concretes containing slag cement were slightly greater than the values

of concretes with fly ash. For freezing and thawing tests the acceptance criteria at 300

cycles were a weight loss of 7 percent and less, a durability factor of 60 and more, and a

surface rating (ASTM C 672) of 3 or less. Blast-furnace slag concretes complied with

those requirements, but the fly ash concretes had slightly higher weight loss than

required.

Hale (2000) et al. investigated the effects of the cement replacement with 25% by

mass blast-furnace slag on fresh and hardened concrete properties. As a result,

compressive strengths were increased by approximately 25 percent at 28 days as

compared to normal Portland cement mixtures. The use of 25 percent blast-furnace slag

led to minor to moderate reductions in slump and slightly lower air contents as compared

to conventional mixtures.

66

Klieger and Isberner (1967) have conducted a comprehensive study on the

properties of pastes and concretes made with Portland blast-furnace slag cements (ASTM

Type IS). Five commercial IS brands were included in these tests, in addition to a number

of Portland cements. These IS type cements were made by intergrinding a mixture of

Portland cement clinker and granulated blast-furnace slag or by making an intimate and

uniform blend of Portland cement and fine granulated blast-furnace slag. The amount of

slag used in the mixtures was between 20% and 350% by mass of the total cementitious

material.

The compressive strengths of concretes made with type IS cements were generally

lower at early ages than the strengths of concretes made with Type I cement. However, at

3 months, one year, and 3 years, the strengths were generally equal to or greater than

those of the Type I cement. Also, at the same compressive strength, values of splitting

tensile strength were essentially equal for both types of cement.

2.7. Fly Ash Gebler and Klieger (1983) studied concretes containing fly ash in order to

determine its effect on the air-void stability. 10% to 20% by mass of fly ash was used in

the total amount of cementitious material. The tests undertaken indicated that air contents

of concrete containing Class C fly ash appeared to be more stable than those of concrete

containing Class F fly ash. This occurred primarily because Class C fly ashes have lower

organic matter content and carb on content values. The studies revealed that the higher

the organic matter content of a fly ash, the higher would be the air-entraining admixture

requirement for concrete in which the admixture is used. Practically, all concretes

containing fly ash required more air-entraining admixture than concretes without fly ash

and the concretes containing Class C fly ash tended to lose less air than concretes with

Class F fly ash.

Naik and Singh (1997) conducted tests on concretes containing between 15% and

25% by mass Class F and Class C fly ashes, to evaluate time of setting, bleeding,

compressive strength, drying shrinkage, and abrasion resistance. The effects of moisture

and temperature during curing were also examined. The results of the research showed

that concretes containing Class C fly ash and were moist cured at 73°F (23°C) developed

higher early age (1 to 14 days) compressive strengths than concretes with Class F fly ash.

The long-term (90 days and greater) compressive strength of concretes containing fly ash

was not significantly influenced by the class of fly ash.

67

The air-cured concretes containing Class F fly ash did not develop strengths

equivalent to air-cured normal concretes and air-cured concretes containing Class C fly

ash developed relatively greater compressive strengths than air-cured concretes

containing Class F fly ash. For concretes containing either class of fly ash, compressive

strengths at 7 days increased with an increase in curing temperature. Concretes with fly

ash showed less bleeding than conventional ones. Further, concretes with Class C fly ash

showed less bleeding than concretes with Class F fly ash. Also, drying shrinkage results

for concretes containing fly ash were essentially the same as for conventional concretes ,

regardless of initial curing temperature. Drying shrinkage results for concretes with Class

F fly ash were, on the average, slightly less than for concretes with Class C fly ash. The

abrasion resistance of the concretes was essentially dependent on their compressive

strength and time of setting for most of the concretes containing the two types of fly ash

was retarded.

Dietz and Ma (2000) in their research, showed a possible application of lignite fly

ash (LFA) for the production of Self-Compacting Concrete (SCC). The lignite fly ash has

not only some characteristics of potential hydraulic materials, it can also improve the

rheological properties of the fresh concrete because of its fineness, which is a primary

advantage for SCC. Self-compacting concrete with lignite fly ash shows a good flowing

ability and high self- compactability.

Lignite Fly Ashes (LFA) are fine residues of ground lignite burned in the power

plant industry. In comparison with fly ashes from coal, LFA contains obviously more free

lime and sulfate. The chemical and mineralogical composition of the LFA shows wide

variations and because of that, fly ash with a free lime content of approximately 22% was

chosen for the project. The choice of this type of ash was due to its availability and its

constant quality. Two differently lignite fly ashes were used. One LFA, which was

untreated showed a high free lime content and was called Untreated Lignite Fly Ash (U-

LFA). The other fly ash, which was treated with water, was called Treated Lignite Fly

Ash (T-LFA). In the latter case, the free lime has changed into calcium hydroxide.

Cementitious material consisted of 75% cement and 25% fly ash, by mass. It was

discovered that, if the cement is replaced from 10% to 25% by U-LFA or T- LFA, the

water requirement is reduced. This is favorable for the workability of the fresh concrete.

The reduced water requirement indicated that the grains of the cement - LFA mixture are

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more densely compacted. The volume between the particles, which should be filled with

water, became smaller due to the denser packing. Furthermore, the spherical LFA

particles favorably affected the workability of the mixture. It was seen that the U-LFA set

very quickly. The setting and hardening of the cement-U-LFA paste was clearly

shortened by U-LFA. The higher the U-LFA proportion was, the faster the paste hardened

and, because of this, U-LFA was replaced by T-LFA, which shortened the setting times

only slightly.

The slump flow and funnel tests showed values within the ranges of other tests

previously undertaken. The compressive strengths of hardened concrete specimens

decreased with the increasing proportion of U-LFA over 25%, while they remained

approximately constant when T-LFA was used in percentages that exceeded 25%. After

28 days, compressive strengths between 50 MPa and 60 MPa and splitting tensile

strengths between 4 and 5 MPa were obtained for self-compacting concretes, with w/c

ratios ranging from 0.3 to 0.46.

2.8 Silica Fume

In their study, Khaloo and Houseinian (1999) investigated the influence of silica

fume on compressive strength and durability of concrete. The percentage of silica fume

was between 1% and 15% and the water-cement ratios ranged from 0.3 to 0.6. The coarse

and fine aggregates consisted of river gravel and sand with maximum size of 25 mm and

5 mm, respectively.

The test results indicated that 5 to 10 percent by mass replacement of silica fume

for cement provided the highest strength for short and long terms. Compressive strength

of silica fume concrete at 28 days compared to conventional concrete increased by 20 to

40 percent, for all the variables considered. After 300 cycles, all of the concrete

specimens passed ASTM C 666 for freezing and thawing durability test.

Khayat (1997) et al. evaluated the influence of silica fume blended with cement on

some properties of fresh and hardened concrete. The properties studied were bleeding,

slump loss, time of setting, compressive strength. A total of 26 commonly used concrete

mixtures in the Canadian construction industry were developed. Half of the mixtures were

air-entrained and had water- cement ratios ranging from 0.3 to 0.6. The remaining half

contained non air-entrained mixtures and the water-cement ratios varied between 0.45 and

0.7.

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Studies undertaken revealed that the addition of small percentages of silica fume,

usually under 10%, and proper amount of high range water-reducing admixture

(superplasticizer) could decrease the viscosity of the paste, thus reducing the water

demand and the risk of bleeding. The small particles of silica fume can displace some of

the water present among flocculated cement particles and fill some of the voids between

the coarser particles, which otherwise can be occupied by some of the mix water. This

causes some gain in workability and densification of the fresh paste. Concrete mixtures

made with blended silica fume cement exhibited substantially less bleeding than those

made with type I Portland cement. In addition, mixtures made with blended silica fume

cement showed 15 to 20 mm greater loss of slump than concretes without silica fume.

In general, concrete mixtures made with type I Portland cement and blended silica

fume cement exhibited similar initial times of setting that were within one hour apart.

When 15% of silica fume was added with a high dosage of superplasticizer, initial and

final times of setting were delayed by approximately 1 and 2 hours, respectively.

Regarding the compressive strength, Khayat (1997) et al. found out that after three days

of curing, no effect of cement type was observed on the development of compressive

strength for concretes. However, starting with the seventh day, mixtures containing

blended silica fume cement exhibited greater strength than those made with type I

Portland cement. After 28 days, in non air-entrained concretes, the use of blended silica

fume cement resulted in approximately 20% strength gain compared with mixtures

containing only Portland cement. Similar results were obtained in air-entrained concrete.

Ray and Chattopadhyay (1999) carried out studies on the effects of 4, 8, 12, 16%

of silica fume by weight of cement on compressive strength and resistance against

chemicals (acids and sulfates) of concretes. For testing of resistance against acids and

sulfates 50 mm cubic samples were oven dried at 105ºC and immersed in 2% HNO3, 2%

H2SO4, and 5% Na2SO4 solutions for 45 days. The weight and strength losses were noted

with reference to a set of undisturbed samples cured in water. Conventional concrete

exhibited slight bleeding, but this phenomenon was completely eliminated when silica

fume has been added in the mixture. Also, the values of air content decreased with the

increase in silica fume content. They dropped from 5.5% for normal concrete to 3.5% for

16% of silica fume replacement. Concretes with a content of 8% silica fume showed

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the highest compressive strength values after 28 days (45 MPa), followed by concretes

having 4, 12, and 16%. Addition of silica fume at all percentages improved the flexural

strength, with a significant rise for a 4% content (8.5 MPa).

As regarding the resistance against acids and sulfates, test results showed that

immersion in H2SO4 has caused maximum loss in weight and strength, followed by

HNO3 and Na2SO4. The maximum strength loss of 24% has occurred for mixtures

without any silica fume, whereas the minimum loss of 12% occurred for mixtures

containing 4% of silica fume.

The influence of silica fume on workability and compressive strength of concretes

were the major research objectives for Duval and Kadri (1998). Concretes that have been

investigates had low water-cement ratios (0.25 to 0.40). The type I Portland cement was

replaced by 10-30% by mass silica fume and superplasticizer was added. It was found

that silica fume increased best the compressive strength (25%) and the workability of

concretes when its content was between 4 and 8 percent. Duval and Kadri also found out

that if silica fume exceeds 15% of the cementitious material, both compressive and tensile

strengths are reduced.

2.9. Chemical Admixtures

Chemical admixtures represent those ingredients which can be added to the

concrete mixture immediately before or during mixing. The use of chemical admixtures

such as water reducers, retarders, high-range water reducers or superplasticizers (SP), and

viscosity-modifying admixtures is necessary in order to improve some fundamental

characteristics of fresh and hardened concrete. They make more efficient use of the large

amount of cementitious material in high strength and self-compacting concretes and help

to obtain the lowest practical water to cementing materials ratio.

Chemical admixtures efficiency must be evaluated by comparing strengths of trial

batches. Also, compatibility between cement and supplementary cementing materials, as

well as water reducers, must be investigated by trial batches. From these, it will be

possible to determine the workability, setting time, bleeding, and amount of water

reduction for given admixture dosage rates and times of addition. Due to the fact that this

71

research dealt only with superplasticizers and viscosity modifiers, papers found in the

literature about these types of chemical admixtures would be presented in the following.

2.10. Superplasticizers

A study of four commercially available superplasticizers used in type I Portland

cement concrete mixes was done by Whiting (1979). They represented both melamine-

and naphthalene- based formaldehyde condensation products. Hardened concrete

specimens were prepared and tested for compressive strength development, drying

shrinkage, freeze-thaw resistance, and resistance to deicing scaling. From his research,

Whiting found out that high range water reducers were capable of lowering the net water

content of concrete mixtures from 10% to 20% when used in dosages recommended by

the manufacturers.

Also it was found out that one- and three-day compressive strengths could be

substantially increased through use of high range water reducers. Compressive strengths

over 70 MPa were obtained after 28 days of curing. The drying shrinkage was slightly

reduced in the attempt to lower the net water content of the concrete mixtures. Freeze-

thaw durability and resistance to deicer scaling of air-entrained concretes containing

superplasticizer were equal to or slightly better than air-entrained normal concretes

prepared with equal slump and cement content.

Ozkul and Dogan (1999) studied the effect of a N-vinyl copolymer

superplasticizer on the properties of fresh and hardened concretes. Workability of

concrete was measured by slump flow test and in situ tests were undertaken to find out

the pumping ability of superplasticized concrete. The coarse aggregate was crushed stone

with the maximum size of 25 mm. By using this chemical admixture, which was a little

bit different from the conventional ones, the ability of water reduction was increased

along with the retention of high workability for a longer time.

In situ test results obtained by Ozkul and Dogan (1999) demonstrated that the

superplasticized concrete could be pumped easily from a height of about 13 m and the

filling capacity was greater than 85%. The pumping pressure was the same as for normal

pumpable concrete and no segregation was observed. For mixtures with water-cement

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ratios between 0.3 and 0.45, the slump diameters were between 500 mm and 740 mm and

the compressive strength varied between 53 MPa and 68 MPa at 28 days of age.

In their work, Roncero (1999) et al. evaluated the influence of two

superplasticizers (a conventional melamine based product and a new-generation comb-

type polymer) on the shrinkage of concrete exposed to wet and dry conditions. Tests of

cylinders with embedded extensometers have been used to measure deformations over a

period of more than 250 days after casting. In general, it was observed that the

incorporation of superplasticizers increased the drying shrinkage of concretes when

compared to conventional concretes, whereas it did not have any significant influence on

the swelling and autogenous shrinkage under wet conditions. The melamine-based

product led to slightly higher shrinkage than the comb-type polymer.

Kasami (1978) et al. have investigated the pumpability of superplasticized

concrete under field conditions. In their experiment, about 2,000 m³ of normal and

lightweight aggregate concrete, involving 14 mixes with and without superplasticizers

were pumped horizontally. The pumping distance was 109 m and line diameter 125 mm.

The dosage of the naphthalene-based superplasticizer was in the range of 0.03% to 0.04%

by weight of cement and concrete mixing was done in ready-mix agitator-type trucks.

After the addition of the superplasticizer, the mixer was rapidly agitated for one minute.

Following this process, the concrete was pumped at rates of 10, 20, 30, 40, 50, and 60

m3/h. Pump pressure and line pressure were measured at each pumping rate. The tests

data indicated that pumping pressure and line pressure loss for normal weight concrete

were reduced by about 30%, whereas those for lightweight concrete were reduced by no

more than 10%.

The effect of superplasticizer on the balance between flowability and viscosity of

paste in self-compacting concrete was investigated by Ouchi (1996) et al. From

experimental results, the ratio of V-funnel speed to flow area of cement paste with a fixed

amount of superplasticizer was found to be almost constant, independent of the water-

cement ratio. A higher amount of superplasticizer resulted in a lower ratio of V-funnel

speed to flow area. The ratio was proposed as an index for the effect of superplasticizer

73

on cement paste flowing ability and viscosity from the viewpoint of achieving self-

compactability. However, the relationship between high range water reducer amount and

its effect was found to differ depending on the type of cement or chemical admixture.

A rational mix-design method (Figure 2.6) for self-compacting concrete was

proposed by Okamura (1997) et al. and the indexes for flowability and viscosity were

defined as Γm and Rm, respectively. They were defined as follows:

Γm = (r1r2 – r20)/ r20 (2.3) Rm = 10/t (2.4)

where: r1 and r2 are the measured flow diameters perpendicular on each other; r0 is the

flow cone’s bottom diameter; and t is the measured time (in seconds) for cement paste to

flow through the funnel

Figure 2.6 Rational mix-design method for self-compacting concrete (Ouchi et al., 1996).

These indexes are practical to use because they are easy to obtain from simple test

results. Larger Γm values indicate higher flowability and smaller Rm values indicate

higher viscosity. A cement paste with Γm = 5 and Rm = 1 was found to be the most

appropriate mixture for achieving self-compacting concrete.

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2.11. Viscosity Modifiers

The viscosity modifiers or viscosity modifying admixtures (VMA) were

developed in order to improve the rheological properties of cement paste in concretes

(Khayat and Guizani, 1997). These admixtures enhance the viscosity of water and

eliminate as much as possible the bleeding and segregation phenomena in the fresh

concrete. Because not all types of viscosity modifiers have showed satisfactory results,

research has concentrated on only two types: welan gum and antiwashout admixtures.

In their research, Takada (1999) et al. investigated the influence of welan gum, a

kind of natural polysaccharide-based viscosity agent, on the water-cementitious material

ratio. It was found that the viscosity modifier raised the value of the ratio due to its

characteristics to make the mixture viscous. Welan gum increased the viscosity of the free

water in the fresh concrete by the ability of its polymers’ characteristics to associate each

other in water. The tests results showed that a slump flow value of 650 ± 30 mm and a V-

funnel time of 11 ± 2 sec were achieved by using 0.01 to 0.02 percent viscosity agent and

0.025 to 0.035 percent superplasticizer from the total cementitious material. The values

were considered adequate for a workable self-compacting concrete.

.

Khayat (1997) et al. evaluated the properties of welan gum in achieving self-

compacting concrete for use in congested members and confined areas. The viscosity-

modifying admixture (welan gum) was used to ensure adequate stability for concrete cast

in deep structural members and wall elements in order to avoid segregation and bleeding

which can result in local structural defects that can affect its mechanical properties. All

the SCC mixtures had high filling capacities ranging between approximately 60 and 70

percent, indicating excellent deformability without blockage among closely spaced

obstacles. No external bleeding was observed on the top surface of any of the cast wall

elements and the settlement values of the self-compacting mixtures measured on 150 cm

walls ranged between 1.4 and 2.9 mm. This corresponds to 0.1 and 0.2 percent of the wall

heights and is less than that for normal concrete, which was around 0.4 percent.

In order to verify the properties of self-compacting concrete, Dehn (2000) et al.

studied the interaction between the superplasticizer and viscosity-modifying agent and the

75

bonding between the reinforcing bars and self-compacting concrete. They found out that

the polymer in the viscosity modifier (welan gum) and the polymer in the superplasticizer

restrain each other and this phenomena results in a higher segregation resistance and

some larger dosage of SP for a particular deformability. It was also seen that depending

on the mix design and chemical admixtures dosages the bond behavior in self-compacting

concrete was better than the bond in conventional concrete.

Trial mixes with varying dosages of viscosity-modifying admixture (VMA) and

high range water reducing admixture (HRWR) to achieve a wide range of flow behavior

were investigated by Ferraris (1999) et al. In these mixes, the VMA was incorporated in

order to enhance the yield value and viscosity of the fluid concrete, hence reducing

bleeding, segregation, and settlement. The enhanced cohesiveness could ensure better

suspension of solid particles in the fresh concrete and therefore good deformability and

filling capacity was achieved during casting. The HRWR used was a carboxylated

copolymer-based mixture and the VMA was a modified cellulose product. Even though

the dosages of chemical admixtures have been varied, the slump flow tests undertaken,

were not enough to determine whether a flowable concrete was self-compacting or not.

Subramanian and Chattopadhyay (2002) carried out several trials to achieve an

approximate mix proportion of self-compacting concrete. At the initial stages of

development, mixtures were formulated without incorporating any viscosity-modifying

agents. After several trials, it was apparent that these admixtures imparted exceptional

stability to the mixture. The viscosity-modifying agent was then required, because slight

variations in the amount of water or in the proportions of aggregate and sand would have

made the concrete unstable, that is, water or slurry might have separated from the

remaining material. However, not all VMAs were suitable for concrete applications, due

to the fact that some of them restricted the choice of superplasticizer. The welan gum that

was used, a well-known viscosity-modifying agent, was found incompatible with

melamine formaldehyde condensate-based type of superplasticizer, but after a few trials,

a naphthalene formaldehyde condensate and an acrylic polymer superplasticizers were

found to be suitable for application in self-compacting concrete. Another two types of

viscosity-modifiers, a hydroxy propyl methyl cellulose (HPMC) and guar gum, were also

76

selected for being used along with the concrete, but they failed to react properly with the

HRWR admixture. The guar gum had to be made into a suspension in water after heating

it to 60˚C and stirring for about one hour, but it lost its suspending power after 12 hours.

The HPMC entrained excessive air, causing a reduction in strength. Subramanian and

Chattopadhyay (2002) found out that with a combination corresponding to 0.012 percent

of welan gum and 0.036 percent acrylic polymer superplasticizer by weight of

cementitious material, a satisfactory self- compacting mixture could be obtained.

Investigations regarding the effects of viscosity-modifying admixture (VMA)

concentration, placement height, and mode of consolidation on enhancing the stability of

mixtures were done by Khayat and Guizani (1997). In a first phase, bleeding and

settlement were determined using 70 cm high columns cast with concrete containing

0.035 and 0.07 percent viscosity modifiers dosages. The water-cement ratios were

between 0.50 and 0.70 and the slump values from 140 to 200 mm. In the second phase,

bleeding, settlement, and segregation were evaluated for concretes with 200 mm slump,

cast in 50, 70, and 110 cm high columns. This time the mixtures had a water-cement ratio

of 0.50 and the same amounts of VMA, which was chosen to be welan gum. The

superplasticizer used was a liquid sulfonated naphthalene.

The studies showed that the addition of welan gum affected the aqueous phase of

the cement paste where chains of the water-soluble polymer could imbibe some of the

free water in the system, thus enhancing the viscosity of the cement paste. As a result,

less free water can be available for bleeding. The enhanced viscosity of the cement paste

can also improve the capacity of the paste to suspend solid particles, process that reduces

the sedimentation. Mixtures containing a viscosity modifier exhibited a shear thinning

behavior whereas the apparent viscosity decreased with the increase in shear rate. The

mixtures incorporated 0.035 and 0.07 percent of viscosity-modifying admixture and

between 0.022 and 0.035 superplasticizer, by mass of cementitious materials. All

mixtures incorporating VMA exhibited lower rates of increase in bleeding and settlement

than those without VMA, regardless of water-cement ratios.

Also, concretes containing 0.035 and 0.07 percent viscosity-modifying admixture

had approximately 30 and 50 percent lower segregation coefficients than conventional

77

ones, regardless of the height of casting. As seen from the above investigations, it is

important to enhance the stability of fluid concrete used to facilitate the casting in

congested or restricted areas. The enhanced cohesiveness of such concrete can reduce

structural defects resulting from increased porosity under aggregate and embedded

reinforcement. This can lead to improved tensile strength, impermeability, and bond

strength with reinforcement, especially in deep structural sections, which can contribute

to the reduction in congestion.

2.12. Bonding between Aggregate and Cement Paste

Physical strength and integrity of the bond achieved at the aggregate-paste

interface variously depends upon the character of the aggregate particle surface and the

nature of the immediately adjacent hydrated cement, so practically the nature of the

interface is controlled by the properties of both the aggregate and the cement paste (Dhir

and Dyer, 1999). Aggregates used in concrete have varying degrees of porosity, shape

and surface roughness as well as the possibility of adherent dust and dirt (Barksdale,

1991). The interfacial region of paste surrounding the aggregate has been shown to be

different from that of the bulk paste and has been called interfacial transition zone (ITZ).

Subramanian (1999) has shown that the parameters of concrete could be altered

for the better by choosing proper materials or by modifying the physical interfaces

between the materials. He found that in a 25-50 µm thick zone surrounding the aggregate,

a duplex layer of calcium hydroxide - Ca(OH)2 – and a porous shell, having properties

different from the bulk cement paste, were present. These factors encourage the

deposition of oriented crystals of calcium hydroxide, giving rise to weak planes along

which microcracks occur. Some methods found to improve the aggregate paste interface

were to reduce the water-cement ratio, to add small amounts of microsilica, and to coat

the aggregate faces with a reactive layer. By precoating the aggregate particles with

cement-microsilica slurry, the bond strength increased, visible through a compressive

strength increase, and the porosity at the transition zone was practically eliminated.

Regarding the aggregate in high-strength concretes, Kosmatka (2002) et al.

indicated that careful attention must be given to aggregate size, shape, surface texture,

78

mineralogy, and cleanness. In high-strength concretes, the strength of the aggregate itself

and the bond with the cement paste became very important factors. Tests have shown that

crushed-stone aggregates produce higher compressive strength in concrete than gravel

aggregate using the same size aggregate and the same cementing materials content. It has

been assumed that the increase in strength was due to a superior aggregate-paste bond

when using rough, angular, crushed material. In addition, coarse aggregates used in high-

strength concrete should be clean, that is, free from detrimental coatings of dust and clay,

since they might affect the quantity of fines and consequently the water demand and

aggregate-paste bond of a concrete mix.

Bijen and Rooij (1999) discovered that the composition of the interfacial

transition zone (ITZ) is weak and porous and influences the bulk properties of concrete,

such as strength, bonding between aggregate and cement paste, and transportability for

water and ions in the pore water. Because of its thickness (around 50 µm) and porosity, a

large fraction of the cement matrix belongs to it, fact which affects the bonding between

aggregate and the cement paste.

An investigation into the reasons for the existence of the interfacial transition zone

has revealed that a phenomenon called syneresis is responsible for the formation of a

water-rich layer around the aggregate, which weakens the aggregate-paste bond.

Syneresis takes place when a system undergoes rapid flocculation and the result is a loose

flock in which most particles tend to be linked to two or three other particles. The

structure of these flocks is tenuous and contains a substantial amount of entrapped water.

The formation of a great number of contacts leads to a contraction of the dispersed phase,

and when its volume decreases the water is spontaneously expelled from the flocks. Bijen

and Rooij (1999) have also discovered that the addition of fly ash and silica fume in

concrete decreased the thickness of the interfacial transition zone due to the pozzolanic

reaction mechanisms.

Detwiler (1988) et al. examined the orientation of calcium hydroxide crystals in

the interfacial zone and discovered that the crystals of calcium hydroxide in this zone

strictly oriented. They have seen that the axes of the crystals were perpendicular to the

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aggregate surface and the degree of such orientation grew currently with time, without

being dependent on the sizes and types of the aggregate particles.

Research regarding the influence of the surface condition of aggregate on the

cement- aggregate bond and compressive strength of concrete was carried out by Perry

and Gillott (1977). They utilized ground glass balls with diameters of 15 mm and various

degrees of roughness as aggregate particles. The research have demonstrated that the

gradually increased roughness degree of the aggregate particles constrained the process of

formation and propagation of microcracks at the interfacial transition zone, and thus

promoted improvement of the compressive strength and cement-aggregate bond of the

concrete.

However, it was seen that, in general, the strength of concrete made with

aggregate carefully selected was governed by the strength either of the cement paste or of

the bond between the paste and the aggregate particles.

2.13 Examples of Self-Compacting Concrete Applications

Since the development of the prototype of self-compacting concrete in 1988, the

use of this type of concrete in actual structures has gradually increased. Due to its special

properties, self-compacting concrete has been chosen to partially replace the conventional

concrete in a few construction projects of major importance, in Japan and Canada. The

following are some examples of construction applications, which used self-compacting

concrete.

The Bankers Hall project, which was one of the largest commercial office projects

in Calgary, Western Canada, involved the placement of self-compacting concrete in two

mat foundations with congested reinforcement (Nmai and Violetta, 1996). The amount of

concrete used was approximately 9,000 m³ and the mixture was proportioned so that it

would have very good flowing characteristics in order to satisfy the pumping and

placement requirements, because of the intricate reinforcement.

A very important application of self-compacting concrete was the two anchorages

of Akashi-Kaikyo (Straits) Bridge opened in April 1998 in Japan (Ouchi and Hibino,

2000), a suspension bridge with the longest span in the world, approx. 1,991 meters

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(Figure 2.7). The volume of the cast concrete in the two anchorages was around 2,90,000

m³. A new construction system, which made full use of the performance of self-

compacting concrete, was introduced for this. The concrete was mixed at the batching

plant beside the site and was pumped out of the plant. It was transported 200 meters

through pipes to the casting site, where the pipes were arranged in rows of 3 to 5 meters

apart. The concrete was cast from gate valves located at 5- meter intervals along the

pipes. These valves were automatically controlled so that a surface level of the cast

concrete could be maintained. In the final analysis, the use of self-compacting concrete

shortened the anchorage construction period by 20%, from 2.5 to 2 years.

Figure 2.7 Anchorage of Akashi-Kaikyo Bridge, Japan (Ouchi and Hibino, 2000).

Self-compacting concrete was also used with success for the wall of a large Liquid

Nitrogen Gas (LNG) tank belonging to the Osaka Gas Company, Japan, whose concrete

casting was completed in June 1998 (Ouchi and Hibino, 2000). In this case, the volume of

the concrete used in the tank amounted 12,000 m3 and was transported from the batching

plant using ready- mixed trucks.

A new developed construction system used for casting concrete is the so-called

sandwich structure, where concrete is filled into a steel shell (Ozawa, 1989). This sort of

structure has already been completed in Kobe, Japan, which could not have been achieved

without the development of self-compacting concrete (Figure 2.8).

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Figure 2.8 Sandwich structure applied to immersed tunnel in Kobe, Japan (Ozawa, 1989).

Nowadays, self-compacting concrete applications are limited to special cases

where it is impossible to use ordinary concretes. In these cases, the quality control relies

on several different non-standard, and mostly not fully applicable, tests supplemented by

a significant personal expertise of specialist suppliers or contractors. Due to this fact,

special measures must be taken in order for the self-compacting concrete to be considered

a standard concrete.

2.14. Criteria

Since SCC was first produced, great efforts have been made to produce

guidelines and standardised methods of specification and testing. Some of the widely

accepted guidelines are demonstrated in this section.

2.14.1. Guidelines in Japan

Originally developed in Japan, SCC was extensively investigated by several

different organizations in the 1990’s. Based on the results of each research,

recommendations were made to spread the benefits and to take the technology

of SCC into practical use. The following pioneering recommendations provided

complete information for researchers, producers and users up to that time.

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1. ‘Recommendations for mix design and construction practice of high consistence

concrete’ by the Architectural Institute of Japan in 1997.

2. ‘Recommendation for construction of self-compacting concrete’ by the Japan Society of Civil Engineers in 1998.

3. ‘Manual for manufacturing of self-compacting concrete’ by the Ready-mixed Concrete Industry Association of Japan in 1998.

These defined SCC’s characteristics and many technical terms, listed applicable

materials, provided typical methods to design and judge acceptable performance, and also

covered the requirements of production and quality control on site. They classified SCC

into three types (powder, viscosity and combined), ranked its characteristics according

to reinforcement conditions, related SCC performance with Bingham parameters

and emphasized the importance of surface moisture of aggregate on the production.

They established a solid base for further research and developments.

However, different organizations produced different recommendations, and there

were no national standards for SCC test methods.

Similarly, subsequent research on SCC that has been carried out in individual

organizations in North America and Canada has not produced any co-ordinated or national

recommendations.

2.14.2 Guidelines in Europe

SCC has been growing rapidly across Europe since mid 1990’s. As a result,

many guidelines were proposed in European countries.

The first edition of European guidelines was produced in 2002:

“Specification and Guidelines for Self-Compacting Concrete by the European Federation of Producers and Contractors of Specialist Products for Structures” by EFNARA in February 2002.

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These were based on the latest research results and abundant practical

experience. It defined SCC’s key properties (filling ability, passing ability and segregation

resistance) more clearly and specified the requirements for constituent materials and

practical applications of SCC.

It stated that besides fly ash, silica fume and GGBS, finely crushed stone,

ground glass and pigments all can be used in SCC, which encouraged studies on

more types of powders in SCC. Steel or polymer fibres could also be used

which extends SCC to wider applications. The guidelines provided typical test

combinations and acceptance criteria for SCC with a maximum aggregate size

up to 20 mm and slump flow in the range of 650~800 mm, which is more

flowable than that in Japan. Compared with those in Japan, SCCs in Europe are

higher in fine aggregate content and lower in powder content. Some tests

developed in the early stages of SCC development, e.g. U-box test and the

filling box test were described. The sieve stability test for segregation and a

value of 5~15% were recommended. They also recommended tolerances, for

example, ±50 mm for slump flow but this was based on experience not on

precise data. It did not specify mix design methods, but took an example based

on Japanese’s general purpose method and provided typical ranges of mix

proportions of SCC.

These guidelines were updated in 2005:

The European guidelines for SCC (The SCC European Project Group, 2005) and

provided state of the art information for producers, designers, users, specifiers and

purchasers.

Based on increasing amounts of research and experience, these guidelines

properly defined SCC, classified its various properties, proposed test methods

and the potential for standards, provided information of constituent materials

and overall properties, and recommended acceptance values for various

applications. It therefore has been gradually accepted by many countries beyond

Europe. The recommended classes of SCC are summarised in Table 2.4 (Testing-SCC,

2005; The Concrete Society and BRE, 2005).

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Table 2.4 European classes on SCC (Testing-SCC, 2005;

The Concrete Society and BRE, 2005)

The deformation capacity of SCC is divided into three classes based on slump

flow, SF1, SF2 and SF3 which are for low, good and high filling ability respectively.

1. SF1 is the minimum requirement for SCC. Mixes of slump flow less than

600 mm may require minor vibration in practical applications.

2. Mixes of SF2 are suitable for most practical applications. A case study

indicates that nearly half of the applications of SCCs fell in class SF1 and

35% in SF2 (Domone, 2006b).

3. Mixes SF3 usually flow very easily, rapidly and for long distances which

may be required in casting of very complex shapes or heavily reinforced

concrete elements. Particular attention must be paid to the passing ability

and segregation resistance of the concrete in this range to ensure its

homogeneity.

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Property Class SF1 550~650 SF2 660~750 SF3

Slump flow (mm) 760~850

VS1/VF1 ≤ 2 ≤ 8

Filling ability

VS2/VF2 T500 (s)

> 2 V-funnel time

(s) 9~25

PA1 ≥ 0.80 (2 bars)

Sj ≤ 15 (59 mm

bar spacing) Passing

ability

PA2

blocking ratio of L- box ≥ 0.80

(3 bars)

Step height in the J-ring (mm) Sj ≤ 15

(41 mm bar

spacing) SR1 ≤ 20 Segregation

resistance SR2 Sieve segregation

(%) ≤ 15

The deformation velocity of SCC is classified two grades:

1. T500 from the slump flow test ≤ 2 seconds or V-funnel time (tv) ≤ 8

seconds which indicates high deformation velocity;

2. T500 more than 2 seconds or tv in the range of 9~25 seconds indicating low or moderate deformation velocity.

The typical range of T500 and tv are 2~5 seconds and 5~12 seconds

respectively. It hould be noted that no segregation is the prerequisite to the

measurements of T500 and tv.

Passing ability of SCC can be classified by the blocking ratio of L-box (BR). The

minimum value of BR is recommended as 0.80. Mixes with BR ≥ 0.80 with 2 bars have

adequate passing ability for general-purpose applications with light or no reinforcement.

Mixes with BR ≥0.80 with 3 bars are suitable for placing into formwork with more closely

spaced, denser reinforcement.

The passing ability also can be classified by the step height of the J-ring (SJ):

1. SJ of 1~10 mm indicating low risk of blocking. SCC is suitable for dense reinforcement structures. No blocking was reported if SJ is less than10 mm for a SCC with V-funnel time of 4~7 seconds and slump flow of 750~800 mm (Wustholz, 2003).

2. SJ in the range of 10~20 mm indicating moderate to high risk of blocking. SCC is suitable for structures with widely spaced or no reinforcement and few obstacles.

The typical range of SJ and BR are 3~20 mm and 0.85~0.95 respectively.

Segregation index (SI) of SCC has two classes: mixes with SI ≤15 have good resistance

to static segregation; mixes with SI ≤20 show adequate resistance to static segregation. The

typical range of SI is 10~20%. The mixes of SI less than 5% may be too viscous to be self-

compacted.

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CHAPTER 3

Self-Compacting Concrete Composition

CHAPTER 3 Self-Compacting Concrete Composition

3.0 Introduction

Self-compacting concrete (SCC) is a fluid mixture, which is suitable for placing in

difficult conditions and in structures with congested reinforcement, without vibration

(Bartos, 2000). In principle, a self-compacting or self-consolidating concrete must:

1. Have a fluidity that allows self-compaction without external energy,

2. Remain homogeneous in a form during and after the placing process, and

3. Flow easily through reinforcement

The technology of SCC is based on adding or partially replacing Portland cement

with amounts of fine material such as fly ash, blast furnace slag, and silica fume without

modifying the water content compared to common concrete. This process changes the

rheological behavior of the concrete (Johansen and Hammer, 2002).

Generally, SCC has to have a proper flowability and viscosity, so that the coarse

aggregate can float in the mortar without segregating. To achieve a balance between

flowability and stability, the total content of particles finer than the 150 µm has to be

high, usually about 520 to 560 kg/m³ (880 to 950 lb/yd³) (Kosmatka et al., 2002). Self-

compacting concrete is very sensitive to fluctuation in water content; therefore, stabilizers

or viscosity-modifying agents such as polysaccharides are used. Figure 3.1 shows an

example of mix proportions used in SCC as compared to a regular concrete mix.

In Japan, self-compacting concretes are divided into three different types

according to the composition of the mortar:

1. Powder type

2. Viscosity-modifying agent (stabilizer) type

3. Combination type

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Figure 3.1 Materials used in regular concrete and self-compacting concrete

by absolute volume (Kosmatka et al., 2002).

For the powder type, a high proportion of fines produce the necessary mortar

volume, whilst in the stabilizer type, the fines content can be in the range admissible for

vibrated concrete. The viscosity required to inhibit segregation will then be adjusted by

using a stabilizer (Kosmatka et al., 2002). The combination type is created by adding a

small amount of stabilizer to the powder type to balance the moisture fluctuations in the

manufacturing process.

However, after completion of proper proportioning, mixing, placing, curing, and

consolidation, hardened concrete becomes a strong, durable, and practically impermeable

building material that requires no maintenance.

3.1 Portland Cement

Portland cement concrete is foremost among the construction materials used in

civil engineering projects around the world. The reasons for its often use are varied, but

among the more important are the economic and widespread availability of its

constituents, its versatility and adaptability, as evidenced by the many types of

construction in which it is used, and the minimal maintenance requirements during

service (Mindess et al., 2003). Concrete is unique among major construction materials in

that it is generally designed specifically for a particular project using locally available

materials (Lay, 1990).

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Regarding its composition, concrete is considered a composite material made of

coarse granular material (the aggregate or filler) embedded in a hard matrix of material

(the cement or binder) that fills the space between the aggregate particles and glues them

together (Mindess et al., 2003). Aggregates can be obtained from many different kinds of

materials, but the most used materials from the nature are common rocks.

There is a wide variety of cements that are used to some extent in the construction

and building industries, or to solve special engineering problems (Bentz, 2001). The

chemical compositions of these cements can be quite diverse, but by far the greatest

amount of concrete used today is made with Portland cements (Atkins, 2003). In

principle, the manufacture of Portland cement is very simple and relies on the use of

abundant raw materials. An intimate mixture, usually of limestone and clay, is heated in a

kiln to 1400 to 1600°C (2550 to 2900°F), which is the temperature range in which the two

materials interact chemically to form the calcium silicates. High-quality cements require

raw materials of adequate purity and uniform composition.

Limestone (calcium carbonate) is the most common source of calcium oxide,

although other forms of calcium carbonate, such as chalk, shell deposits, and calcareous

muds, are used (Mindess et al., 2003). Usually, iron-bearing alumino-silicates are

invariably used as the primary source of silica, but clays or silts are preferred since they

are already in a finely divided state.

A typical chemical composition of an ordinary Portland cement is given in Table

3.1. It can be noted that the quantities do not add up to 100%, the missing percentages

being accounted for by impurities.

Table 3.1 Typical composition of ordinary Portland cement (Mindess et al., 2003).

Chemical Name Chemical Formula

Shorthand Notation

Weight Percent

Tricalcium silicate 3CaO.SiO2 C3S 55

Dicalcium silicate 2CaO.SiO2 C3S 18

Tricalcium aluminate 3CaO.Al2O3 C3A 10

Tricalcium aluminoferrite 4CaO.Al2O3.Fe2O3 C4AF 8

Calcium sulfate dihydrate(gypsum) CaSO4.2H2O CSH2 6

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When Portland cement is mixed with water, its constituent compounds undergo a

series of chemical reactions that are responsible for the eventual hardening of concrete.

Reactions with water are designated hydration, and the new solids formed on hydration

are collectively referred to as hydration products.

Figure 3.2 shows schematically the sequence of structure formation as hydration

proceeds. This involves the replacement of water that separates individual cement grains

in the fluid paste (Figure 3.2a) with solid hydration products that form a continuous

matrix and bind the residual cement grains together over a period of time, as illustrated in

Figure 3.2(b-d).

The calcium silicates provide most of the strength developed by Portland cement.

C3S provides most of the early strength (in the first three to four weeks) and both C3S

and C2S contribute equally to ultimate strength (Neville, 1993). In commercial cements,

the calcium silicates contain small impurities of some oxides present in the clinker, which

have a strong effect on the properties of the calcium silicate hydrate (C-S-H). Calcium

silicate hydrate is essentially amorphous and develops as a mass of extremely small

irregular particles of indefinite morphology. The particles are so small that they can be

studied only by scanning electron microscope, and even cannot be completely resolved

(Mindess et al., 2003).

Figure 3.2 Microstructural development in Portland cement pastes (Mindess et al., 2003).

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The hydration reactions of the two calcium silicates are very similar, differing

only in the amount of calcium hydroxide formed as seen in the following equations

(Mindess et al., 2003).

2C3S + 11H → C3S2H8 + 3CH (3.1) Tricalcium water calcium calcium

Silicate silicate hydroxide Hydrate 2C2S + 9H → C3S2H8 + CH (3.2) Dicalcium water calcium calcium

Silicate silicate hydroxide Hydrate

Calcium Silicat Hydrate or C3S2H8 is called calcium silicate hydrate and is the

principal hydration product. The formula C3S2H8 is only approximate because the

composition of this hydrate is actually variable over quite a wide range.

In Portland cement, the hydration of tricalcium aluminate - C3A - involves

reactions with sulfate ions that are supplied by the dissolution of gypsum, which is added

to temper the strong initial reaction of C3A with water that can lead to flash set. The

primary initial reaction of C3A is as follows:

C3A + 3C

S H2 + 26H → C3A

S 3H32 (3.3) Tricalcium gypsum water ettringite aluminate

Where

S is equivalent to SO3 and ettringite is a stable hydration product only while there

is an ample supply of sulfate available.

The ferrite phase – C4AF - forms similar hydration products to C3A, with or

without gypsum, but the reactions are slower and involve less heat. C4AF seldom

hydrates rapidly enough to cause flash set and gypsum retards C4AF hydration even more

drastically than it does C3A. Usually, changes in the composition of the ferrite phase

affect only the rate of hydration and when the iron content is raised, hydration becomes

slower.

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3.2 Aggregates

Generally, aggregates occupy 70% to 80% of the volume of concrete and have an

important influence on its properties. They are granular materials, derived for the most

part from natural rock (crushed stone, or natural gravels) and sands, although synthetic

materials such as slags and expanded clay or shale are used to some extent, mostly in

lightweight concretes (Mindess et al., 2003). In addition to their use as economical filler,

aggregates generally provide concrete with better dimensional stability and wear

resistance. Although aggregate strength can play sometimes an important role, for

example in high-strength concretes, for most applications the strength of concrete and

mix design are essentially independent of the composition of aggregates. However, in

other instances, a certain kind of rock may be required to attain certain concrete

properties, e.g., high density or low coefficient of thermal expansion (Neville, 1993).

In order to obtain a good concrete quality, aggregates should be hard and strong,

free of undesirable impurities, and chemically stable (Garber and Hoel, 1988). Soft and

porous rock can limit strength and wear resistance, and sometimes it may also break

down during mixing and adversely affect workability by increasing the amount of fines.

Rocks that tend to fracture easily along specific planes can also limit strength and wear

resistance (Neville, 1993). Aggregates should also be free of impurities like silt, clay, dirt,

or organic matter. If these materials coat the surfaces of the aggregate, they will isolate

the aggregate particles from the surrounding concrete, causing a reduction in strength.

Silt, clay and other fine materials will increase the water requirements of the concrete,

and the organic matter may interfere with the cement hydration.

3.3 Blast Furnace Slag

Slags are by-products from metallurgical processes, either from production of

metals from ore or refinement of impure metals. They are derived from lime-based

inorganic fluxes used to extract impurities from metals, which solidify on cooling (St

John, 1998). The slags used in concrete come from the blast furnace production of iron

from ore and not from metals, and are rich in lime, silica, and alumina.

Reactivities can vary widely from slag to slag and there is not a reliable

quantitative relationship between slag composition and its reactivity (Kosmatka et al.,

92

2002). ASTM C 989 classifies slag by its increasing level of reactivity as Grade 80,100,

or 120. Blast furnace slag reacts slowly with water, so that it may take several months for

a pure slag concrete to reach the equivalent 28-day strength of a concrete made with

Portland cement. This is thought to be due to the presence of impervious coatings of

amorphous silica and alumina that form around slag particles early in the hydration

process (St John, 1998). Slag needs to be activated by alkaline compounds, which can be

either soluble sodium salts, like NaOH, Na2CO3, or NaSiO3, or calcium hydroxide

Ca(OH)2, but they are most commonly activated by Portland cement, where Ca(OH)2

formed during hydration is the principal activator. Although only 10-20% of cement is

needed for activation, slag-cement blends usually contain much more cement. The slag,

which is ground to less than 45 microns, has a surface area fineness of about 40.77 to

61.16 m²/N and its relative density is in the range of 2.85 to 2.95.

Ground granulated blast-furnace slag, when used in general purpose concrete in

North America, commonly constitutes between 30% and 45% by mass of the cementing

material in the mix (Mindess et al., 2003), even though some slag concretes have a slag

component of 70% or more of the cementitious material. It usually decreases water

demand by 1% to 10%, depending on dosage, and due to its smooth surface

characteristics and fineness, it increases pumpability, workability and reduces bleeding of

cast concrete. The use of slag will generally retard the setting time of concrete, fact,

which is advantageous during hot weather, because it allows more time to place and

finish the concrete, but has a negative effect on the early strength of it. However, the 28-

days strength is sometimes improved but, because of the slow pozzolanic reaction,

continuous wet curing and favorable temperatures may need to be provided for longer

periods than normally required. Because additional calcium silicate hydrate forms when

slag is added to the fresh concrete, its permeability will be reduced and the durability will

be increased. Ground slag also improves the resistance of concrete to sulfate attack and

significantly reduces alkali-silica reactivity.

3.4. Fly Ash

Fly ash is one of the most extensively used by-product materials in the

construction field resembling Portland cement (Pfeifer, 1969). It is an inorganic,

noncombustible, finely divided residue collected or precipitated from the exhaust gases of

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any industrial furnace (Halstead, 1986). Most of the fly ash particles are solid spheres and

some particles, called cenospheres, are hollow (Figure 3.3) (Kosmatka et al., 2002). Also

present are plerospheres, which are spheres containing smaller spheres inside. The

particle sizes in fly ash vary from less than 1 µm to more than 100 µm with the typical

particle size measuring under 20 µm. Their surface area is typically 30.58 to 50.97 m²/N,

although some fly ashes can have surface areas as low as 20.38 m²/N and as high as

71.35m²/N. Fly ash is primarily silicate glass containing silica, alumina, iron, and

calcium. The relative density or specific gravity of fly ash generally ranges between 1.9

and 2.8 and the color is generally gray or tan (Halstead, 1986).

Figure 3.3 SEM micrograph of fly ash particles (Kosmatka et al., 2002).

Fly ashes are subdivided into two classes, F and C, which reflect the composition

of the inorganic fractions. Class F fly ashes are produced from bituminous and

subbituminous coals and contain as active components aluminosilicate glasses, whereas

class C fly ashes derive from the lignitic coals and contain calcium aluminosilicate

glasses with the high levels of calcium oxide, comprised in the glassy fraction (Mindess

et al., 2003). Although their usage is mainly economic (fly ash is less than one-half the

price of cement), the addition of fly ash has many technical benefits.

Many class C ashes when exposed to water will hydrate and harden in less than 45

minutes. In concretes, class F fly ash is often used at dosages of 15% to 25% by mass of

cementitious material and class C fly ash is used at dosages of 15% to 40% (Halstead,

1986). Dosage varies with the reactivity of the ash and the desired effects on the concrete

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(Mindess et al., 2003). Because of their spherical morphology, when using fly ash

admixtures as replacement for cement, workability and long-term strengths are achieved

in concretes. In such cases, they act like small balls to reduce interparticle friction. Fly

ashes are also used in concrete mixes in order to reduce the heat of hydration,

permeability, and bleeding. The durability is improved by providing a better sulfate

resistance, control of the alkali-silica reaction, decreased chloride diffusion, and reduction

of leaching from the reduction in calcium hydroxide (which is the most soluble of the

hydration products) and changes in pore structure. However, there are some

disadvantages related to the use of fly ash regarding the reduced air-entraining ability and

early strength due to the influence of residual carbon from the ash (Gebler and Klieger,

1986).

Fly ashes exhibit pozzolanic activity. The American Society for Testing and

Materials (ASTM) defines a pozzolan as "a siliceous or siliceous and aluminous material

which in itself possesses little or no cementitious value but which will, in finely divided

form and in the presence of moisture, chemically react with calcium hydroxide at

ordinary temperature to form compounds possessing cementitious properties." Fly ashes

contain metastable aluminosilicates that will react with calcium ions, in the presence of

moisture, to form calcium silicate hydrates.

More than 2000 years ago, Roman builders recognized that certain volcanic ashes

were capable of forming effective cements when combined with lime. The Romans

widely exploited this pozzolanic property of volcanic ashes, and many structures from the

Roman period are still intact. The modern recognition that fly ash is pozzolanic has led to

its use as a constituent of contemporary Portland cement concrete. Typical characteristics

of good quality fly ash are as follows:

1. fineness (Blaine’s): 32.62 m2/N (Min.)

2. Lime Reactivity: 4.5 N/mm2 (Min.)

3. Loss on ignition: 5% (Max.)

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3.5 Silica Fume

Silicon, ferrosilicon and other silicon alloys are produced by reducing quartz, with

coal and iron or other ores, at very high temperatures (2000°C) in electric arc furnaces (St

John, 1998). Some silicon gas or fume is produced in the process, which reaches the top

of the furnace with other combustion gases, where it becomes oxidized to silica in contact

with the air and then condenses as < 0.1 µm to 1 µm spherical particles of amorphous

silica. This material is usually known as silica fume. It is also referred to as microsilica or

more properly, condensed silica fume (csf). Silica fume is an ultra fine powder, with

individual particle sizes between 50 and 100 times finer than cement, comprising solid

spherical glassy particles of amorphous silica (85-96 percent SiO2). However, the

spherical particles are usually agglomerated so that the effective particle size is much

coarser. Silica fume used in concrete derives from the manufacture of ferrosilicon alloys

and is modified by densification, micropelletization or slurrification, to facilitate

transportation and handling (St John, 1998). Condensed silica fume has a surface area of

about 2038 m²/N and a relative density generally in the range of 2.20 to 2.5 (Kosmatka et

al., 2002).

The pozzolanic reactions take place when silica fume is added to the concrete

mixture, and the amorphous silica, which is the major component of the pozzolan, reacts

with calcium hydroxide formed from the hydration of the calcium silicates with the

resulting product being a calcium silicate hydrate (C-S-H) (Mindess et al., 2003). Usually,

after microsilica is being added to the concrete mix, the matrix of microsilica concrete

becomes very dense (St John, 1998). This denseness effect has been attributed to the

extreme fineness of microsilica, due to the fact that 50,000 to 100,000 microspheres exist

for every cement grain, allowing microsilica hydration products to infill the water spaces

usually left within the cement hydrates, as showed in Figure 3.4. Silica fume is used in

amounts between 5% and 10% by mass of the total cementitious material, in applications

where high degree of impermeability and high compressive strength are needed in

concrete. In some situations, the water demand of concrete containing silica fume

increases with increasing amounts of silica fume, unless a water reducer or plasticizer is

used Some lean mixes may not experience an increase in water demand when only a

small amount(less than 5%) of silica fume is present.

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Figure 3.4 Effect of microsilica in densifying the concrete mix - comparison between conventional and microsilica concretes (St John, 1998).

Microsilica is also very effective in reducing both bleeding and segregation. It

may contribute to stickiness of a concrete mixture, adjustments, including the use of high-

range water reducers, may be required to maintain workability and permit proper

compaction and finishing.

The use of silica fume generally aids the pumpability of concrete and is most

effective in lean mixtures. Because of its low bleeding characteristics, concrete containing

silica fume may exhibit an increase in plastic shrinkage cracking (Mindess et al., 2003).

The problem may be avoided by ensuring that such concrete is protected against drying,

both during and after finishing. With proper proportioning and material selection, silica

fume can improve the durability of concrete, its resistance to sulfate attack, and the early

strength development (Ramachandran, 1984).

3.6 Superplasticizers

Superplasticizers (high-range water-reducers) are low molecular-weight, water-

soluble polymers designed to achieve high amounts of water reduction (12-30%) in

concrete mixtures in order to attain a desired slump (Gagne et al., 2000). These

admixtures are used frequently to produce high-strength concrete (> 50 MPa), since

workable mixes with water-cement ratios well below 0.40 are possible (Whiting, 1979).

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They also can be used without water reduction to produce concretes with very

high slumps, in the range of 150 to 250 mm. At these high slumps, concrete flows like a

liquid (Figure 3.5) and can fill forms efficiently, requiring very little vibration. These

highly workable mixtures are called flowing concretes and require slumps to be in excess

of 190 mm.

Figure 3.5 Effect of superplasticizer on cement: (a) Cement and water; (b) Cement, water, and superplasticizer (Ramachandran, 1984).

Water-reducing admixtures are negatively charged organic molecules that adsorb

primarily at the solid-water interface, whereas solid particles carry residual charges on

their surfaces, which may be positive, negative, or both (Russell, 1983). In cement paste,

opposing charges on adjacent particles of cement can exert considerable electrostatic

attractions, causing the particles to flocculate (Figure 3.6a). A considerable amount of

water is tied up in these agglomerates and adsorbed on the solid surfaces, leaving less

water available to reduce the viscosity of the paste and hence that of the concrete.

Molecules of the water-reducing admixtures interact to neutralize these surface charges

and cause all surfaces to carry uniform charges of like sign (Mindess et al., 2003).

Particles now repel each other, rather than attract, and remain fully dispersed in the paste

(Figure 3.6b), thus, most of the water is available to reduce the viscosity of the paste and

of the concrete. Because superplasticizers have air-detraining properties, an air-

entraining agent must be added to the concrete to get a stable air void system before a

superplasticizer is added (Gagne et al., 1996).

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Figure 3.6 Dispersing action of water-reducing admixtures: (a) flocculated paste; (b)

dispersed paste (Mindess et al., 2003).

Some high-range water-reducing admixtures can retard final set by one to almost

four hours and if prolonged setting times are not convenient, the admixture can be

combined with an accelerating admixture to counteract the retarding tendencies or even to

provide some net acceleration of setting. When water-reducing admixtures are used in

concrete mixtures, some increases in compressive strength can be anticipated and these

increases can be observed in as early as one day if excessive retardation does not occur. It

is generally agreed that increases in compressive strength are up to 25% greater than

would be anticipated from the decrease in water-cement ratio alone. Probably, this

reflects the development of a uniform microstructure when the cement is dispersed

(Ozyildirim, 2003). The reduction of the water-cement ratio and the creation of a more

uniform pore structure means that the permeability of concrete can be reduced by the use

of superplasticizers, along with a general improvement of durability.

3.7 Viscosity-Modifying Admixtures

Viscosity modifiers are high molecular-weight, water-soluble polymers used to

raise the viscosity of water. Such compounds increase the cohesiveness of fresh concrete,

reducing its tendency to segregate and bleed (Ferraris, 1999). They work by attaching

their long molecules to the water molecules, process which inhibits the free displacement

of water. These admixtures are helpful in improving the properties of lean concretes with

low cement contents, concrete placed under water, and concretes or grouts that are placed

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by pumping. In the latter case, they reduce pumping pressures through improved

lubricating properties, as well as reducing segregation tendencies. When compounds in

this category are used to improve the cohesiveness of concrete being placed underwater,

they are classified as antiwashout admixtures. Viscosity-modifying admixtures are added

in concretes used in places with extreme congestions due to reinforcement configurations

or unusual geometry forms, where fluid but cohesive concrete is required in order to resist

bleeding and segregation (Dodson, 1990).

The materials commonly used are polyethylene oxides, cellulose ethers, natural

gums, and polyacrylamides or polyvinyl alcohol. Other materials used are finely divided

solids such as clays and lime, but they tend to reduce the strength of the concrete and for

this reason is primarily used in grouts when strength is not of major importance. 3.8. Fibres

SCC spreads homogenously due to its own weight, without any additional

compaction energy and does not entrap air. The main characteristics of SCC in the fresh

state are filling ability, passing ability and segregation resistance. Fibres have been

produced in a wide range of materials, shapes and characteristics. They improve the

performance (strength and toughness) of brittle cement based materials by bridging

cracks, transmitting stress across a crack and counteracting the crack growth. The steel

fibre is the most common fibre type in the building industry; other fibre types like plastic,

glass and carbon fibres contribute with a smaller part to the market. Dependent on the

type and the content of the fibres the workability of concrete can be significantly affected.

With fibres concrete becomes more ductile, less material has environmental benefits and

more slender structures require less reinforcement. Fibres improve the abrasion and

impact resistance; applications with fibres can be economical and bar reinforcement can

be replaced. The production process can be facilitated with SCC. SCFRC can be

combined with prestressing strands, used for remote casting, to enhance the fire

resistance, to obtain smaller crack widths and to improve the durability.

Composing SCFRC with defined performance in the fresh and the hardened state

is a complex task; several design tools are described in this paper. SCFRC can be

optimized for various purposes to apply the highest possible fibre content, to obtain the

best performance cost ratio, to design the granular skeleton for the highest packing

density and/or to produce concrete with the lowest possible costs.

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3.8.1. The effect of fibres on workability Fibres affect the characteristics of SCC in the fresh state. They are needle-like

particles that increase the resistance to flow and contribute to an internal structure in the

fresh state. Steel fibre reinforced concrete is stiffer than conventional concrete. In order to

optimize the performance of the single fibres, fibres need to be homogeneously

distributed; clustering of fibres has to be avoided. The effect of fibres on workability is

mainly due to four reasons First, the shape of the fibres is more elongated than the

aggregates, the surface area at the same volume is higher. Second, stiff fibres change the

structure of the granular skeleton, whereas flexible fibres fill the space between them.

Stiff fibres push apart particles that are relatively large compared to the fibre length,

which increases the porosity of the granular skeleton. Third, the surface characteristics of

fibres differ from that of cement and aggregates, e.g. plastic fibres might be hydrophilic

or hydrophobic. Finally, steel fibres often are deformed (i.e. have hooked ends or are

wave-shaped) to improve the anchorage between them and the surrounding matrix. The

size of the fibres relative to the aggregates determines their distribution. To be effective in

the hardened state it is recommended to choose fibres not shorter than the maximum

aggregate size [Johnston, 1996; Vandewalle,1993]. Usually, the fibre length is 2-4 times

that of the maximum aggregate size.

3.8.2. Maximum fibre content

The maximum fibre content, at which a self-compacting concrete can be

produced, depends on the fibre type, the mixture composition, the mixing process and the

characteristics of the concrete in the fresh state. For plain concrete, the compaction

technique also affects this parameter. In order to determine the maximum fibre content of

SCFRC, different series of mixtures were tested and the fibre content was increased in

steps of 20 kg/m³. The ‘maximum fibre content’ is defined to be the highest possible

amount of steel fibres, which can be added to SCC. SCFRC is self-compacting below this

fibre content. The following criteria were applied to determine the maximum fibre

content a slump flow of at least 600 mm and a homogenous distribution of SCC and

fibres along the flow (slump flow test).

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Three observations of the slump flow indicated that the maximum fibre content

was surpassed. Fibre types having a large surface area decrease the flowability of SCC.

The fibres are homogenously distributed but the contour of the flownout concrete is not

round. This flow pattern often corresponds with a flow diameter smaller than 600 mm.

Long fibres and/or large aggregates tend to cluster along the flow; the flow diameter is

barely affected.

3.9. Concrete Mix and Tests

The concrete plant made different mixes, all with 0.8 volume-percent 60 mm steel

fibers. Segregation was a challenge and the best mix, shown in Table 3.2 was used at the

building site. The mix design of fiber reinforced concrete (FRSCC) was done using the

particle matrix model, (1). The concrete was delivered with a slump flow of 725 mm. A

blend of normal and rapid cement made the concrete sticky and less prone to segregation.

Condensed Silica Fume (CSF) was necessary to decrease the segregation of the SCC at

the building site, and a test program with 5.0 %, 7.5 % and 10 % CSF of cement weight

was carried out.

The mix with 7.5 % CSF was used in the delivery to SIBO Village. The addition

of a copolymer based superplasticizing agent was normally done at the ready-mix plant,

and it was observed that the slump flow measure increased by 20 to 30 mm during the

transport to site. However it was sometimes necessary to add copolymer at the building

site as well. The type of copolymer was also tested and there was an effect of segregation

of steel fibers. Glenium 27 from Degussa gave a high slump flow without the segregation

of the steel fibers.

The main reason for using an Air Entraining Agent was to increase the matrix plus

air volume. Preliminary tests revealed that to make FRSCC the matrix volume had to be

40-50 l/m³ higher than for ordinary SCC. Dispersed fine air bubbles made the concrete

flow better without segregation. Air bubbles have only one fourth of the effect of

increasing the cement paste, but cost less and decrease the water content, (2). Five percent

air (50 liters) corresponds to a paste volume of 12 to 15 l/m³. Further crushed fine sand (0

– 0.5 mm), with 15% filler was used to increase the matrix volume as well as the fine

sand content.

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Table 3.2: Concrete composition, dry materials

Concrete Composition N/m³ l/m³ Norcem Anlegg, CEM I 52.5 N-LA (HSC) 25.99 82 Norcem Industri, CEM I 42.5 RR (RPC) 9.28 29 Condensed silica fume from Elkem 2.65 12 Free water 21.61 212 Absorbed water 1.73 Fine aggregate, 0-8 mm from Vang 86.65 Fine crushed sand, 0-0.5 mm from Feiring 14.98 Crushed aggregate, 8-16 mm 63.20 Copolymer, Glenium 27, Degussa 0.68 AEA Scanair 1:9 0.86 Volume Bekeart RC65/60 steel fiber 6.73 8 Paste volume 340 Matrix 375 Matrix plus 5 % air 425 Nominal concrete density excluded fibers 224.57

In total the FRSCC contained 340 l/m³ paste, 375 l/m³ matrix and 425 l/m³ matrix

plus air. This was necessary to make the steel fiber flow.

Laboratory methods Both the L-box and the slump flow were used. Due to

relatively high fiber content the L-box did not operate successfully. The slump flow,

based on the ordinary slump cone test, was more successful, but it was urgent to lift the

cone vertically as fast as possible.

Verification of the fiber content a piece of equipment with a simple design was

made for controlling the steel fiber content. A volume of 10 liters concrete was used. The

concrete is poured on a sieve and washed down an inclined plate with a fish-bone pattern.

During this process the steel fibers are removed with a magnet held by hand. The

removed steel fibers were in good accordance with the dosed quantities of fiber.

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CHAPTER 4

Design of a Suitable SCC Mix

CHAPTER 4 Design of a Suitable SCC Mix

4.0 Materials for Self-Compacting Concrete:

4.0.1. Cement Ordinary Portland cement, 43 or 53 Grade can be used care is taken that it is

freshly produced and from a single producer.

4.0.2. Aggregates:

4.0.2.1. Fine aggregate: Fine aggregates can be natural or manufactured. The grading must be uniform

through out the work. The moisture content or absorption characteristics must be closely

monitored, as quality of SCC will be sensitive to such changes. Particles smaller than

0.125mm are considered as Fines, which contribute to the fine content.

4.0.2.2. Coarse aggregate:

Aggregate of size 10-12mm is desirable for structures having congested

reinforcement. Wherever possible aggregates of size higher than 20mm could also be

used. Well-graded cubical or rounded aggregates are desirable. Aggregates should be of

uniform quality with respect to shape and grading.

4.0.3. Admixtures: Admixtures are defined as, other than cement, aggregate and water which is added

to the concrete before or after mixing it.

4.0.3.1. Mineral Admixtures:

1. Ground Granulated Blast Furnace Slag (GGBS): GGBS, which is both

cementitious, and puzzolonic material may be added to improve rheological

properties.

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2. Silica Fume: Silica fume may be added to improve the mechanical properties of

SCC.

3. Stone Powder: Finely crushed limestone, dolomite or granite may be added to

increase the powder content. The fraction should be less than 125 micron.

4. Fibres: Fibres may be used to enhance the properties of SCC in the same way as

for normal concrete.

Plain concrete possesses a very low tensile strength, limited ductility and little

resistance to cracking. Internal micro cracks are inherently present in the concrete and its

poor tensile strength is due to the propagation of such micro-cracks, eventually leading to

the brittle fracture of the concrete.

In the past, attempts have been made to impart improvement in tensile properties

of concrete members by way of using conventional reinforced steel bars and also by

applying restraining techniques. Although both these techniques provide tensile strength

to the concrete members, they however, do not increase the inherent tensile strength of

concrete itself.

It has been recognized that the addition of small, closely spaced and uniformly

dispersed fibers to concrete would act as crack arrester and would substantially improve

its static and dynamic properties.

Fiber reinforced concrete can be defined as a composite material consisting of

mixtures of cement, mortar or concrete and discontinuous, discrete, uniformly dispersed

suitable fibres.

Glass fibre is a recent introduction in making fibre concrete. It has very high

tensile strength 1020 to 4080N/mm2

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4.0.3.2. Fly ash:

Fly ash is a by-product of the combustion of pulverized coal in thermal power

plants. The dust-collection system removes the fly ash, as a fine particulate residue, from

the combustion gases before they are discharged into the atmosphere.

Fly ash particles are typically spherical, ranging in diameter from <1 µm up to 150

µm. The type of dust collection equipment used largely determines the range of particle

sizes in any given fly ash.

Fly ashes exhibit pozzolanic activity. The American Society for Testing and

Materials (ASTM) defines a pozzolan as "a siliceous or siliceous and aluminous material

which in itself possesses little or no cementitious value but which will, in finely divided

form and in the presence of moisture, chemically react with calcium hydroxide at

ordinary temperature to form compounds possessing cementitious properties." Fly ashes

contain metastable aluminosilicates that will react with calcium ions, in the presence of

moisture, to form calcium silicate hydrates.

More than 2000 years ago, Roman builders recognized that certain volcanic ashes

were capable of forming effective cements when combined with lime. The Romans

widely exploited this pozzolanic property of volcanic ashes, and many structures from the

Roman period are still intact. The modern recognition that fly ash is pozzolanic has led to

its use as a constituent of contemporary Portland cement concrete.

Typical characteristics of good quality fly ash are as follows:

1. fineness (Blaine’s): 32.62 m2/N (Min.)



4.0.3.2.1. Advantages of Fly ash:

Cement production requires huge amounts of energy. Partial replacement of

cement with fly ash is economical. In the case of mass concreting and large-scale works,

it is proved to be most economical. It is practically revealed that up to 40 to 50% cement

is replaced and the desired strengths are achieved.

106

1. It reduces the water requirement and improves paste flow behavior.

2. Improves workability

3. Increases cohesion, pumpability, finish ability and flow properties

4. Reduces heat of hydration, Segregation and bleeding

5. Cracking

6. Enhances durability

7. High resistance against chemical attack by sulphates, soil and sea water

8. Improves serviceability of concrete

9. Less shrinkage and creep

10. Improves resistance against freezing and thawing.

4.0.3.2.2 Environmental Protection:

Fly ash poses threat to the environment when proper attention is unpaid. A large

quantity of fly ash is generated from thermal power plants and some other industries. It is

dumped in yards and poses problems in and around.

By the use of fly ash in concrete, a serene, salubrious and cogenial atmosphere is

maintained. It will eliminate air pollution of ambient air, reduces greenhouse effect and

control dust nuisance.

1. Cost of fly ash is very less

2. Replaces cement to some extent

3. Utilization of a waste product

4. Reduces pollution

5. Saves energy in producing cement

4.0.3.2.3. Areas of usage of Fly ash:

It is a waste product of thermal power plants. It is suitable to use in concrete

because of its inherent properties. It is having pozzolonic and cementations properties.

Fly ash is widely used to provide

1. Mass concrete

2. Structural concrete

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3. High strength concrete

4. Light weight concrete

It is an appropriate quantity may be added to improve the quality and durability of SCC.

4.0.3.2.4. Chemical Admixtures:

A ‘Chemical admixture’ is any chemical additive to the concrete mixture that

enhances the properties of the concrete in the fresh or hardened state. ACI-116R [2000]

defines the term admixture as ‘a material other than water, aggregates, hydraulic cement,

used as an ingredient of concrete or mortar, and added to the batch immediately before or

during its mixing’.

A number of types of Chemical admixtures are used for concrete. The general

purpose chemicals include those that reduce water demand for a given workability(‘water

reducers’),those entraining air in the concrete for providing resistance to freezing and

thawing action(‘air entrainers’),and those chemicals that control the setting time and

strength gain rate of concrete(‘accelerators’ and ‘retarders’).Apart from these chemicals,

there are others for special purposes-namely, Viscosity Modifying Agents, Shrinkage

Reducing Chemicals, Corrosion inhibiting admixtures, and alkali-silica reaction

mitigating admixtures.

A ‘water reducing chemical’, as the name implies, is used to reduce the water

content of a concrete mixture while maintaining a constant workability. The resultant

effect of the reduced water content is the increased strength and durability of concrete.

However, water reducers may also be employed to ‘plasticize’ the concrete,i.e.make

concrete flowable.In this case, the water content(or water to cement ratio)is held constant,

and the addition of the admixtures makes the concrete flow better, while the compressive

strength(which is a function of water to cement ratio),is not affected. Another use of

water reducers is to low the amount of cement (since water is proportionally reduced)

without affecting both strength and workability. This makes the concrete cheaper and

environmentally friendly, as less cement is consumed.

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Water reducers are classified broadly into two categories: Normal and High

Range Water Reducers. The normal water reducers are also called ‘plasticizers’, while the

high range water reducers are called ‘superplasticizers’. While the normal water reducers

can reduce the water demand by 5-10%, the high range water reducers can cause a

reduction of 15-40%.

4.0.4. Superplasticizer:

In present days Superplasticizers are powerful enough to keep a concrete mix

highly workable for more than one hour with much less water.

4.0.4.1. Advantages of Superplasticizer: 1. Improved workability enables easy placing and compaction

2. Increases strength at faster rate

3. Improves quality of concrete and make durable

4. Highly cohesive concrete production thereby less segregation and bleeding

5. Enhances resistance to freezing and thawing

6. Produces high workability concrete requiring little or no vibration during

placing

7. Produces high strength, high grade concrete, by substantial reduction in water

resulting in low permeability and high early strength.

4.0.4.2. Dosage:

The optimum dosage is best determined by site trails with the concrete mix

which enables the effects of workability, strength gain or cement reduction to be

measured. As a guide the rate of addition is generally in the range of 1 to 4 lit per cubic

meter of concrete

4.0.5. Viscosity modifying Agent (VMA):

Today’s concrete has to fulfill a wide range of requirements in both the fresh and

hardened state. Concrete can be pumped both vertically and horizontally over a long

distance even with high flow, self-compacting properties.

109

The more advanced the concrete becomes (self-compacting concrete, high

performance concrete, underwater concrete, pumpable concrete, etc.) the more sensitive it

gets to material variations and fluctuations during production and placing. Production

sites are often faced with problems caused by variations in the moisture content or

grading of the aggregates and with fluctuations in the fine content of the sand. Viscosity

Modifying Admixtures can be used to produce concrete with better robustness against the

impact of variations in the concrete constituents and in site conditions, making it easier to

control and friendlier for the producer and the user.

If the test results between different batches or loads vary considerably, the cause

can be the variation of:

1. Cement characteristics,

2. Addition characteristics,

3. Grading of aggregates,

4. Moisture content of aggregates,

5. Temperature,

6. Mixing procedure, time of testing

The use of a viscosity-modifying agent can suppress some of these variations to a

certain extent.

The inclusion of VMA ensured the homogeneity and the reduction of the

tendency of highly fluid mix to segregate Gelinium-2 VMA is used for this work. The use

of a VMA gives more possibilities of controlling segregation when the amount of powder

is limited.

GLENIUM-2 is a premier ready-to-use, liquid, organic, viscosity-modifying

admixture (VMA) specially developed for producing concrete with enhanced viscosity

and controlled rheological properties. Concrete containing GLENIUM-2 admixture

exhibits superior stability and controlled bleeding characteristics, thus increasing

resistance to segregation and facilitating placement.

Reaching the right balance between fluidity and resistance to segregation

apparently opposing properties – is essential for this type of mix. This balance is lacking

when the fluidity of the concrete is obtained by adding water. Although a superplasticiser

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admixture gives high fluidity, alone it does not guarantee the necessary properties to

ensure a good degree of self-compacting. That is why GLENIUM-2 is a fundamental

admixture.

An overdose of VMA could make the fresh concrete mix too cohesive and slow the

placing rate. This effect can usually be overcome by increasing the superplasticizer

content.

4.0.5.1. Advantages: 1. Increased viscosity & thixotropic properties

2. Improved stability during transport & placing

3. Controlled bleeding

4. Reduced segregation, even with highly fluid mix

5. Enhanced pumping and finishing

6. Reduced sagging – dimensional stability

7. Enables flexibility in mixture proportioning.

GLENIUM STREAM 2 is chloride-free and compatible with all cements.

Table.4.1. Typical Properties of Glenium-2:

4.0.5.2. Dosage:

GLENIUM-2 is dosed at the rate of 50 to 500 ml/100 kg of cementitious material.

Other dosages may be recommended in special cases according to specific job site

conditions.

4.0.6. Water: This is the least expensive but most important ingredient in concrete. The water,

which is used for making concrete, should be clean and free from harmful impurities such

alkali, and acid etc. in general, the water is fit for drinking, should be used for concrete.

Water confirming to IS 456-2000.

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Aspect: Colourless free flowing liquid Relative Density: 1.01 ± 0.01 at 25°C pH : > 6 Chloride ion content: < 0.2%

4.1. Mix Design:

SCC looks very different from conventional concrete while mixing. Concrete

producers must “retrain their eyes” for this very fluid mixture as it turns corners and fills

forms. Traditionally, concrete with the fluidity of SCC has had a very high water-to-

cement ratio, which would lower compressive strengths and compromise durability.

Properly designed SCC can save time and labour without sacrificing performance.

Two important properties specific to SCC in its plastic state are its flowability and

stability. The high flowability of SCC is generally attained by using high-range water-

reducing (HRWR) admixtures and not by adding extra mixing water. The stability or

resistance to segregation of the plastic concrete mixture is attained by increasing the total

quantity of fines in the concrete and/or by using admixtures that modify the viscosity of

the mixture. Increased fines contents can be achieved by increasing the content of

cementitious materials or by incorporating mineral fines.

Admixtures that affect the viscosity of the mixture are especially helpful when

the grading of available aggregate sources cannot be optimized for cohesive mixtures or

with large source variations. A well distributed aggregate grading helps to achieve SCC

with reduced cementitious materials content and/or reduced admixture dosage. While

SCC mixtures have been successfully produced with 1 ½ inch (38 mm) aggregate, it is

easier to design and control with smaller-sized aggregate. Control of aggregate moisture

content is also critical in producing a good mixture. SCC mixtures typically have a higher

paste volume, less coarse aggregate, and higher sand-to-coarse aggregate ratio than

typical concrete mixtures.

SCC mixtures can be designed to provide the required hardened concrete properties

for an application, similar to regular concrete. If the SCC mixture is designed to have

higher paste content or fines compared to conventional concrete, an increase in shrinkage

may occur.

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4.1.1. Mix Design Principles:

To achieve the required combination of properties in fresh SCC mixes:

1. The fluidity and viscosity of the paste is adjusted and balanced by careful

selection and proportioning of the cement and additions, by limiting the

water/powder ratio and then by adding a superplasticiser and (optionally) a

viscosity-modifying admixture. Correctly controlling these components of SCC,

their compatibility and interaction is the key in achieving good filling ability,

passing ability and resistance to segregation.

2. In order to control temperature rise and thermal shrinkage cracking as well as

strength, the fine powder content may contain a significant proportion of type l or

ll additions to keep the cement content at an acceptable level.

3. The paste is the vehicle for the transport of the aggregate; therefore the volume of

the paste must be greater than the void volume in the aggregate so that all

individual aggregate particles are fully coated and lubricated by a layer of paste.

This increases fluidity and reduces aggregate friction.

4. The coarse to fine aggregate ratio in the mix is reduced so that individual coarse

aggregate particles are fully surrounded by a layer of mortar. This reduces

aggregate interlock and bridging when the concrete passes through narrow

openings or gaps between reinforcement and increases the passing ability of the

SCC.

These mix design principles result in concrete that, compared to traditional

vibrated concrete, normally contains:

1. Lower coarse aggregate content

2. Increased paste content

3. Low water/powder ratio

4. Increased superplasticiser

5. Sometimes a viscosity modifying admixture.

113

4.1.2. General requirements in the Mix Design:

4.1.2.1. A high volume of paste:

The friction between the aggregates limits the spreading and the filling ability of

SCC. This is why SCC contains high volume of paste (cement+ additions+ efficient

water+ air), typically 330 to 440lit/m3, the role of which is to maintain aggregate

separation.

4.1.2.2. A high volume of fine particles (<80m):

In order to ensure sufficient workability while limiting the risk of segregation or

bleeding, SCC contains a large amount of fine particles (around 500kg/m3). Nevertheless,

in order to avoid excessive heat generation, the Portland cement is generally partially

replaced by mineral admixtures like lime stone filler or fly ash (cement should not be

used as filler). The nature and the amount of filler added are chosen in order to comply

with the strength and durability requirements.

4.1.2.3. A high dosage of superplasticizer:

Super plasticizers are introduced in SCC to obtain the fluidity. Nevertheless, a

high dosage near the saturation amount can increase the proneness of concrete to

segregate.

4.1.2.4. The possible use of viscous agent (water retainer):

These products are generally cellulose derivative, polysaccharides or colloidal

suspensions. These products have the same role as the fine particles, minimizing bleeding

and coarse aggregate by thickening the paste and retaining the water in the skeleton. The

introduction of such properties in SCC seems to be justified in case of SCC with high

water to binder ratio (for example: house building). On the other hand they may be less

useful for high performance SCC (strength higher than 50Mpa) with low water to binder

ratio.

114

For intermediate SCC the introduction of viscosity agent has to be studied for each case.

Viscosity agents are assumed to make SCC less sensitive to variations in water content of

aggregates occurring in concrete plants. Because of small quantities of viscosity agents

required, it may be difficult to achieve accuracy of dosage.

4.1.2.5. A low volume of core segregate:

It is possible to use natural rounded, semi-crushed aggregates to produce SCC.

Nevertheless as the coarse aggregate plays an important role on the passing ability of

SCC in congested areas, the volume has to be limited. On the other hand the use of coarse

aggregate allows optimizing the packing density of the skeleton of the concrete and

reduction of the paste volume needed for the target workability. Generally speaking, the

maximum aggregate size, Dmax, is between 10 and 20mm. The passing ability decreases

when Dmax increases which leads to a decrease of the coarse aggregate content. The

choice of higher Dmax is thus possible but is only justified with reinforcement content

admixtures added to SCC can have a retarding effect on strength and temperature

development in the fresh concrete and this will have to be borne in mind in the

construction process.

4.1.3. Mix Design: Laboratory trials should be used to verify properties of the initial mix composition

with respect to the specified characteristics and classes. If necessary, adjustments to the

mix composition should then be made. Once all requirements are fulfilled, the mix should

be tested at full scale in the concrete plant and if necessary at site to verify both the fresh

and hardened properties.

The mix design is generally based on the approach outlined below:

1. Evaluate the water demand and optimize the flow and stability of the paste.

2. Determine the proportion of sand and the dose of admixture to give the required

robustness.

3. Test the sensitivity for small variations in quantities( the robustness)

4. Add an appropriate amount of coarse aggregate.

5. Produce the fresh SCC in the laboratory mixer, perform the required tests.

115

6. Tests the properties of the SCC in hardened state.

7. Produce trial mixes in the plant mixer.

8. Mix design selection and adjustment can be made according to the procedure

below:

`

Fig. 4.1. Mix design flow chart

In designing the mix it is useful to consider the relative proportions of the key

components by volume rather than by mass.

In the event that satisfactory performance cannot be obtained, then consideration

should be given to fundamental redesign of the mix. Depending on the apparent problem,

the following courses of action may be appropriate:

1. Adjust the cement/powder ratio and the water/powder ratio and test the flow and

other properties of the paste

2. Try different types of addition (if available)

3. Adjust the proportions of the fine aggregate and the dosage of superplasticiser

4. Consider using a viscosity modifying agent to reduce sensitivity of the mix

5. Adjust the proportion or grading of the coarse aggregate.

116

Set required performance

Select materials (from site)

Design and adjust mix composition

Verify or adjust performance in laboratory

Verify performance in concrete plant or site

Evaluate alternate methods

Not OK

6. The use of alternate types of super plasticizer (and or VMA), which may be more

compatible with local materials.

4.1.4. Various procedures for Mix Design: There is no standard method for SCC mix design and many academic

institutions, admixture, ready-mixed, precast and contracting companies have developed

their own mix proportioning methods.

There are many procedures available in literature for proportioning Portland

cement Concrete. Mix designs often use volume as a key parameter because of the

importance of the need to over fill the voids between the aggregates particles. Some

methods try to fit available constituents to an optimized grading envelope. Another

method is to evaluate and optimize the flow and stability of first the paste and then the

mortar fractions before the coarse aggregate is added and the whole SCC mix tested.

The bureau of Indian standards recommended a set of procedure for design of

concrete mix mainly based on the work done in national laboratories. The mix design

procedures are covered in IS 10262-1982.The method can be applied for both medium

strength and high strength concrete. The Step-by-step procedure of Mix Design is as

follows:

1. Determine the mean target strength ft from the specified characteristic

compressive strength at 28-day fck and the level of quality control.

ft = fck + 1.65 x S

Where S is the standard deviation obtained from the Table of approximate

contents given after the design mix.

2. Obtain the water cement ratio for the desired mean target using the emperical

relationship between compressive strength and water cement ratio so chosen is

checked against the limiting water cement ratio. The water cement ratio so chosen

is checked against the limiting water cement ratio for the requirements of

durability given in table and adopts the lower of the two values.

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3. Estimate the amount of entrapped air for maximum nominal size of the aggregate

from the table.

4. Select the water content, for the required workability and maximum size of

aggregates (for aggregates in saturated surface dry condition) from table.

5. Determine the percentage of fine aggregate in total aggregate by absolute volume

from table for the concrete using crushed coarse aggregate.

6. Adjust the values of water content and percentage of sand as provided in the table

for any difference in workability, water cement ratio, grading of fine aggregate

and for rounded aggregate the values are given in table.

7. Calculate the cement content form the water-cement ratio and the final water

content as arrived after adjustment. Check the cement against the minimum

cement content from the requirements of the durability, and greater of the two

values is adopted.

8. From the quantities of water and cement per unit volume of concrete and the

percentage of sand already determined in steps 6 and 7 above, calculate the

content of coarse and fine aggregates per unit volume of concrete from the

following relations:

100011

fa

a

C Sf

pSCWV

10001

11

ca

a

C SC

pSCWV

Where V = absolute volume of concrete

= Gross volume (1m3) minus the volume of entrapped air

Sc = specific gravity of cement

W = Mass of water per cubic metre of concrete, kg

C = mass of cement per cubic metre of concrete, kg

P = ratio of fine aggregate to total aggregate by absolute volume

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fa, Ca = total masses of fine and coarse aggregates, per cubic meter of

concrete, respectively, kg, and

Sfa, Sca = specific gravities of saturated surface dry fine and coarse

aggregates, respectively

9. Determine the concrete mix proportions for the first trial mix.

10. Prepare the concrete mix using the calculated proportions, cast the cubes and test

them wet after 28-days moist curing and check for the strength.

11. Prepare trial mixes with suitable adjustments till the final mix proportions are

arrived at.

4.2. By EFNARC Guidelines:

Table 4.2. Mix composition as per EFNARC guidelines:

Constituent Typical range by mass

(kg/m3)

Typical range by volume

(liters/m3)

Powder 380-600

Paste 300-380

Water 150-210 150-210

Coarse aggregate 750-1000 270-360

Fine aggregate (sand)

Content balances the volume

of the other constituents

typically 48-55% of the total

aggregate weight

Water/powder ratio by

volume 0.85-1.1

4.2.1. Guidelines to find reasons of Faulty mixes: If the test results between different batches or loads vary considerably, the cause can

be the variation of:

1. Cement characteristics,

2. Addition characteristics,

3. Grading of aggregates,

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4. Moisture content of aggregates,

5. Temperature,

6. Mixing procedure, time of testing

The use of a viscosity-modifying agent can suppress some of these variations to a

certain extent.

4.2.2. Mix Design and Trial Proportion:

The ingredients for self-compacting concrete are similar to conventional

concrete. It consists of cement, coarse and fine aggregates, and water, mineral and

chemical admixtures. Similar to conventional concrete, self-compacting concrete can also

be affected by the physical characteristics of materials and mixture proportioning. A

rational mix design method for self-compacting concrete using a variety of materials is

necessary. The coarse and fine aggregate contents are fixed so that self-compacting

ability can be achieved easily by adjusting the water-powder ratio, super plasticizer

dosage and VMA dosage only. In the mix proportioning of conventional concrete, the

water-cement ratio is fixed at first from the viewpoint of obtaining the required strength.

With self-compacting concrete, however the water-powder ratio has to be decided taking

into account self-compactability because self-compactability is very sensitive to this ratio.

In most cases, the required strength does not govern the water-cement ratio because the

water-powder ratio is small enough for obtaining the required strength for ordinary

structure unless most of the powder materials in use are not reactive

The mortar or paste in self-compacting concrete requires high viscosity as

well as high deformability. This can be achieved by the employment of super plasticizer,

which results in a low water-powder ratio for high deformability and VMA for high

viscosity. The characteristics of powder, super plasticizer and VMA largely affect the

mortar property and so the proper water-powder ratio, super plasticizer dosage and VMA

dosage cannot be fixed without trial mixing at this stage. Therefore, once the mix

proportion is decided, self-compactability has to be tested by slump flow, L-Box and V-

Funnel test.

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In this investigation Gelinium-2 as VMA along with Glenium B233 as super

plasticizer is used.

As an engineered concrete, SCC offers characteristics that engineer’s value.

Improved constructability to produce homogeneous and uniform concrete allows for

higher reliability in design assumptions. Engineering properties and their inter-

relationships remain unchanged from those of conventional concrete and any differences

are adequately addressed by conservatism in the design codes. The principles of concrete

durability with respect to reduced permeability, resistance to freezing and thawing and

sulphate attack, alkali-aggregate reactions, thermal stresses and corrosion protection of

reinforcement also apply similarly to SCC. SCC's superior rheology allows for the design

and construction of complex shapes with congested reinforcement, and its non-

segregating qualities are important for deep-section or long-span applications. The

fluidity of SCC can be engineered in terms of its viscosity- both the rate and degree of

flow- to allow for a wider variety of placement and construction means and methods.

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CHAPTER 5

Quality Aspects of Self-Compacting Concrete

CHAPTER 5 Quality Aspects of Self-Compacting Concrete

5.0. Test Methods 5.0.1. Introduction

It is important to appreciate that none of the test methods for SCC has yet been

standardized, and the tests described are not yet perfected or definitive .The test method

presented here are descriptions rather than fully procedures. They are mainly adhoc

method, which have been devised specifically for SCC

In considering these tests, there are a number of points, which should be taken into

account:

1. One principal difficulty in devising such tests is to asses three distinct,

properties of fresh SCC – its filling ability (flow ability), its passing ability

(free from blocking at reinforcement), and resistance to segregation (stability).

No single test so far devised can measure all three properties.

2. There is no clear relation between test results and performance on site.

3. There is little precise data, therefore no clear guidance on compliance limits.

4. Duplicate tests are advised.

5. The test methods and values are stated for maximum aggregate size of up to

20mm, difference test values and / or different equipment dimensions may be

appropriate for other aggregate size.

6. Different test values may be appropriate for different reinforcement densities.

7. Similarly, different test values may be appropriate for being placed in vertical

and horizontal elements.

8. In performing the test, concrete should be sampled in accordance with

EN 12350-1.It is wise to remix the concrete first with a scoop, unless the

procedure indicates otherwise.

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5.0.2. Slump Flow Test / and T50 cm test: The slump flow is used to assess the horizontal free flow of SCC in the absence of

obstructions. It was first developed in Japan for use in assessment of underwater concrete.

The diameter of the concrete circle is a measure for the filling ability of concrete.

5.0.2.1. Assessment of test: This is a simple, test procedure, two people are needed if the T50 time is to be

measured. It can be used on site, though the size of the base plate is somewhat unwidely

and level ground is essential. It is most commonly used test, and gives a good assessment

of filling ability. It gives no indication of the ability of resistance to segregation. It can be

argued that the completely free flow, unrestrained by any boundaries, is not representative

of what happens in practice in concrete construction, but the test can be profitably be used

to assess the consistency of supply of ready mixed concrete to a site from load to load.

5.0.2.2. Equipment:

(a) (b) Figure.5.1.Showing the apparatus of Slump Flow and slump flow in (a) & (b) respectively

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1. Mould the shape of a truncated cone with the internal dimensions 200 mm

diameter at the base 100 mm diameter at the top and a height of 300 mm.

2. Base plate of a stiff non absorbing material, at least 700 mm square,

marked with a circle marking the central location for the slump cone, and a

further concentric circle if 500 mm diameter.

3. Trowel

4. Scoop

5. Ruler

6. Stopwatch (optional)

5.0.2.3. Procedure:

1. About 6 liters of concrete is needed to perform the test, sampled normally.

2. Moisten the base plate and inside slump cone.

3. Place base plate on level stable ground and slump cone centrally on the

base plate and hold down firmly.

4. Fill the cone with the scoop. Do not tamp, simply strike off the concrete

level with the top of the cone with the trowel.

5. Remove any surplus concrete from around the base of the cone.

6. Raise the cone vertically and allow the concrete to flow out freely.

7. Simultaneously, start the stopwatch and record the time taken for the

concrete to reach the 500mm spread circle. (this is the T50 time).

8. Measure the final diameter of the concrete in two perpendicular directions.

9. Calculate the average of the two measured diameters.(this is the slump

flow in mm)

10. Note any border of mortar or cement paste without coarse aggregate at the

edge of the pool of concrete.

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5.0.2.4. Interpretation of results:

The higher the slump flow (SF) value, the greater is the ability to fill the

formwork under its own weight. A value at least 650 m is required for SCC. There is no

generally accepted advice on what are reasonable tolerances about a specified value,

though ± 50mm, as with the related flow table test might be appropriate.

The T50 time is a secondary indication of flow. A lower time indicates greater

flow ability. The Brite Eu Ram research suggested that a time of 3-7 seconds is

acceptable for civil engineering applications, and 2-5 seconds for housing applications.

In the case of several segregations most coarse aggregate will remain in the

center of the pool of the concrete and mortar and cement paste at the concrete periphery.

In case of minor segregation a border of mortar without coarse aggregate can occur at the

edge of the pool of concrete. If none of these phenomena appear it is no assurance that

segregation will not occur since this is a time related aspect that can occur after a longer

period.

5.0.3. V funnel test: 5.0.3.1. Introduction:

The test was developed in Japan and used by Ozawa et al. the equipment consists

of a V-shaped funnel, shown in figure.5.2

The described V funnel test is used to determine the filling ability (flow ability)

of the concrete with a maximum aggregate size of 20 mm. the funnel is filled with about

12 liter of concrete and the time taken for it to flow through the apparatus measured.

After this the funnel can be refilled concrete and left for 5 minutes to settle. If

the concrete shows segregation then the flow time will increase significantly.

5.0.3.2 . Assessment of test: Though the test is designed to measure flowability, the result is effected by

concrete properties other than flow – the inverted cone shape will cause any liability of

the concrete to block to be reflected in the result – if, for example there is too much

Coarse aggregate. High flow time can also be associated with low deformability due to a

high paste viscosity, and with high inter particle friction.

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While the apparatus is simple, the effect of the angle of the funnel and the wall effect

on the flow of concrete are not clear.

5.0.3.3 Equipment:

Fig.5.2 showing the apparatus of V-funnel test

1. V – funnel 2. Bucket 12 liter 3. Trowel 4. Scoop 5. Stopwatch

5.0.3.4 . Procedure of flow time:

1. About 12 liter of concrete is needed to perform the test, sampled normally.

2. Set the v-funnel on firm ground

3. Moisten the inside surfaces of the funnel

4. Keep the trap door open to allow any surplus water to drain

5. Close the trap door and place the bucket underneath

6. Fill the concrete completely without compacting or lapping; simply strike off the

concrete level with the top with a trowel.

7. Open the trap door within 10 seconds after filing and allow the concrete to flow

out under gravity.

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8. Simultaneously, start the stop watch and record the time.

9. Start the stopwatch when the trap door is opened, and record the time for the

discharge to complete (the flow time). This is taken to be when light is seen from

above through the orifice section.

10. The whole test has to be performed within 5 minutes.

5.0.3.5. Procedure for flow time at T 5 minutes:

1. Do not clean or moisten the inside surface of the funnel again.

2. Close the trap door refill the V-funnel immediately after measuring the flow

time.

3. Place a bucket underneath

4. Fill the apparatus completely with concrete without compacting or tapping,

simply strike off the concrete level with the top with the trowel.

5. Open the trap door 5 minutes after the second fill of the funnel and allow the

concrete of flow out under gravity.

6. Simultaneously start the stopwatch when the trap door is opened and record

the time for the discharge to complete (the flow time at T5 minutes). This is

taken to the consideration when light is seen from above through the funnel.

5.0.3.6. Interpretation of results: This test measures the ease of flow of the concrete; shorter flow times indicate

greater flowability. For SCC a flow time of 10 seconds is considered appropriate. The

inverted cone shape restricts flow. And prolonged flow times may give some indication of

the susceptibility of the mix to blocking.

After 5 minutes of setting, segregation of concrete will show a less continuous

flow with an increase in flow time.

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5.0.4. L –Box test method: 5. 0.4.1. Introduction This test, based on a Japanese design for underwater concrete, has been

described by Peterson. These assess the flow of the concrete, and also the extent to which

it is subject to blocking by reinforcement. The apparatus is shown in figure.5.3

The apparatus consists of a rectangular section box in the shape of an ‘L’, with

a vertical and horizontal section, separated by a movable gate, in front of which vertical

length of reinforcement bar are fitted.

The vertical section is filled with concrete, and then the gate lifted to let the

concrete flow into the horizontal section. When the flow has stopped, the height of the

concrete at the end of the horizontal section is expressed as a proportion of that remaining

in the vertical section (H2/H1 in the diagram). It indicates the slope of the concrete when

at rest.

This is an indication passing ability, or the degree to which the passage of

concrete through the bars is restricted.

The horizontal section of the box can be marked at 200 mm and 400 mm from the

gate and the times taken to reach these points measured. These are known as the T20 and

T40 times and are an indication for the filling ability.

The section of the bar can be of different diameters and spaced at different

intervals in accordance with normal reinforcement considerations, 3 times the maximum

aggregate size might be appropriate.

The bar can be principally set at any spacing to impose a more or less severe test of

the passing ability of the concrete.

5.0.4.2. Assessment of test:

This is a widely used test, suitable for laboratory, and perhaps site use, it assesses

filling and passing ability of SCC. And serious lack of stability (segregation) can detect

visually. Segregation may also be detected by subsequently sawing and inspecting section

of the concrete in the horizontal section.

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Unfortunately there is no agreement on material, dimensions, or reinforcing bar

arrangement, so it is difficult to compare test results-there is no evidence of what effects

the wall of the apparatus and the consequent ‘wall effect’ might have on concrete flow,

but this arrangement does, to some extent, replicate what happens to concrete on site

when it is confined within formwork.

Two operators are required if times are measured, and a degree of operator error is

inevitable.

5.0.4.3. Equipments:

Fig.5.3. L-Box Apparatus

1. L box of a stiff non absorbing material

2. Trowel

3. Scoop

4. Stopwatch

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5.0.4.4. Procedure

1. About 14 liter of concrete is needed to perform the test, sampled normally.

2. Set the apparatus level on firm ground, ensure that the sliding gate can open

freely and then close it.

3. Moisten the inside surface of the apparatus, remove any surplus water fill the

vertical section of the apparatus with concrete sample.

4. Leave it to stand for 1 minute.

5. Lift the sliding gate and allow the concrete to flow out into the horizontal

section. Simultaneously, start the stopwatch and record the time taken for the

concrete to reach the 200mm and 400mm marks.

6. When the concrete stops flowing, the distance “H1” and “H2” are measured.

7. Calculate H1/H2, the blocking ratio.

8. The whole test has to be performed within 5 minutes.

5.0.4.5. Interpretation of results:

If the concrete flows as freely as water, at rest it will be horizontal, so H1/H2

=1.Therefore the nearer this test value, the blocking ratio, is to unity, the better the flow

of the concrete. The EU research team suggested a minimum acceptable value of 0.8.

T20 and T40 times can give some indication of ease of flow, but no suitable values have

been generally agrees. Obvious blocking of coarse aggregate behind the reinforcing bars

can be detected visually.

5.1. Case Studies Overseas:

Here some of the applications of SCC around the World are described. 5.1.1. Shark and Pengium Aquariums at the Oceanopole Marine Park in

Brest. 5.1.1.1 Main project description: An extension of marine park ocean polis near Brest of Brittany, building of two

giant aquariums with very large openings on the fair-faced concrete walls.

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5.1.1.2. Why SCC was used: Very dense net work of reinforcing bars. Better placing of concrete was desired.

Surface with very regular aspect and colour were required. No segregation at the bottom

of the walls.

5.1.1.3 Project requirements:

Concrete with high flow characteristics to completely fill the formwork,

especially around the large formworks.

5.1.2. Basement for Research and Development building in Tokyo, Japan.

5.1.2.1. Main project description: Erection of new R & D building in Tokyo, Japan. For the complex basement new

concrete technology were necessary.

5.1.2.2. Why SCC was used: HSC was required for this structure to improve the earthquake resistance for the

construction and complex design with extreme reinforcement easy pumping and placing

was required.

5.1.3. Pipe screen for a Tail Tunnel at the Meinrad Leinert Square, Zurich,

Switzerland.

5.1.3.1. Main project requirements: A pipe screen had to be installed to give additional support to the very thin ground

cover over the new rail tunnel at the Meinard Lienert Square in the center of Zurich. Ten

concrete pipes of 1.55m diameter (was thickness 150mm) were pipe jacketed 138 to 150

meters in to the soil from as access trench to form the pipe screen in advance of tunnel

boring. The soil from inside the pipes was removed and the soil around the pipes injected

to consolidate it. Reinforcing steel cages were into the pipes and they were concreted

section by section with SCC.

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5.1.3.2. Why SCC was used:

The decision was made to use the SCC, because the concrete had to be pumped at

least 50m then placed with no possibility of additional vibration, ensuring that complete

pipe was filed without segregation and bleeding. Constant watertight quality had to be

maintained.

5.1.4. Modular hotel room units by old castle Precast Rehoboth, MA (USA):

5.1.4.1. Main project description:

The project concerned of modular building system incorporating a 5cm insulator

layer sandwiched between a 3.75 cm structural concrete layer separated by fiber connect

rods.

5.1.4.2. Why SCC was used:

The design configuration made it very difficult to pour standard super plasticizer

concrete, even a wet mix with a lot of vibration resulted in a lot of poorly compacted

concrete.

SCC has already been successfully applied in large number of bridge projects. A

bridge in Texas (Loetta bridge) has utilized ‘U’ – shaped HPC deck girders. The concrete

was poured from the top on web; allow traveling down the web, soffit and travel up to the

second web till the concrete reaches the top. No vibrators were used.

5.1.5. Case study in land:

SCC was first recently used, for the first time in India, at Kaiga nuclear power

plant project for connecting the heavily reinforced columns.

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5.2. Requirements of Self-Compacting Concrete:

5.2.1. Application area:

SCC may be used in pre-cast applications or for concrete placed on site. It can be

manufactured in a site batching plant or in a ready mix concrete plant and delivered to site

by truck. It can then be placed either by pumping or pouring into horizontal or vertical

structures. In designing the mix, the size and the form of the structure, the dimension and

density of reinforcement and cover should be taken in consideration. These aspects will

all influence the specific requirements for the SCC. Due to the following characteristics

of SCC it may be difficult to cast to a fall unless contained in a form. SCC has made it

possible to cast concrete structures of a quality that was not possible with the existing

concrete technology.

5.2.2. Requirements:

Self-compacted concrete is defined as a category of high performance concrete that

has excellent deformability in the fresh state and high resistance to segregation and can be

placed and compacted under its self weight without applying vibration.

SCC can be designed to fulfill the requirements of EN 206 regarding density,

strength development, final strength and durability. Due to the high content of powder,

SCC may show more plastic shrinkage or creep than ordinary concrete mixes. These

aspects should therefore be considered during designing and specifying SCC. Special care

should also be taken to begin curing the concrete as early as possible. The workability of

SCC is higher than the highest class of consistence described within EN 206 and can be

characterized by the following properties:

5.2.2.1. Filling Ability: The property of self-compacted concrete to fill all corners of a formwork under its

own weight is known as filling ability. Slump flow test is used to assess this

characteristic.

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5.2.2.2. Passing Ability: Ability to overcome obstacles under its own weight without hindrance. Obstacles

are e.g. reinforcement and small openings etc. L-Box test and U-Box test will assess this

characteristic.

5.2.2.3. Resistance to Segregation: The property of self-compacted concrete to flow without segregation of the

aggregates i.e. to remain homogenous in composition during transporting and placing. V-

funnel test for T5 is used to assess this characteristic.

To meet the concrete requirements, three types of SCC are available:

1. The powder type SCC is characterized by the large amounts of powder (all

material < 0.15 mm), which is usually in the range of 56.06 to 66.26 N/m3. This

provides the plastic viscosity and hence the segregation resistance. The yield point

is determined by the addition of superplasticizer.

2. In the viscosity type SCC the powder content is lower (35.68 to 45.87 N/m3). A

VMA and the yield point mainly control the segregation resistance by the addition

of superplasticizer.

3. In the combination type of SCC the powder content is between 45.87 to 55.06

N/m3

but in addition the rheology is also controlled by a VMA as well as an

appropriate dosage of the superplasticizer.

A concrete mix can only be classified as Self-compacting Concrete if the

requirements for all three characteristics are fulfilled.

Many different test methods have been developed in attempts to characterize the

properties of SCC.So far no single method or combination of methods has achieved

universal approval and most of them have their adherents. Similarly no single method has

been found which characterizes all the relevant workability aspects so each mix design

should be tested by more than one test method

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for the different workability parameters. Alternative test methods for the different

parameters are listed in tables 5.1 and 5.2.

For the initial mix design of SCC all the three workability parameters need to

be assesses to ensure that all aspects are fulfilled. A full-scale test should be used to

verify the Self-compacting characteristics of the chosen design for a particular

application. Specification and Guidelines for Self-compacting concrete for site quality

control, two set methods are generally sufficient to monitor production quality. Typical

combinations are Slump-flow and V-funnel or Slump-flow and J-ring. With consistent

raw material quality, a single test method operated by a trained and experienced

technician may be sufficient.

Table 5.1. List of methods for workable properties of SCC: S.no METHOD PROPERTY 1 Slump flow by Abrams cone Filling ability

2 T50 Slump flow Filling ability

3 J-Ring Passing ability

4 V-Funnel Filling ability

5 V-Funnel at T5 minutes Segregation resistance

6 L-Box test Passing ability

7 U-Box test Passing ability

8 Fill Box Passing ability

9 GTM Screen Stability Test Segregation resistance

10 Orimet Filling ability

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5.2 Workability properties of SCC and alternative methods:

Test methods Property

Lab (mix design)

Field (OC)

Modification of test according to max.

aggregate size

Filling ability 1.Slump flow 2.T50 Slump flow 3.V-Funnel 4.Orimet

1.Slump flow 2.T50 Slump flow 3. V-Funnel 4.Orimet

None Max 20mm

Passing ability

5.L-Box 6.U-Box 7.Fill Box

5.J-Ring Different openings in L-Box, U-Box and J-Ring

Segregation resistance

8.GTM Test 6.GTM Test None

5.3. Workability criteria for the fresh SCC: These requirements are to be fulfilled at the time of placing. Likely changes in

workability during transport should be taken into account in production. Typical

acceptance criteria for Self-compacting Concrete with a maximum aggregate size upto

20mm are shown in the table 5.3

Table.5.3 Acceptance criteria for SCC as per EFNARC guide lines: Typical range of values

Method

Unit Minimum Maximum

Slump flow by Abrams cone mm 650 800

T50 slump-flow Sec 2 5 J-Ring mm 0 10 V-funnel Sec 6 12 V-funnel at T5 minutes Sec 0 15

L-Box H2/H1 0.8 1.0

U-Box (h2-h1)mm 0 30

Fill Box % 90 100

GTM Screen Stability Test % 0 15

Orimet Sec 0 5

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These typical requirements shown against each test method are based on current

knowledge and practice. However future developments may lead to different

requirements being adopted. Values outside these ranges may be acceptable if the

producer can demonstrate satisfactory performance in the specific conditions,e.g.,large

spaces between reinforcement, layer thickness less than 500mm,short distance of flow

from point of discharge, very few obstructions to pass in the form work,etc. Special care

should always be taken to ensure no segregation of the mix is likely as, at present, there is

not a simple and reliable test that gives information about segregation resistance of SCC

in all practical situations.

5.4. Complexities Involved In Making SCC:

Normal strength concrete itself is a complex material. High strength concrete with

lower water/binder ratio adds to the complexity. Making SCC particularly of high

strength adds further to the complexity.

Generally SCC is used in situations where high strength say over 40 Mpa to

100Mpa or more is required. In order to produce such a high strength concrete, it is

required to lower the water/binder ratio. Use of binder material will reduce the

workability to an unacceptable level for self-compacting requirements. To restore this

workability or even to increase the workability, a high dosage of Super plasticizer is

added. Two major problems arise in that case. Firstly, all the super plasticizers available

in the market are not suitable at high dosage. Therefore care should be taken in not

causing any adverse side effect such as excessive retardation. And also slump should

retain for longer time. The super plasticizers based on Naphthalene or Melamine is

generally not suitable for Self Compacting Concrete requiring very high strength

concrete.

Initial trial for finding the compatibility between Super plasticizer and cement,at

very low water-binder ratio is also required to be ascertained.

In case if large binder paste volume is used in order to obtain high strength and

self-compacting properties, there arises a problem that it would lead to higher heat of

hydration, greater shrinkage and Creep.

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EFNARC specification and Guidelines recommend the paste volume to be more

than 40% of the volume of the mix. But the other authorities have recommended that the

paste volume not to be more than 35% for concrete to be considered as high performing.

This results in further complexities. Though the higher paste volume may result in higher

shrinkage and creep in SCC the mechanical properties such as strength, elastic modulus,

creep and shrinkage of SCC and Conventional Concrete did not show significant

difference, when the strength was kept constant.

5.5. Limitations of SCC:

1. Apparent lack of reliable test standard that can qualify the physical properties of

SCC.

2. Higher material cost not only for admixtures but also for increased quality control

testing needed for concrete and aggregate.

3. Mixing time and finishing times will likely be longer.

4. Because of SCC high fluidity, grout leakage could be the problem in forms that do

not completely seal.

Since SCC is inherently self-leveling form that is not level could conceivably

cause problems.

5.6. Advantages of SCC:

1. Industrialized production of concrete.

2. Significant reduction in the cost of cast in situ concrete construction by

eliminating compaction needed during the concreting, labour and equipment wear

and tear cost related to compaction.

3. Reduction in the construction time by accelerating the construction process.

4. Promote the development of more rational concreting production.

5. Improve the quality, durability and reliability of concrete structures.

6. Improve the working environment at construction sites by reducing noise

pollution

7. Easily placed in thin walled elements with limited access.

8. ‘White fingure syndrome’ a serious injury from vibration equipment is prevented

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9. SCC can be placed at a faster rate with no mechanical vibration and less

screenings, resulting in savings in placement costs.

10. Improved and more uniform architectural surface finish with little to no remedial

surface work.

11. Ease of filling restricted sections and hard-to-reach areas. Opportunities to create

structural and architectural shapes and surface finishes not achievable with

conventional concrete.

12. Improved consolidation around reinforcement and bond with reinforcement.

13. Improved pumpability.

14. Improved uniformity of in-place concrete by eliminating variable operator-related

effort of consolidation.

15. Labor savings.

16. Shorter construction periods and resulting cost savings.

17. Reduction or elimination of vibrator noise, potentially increasing construction a

hours in urban areas.

18. Minimizes movement of ready mixed trucks and pumps during placement.

19. Increased jobsite safety by eliminating the need for consolidation.

5.6.1. Some Architectural Advantages of SCC Include:

1. Improved constructability

2. Virtually flawless finish

3. Homogenous and uniform concrete

4. Better reinforcement bonding

5. Flows easily into complex shapes and through congested reinforcement

6. Superior strength and durability

7. Allows for innovative architectural Features.

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5.7. Economic Impact of Self-Compacting Concrete in Precast

The economic impact of SCC in precast / prestress applications can be assessed in

three categories: concrete mixture proportions and raw materials, production costs, and

finished product improvements.

Due to the larger quantities of Portland cement or supplementary cementitious

materials used in SCC, the cost of the raw materials is usually greater. Cementitious

material may be required more to increase the fines content to achieve stability that is

needed on the basis of strength alone. In addition to cement, the cost of admixtures, such

as HRWR and possibly a Viscosity Modified Admixture (VMA), will also increase the

cost of SCC. Many precast concrete producers have switched from more angular coarse

aggregates to more rounded aggregates. Typically, precast concrete producers will pay an

additional 8-12% on average for raw materials in a SCC mixture relative to the raw

materials cost of traditional concrete mixtures.

Chemical admixtures can increase the cost of the SCC mixture, but are necessary

to achieve the desired concrete properties. Such is the case with VMA’s, which are added

to improve the stability and help prevent segregation during placement. The extra cost

would be around 2% of the cost of the mixture, but can yield savings by minimizing the

need to increase the cement content in the SCC mixture, allow a broader variety of

aggregates to be used and minimize the impact of moisture content in the aggregates.

The SCC mixture cost can also be reduced by the use of pozzolanic materials such

as fly ash, which is typically one-third to one-half the cost of cement. Fly ash can also

help improve the flowability and stability of the SCC mixture.

The extra cost of the SCC mixture is compensated by production cost efficiencies

such as reduction in placing time, vibrator use and maintenance, form maintenance, and

improvement worker safety. Placing time is the time it takes to transfer the concrete from

the transportation unit to the form and consolidate it. Improved productivity by reducing

time, labor or equipment may easily compensate for additional material costs.

140

A case study for tracking the time required for placing double-tee beds in a precast

plant reported a reduction of 20% compared to a conventional mixture, with a 32%

reduction of labor involved in the process . Regardless of the applications, an average

reduction in labor during the placing process is estimated to be about 30% using SCC.

The service life of vibration equipment and forms will increase with the use of

SCC. A reduction in vibration operations will not only reduce maintenance and

investment cost, but also improves the operating conditions at the plant by reducing noise

levels. Reducing the exposure of workers and eliminating requirements for hearing

protection may reduce insurance and safety costs. Due to the elimination of vibration to

consolidate the mixtures, the forms use in the precast operations will receive less wear

and tear, decreasing the regular maintenance costs and the costs of investing in new

forms.

Patching operations and finished product improvements may be critical for certain

precast concrete producers, especially for architectural panels. Properly proportioned

SCC has been proven to reduce the number of “bug holes,” honeycombing and other

surface imperfection on the finished concrete surface and others however, have noted that

poorly proportioned SCC can result in-significant segregation and very poor surface

finish.

Bug holes are small imperfections located on the surface created by air trapped

between the form and the concrete. Effective vibration can minimize the amount of bug

holes, but never eliminate them entirely. Bug holes are also affected by admixtures and

release agents. With a properly proportioned SCC mixture, the concrete can freely fill all

the spaces of the form under its own weight minimizing or even eliminate the trapped air.

A key economic factor for using SCC in prestressed girders is the finishing of the

product. Several state transportation agencies, such as NCDOT, require all the products to

have a smooth finish with minimal bug holes for both sides of the girders.

If the quantity and size of bug holes can be minimized, the amount of work and

cost related to finishing the girders will be significantly reduced. Finishing and retouching

of the girders can represent a significant part of labor costs in the precast concrete

operations

141

Honeycombing is an imperfection caused by insufficient or inadequate vibration.

Although the occurrence of honeycombing is relatively low in a well-controlled precast

plant, it also represents an increase in the cost due to retouching and finishing.

Honeycombing can be reduced with a properly proportioned SCC mixture. The use of

SCC can reduce patching expenses and manpower needed for patching finished precast

elements. In many examples of structural, architectural, and utility products, producers in

the United States have reported a decreased patching labor cost from 25-75%.

5.7.1. Applications:

1. Architectural Concrete

2. Columns

3. Residential structures

4. Beams

5. Civil Projects

6. Tanks

7. Pumped Concrete

8. Footers

The cost of the materials required for SCC is about 10-15% higher. By taking into

consideration that the cost of compaction, finishing etc, the overall cost when compared

to Conventional Concrete is low.

5.8. Performance:

SCC gives architects more design flexibility. SCC's unique characteristics give

architects much more flexibility for vertical and horizontal applications. SCC's

flowability allows for more complex and aesthetic concrete design features. Unlimited

opportunities exist with innovative options for color and texture of exposed surfaces.

Perhaps most importantly, SCC produces exposed surfaces that are virtually defect free,

allowing concrete's beauty to shine.

142

1. Regular concrete with vibration (a): This picture demonstrates the “bug holes”

on the surface of conventional concrete that has been placed into a form and

vibrated. Precasters spend valuable time and money “rubbing out” surface

imperfections when using conventional concrete.

2. Self-Compacting Concrete (b): The surface of this SCC has been improved

tremendously when placed at a 28-inch flow diameter with no vibration

(a) (b)

Fig.5.4.Showing the performance of Conventional Concrete & SCC in (a) and (b) respectively.

143

CHAPTER 6

Experimental Procedures

CHAPTER 6 Experimental Procedures

6.0. General

The development of Self-Compacting Concrete (SCC) marks an important

milestone in improving the product quality and efficiency of the building industry. SCC

improves the efficiency at the construction sites, enhances the working conditions and the

quality and appearance of concrete. Use of glass fibers in SCC bridge the cracks and

enhance the performance of concrete by not only avoiding the propagation of cracks but

also contribute to increased energy absorption compared with plain concrete. Glass Fiber

Reinforced Self- Compacting Concrete (GFRSCC) combines the benefits of SCC in the

fresh state and shows an improved performance in the hardened state compared with

conventional vibrated concrete. In the present work, the stress-strain curve for GFRSCC

has been suggested and an analytical stress-strain model was developed based on the

experimental results.

6.1. Introduction Self Compacting Concrete (SCC) facilitates and ensures proper filling and

good structural performance in restricted areas and heavily reinforced structural

members. Developed by Professor Hajime Okamura in Japan during the 1980s, it has

gained wide acceptance in today’s concrete works. SCC can be considered as an

engineered composite material, tailor made to achieve performance related properties to

suit specific applications. The mechanical properties of the brittle SCC under axial

loading may be improved by introducing randomly oriented short discrete fibers, which

prevent or control initiation and propagation or coalescence of cracks. Glass Fiber

Reinforced Self Compacting Concrete (GFRSCC) is one such composite, developed with

an idea of modifying the other wise inferior properties of Self Compacting Concrete

(SCC) alone. The properties of fibers that are usually of interest are fiber concentration,

fiber geometry, fiber orientation and fiber distribution. Glass fibers have very good

applications in changing the behavior of the material by bridging of fibers across the

cracks. In other words, ductility is provided with fiber reinforced cementitious

1 4 4

composites, because fibers bridge crack surfaces and delay the onset of the extension

of localized crack. In the present work an analytical stress-strain model was proposed of

this wonderful composite viz., Glass Fiber Reinforced Self Compacting Concrete

(GFRSCC).

6.2. Research Significance

An effort has been made in the present investigation to develop an analytical

stress- strain model for SCC & compare the mechanical properties of SCC without and

with glass fibers. The mix proportion suitable for Glass Fiber Reinforced Self

Compacting Concrete (GFRSCC) accommodating finer filler materials was developed

modifying the existing Nansu’s method of mix design. This study examines and compares

the mechanical properties and the stress-strain behavior of self compacting concrete for

GFRSCC. The present work provides very useful information for the practical use of

fibrous self-compacting concretes. An analytical model was suggested for fibrous SCC

and the stress-block parameters are proposed. The relationship between fibrous SCC with

respect to stress, strain at 85% and ductility is proposed.

6.3. Experimental Programme The experimental program was done in two phases. In the first phase the aim

was to develop GFRSCC and come out with an optimum GF content based on fresh and

hardened properties. In the second phase the mechanical behavior of the optimized

GFRSCC was investigated and the stress-strain curve was established and model was

proposed for Glass Fibre Reinforced Self-Compacting Concrete at 28 days for M50 Grade

of Concrete.

Five different types of GFRSCC specimens were developed in the laboratory and

Cubes of 100mm size and cylinders of 150 mm diameter and 300 mm long were cast for

testing in compression.

6.4. Materials Used: 6.4.1. Cement

Ordinary Portland cement of 53 grade available in local market is used in the

investigation. The Cement used has been tested for various proportions as per IS 4031-

1988 and found to be confirming to various specifications as per IS 12269-1987.The

specific gravity was 3.03 and fineness was 2800cm2/gm.

145

Table 6.1. Physical properties of Cement

Specific Gravity of Cement 3.03

Initial Setting time Min. 30 min

Final Setting time Max. 600 min

Normal Consistency 31%

Compressive Strength 54.7 N/mm2

Table 6.2.Chemical compositions of Cement as per manufacturers test report

S.No Chemical property Results Limits as per IS

1 Lime saturation Factor (%) 0.78 0.66 min - 1.02 max

2 Alumina Iron Ratio (%) 1.2 Min 0.665

3 Insoluble Residue (%) 0.8 Max 2%

4 Magnesia (%) 2.1 Max 6%

5 Sulphuric Anhydride (%) 1.1 2.5% to 35

6 Loss on ignition (%) 2.0 Max 5%

6.4.2. Fine aggregate:

River sand was used as fine aggregate is natural and obtained from local market. The

physical properties like specific Gravity, bulk density, gradation fineness modulus are

tested in accordance with IS 2386.

6.4.3. Coarse aggregate:

The crushed angular granite metal of coarse aggregate of 20 mm maximum size as

well as 12mm size are obtained from the local crushing plant, is used in the present study.

The physical properties of the coarse aggregate like specific gravity, bulk density,

gradation fineness modulus are tested in accordance with IS 2386.

146

6.4.4. Mineral Admixtures:

6.4.4.1. Fly ash:

In the present investigation work, Type-II fly ash from Vijayawada Thermal

Power Station, Andhra Pradesh was used as cement replacement material. The specific

surface area of fly ash is found to be 484.20 m2/N by Blane’s Apparatus. The properties

of fly ash are confirming to I.S. 3812 -1981of Indian Standard Specification for Fly Ash

for use as Pozzolana and admixture. & IS 456-2000 can be used to produce good quality

concrete. Typical characteristics of good quality fly ash are as follows:

1. Fineness (Blaine’s): 48.42 m2/N (Min.)



Table 6.3 Physical characteristics of VTPS fly ash: (Obtained from Vijayawada Thermal Power station)

Characteristics Experimental results

Fineness, m2/kg (Blain’s permeability) 475 Lime reactivity 4

Compressive strength, 21 days >80% of the Corresponding plain Cement mortar cubes

Drying shrinkage, % 0.08 Autoclave shrinkage 0.68

Table 6.4 Chemical composition of VTPS fly ash: (Obtained from Vijayawada Thermal Power station)

Characteristics Percentage

SiO2 +Al2O3+Fe2O3 86.7 SiO2 54 MgO 0.1 Total sulfur as SO3 0.11 Available alkali as sodium oxide (Na2O) 2.16 Loss on ignition 2

6.4.5. Chemical Admixture

Super plasticizer (Glenium -B233) (With base material Poly Corboxylic Eather)

147

6.4.6. Viscosity Modifying Agent A Viscosity modified admixture for Glenium -2 (With base material Poly Corboxylic Eather) which is free flowing liquid Chloride Content was used as Viscosity Modifying Agent. 6.4.7. Glass Fibres:

The glass fibres are of Cem-FIL Anti – Crack HD (High Dispersion) Glass Fibres

with Modulus of Elasticity 72 GPa, Filament Diameter 14 Microns, Specific Gravity 2.68,

Filament length 12mm and having Aspect Ratio of 857: 1. The number of fibres per 1 kg

is 212 million fibres. The properties of Glass Fibres are shown below in table 6.5.

6.4.7.1. Effect of Glass fibre on Bleeding On the basis of the experimental study it was concluded that addition of Glass

Fibres in concrete gives a reduction in bleeding. A reduction in bleeding improves the

surface integrity of concrete, improves its homogeneity, and reduces the probability of

cracks occurring where there is some restraint to settlement.

Table 6.5. Properties of Selected Glass Fibres:

(Obtained from Asian Journal of Civil Engineering ‘Building and Housing’Vol.9, No.5

(2005) page 461)

1 Trade Name Cem FIL anti-crack High Dispersion Glass Fibres

2 Number of fibres 212 million/Kg

3 Aspect ratio 857:1

4 Specific surface area 105m2/Kg

5 Typical addition rate 0.6 Kg/m3 of concrete

6 Tensile strength 1700 N/mm²

7 Modulus of Elasticity 73 GPa

8 Corrosion resistant Excellent

9 Specific gravity 2.6

10 Density 26 kN/m3

11 Filament diameter 14 µm

12 Filament length 12mm

148

6.4.8. Water: Confirming to IS 456-2000. 6.5. Mix Proportion: M50 grade SCC mix was designed based on Indian Standard Recommended Method of

Concrete Mix Design (IS 10262-1982), and was further modified by fine tuning the relative

proportions of fine and coarse aggregate, filler material like fly ash, glass fiber along with

super plasticizers and viscosity modifying agents.

6.5.1. Trail Mixes:

Aim is to arrive the Mix Proportion for M50 Grade Self Compacting Concrete

Hence Mix I to Mix IV in the Trail Mixes for evaluating the Self Compatibility of

Concrete .

In Mix I, all the materials quantities used which are obtained to BIS Method of

Mix designing without any modifications. During Mix Proportions, it is found that the

water Content is not sufficient to produce SCC. Therefore it is failed in V- Funnel T5 Test

and this Mix is not fit for SCC.

In Mix II, the water content incremented to Increase the flow ability of concrete

Mix, According to this changing powder content is increased in the Mix Design and

considering the Dosage of Super Plasticizer of 80 to 90 % of cementatious material..

Here it is observed that the Mix passed and the values are within allowable limits but in V

Funnel T5 Test, Segregation occurred and the Mix is not fit for SCC.

In Mix III , the material quantities are same as used in the above Mix, but the

quantity of super plasticizer is decreased and VMA dosage is slightly increased

accordingly resulting in the blocking g of coarse aggregate due to rapid settlement of

coarse aggregate. Hence in the Mix III the segregation of concrete showed a less

contentious flow so this Mix is not fit for SCC.

In Mix IV, the material quantities are same as used in the above Mix including the

quantity of super plasticizer, only reducing the dosage of VMA is changed. Here the Mix

passed and the values are within limits. Thus the Mix is considered as the final Mix.

149

Table 6.6 Details of Mix Proportions for M50 grade concrete

Mix Cement Kg/m3

Fine aggrega

te Kg/m3

Coarse aggrega

te Kg/m3

(12mm)

Coarse aggrega

te Kg/m3

(20mm)

Fly ash

Kg/m3

Glass fibers Kg/m3

Water Kg/m3

Super plasticizer

ml

VMA ml

Mix1 419 767 644 261 201

0.60

181 88 6

Mix2 425 795 627 269 209 0.60 190 93 6

Mix3 425 794 627 269 209 0.60 190 85 9

Mix4 425 794 627 269 209 0.60 190 85 3

Final Mix proportion: Cement: Fine Aggregate: Coarse aggregate

1 : 1.642 : 2.156

Cement is replaced by 33% with Fly ash.

Table 6.7 Quantities per m3 of the final mix arrived for GFRSCC M50 grade

Material Quantity (kg/m3)

Cement 425 Fine Aggregate 794.93

Coarse Aggregate 896.40 (627+269) (70%+30%)

Water 190 Fly ash 209 Glass Fibres 0.60 Super plasticizer 85 ml (0.04132 m³) Viscosity modifying agent 3 ml

6.6. Development of Glass Fiber Reinforced Self Compacting Concrete

(GFRSCC)

Fresh SCC must possess the key properties including filling ability, passing

ability and resistance to segregation at required level. To satisfy these conditions

EFNARC has formulated certain test procedures. The fresh properties of SCC with

glass fiber are shown in Table 6.8. Companion cube specimens of standard dimensions

100mm x 100mm were also cast and tested for the strength.

150

The results of the compressive strength are also presented in Table 6.8. The

corresponding compressive strength of cube specimens presented in Table 6.10. Thus, the

optimum mix proportions for GFRSCC were arrived at the end of this phase of study.

Table 6.8. Fresh properties of GFRSCC:

6.7. Workability

The properties of the Self Compacting Concrete and Glass fibre Reinforced Self

Compacting Concrete mixes in the fresh state. As it is evident, the basic requirements of

high flowability and segregation resistance as specified by guidelines on Self Compacting

Concrete by EFNARC are satisfied. The workability values are maintained by adding

suitable quantities of superplasticizers

6.8. Testing of SCC in Fresh State:

Slump flow, V-funnel and L-box tests were performed in the laboratory on fresh

SCC to find filling ability, passing ability and segregation resistance. The prescribed

limits of the tests as per the EFNARC specifications are as shown in Table 6.8.

6.9. Specimen Preparation:

After satisfying the requirements GFRSCC in fresh state was poured in moulds of

cubes & cylinders. Using 6mm diameter. Mild steel rings as transverse reinforcement,

five different types of cylinders were cast i.e., placing no rings, 3rings, 4rings, 5rings and

6rings. Specimens were prepared with varying percentages of Confinement. For GFR

SCC mix 15 cylinders and GFSCC mix cubes were cast. 151

Requirement as per EFNARC Name of

the test Property Unit Result Min Max

Slump flow Filling Ability mm 675 650 800

T 50cm Slump Flow Filling Ability sec 3.08 2 5

V- Funnel Filling Ability sec 6 6 12

V- Funnel at 5minutes Seg. Resistance sec 9 0 15

L-Box Passing Ability H2/H1 0.8 0.8 1

After the concrete has set in moulds the cylindrical specimens which were to be

tested in axial compression were capped with a thin layer of stiff neat Portland cement

paste. After 24 hours of casting the specimens were de-moulded and placed in water for

curing. After 28 days of curing the specimens were taken out from water and allowed the

surfaces for drying.

15 Specimens namely

GF SCC Plain (without any confinement) : 3 specimens

GFR SCC with 0.798% Confinement : 3 specimens




6.10. Casting: Standard cast iron Cylindrical moulds of dimensions 150 mm x 300 mm and

Cubes of dimensions 100mm x 100mm x 100mm were used to cast the specimens for

compression test. The side plates of the mould where sufficiently stiff to eliminate

spreading and warping. Before the concrete was placed in the mould, all the joints were

checked thoroughly for any leakage.

A thin film of grease was applied to cover the joints between the halves of the

mould at the bottom surface of the mould and its base plate in order to ensure that no

water escapes.

6.11. Curing: After casting, the moulded specimens are stored in the laboratory at room

temperature for 24 hours. After these periods the specimens are removed from the moulds

and immediately submerged in clean, fresh water of curing tank and specimens are cured

for 28 days in the present investigation work. As per IS 9013:1978 Specifications.

6.12. Compressive Strength: Of the various strengths of concrete the determination of compressive strength has

received a large amount of attention because the concrete is primarily meant to withstand

compressive stresses. Generally cubes are used to determine the compressive strength.

The cubes are usually of 100 x 100 x 100mm (or) 150 x 150 x 150 mm size.

152

In the present investigation the size of 100 x 100 x 100 mm are used. In the

compressive test, the cube while cleaned to wipe of the surface water, is placed with the

cast faces in contact with the planes of the testing machine, i.e. the position of the cube

then tested is at right angles to that as cast.

The specimens were removed from the moulds and submerged in clean fresh

water until just prior to testing. The temperature of water in which the cylinders were

submerged was maintained at 27o C+2o C and 90% relative humidity for 24 hours. The

specimens were cured for 28 days.

6.13. Tests of GFRSCC with and Without Confinement in Hardened State:

1. Compressive strength tests were carried out on cubes of 100 mm size using a

compression testing machine of 1000 kN capacity as per IS 516:1959.

2. The cylinders which were capped, were tested in compression using 1000kN

capacity computer controlled UTM under strain rate control as per IS 516:1959

to get the stress strain characteristics.

3. Rate of Strain is 0.02mm/sec.

After testing GFRSCC in hardened state, the hardened properties of GFRSCC are

shown in Table 6.9

Table 6.9. Hardened properties of M50 grade GFRSCC with & without Confinement at 28days (Cylinder):

Sl. No Designation Volume of Confinement reinforcement

%

Cube Compressive

Strength MPa

Cylindrical Compressive Strength in

MPa

Strain at Peak Stress

1 GFSCC p 0 - 43.0072 0.002792

2 GFRSCC (3R) 0.798 - 46.4025 0.002933

3 GFRSCC (4R) 1.062 - 49.7980 0.003667

4 GFRSCC (5R) 1.327 - 52.0614 0.004333

5 GFRSCC (6R) 1.591 - 57.7202 0.004833

153

Table 6.10 Compressive strength of Cubes tested at 28 days (without Confinement):

Target strength 50 N/mm2

Sl. No

Designation

Compressive

Strength of Cubes in N/mm2

1 GFSCCP 61.17 2 GFSCCP 53.77 3 GFSCCP 52.96 4 GFSCCP 55.81 5 GFSCCP 52.86 6 GFSCCP 51.34 7 GFSCCP 55.80 8 GFSCCP 55.92 9 GFSCCP 55.10

10 GFSCCP 55.96 11 GFSCCP 58.25 12 GFSCCP 57.79 13 GFSCCP 58.69 14 GFSCCP 64.03

Compressive strength of Cubes of all the 14 Specimens is more than 50 N/mm2,

which is more than the required strength.

6.14. Failure mode of Test Specimen in Compression: Compression Tests will be carried out on hardened test cylinders, the cylindrical

test specimens have a length equal to twice the diameter they are of 150mm in diameter

and 300mm long. Compression test develops a rather more complex system of stress. Due

to compression load, the cube or cylinder under goes lateral expansion owing to the

position’s ratio effect. The steel platens do not undergo lateral expansion to the some

extent that of concrete. With the result that the steel restrains the expansion tendency of

concrete in the lateral direction.

154

This induces a tangential force between the end surfaces of the concrete specimen and the

adjacent steel platens of the testing machine. Cracks are developed on the surface of test

specimen when it attains peak load in compression. On Central portion of test specimen

it observed that cracks are identified. This shows that failure of test specimen occurred

due to insufficient cover to confined steel specimen.

Fig 6.1 Casted cylinder specimen Fig. 6.2 Casted cube specimen under

tested UTM tested under Compression testing Machine

155

Fig. 6.3. Cracks being visible on the test specimen

6.15: Comparison with Conventional Concrete to GFRSCC:

6.15.1: Conventional Concrete:

In the case of conventional concrete is being used, when large quantity of heavy

reinforcement is to be placed in reinforced concrete members it is difficult to ensure that

the form work gets completely filled with concrete, i.e, fully compacted without voids or

honeycombs. Vibrating concrete in congested locations may cause some risk to labour

and there are always doubts about the strength and durability of concrete placed in such

locations.

6.15.2: Glass Fibre Reinforced Self Compacting Concrete (GFRSCC):

Glass Fibre Reinforced Self Compacting Concrete (GFRSCC) is being made with

a combination of SCC and Glass Fibre Reinforced Concrete (GFRC). The advantages of

SCC and Glass Fibre Reinforced Concrete are added for GFRSCC is that concrete which

is able to flow under its own weight and completely fill the form work without

segregation, even in the presence of dense reinforcement without the need of any

vibration whilst maintaining homogeneity.GFRC is composed of concrete, reinforced

with glass fibres to produce a thin, light weight, yet strong material, it has high

compressive and flexural strengths, ability to reproduce fine surface details, low

maintenance requirements, low coefficients of thermal expansion, high fire resistance.

156

6.16. Development of Analytical Stress-Strain Model for Glass Fiber Reinforced Self Compacting Concrete with & without Confinement:

6.16.1. Effect of fiber on ultimate Strength and Strain

From the stress-strain curves explained in Figs 6.4, the ultimate strength ( f u

), Strain at ultimate strength ( ε u ), strain at 85% of the ultimate on the ascending

portion ( ε 0.85u asc) and 85% of ultimate on the descending portion ( ε 0.85u des)

are obtained. These are shown in Table 6.11. From these values the stress ratio ( f u / f ′ ),

the strain ratio ( ε u / ε ′ ) and the Ductility Factor (DF) , were obtained for different

confinements and Fiber Index value (corresponding to different confinements and fiber

concentrations).

Fig.6.4.Typical Stress-strain behavior of (M50 Grade GFRSCC) with and

without confinement at 28 days

157

Fi = 0.225

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

0.00

0

0.00

1

0.00

2

0.00

3

0.00

4

0.00

5

0.00

6

0.00

7

0.00

8

0.00

9

Strain

Stre

ss (N

/mm

²)

SCC pSCC 3R (0.798)SCC 4R (1.062)SCC 5R (1.327)SCC 6R (1.591)

Table 6.11 :Peak Stress and Peak Strain Values of M50 grade GFRSCC with

different Confinement Variation

6.16.2. Relationship between Fiber Index, stress ratio and strain ratio:

The relationship between Fiber Index (Fi) vs stress ratio and Fiber Index (Fi) vs

strain ratio for Glass Fiber Reinforced SCC is shown below.

iu F

ff

1074.01' (1)

iu F3732.01' (2)

The plots for the above are shown in Figs 6.5 and 6.6 respectively. It can be noted that

there is an increase in stress ratio and strain ratio with increase Confinement and Fiber

Index (Fi). The strain ratio is more predominant than the stress ratio. The glass fibers

hence improve the deformation capacity significantly in the structural members.

158

Sl. No Designation Fibre

Index Confine

ment

Peak stress

N/mm2

fu

fu/f'

Strain at

peak stress

єu

єu/є' є0.85u Ase x 10^ˉ6

є0.85u Des x 10^ˉ6

Ductility Factor

1 GFSCC p 0.225 0 43.0072 1.000 0.0028 1.000 857.09 2911.25 3.40 2 GFRSCC (3R) 0.225 0.798 46.4025 1.079 0.0029 1.051 854.67 3123.75 3.65 3 GFRSCC (4R) 0.225 1.062 49.7980 1.158 0.0037 1.313 913.32 3966.52 4.34 4 GFRSCC (5R) 0.225 1.327 52.0614 1.211 0.0043 1.552 924.32 4427.23 4.79 5 GFRSCC (6R) 0.225 1.591 57.7202 1.342 0.0048 1.731 977.50 4696.25 4.80

Fig 6.5 Stress Ratio ( fu/f’ )Vs Fibre Index (Fi)

Fig 6.6 Strain Ratio (єu/є’ ) Vs Fibre Index (Fi)

159

R²=0.7938

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

0 0.05 0.1 0.15 0.2 0.25

Fibre Index

Stre

ss R

atio

"y=0.1074x+1"

R²=0.8487

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

1.800

2.000

0 0.05 0.1 0.15 0.2 0.25

Fibre Index

Stra

in R

atio

Y=0.3732X+1

6.16.3. Ductility Factor Vs Fiber Index

The ratio of strains at 85% of the ultimate strength in the descending portion to

that of 85% in the ascending portion gives the Ductility Factor (DF). A plot of Fiber

Index vs Ductility Factor indicates an increase in Ductility with increase in confinement

and in the Fiber Index. This is shown in Fig 6.7.

The equation for the same is given below

F = 2.4577 + 2.0912 iF ( 3 )

Fig 6.7 Fibre Index (Fi) Vs Ductility Factor (DF)

160

R² =0.9532

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0 0.05 0.1 0.15 0.2 0.25

Fibre Index

Duc

tility

Fac

tor

(DF)

Y=2.0912x+2.4577

Fig 6.8 Normalized Stress Vs Normalized Strain

6.16.4. Non-Dimensionalised Stress-Strain Curve

An examination of the curves in Figs 6.4 and ind icates that the behaviour is

similar for the entire confinements M50 grade, meaning that the stress-strain behaviour

is linear upto 80-90% of the ultimate and non linear beyond this. The post peak stress-

strain response for all the GFRSCC specimens is gradual and appears to have a

consistent and constant gradient. This similarity leads to the conclusion that if the stress

is expressed as stress ratio by dividing the stress at any level by the corresponding stress

at ultimate and the strain ratio obtained by dividing the strain at any level by the

corresponding to the strain at ultimate strength, the plot of these two ratios falls into the

same pattern. Thus by non-dimensionalising the stresses and strains as explained above

the effect of Fiber Index (Fi) can be eliminated. Fig 6.8 shows the values of the non-

dimensionalised stress as ordinate and the normalized strain as abscissa. The

characteristic values and the analytical values are plotted in the figure. The stress-strain

behavior can be represented by a general curve, which functions as a stress block. A

single polynomial of the form shown in equation 4 is used in the current investigation.

161

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.00

00.

200

0.40

00.

600

0.80

01.

000

1.20

01.

400

1.60

01.

800

2.00

0

Normalized Strain

Nor

mal

ized

Str

ess

The model is of the form

21

CBDAf

(4)


non-dimensional stress-strain curves the following form is proposed.

2

111

11

uu

u

uCB

DA

ff

(5)





The boundary conditions common for both ascending and descending portions of stress – strain curve

At ;0;0 uu ff

At ;1;1

uu ff

and At 0;1

u

u

u d

ffd

(6)

6.16.5. Model Calculations for Normalized Stress – Normalized Strain Curve

of GFRSCC (0.798% Confinement):

Additional Boundary condition for ascending portion of stress- strain curve

(ε/εu)1 = 0.23 ; (f/fu)1 = 0.44 (ε/εu)2 = 0.33 ; ( f/fu)2 = 0.56 ; (7)

Additional Boundary condition for descending portion of stress- strain curve

(ε/εu)1 = 1.14 ; (f/fu)1 = 0.95 ; (ε/εu)2 = 1.36 ; ( f/fu)2 = 0.90 ; ( 8)

162

Satisfying the above boundary conditions the constants for ascending

and descending portions of the curve were obtained.

The values were A1 = 2.50, B1 = 1.104, C1 = 1.0, D1 = 0.0 (for Ascending

Portion) and A1 = 1.336, B1 = -0.611, C1 = 1.0, D1 = 0.0 (for Descending Portion)

Thus, the stress-strain equations for the ascending portion of the GFRSCC curve is

2

0.1104.11

50.2

uu

u

uff

(9)

While the stress-strain equation for the descending portion of the GFRSCC curve is

2

0.1611.01

336.1

uu

u

uff

(10)

In the same way we can write the stress-strain equation for the cylinder with

1.062% steel for the ascending portion of the GFRSCC curve as

2

0.1245.11

771.2

uu

u

uff

(11)

Similarly we can write the stress-strain equation for the cylinder with 1.062%

steel for the descending portion of the GFRSCC curve is given by

2

0.1765.01

163.1

uu

u

uff

(12)

163

The stress-strain equation for the cylinder with 1.327% steel for the ascending

portion of the GFRSCC curve is given by

2

0.1593.11

315.3

uu

u

uff

(13)

The stress-strain equation for the cylinder with 1.327% steel for the descending


2

0.1345.11

641.0

uu

u

uff

(14)

.

The stress-strain equation for the cylinder with 1.591% steel for the ascending


2

0.1217.21

338.3

uu

u

uff

(15)

The stress-strain equation for the cylinder with 1.591% steel for the descending


2

0.1610.11

387.0

uu

u

uff

(16)

In the present investigation, Cylinders with and without confinement were tested

under Universal Testing Machine controlled by Computer, the test results are as follows.

164

6.17. Experimental Results 6.17.1. Stress-Strain values of Cylinder without confinement (M50

gradeGFSCC)

Peak Load=760Kn; Compressive strength=43.0072 N/mm2

Table 6.12 Stress-Strain values of Cylinder without confinement

Normalized Stress-Strain Values

Actual Values Equation Values Load in KN

Mean-

Displace-

ment in

mm

Stress in

N/mm²

f

Strain

uff u uff u

0 0.0000 0.00 0.00 0.00 0.00 0.00 0.00

20 0.0100 1.13177 0.0000333 0.03 0.01 0.02 0.00

40 0.0195 2.26354 0.0000650 0.05 0.02 0.04 0.01

60 0.0270 3.39531 0.0000900 0.08 0.03 0.07 0.02

80 0.0350 4.52707 0.0001167 0.11 0.04 0.10 0.03

100 0.0475 5.65884 0.0001583 0.13 0.06 0.12 0.05

120 0.0600 6.79061 0.0002000 0.16 0.07 0.15 0.06

140 0.0725 7.92238 0.0002417 0.18 0.09 0.17 0.08

160 0.0800 9.05415 0.0002667 0.21 0.10 0.20 0.09

180 0.0925 10.1859 0.0003083 0.24 0.11 0.23 0.10

200 0.1050 11.3177 0.0003500 0.26 0.13 0.25 0.12

220 0.1175 12.4495 0.0003917 0.29 0.14 0.28 0.13

240 0.1300 13.5812 0.0004333 0.32 0.16 0.31 0.15

260 0.1475 14.713 0.0004917 0.34 0.18 0.33 0.17

280 0.1600 15.8448 0.0005333 0.37 0.19 0.36 0.18

300 0.1750 16.9765 0.0005833 0.39 0.21 0.38 0.20

320 0.1900 18.1083 0.0006333 0.42 0.23 0.41 0.22

340 0.2000 19.2401 0.0006667 0.45 0.24 0.44 0.23

360 0.2150 20.3718 0.0007167 0.47 0.26 0.46 0.25

165

380 0.2300 21.5036 0.0007667 0.50 0.27 0.49 0.26

400 0.2400 22.6354 0.0008000 0.53 0.29 0.52 0.28

420 0.2550 23.7671 0.0008500 0.55 0.30 0.54 0.29

440 0.2700 24.8989 0.0009000 0.58 0.32 0.57 0.31

460 0.2900 26.0307 0.0009667 0.61 0.35 0.60 0.34

480 0.3050 27.1624 0.0010167 0.63 0.36 0.62 0.35

500 0.3250 28.2942 0.0010833 0.66 0.39 0.65 0.38

520 0.3500 29.426 0.0011667 0.68 0.42 0.67 0.41

540 0.3675 30.5577 0.0012250 0.71 0.44 0.70 0.43

560 0.4000 31.6895 0.0013333 0.74 0.48 0.73 0.47

580 0.4225 32.8213 0.0014083 0.76 0.50 0.75 0.49

600 0.4500 33.9531 0.0015000 0.79 0.54 0.78 0.53

620 0.4775 35.0848 0.0015917 0.82 0.57 0.81 0.56

640 0.5000 36.2166 0.0016667 0.84 0.60 0.83 0.59

660 0.5300 37.3484 0.0017667 0.87 0.63 0.86 0.62

680 0.5600 38.4801 0.0018667 0.89 0.67 0.88 0.66

700 0.5900 39.6119 0.0019667 0.92 0.70 0.91 0.69

720 0.6450 40.7437 0.0021500 0.95 0.77 0.94 0.76

740 0.7000 41.8754 0.0023333 0.97 0.84 0.96 0.83

760 0.8375 43.0072 0.002792 1.00 1.00 1.00 1.00

740 0.9500 41.8754 0.0031667 0.97 1.13 0.96 1.12

720 0.9900 40.7437 0.0033000 0.95 1.18 0.94 1.17

700 1.0300 39.6119 0.0034333 0.92 1.23 0.91 1.22

680 1.0700 38.4801 0.0035667 0.89 1.28 0.88 1.27

660 1.1050 37.3484 0.0036833 0.87 1.32 0.86 1.31

640 1.1250 36.2166 0.0037500 0.84 1.34 0.83 1.33

620 1.1450 35.0848 0.0038167 0.82 1.37 0.81 1.36

600 1.1550 33.9531 0.0038500 0.79 1.38 0.78 1.37

166

Fig: 6.9. Stress-Strain behaviour of GFRSCC without confinement

Fig: 6.10 Normalized Stress- Normalized Strain Curve of GFRSCC without

confinement

167

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.00

0

0.20

0

0.40

0

0.60

0

0.80

0

1.00

0

1.20

0

1.40

0

1.60

0

Normalized Strain

Nor

mal

ized

Str

ess

0.005.00

10.0015.0020.0025.0030.0035.0040.0045.0050.00

0.00

00

0.00

05

0.00

10

0.00

15

0.00

20

0.00

25

0.00

30

0.00

35

0.00

40

0.00

45

Strain

Stre

ss (N

/mm

²)

Fi = 0.225

6.17.2. Stress-Strain values of Cylinder with 0.798% confinement (M50 gradeGFRSCC)

Peak Load=820 KN; Compressive strength=46.4025N/mm2

Table 6.13 Stress-Strain values of Cylinder with 0.798% confinement:


Actual Values Equation Values Load In KN

Mean-

Displace-

ment

Stress in

N/mm²

f

Strain

uff u uff u

0 0.000 0.000 0.000 0.000 0.000 0.000 0.000

20 0.006 1.132 0.000018 0.02 0.01 0.01 0.00

40 0.011 2.264 0.000037 0.05 0.01 0.04 0.00

60 0.017 3.395 0.000055 0.07 0.02 0.06 0.01

80 0.022 4.527 0.000073 0.10 0.03 0.09 0.02

100 0.028 5.659 0.000092 0.12 0.03 0.11 0.02

120 0.033 6.791 0.000110 0.15 0.04 0.14 0.03

140 0.043 7.922 0.000142 0.17 0.05 0.16 0.04

160 0.049 9.054 0.000162 0.20 0.06 0.19 0.05

180 0.070 10.186 0.000232 0.22 0.08 0.21 0.07

200 0.080 11.318 0.000267 0.24 0.09 0.23 0.08

220 0.091 12.449 0.000302 0.27 0.10 0.26 0.09

240 0.106 13.581 0.000353 0.29 0.12 0.28 0.11

260 0.117 14.713 0.000388 0.32 0.13 0.31 0.12

280 0.137 15.845 0.000457 0.34 0.16 0.33 0.15

300 0.153 16.977 0.000508 0.37 0.17 0.36 0.16

320 0.173 18.108 0.000577 0.39 0.20 0.38 0.19

340 0.194 19.240 0.000645 0.41 0.22 0.40 0.21

360 0.204 20.372 0.000680 0.44 0.23 0.43 0.22

380 0.220 21.504 0.000732 0.46 0.25 0.45 0.24

400 0.240 22.635 0.000800 0.49 0.27 0.48 0.26

168

420 0.261 23.767 0.000868 0.51 0.30 0.50 0.29

440 0.271 24.899 0.000903 0.54 0.31 0.53 0.30

460 0.287 26.031 0.000955 0.56 0.33 0.55 0.32

480 0.312 27.162 0.001040 0.59 0.35 0.58 0.34

500 0.333 28.294 0.001108 0.61 0.38 0.60 0.37

520 0.353 29.426 0.001177 0.63 0.40 0.62 0.39

540 0.380 30.558 0.001267 0.66 0.43 0.65 0.42

560 0.400 31.690 0.001333 0.68 0.45 0.67 0.44

580 0.425 32.821 0.001417 0.71 0.48 0.70 0.47

600 0.445 33.953 0.001483 0.73 0.51 0.72 0.50

620 0.465 35.085 0.001550 0.76 0.53 0.75 0.52

640 0.485 36.217 0.001617 0.78 0.55 0.77 0.54

660 0.500 37.348 0.001667 0.80 0.57 0.79 0.56

680 0.520 38.480 0.001733 0.83 0.59 0.82 0.58

700 0.550 39.612 0.001833 0.85 0.63 0.84 0.62

720 0.565 40.744 0.001883 0.88 0.64 0.87 0.63

740 0.590 41.875 0.001967 0.90 0.67 0.89 0.66

760 0.625 43.007 0.002083 0.93 0.71 0.92 0.70

780 0.665 44.139 0.002217 0.95 0.76 0.94 0.75

800 0.725 45.271 0.002417 0.98 0.82 0.97 0.81

820 0.880 46.4025 0.002933 1.00 1.00 1.00 1.00

800 0.945 45.271 0.003150 0.98 1.07 0.97 1.06

780 1.005 44.139 0.003350 0.95 1.14 0.94 1.13

760 1.100 43.007 0.003667 0.93 1.25 0.92 1.24

740 1.200 41.875 0.004000 0.90 1.36 0.89 1.35

720 1.300 40.744 0.004333 0.88 1.48 0.87 1.47

700 1.400 39.612 0.004667 0.85 1.59 0.84 1.58

680 1.525 38.480 0.005083 0.83 1.73 0.82 1.72

169

..

Fig: 6.11. Stress-Strain behaviour of GFRSCC (0.798% Confinement)

Fig: 6.12. Normalized Stress- Normalized Strain Curve of GFRSCC (0.798% Confinement)

170

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.00

00.

200

0.40

00.

600

0.80

01.

000

1.20

01.

400

1.60

01.

800

2.00

0

Normalized Strain

Nor

mal

ized

Str

ess

0.005.00

10.0015.0020.0025.0030.0035.0040.0045.0050.00

0.00

00

0.00

10

0.00

20

0.00

30

0.00

40

0.00

50

0.00

60

Strain

Stre

ss (N

/mm

²)

Fi = 0.225

6.17.3. Stress-Strain values of Cylinder with 1.062% confinement (M50 gradeGFRSCC)

Peak Load=880 KN ; Compressive strength=49.798 N/mm2

Table 6.14 Stress-Strain values of Cylinder with 1.062% confinement


Actual Values Equation

Values Load In KN

Mean-

Displace-

ment

Stress in

N/mm²

f

Strain

uff u uff u 0 0.000 0.000 0.000 0.000 0.000 0.000 0.000

20 0.006 1.132 0.000018 0.02 0.01 0.01 -0.01 40 0.011 2.264 0.000037 0.05 0.01 0.04 0.00 60 0.017 3.395 0.000055 0.07 0.02 0.06 0.01 80 0.022 4.527 0.000073 0.09 0.02 0.08 0.01 100 0.028 5.659 0.000092 0.11 0.03 0.10 0.02 120 0.033 6.791 0.000110 0.14 0.03 0.13 0.02 140 0.043 7.922 0.000142 0.16 0.04 0.15 0.03 160 0.049 9.054 0.000162 0.18 0.04 0.17 0.03 180 0.070 10.186 0.000232 0.20 0.06 0.19 0.05 200 0.080 11.318 0.000267 0.23 0.07 0.22 0.06 220 0.091 12.449 0.000302 0.25 0.08 0.24 0.07 240 0.106 13.581 0.000353 0.27 0.10 0.26 0.09 260 0.117 14.713 0.000388 0.30 0.11 0.29 0.10 280 0.137 15.845 0.000457 0.32 0.12 0.31 0.11 300 0.153 16.977 0.000508 0.34 0.14 0.33 0.13 320 0.173 18.108 0.000577 0.36 0.16 0.35 0.15 340 0.194 19.240 0.000645 0.39 0.18 0.38 0.17 360 0.204 20.372 0.000680 0.41 0.19 0.40 0.18 380 0.220 21.504 0.000732 0.43 0.20 0.42 0.19 400 0.240 22.635 0.000800 0.45 0.22 0.44 0.21 420 0.261 23.767 0.000868 0.48 0.24 0.47 0.23 440 0.271 24.899 0.000903 0.50 0.25 0.49 0.24 460 0.287 26.031 0.000955 0.52 0.26 0.51 0.25

171

480 0.312 27.162 0.001040 0.55 0.28 0.54 0.27 500 0.333 28.294 0.001108 0.57 0.30 0.56 0.29 520 0.353 29.426 0.001177 0.59 0.32 0.58 0.31 540 0.380 30.558 0.001267 0.61 0.35 0.60 0.34 560 0.400 31.690 0.001333 0.64 0.36 0.63 0.35 580 0.425 32.821 0.001417 0.66 0.39 0.65 0.38 600 0.445 33.953 0.001483 0.68 0.40 0.67 0.39 620 0.465 35.085 0.001550 0.70 0.42 0.69 0.41 640 0.485 36.217 0.001617 0.73 0.44 0.72 0.43 660 0.500 37.348 0.001667 0.75 0.45 0.74 0.44 680 0.520 38.480 0.001733 0.77 0.47 0.76 0.46 700 0.550 39.612 0.001833 0.80 0.50 0.79 0.49 720 0.565 40.744 0.001883 0.82 0.51 0.81 0.50 740 0.590 41.875 0.001967 0.84 0.54 0.83 0.53 760 0.625 43.007 0.002083 0.86 0.57 0.85 0.56 780 0.665 44.139 0.002217 0.89 0.60 0.88 0.59 800 0.725 45.271 0.002417 0.91 0.66 0.90 0.65 820 0.830 46.403 0.002767 0.93 0.75 0.92 0.74 840 0.895 47.534 0.002983 0.95 0.81 0.94 0.80 860 1.005 48.666 0.003350 0.98 0.91 0.97 0.90 880 1.100 49.798 0.0036667 1.00 1.00 1.00 1.00 850 1.200 48.100 0.004000 0.97 1.09 0.96 1.08 820 1.300 46.403 0.004333 0.93 1.18 0.92 1.17 790 1.400 44.705 0.004667 0.90 1.27 0.89 1.26 760 1.525 43.007 0.005083 0.86 1.39 0.85 1.38 730 1.600 41.310 0.005333 0.83 1.45 0.82 1.44 700 1.750 39.612 0.005833 0.80 1.59 0.79 1.58

172



173

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.00

0

0.20

0

0.40

0

0.60

0

0.80

0

1.00

0

1.20

0

1.40

0

1.60

0

1.80

0

Normalized Strain

Nor

mal

ized

Str

ess

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0.00

0

0.00

1

0.00

2

0.00

3

0.00

4

0.00

5

0.00

6

0.00

7

Strain

Stre

ss (N

/mm

²)

Fi = 0.225

6.17.4 Stress-Strain values of Cylinder with 1.327% confinement (M50 gradeGFRSCC)

Peak Load=920 KN ; Compressive strength=52.0614N/mm2



Actual Values Equation

Values Load In KN

Mean-

Displace-

ment

Stress in

N/mm²

f

Strain

uff u uff u 0 0.000 0.000 0.000000 0.00 0.00 0 0

20 0.006 1.132 0.000018 0.02 0.00 0.01 0.00 40 0.011 2.264 0.000037 0.04 0.01 0.03 0.00 60 0.017 3.395 0.000055 0.07 0.01 0.06 0.00 80 0.022 4.527 0.000073 0.09 0.02 0.08 0.01 100 0.028 5.659 0.000092 0.11 0.02 0.10 0.01 120 0.033 6.791 0.000110 0.13 0.03 0.12 0.02 140 0.043 7.922 0.000142 0.15 0.03 0.14 0.02 160 0.049 9.054 0.000162 0.17 0.04 0.16 0.03 180 0.070 10.186 0.000232 0.20 0.05 0.19 0.04 200 0.080 11.318 0.000267 0.22 0.06 0.21 0.05 220 0.091 12.449 0.000302 0.24 0.07 0.23 0.06 240 0.106 13.581 0.000353 0.26 0.08 0.25 0.07 260 0.117 14.713 0.000388 0.28 0.09 0.27 0.08 280 0.137 15.845 0.000457 0.30 0.11 0.29 0.10 300 0.153 16.977 0.000508 0.33 0.12 0.32 0.11 320 0.173 18.108 0.000577 0.35 0.13 0.34 0.12 340 0.194 19.240 0.000645 0.37 0.15 0.36 0.14 360 0.204 20.372 0.000680 0.39 0.16 0.38 0.15 380 0.220 21.504 0.000732 0.41 0.17 0.40 0.16 400 0.240 22.635 0.000800 0.43 0.18 0.42 0.17 420 0.261 23.767 0.000868 0.46 0.20 0.45 0.19 440 0.271 24.899 0.000903 0.48 0.21 0.47 0.20 460 0.287 26.031 0.000955 0.50 0.22 0.49 0.21

174

480 0.312 27.162 0.001040 0.52 0.24 0.51 0.23 500 0.333 28.294 0.001108 0.54 0.26 0.53 0.25 520 0.353 29.426 0.001177 0.57 0.27 0.56 0.26 540 0.380 30.558 0.001267 0.59 0.29 0.58 0.28 560 0.400 31.690 0.001333 0.61 0.31 0.60 0.30 580 0.425 32.821 0.001417 0.63 0.33 0.62 0.32 600 0.445 33.953 0.001483 0.65 0.34 0.64 0.33 620 0.465 35.085 0.001550 0.67 0.36 0.66 0.35 640 0.485 36.217 0.001617 0.70 0.37 0.69 0.36 660 0.500 37.348 0.001667 0.72 0.38 0.71 0.37 680 0.520 38.480 0.001733 0.74 0.40 0.73 0.39 700 0.550 39.612 0.001833 0.76 0.42 0.75 0.41 720 0.565 40.744 0.001883 0.78 0.43 0.77 0.42 740 0.590 41.875 0.001967 0.80 0.45 0.79 0.44 760 0.625 43.007 0.002083 0.83 0.48 0.82 0.47 780 0.675 44.139 0.002250 0.85 0.52 0.84 0.51 800 0.750 45.271 0.002500 0.87 0.58 0.86 0.57 820 0.850 46.403 0.002833 0.89 0.65 0.88 0.64 840 0.945 47.534 0.003150 0.91 0.73 0.90 0.72 860 1.005 48.666 0.003350 0.93 0.77 0.92 0.76 880 1.100 49.798 0.003667 0.96 0.85 0.95 0.84 900 1.200 50.930 0.004000 0.98 0.92 0.97 0.91 920 1.300 52.061 0.004333 1.00 1.00 1.00 1.00 890 1.400 50.364 0.004667 0.97 1.08 0.96 1.07 860 1.525 48.666 0.005083 0.93 1.17 0.92 1.16 830 1.600 46.968 0.005333 0.90 1.23 0.89 1.22 800 1.725 45.271 0.005750 0.87 1.33 0.86 1.32 770 1.800 43.573 0.006000 0.84 1.38 0.83 1.37 730 1.900 41.310 0.006333 0.79 1.46 0.78 1.45 700 2.000 39.612 0.006667 0.76 1.54 0.75 1.53

175



176

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00

0

0.20

0

0.40

0

0.60

0

0.80

0

1.00

0

1.20

0

1.40

0

1.60

0

1.80

0

Normalized Strain

Nor

mal

ized

Str

ess

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0.00

00

0.00

10

0.00

20

0.00

30

0.00

40

0.00

50

0.00

60

0.00

70

Strain

Stre

ss (N

/mm

²)

Fi = 0.225

6.17.5 Stress-Strain values of Cylinder with 1.591% confinement (M50 gradeGFRSCC)

Peak Load=1020 KN ; Compressive strength=57.720 N/mm2



Actual Values Equation Values Load In KN

Mean-

Displace-

ment

Stress in

N/mm²

f

Strain

uff u uff u

0 0.000 0.000 0.000000 0.00 0.00 0 0 20 0.010 1.132 0.000033 0.02 0.01 0.01 0.00 40 0.020 2.264 0.000065 0.04 0.01 0.03 0.00 60 0.027 3.395 0.000090 0.06 0.02 0.05 0.01 80 0.035 4.527 0.000117 0.08 0.02 0.07 0.01

100 0.048 5.659 0.000158 0.10 0.03 0.09 0.02 120 0.060 6.791 0.000200 0.12 0.04 0.11 0.03 140 0.073 7.922 0.000242 0.14 0.05 0.13 0.04 160 0.080 9.054 0.000267 0.16 0.06 0.15 0.05 180 0.093 10.186 0.000308 0.18 0.06 0.17 0.05 200 0.105 11.318 0.000350 0.20 0.07 0.19 0.06 220 0.118 12.449 0.000392 0.22 0.08 0.21 0.07 240 0.130 13.581 0.000433 0.24 0.09 0.23 0.08 260 0.148 14.713 0.000492 0.25 0.10 0.24 0.09 280 0.160 15.845 0.000533 0.27 0.11 0.26 0.10 300 0.175 16.977 0.000583 0.29 0.12 0.28 0.11 320 0.190 18.108 0.000633 0.31 0.13 0.30 0.12 340 0.200 19.240 0.000667 0.33 0.14 0.32 0.13 360 0.215 20.372 0.000717 0.35 0.15 0.34 0.14 380 0.230 21.504 0.000767 0.37 0.16 0.36 0.15 400 0.240 22.635 0.000800 0.39 0.17 0.38 0.16 420 0.255 23.767 0.000850 0.41 0.18 0.40 0.17 440 0.270 24.899 0.000900 0.43 0.19 0.42 0.18 460 0.290 26.031 0.000967 0.45 0.20 0.44 0.19 480 0.305 27.162 0.001017 0.47 0.21 0.46 0.20 500 0.325 28.294 0.001083 0.49 0.22 0.48 0.21 520 0.350 29.426 0.001167 0.51 0.24 0.50 0.23

177

540 0.368 30.558 0.001225 0.53 0.25 0.52 0.24 560 0.400 31.690 0.001333 0.55 0.28 0.54 0.27 580 0.423 32.821 0.001408 0.57 0.29 0.56 0.28 600 0.450 33.953 0.001500 0.59 0.31 0.58 0.30 620 0.478 35.085 0.001592 0.61 0.33 0.60 0.32 640 0.500 36.217 0.001667 0.63 0.34 0.62 0.33 660 0.530 37.348 0.001767 0.65 0.37 0.64 0.36 680 0.560 38.480 0.001867 0.67 0.39 0.66 0.38 700 0.590 39.612 0.001967 0.69 0.41 0.68 0.40 720 0.620 40.744 0.002067 0.71 0.43 0.70 0.42 740 0.660 41.875 0.002200 0.73 0.46 0.72 0.45 760 0.690 43.007 0.002300 0.75 0.48 0.74 0.47 780 0.725 44.139 0.002417 0.76 0.50 0.75 0.49 800 0.760 45.271 0.002533 0.78 0.52 0.77 0.51 820 0.800 46.403 0.002667 0.80 0.55 0.79 0.54 840 0.835 47.534 0.002783 0.82 0.58 0.81 0.57 860 0.875 48.666 0.002917 0.84 0.60 0.83 0.59 880 0.915 49.798 0.003050 0.86 0.63 0.85 0.62 900 0.960 50.930 0.003200 0.88 0.66 0.87 0.65 920 1.015 52.061 0.003383 0.90 0.70 0.89 0.69 940 1.065 53.193 0.003550 0.92 0.73 0.91 0.72 960 1.125 54.325 0.003750 0.94 0.78 0.93 0.77 980 1.190 55.457 0.003967 0.96 0.82 0.95 0.81 1000 1.275 56.588 0.004250 0.98 0.88 0.97 0.87 1020 1.450 57.7202 0.004833 1.00 1.00 1.00 1.00 1000 1.550 56.588 0.005167 0.98 1.07 0.97 1.06 980 1.630 55.457 0.005433 0.96 1.12 0.95 1.11 960 1.685 54.325 0.005617 0.94 1.16 0.93 1.15 920 1.765 52.061 0.005883 0.90 1.22 0.89 1.21 870 1.875 49.232 0.006250 0.85 1.29 0.84 1.28 830 1.950 46.968 0.006500 0.81 1.34 0.80 1.33 780 2.075 44.139 0.006917 0.76 1.43 0.75 1.42 690 2.300 39.046 0.007667 0.68 1.59 0.67 1.58

178

Fig: 6.17 Stress-Strain behaviour of GFRSCC (1.591% Confinement)


179

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00

0

0.20

0

0.40

0

0.60

0

0.80

0

1.00

0

1.20

0

1.40

0

1.60

0

1.80

0

Normalized Strain

Nor

mal

ized

Str

ess

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

0.00

00

0.00

10

0.00

20

0.00

30

0.00

40

0.00

50

0.00

60

0.00

70

0.00

80

0.00

90

Strain

Stre

ss (N

/mm

²)

Fi = 0.225

Table 6.17. Peak stress and strain values corresponding to peak Stress with different confinements of M50 grade

Sl. No Designation Confinement Peak stress N/mm2

Improvement in

compressive strength (%)

Strain at peak stress

1 GFSCC p 0 43.0072 7.52 0.00279

2 GFRSCC (3R) 0.798 46.4025 16.00 0.00293

3 GFRSCC (4R) 1.062 49.798 24.50 0.00367

4 GFRSCC (5R) 1.327 52.0614 30.15 0.00433

5 GFRSCC (6R) 1.591 57.7202 44.30 0.00483

Fig 6.19 % of Different Confinements Vs % of Improvement of Compressive Strength

180

0

5

10

15

20

25

30

35

40

45

50

0 0.5 1 1.5 2

% of Confinement

% o

f Im

prov

men

t of C

ompr

essi

ve S

tren

gth

Table 6.18 Stress -Strain Equations for Different Confinements

of M50 Grade

% of Steel Ascending Descending

A1= 2.395, B1= 0.724 ,

C1= 1.0, D1 =0.0

A1= 0.528, B1= -1.470 ,

C1= 1.0, D1 =0.0

GFSCC plain

2

0.1724.01

395.2

uu

u

uff

2

0.1470.11

528.0

uu

u

uff

A1= 2.50, B1= 1.104 ,

C1= 1.0, D1 =0.0

A1= 1.336, B1= -0.611 ,

C1= 1.0, D1 =0.0 GFRSCC

0.798%

(3R) 2

0.1104.11

50.2

uu

u

uff

2

0.1611.01

336.1

uu

u

uff

A1= 2.771, B1= 1.245 ,

C1= 1.0, D1 =0.0

A1= 1.163, B1= -0.765 ,

C1= 1.0, D1 =0.0 GFRSCC

1.062%

(4R) 2

0.1245.11

771.2

uu

u

uff

2

0.1765.01

163.1

uu

u

uff

A1= 3.315, B1= 1.593 ,

C1= 1.0, D1 =0.0

A1= 0.641, B1= -1.345 ,

C1= 1.0, D1 =0.0 GFRSCC

1.327%

(5R) 2

0.1593.11

315.3

uu

u

uff

2

0.1345.11

641.0

uu

u

uff

A1= 3.338, B1= 2.217 ,

C1= 1.0, D1 =0.0

A1= 0.387, B1= -1.610 ,

C1= 1.0, D1 =0.0 GFRSCC

1.591%

(5R) 2

0.1217.21

338.3

uu

u

uff

2

0.1610.11

387.0

uu

u

uff

181

CHAPTER 7

Discussions of the Test Results

CHAPTER 7 Discussions of the Test Results

7.0. Discussions:

The Fresh and hardened properties of GFRSCC with & without confinement at 28

days cylinder and cubes are shown in Tables 6.9 & 6.10. Peak stress-strain values and the

Normalized stress-strain values for both GFRSCC with & without confinement at 28 days

cylinder are shown in Table 6.12 to 6.16. Stress-strain curves & Normalized Stress-strain

Curves of GFRSCC with & without confinement are shown in Figures 6.9 to 6.18.The

Secant Modulus values for GFRSCC with & without confinement are shown in Table 7.1.

Fig.7.1.Typical Stress-strain behavior of M50 grade GFRSCC with and

without confinement at 28 days

182

Fi = 0.225

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

0.00

0

0.00

1

0.00

2

0.00

3

0.00

4

0.00

5

0.00

6

0.00

7

0.00

8

0.00

9

Strain

Stre

ss (N

/mm

²)

SCC pSCC 3R (0.798)SCC 4R (1.062)SCC 5R (1.327)SCC 6R (1.591)

7.1. Characteristics of GFRSCC Mixes in Hardened State

Effect on

7.1.1. Compressive Strength

The compressive strength values obtained by testing standard Cylinders of

GFRSCC with and without confinement are tabulated in Tables 6.16. All the specimens

with confinement have shown strength above 50 MPa, which is the required strength. The

mix, with and without confinement, containing the mineral admixture of Fly ash (33%)

has shown higher compressive strength compared to other SCC mixes. Further the

GFRSCC with confinement compared to Plain GFSCC has shown an improvement in

compressive strength by 7.52% to 44.30%.

7.1.2. Modulus of elasticity The elastic modulus (E-modulus) of concrete is to larger extent influenced by the

volume of aggregate and by the aggregate properties than by the paste properties. In

comparison with normal concrete the aggregate content of GFR SCC is smaller and

the paste content of GFRSCC is larger. Therefore the elastic modulus of GFRSCC

is expected to be somewhat lower than in normal concrete of the same strength

class, which also is presented in several reports. However, the differences are small

and covered by the safe assumptions included in the formulas within the norms. In

cases where the E-modulus is of special importance, its real value ought to be determined.

7.1.3. Secant Modulus

The term Young’s Modulus of elasticity can strictly be applied only to the straight

part of the Stress-Strain Curve. In case of concrete, since no part of the graph is straight

line is drawn connecting a specified point on the Stress-Strain Curve to the origin of the

curve. Slope of this line is referred as Secant Modulus. In this case Secant Modulus antEsec

obtained at 39% Stress level is shown in Table 7.1. It shows there is an increase in Secant

Modulus with Confinement. The value of Secant Modulus obtained for SCC without

confinement is 28294.25 N/mm2. This is found to be about 24.95 % less than normal

concrete of similar strength (35355.339 N/mm2). An equation relating Young’s modulus

183

(EC) of GFRSCC and its compressive strength (fck) is obtained as EC = 5000 √ fck..

The Secant modulus of GFRSCC with confinement follows the relationship Esec =

5132√fck. The high elastic modulus and high density of steel may be responsible to

increase the ESec of GFRSCC.

Table.7.1 Secant Modulus of SCC

Designation Secant Modulus

N/mm2

GFSCC P 28294.25

GFRSCC 0.798 29958.82

GFRSCC 1.062 31383.02

GFRSCC 1.327 33419.29

GFRSCC 1.591 33657.99

7.1.4. Stress-Strain behaviour of GFRSCC with & without confinement The effect of glass fiber in SCC under axial compression was examined for the

stress-strain behavior of GFRSCC. The Stress-Strain behaviour of M50 grade

GFRSCC at 28 days with and without confinement is shown in Figures 6.9 to 6.18 and

is observed to be almost similar in the ascending portion of the curve. The

proportionality limit increases as the confinement increases. This is due to the lateral

partial restraint of the GFRSCC cylinder provided by confinement. More over the

characteristic compressive strength increases as the confinement increases. Not only

has the ultimate strength of the GFRSCC but also strain at failure stress increased as the

confinement increases.

Figure 7.10 shows typical stress-strain curves of M50 GFRSCC at 28 days under

compression. The ascending part of stress-strain curve is more linear and steeper as the

compressive strength of concrete increases. Figure 7.10 also shows that there is increase

in compressive strength with increasing tie confinements and also it shows that the peak

strain increases slightly with increasing compressive strength. There is not much

difference in the initial portion of stress – strain curves for confined and unconfined state.

Since the confinement provided by lateral circular-hoop reinforcement, is a reaction to the

lateral expansion of concrete, lateral reinforcement becomes effective only after

considerable deformation in the axial direction.

184

The single polynomial equation for the stress-strain response of GFRSCC with and

without confinement have been proposed in the form of 2

111

11

uu

u

uCB

DA

ff

The same polynomial equation is valid for both ascending and descending

portions with different values of constants as shown in Table 7.2.

Table.7.2Constants A1, B1 values for Ascending & Descending Portions

Ascending Portion Descending Portion Designation A1 B1 Rank

Correlation A1 B1 Rank

Correlation GFSCC p 2.395 0.724 0.9947 0.528 -1.470 0.7765 GFRSCC (3R) 2.500 1.104 0.9942 1.336 -0.611 0.8588 GFRSCC (4R) 2.771 1.245 0.994 1.163 -0.765 0.8987 GFRSCC (5R) 3.315 1.595 0.9841 0.641 -1.345 0.7363 GFRSCC (6R) 3.338 2.217 0.9878 0.387 -1.610 0.8253

The proposed empirical equation, the above A1, B1 values shown in the above

table shows good correlation with experimental data.

Table 7.3: Young’s Modulus of Elasticity, Specific Toughness, Energy absorption,

and ductility values for GFRSCC with and without confinement reinforcement

7.1.5. Energy absorption capacity or Toughness

The energy absorption capacity or toughness of concrete in compression has been

defined as the area under the stress – strain curve calculated up to a specified strain value.

The specific toughness of concrete in compression has been defined as the ratio of the

area under the stress – strain curve to the cylinder compressive strength of the concrete.

185

SL No Designation

Secant Modulus (N/mm²)

Peak stress

N/mm2

Area Under Stress– Strain Curve

(N/mm²) x 10ˉ²

Specific Toughness

(%)

Energy Absorption

(% increase)

Strain at peak Stress

Ductility (%

increase)

1 GFSCC p 28294.25 43.0072 1229.50 0.2858 - 0.002792 - 2 GFRSCC (3R) 29958.82 46.4025 1800.00 0.3879 36.12 0.002933 5.05 3 GFRSCC (4R) 31383.02 49.7980 2245.00 0.4508 58.18 0.003667 31.33 4 GFRSCC (5R) 33419.29 52.0614 2510.00 0.4821 69.16 0.004333 55.19 5 GFRSCC (6R) 33657.99 57.7202 3320.00 0.5752 101.82 0.004833 73.10

The increase in energy absorption with confinement is shown in table 7.3. There is

an improvement of energy absorption capacity from 36.12% to 101.82% due to

confinement.

7.1.6. Ductility

Ductility is a mechanical property of materials that measures the degree of plastic

deformation the material can sustain prior to fracture. If little or no plastic deformation

can occur the material is termed "brittle". Ductility can be quantitatively expressed in

terms of either percent eleongation or percent reduction in an area.

Ductility which indicates deformable characteristic of a material is measured in

terms of percentage increase in strain at peak stress with confinement. The percentage

increase in ductility is ranging from 5.05% to 73.10% with confinement.

7.1.7. Analytical expressions:

An examination of the curves in Figs 6.4 and ind icates that the

behaviour is similar for the entire confinements M50 grade, meaning that the stress-

strain behaviour is linear upto 80-90% of the ultimate and non linear beyond this. The

post peak stress-strain response for all the GFRSCC specimens is gradual and appears to

have a consistent and constant gradient. This similarity leads to the conclusion that if the

stress is expressed as stress ratio by dividing the stress at any level by the corresponding

stress at ultimate and the strain ratio obtained by dividing the strain at any level by the

corresponding to the strain at ultimate strength, the plot of these two ratios falls into the

same pattern. Thus by non-dimensionalising the stresses and strains as explained above

the effect of Fiber Index (Fi) can be eliminated. Fig 6.8 shows the values of the non-

dimensionalised stress as ordinate and the normalized strain as abscissa. The

characteristic values and the analytical values are plotted in the figure. The stress-strain

behavior can be represented by a general curve, which functions as a stress block. A

single polynomial of the form shown in equation 4 is used in the current investigation.The

same polynomial equation is valid for both ascending and descending portions with

different values of constants as shown in table 7.2. The normalized stress strain curves for

different % volume of confinement along with the analytical equations proposed are

shown in fig 6.9 to 6.18

186

The model is of the form

21

CBDAf

(4)


non-dimensional stress-strain curves the following form is proposed.

2

111

11

uu

u

uCB

DA

ff

(5)





Fig. 7.2 Graphical representation of increase in strength, Specific Toughness (% increase) with different confinements

187

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2

% of Confinement

Spec

ific

toug

hnes

s

Fig. 7.3 Graphical representation of increase in strength, Energy Absorption (% increase) with different confinements

Fig. 7.4 Graphical representation of increase in strength, ductility (% increase) with different confinements

188

0

20

40

60

80

100

120

0 0.5 1 1.5 2

% of Confinement

Ener

gy A

bsor

ptio

n (%

incr

ease

)

0

10

20

30

40

50

60

70

80

0 0.5 1 1.5 2

% Confinement

Duc

tility

(%in

crea

se)

CHAPTER 8

Conclusions and Recommendations

CHAPTER 8 Conclusions and Recommendations

8.0. Conclusions

Taking into account the findings from this study, The GFRSCC mix developed

and satisfied the requirements of Self-compacting concrete specified by EFNARC

guidelines. The properties like Modulus of Elasticity (Ec), Energy absorption capacity,

Ductility and Stress-Strain behaviour were studied and the following conclusions can be

drawn:

It has been verified, by using the slump flow and U-tube tests, that self-

compacting concrete (SCC) achieved consistency and self-compactability under its own

weight, without any external vibration or compaction. Also, because of the special

admixtures used, SCC has achieved a density between 2400 and 2500 kg/m³, which was

greater than that of normal concrete, 2370-2321 kg/m³.

Self-compacting concrete can be obtained in such a way, by adding chemical and

mineral admixtures, so that its compressive strengths are higher than those of normal

vibrated concrete. An average increase in compressive strength of 60% has been obtained

for SCC.

Also, due to the use of chemical and mineral admixtures, self-compacting

concrete has shown smaller interface microcracks than normal concrete, fact which led to

a better bonding between aggregate and cement paste and to an increase in compressive

strengths. A measure of the better bonding was the greater percentage of the fractured

aggregate in SCC (20-25%) compared to the 10% for normal concrete

In addition, self-compacting concrete has two big advantages. One relates to the

construction time, which in most of the cases is shorter than the time when normal

concrete is used, due to the fact that no time is wasted with the compaction through

vibration. The second advantage is related to the placing. As long as SCC does not

require compaction, it can be considered environmentally friendly, because if no vibration

is applied no noise is made.

189

'

In the high strength concrete which is more brittler than ordinary concrete, using

confinement reinforcement, ductility is increased to a great extent. When confinement

reinforcement spacing is decreased to half, ductility improved twice. As a result, by

decreasing confinement reinforcement spacing, the compressive strength of high strength

concrete can be improved. Decreasing confinement reinforcement spacing has increased

the compressive strength of confined concrete to a maximum of 19%.

Based on experimental study on Glass Fiber Reinforced Self Compacting

Concrete (GFRSCC) the following conclusions can be drawn.

1. Self Compacting Concretes satisfying the specifications laid by EFNARC could

be developed for non fibrous and fibrous concretes. There is a marginal increase in

compressive strength of self compacting concrete with glass fiber additions.

2. Glass Fiber inclusion in Self Compacting Concrete improved the peak strain and

strain at 85% of the ultimate strength in descending portion. The improvements in

strains are pronounced than improvement in strength.

3. The ultimate compressive strength varied linearly with Fiber Index and can be

expressed by a relationship that includes the Fiber Index. The prediction equation for

ultimate strength is

fu=f {(1.0+0.1074Fi)}

4 .The strain at peak stress varies linearly with Fiber Index and can be expressed by a

relationship that includes Fiber Index. The equation obtained by regression

analysis is

εu = ε’ {(1.0+0.1074Fi)}

190

5. The ductility factor (DF) of standard concrete given by the ratio of the strain at

85% of the peak stress on the descending portion of the stress strain curve has

improved with specific surface factor.

DF = 2.4577 + 2.0912 Fi

6. The experimental values compared well with analytical model developed. A non-

dimensionalised stress–strain equation proposed in this investigation can be used to

predict the behaviour of Glass Fiber Reinforced Self Compacting

Concrete(GFRSCC). The stress block parameters presented in this paper can be

used to determine the ultimate moment and corresponding curvature of GFRSCC.

7. Confinement of concrete has increased the strengths at 28 days from 7.52% to 44.30%

in compression.

8. The value of secant modulus (Ec) obtained for M50 grade SCC without confinement is

24.95% less than normal concrete of similar strength.

9. The value of secant modulus (Ec) obtained for M50 grade GFRSCC with confinement

is 2.64% more than ordinary concrete and follows the relationship Ec = 5132√ fck,

10. It observed that the peak stress and corresponding strain at peak stress increases with

the increase in the percentage of confinement.

11.The energy absorption was increased by 101.82% when the percentage of

confinement is 1.591%.

191

Table 8.1. Peak stress and Peak strain for Different confinements of GFRSCC

Sl. No Designation Peak stress N/mm2 Strain at

peak stress

1. GFSCC p 43.0072 0.002792

2. GFRSCC (3R) 0.798 46.4025 0.002933

3. GFRSCC (4R) 1.062 49.7980 0.003667

4. GFRSCC (5R) 1.327 52.0614 0.004333

5. GFRSCC (6R) 1.591 57.7202 0.004833

8.1 Recommendations for Future Research

Following are some suggestions for future research. As GFRSCC technology is

now being adopted in many countries throughout the world, in the absence of suitable

standardized test methods it is necessary to examine the existing test methods and identify

or, when necessary, develop test methods suitable for acceptance as International

Standards. Such test methods have to be capable of a rapid and reliable assessment of key

properties of fresh SCC on a construction site. At the same time, the testing equipment

should be reliable, easily portable and inexpensive. The test procedure should be carried

out by a single operator and the test results have to be interpreted with a minimum of

training. Also, the results have to define and specify different GFRSCC mixes. One

primary application of these test methods would be in verification of compliance on sites

and in concrete production plants, if self- compacting concrete could be manufactured in

large quantities..

Further investigations have to be carried out regarding the self-compacting

concrete. One major topic, which has to be studied, is related to the influence of cement

type and aggregate shape and surface properties on the bonding between cement paste

and coarse aggregate. Also, a thorough investigation has to be carried out in order to

obtain an appropriate relationship between the water-cement ratio and the aggregate-

cement physical interface.

However, unless this work is carried out without delay, there will be a real risk of

each country adopting more or less different test methods, making any future

harmonization very difficult, so that standardization of tests capable of dealing with the

key properties of GFRSCC is urgently required.

192

1. Though GFRSCC enhances all concrete properties by minimizing voids etc, the

long-term behavior of concrete like Creep and Durability has to be studied.

2. The durability properties of GFRSCC can be evaluated by varying mix

proportions, like aggregate content, cement content, superplasticizer content,

maximum aggregate size and the use of different types and quantity of filler.

3. Comparative study related to normal conventional vibrated concrete can be

studied using the mix design adopted in this research.

4. Long-term study on durability of GFRSCC considering rebar corrosion

monitoring in addition to other durable properties of concrete.

5. The same work can be performed with different combinations of mineral and

chemical admixtures.

6. There is a wide scope to further investigations the effect of GFRSCC under long-

term loading.

7. Sufficiently low water powder ratio of 0.24 can be used for getting high

compressive strength self compacting concrete

8. The mechanical properties of self compacting concrete mixes are better, despite

addition of 40-50% fly ash by weight of cement.

9. A reduction in bleeding is observed by addition of glass fibre in the glass fibre self

compacting concrete mixes.

10. A reduction in bleeding improves the surface integrity of concrete, improves

its homogeneity, and reduces the probability of cracks.

11. The variation in compressive strength of glass fibre self compacting concrete

mixes are observed to be 15 % to 20 % when compared with self Compacting

concrete mixes 12. All the cracks observed in glass fibre self compacting concrete mixes on impact

specimens are brittle failure cracks.

193

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6. ASTM C642 (1996). “Standard test method for specific gravity, absorption, and

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199

APPENDIX A

For Mix Proportion of M50 Grade Concrete

The mix proportioning for a concrete of M50 grade is given through steps 1 to 7

1. Stipulations for Proportioning:

a) Grade of designation: M50

b) Type of Cement: OPC 53 grade conforming to IS: 8112:1989(Reaff.2005)

c) Maximum nominal size of aggregate: 20mm

d) Minimum cement content: 320 kg/m³

e) Maximum water – cement ratio: 0.40

f) Workability in terms of Slump: 0.95

g) Exposure condition: Mild (for reinforced concrete)

h) Degree of supervision: Good

i) Type of aggregate: Crushed angular aggregate

j) Maximum cement content: 478.95kg/m³

k) Chemical admixture type: Superplasticiser

2. Test data of materials:

a) Cement: OPC 53 grade conforming to IS 8112

b) Specific gravity of cement: 3.03

c) Chemical admixture: Superplasticiser conforming to IS 9103:1999

d) Specific Gravity of:

Coarse Aggregate: 2.67

Fine Aggregate: 2.60

e) Water Absorption (IS 2386:1963)

Coarse Aggregate: Nil

Fine Aggregate: Nil

f) Free (surface) moisture:

Coarse Aggregate: Nil

Fine Aggregate: Nil

3. Target strength for mix proportioning:

Sff ckck 65.1'

Where ckf ' = target average compressive strength at 28 days

200

ckf = Characteristic compressive strength at 28 days

S = Standard Deviation, = 4N/mm²

Therefore, target strength = 50+ (1.65x4) = 56.60N/mm²

4. Selection of water/cement ratio:

From table 5 of IS 456-2000,

Maximum water cement ratio = 0.55 for Mild exposure.

Let us adopt water/cement ratio as 0.40 only

5. Selection of water content:

Corrections for FA and water content

Change in conditions Adjustment requirement

for water content

Adjustment requirements

for %FA in total

aggregate

Sand conforming to zone II 0 0

Each 0.05 increase (or)

decrease in w/c ratio 0 -4.0 %

Increase or decrease in the

value of compaction factor

by 0.1

+3.0 % 0

For rounded aggregate 0 0

Maximum water content = 186L (for 25 to 50 mm slump range) for 20mm

aggregate

Estimated water content for 100mm slump = 186 + (3/100 x 186) = 191.60L

6. Calculation of cement content:

Water/cement ratio = 0.40

Cement content = 191.60/0.40 = 479 kg/m³

From Table 5 of IS 456-2000,

Minimum cement content for mild exposure condition = 300 kg/m³

479kg/m³ > 300kg/m³,

Hence, adopt Maximum Cement content = 479kg/m³

201

Corrections for FA and Water content

% sand = 35 - 4 = 31%

7. Quantity of FA & CA:

1000

11

fa

a

C Sf

pSCWV

1000

11

1

ca

a

C SC

pSCWV

Where V = absolute volume of concrete

= Gross volume (1m3) minus the volume of entrapped air

Sc = specific gravity of cement

W = Mass of water per cubic metre of concrete, kg

C = mass of cement per cubic metre of concrete, kg

p = ratio of fine aggregate to total aggregate by absolute volume

fa, Ca = total masses of fine and coarse aggregates, per cubic meter of concrete,

respectively, kg, and

Sfa, Sca = specific gravities of saturated surface dry fine and coarse aggregates, respectively

1. Calculation of Aggregate contents:

1000

11

1

ca

a

C SC

pSCWV

For 20 mm aggregate air entrapped =2%

Therefore, entrapped air = 1-(2/100) = 0.98%

202

10001

67.231.0103.34796.19198.0

aC

22.1161aC kg

100011

fa

a

C Sf

pSCWV

1000

16.231.003.3

4796.19198.0

af

03.508af kg

Material quantities obtained as per design method

Materials Quantities (kg/m3)

Cement 479

Fine aggregate 508.03

Coarse aggregate 1161.22

Water 191.60

These mixes are further adjusted using EFNARC guidelines as explained in the

previous chapter and the final quantities are used in the mix proportions.

Material quantities after adjustments as per EFNARC Guidelines


Cement 425

Fine Aggregate 794.93

Coarse Aggregate 896.40

Water 190

Fly ash 209

Super plasticizer 85ml

Viscosity modifying agent 3ml

203

2. Quantity of the materials required for 1m³ concrete:

1. Cement = 425/1440 = 0.2951 m3

2. Fly ash = 209/832 = 0.2512 m3

3. Fine Aggregate = 794.93/1640 = 0.4847 m3

4. Coarse Aggregate = 896.40 = (268.92/1411)+(627.48/1408) = 0.6362 m3

5. Water = 190/1000 = 0.190 m3

Total = 1.8572 m3

i.e. 1.8572 m3 materials produce 1 m3 of cement concrete.

1 m3 material produces 0.5384 m3 of cement concrete.

Mix proportion: Cement: Fine Aggregate : Coarse aggregate

1 : 1.642 : 2.156

The above mix for 10 Kg:

10 : 16.42 : 21.56

Cement is replaced by 33% with Fly ash.

A quantity per m³ of the above mix is shown in the following table


Cement 425

Fine Aggregate 794.93

Coarse Aggregate 896.40

Water 190

Fly ash 209

Glass Fibres 0.60

Super plasticizer 85 ml (0.04132m³)

Viscosity modifying agent 3 ml

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VITA

Badanapuri VenkataRaju was born on July 01, 1966 in Golagamudi village of

Vnkatachalam mandal, SPSR Nellore District, Andhra Pradesh, and graduated from

“Andhra University of Waltair” in 1992. He attended the Andhra University College of

Engineering at Waltair between 1987 and 1991 and received his bachelor of Degree in

Civil Engineering with a specialization in Multi-storey Structures and Pre-stressed

concrete Structures in January 1992, and he then joined in the Andhra Pradesh state

Irrigation & CAD department as Assistant Executive Engineer and rendered 20years of

service. He is member of the Institution of Engineers (INDIA) since 2003. Presently he is

working as Executive Engineer, in Telugu Ganga Project; Gudur of SPSR Nellore

District. He then came to Hyderabad April 2006, to pursue higher education at JNTUH

College of Engineering, Kukatpally Hyderabad – 500085, Andhra Pradesh, India. He

started his Master of Technology, in the Department of Civil Engineering with the

specialization in Structural Engineering and successfully completed his degree

requirements in July 2009.

205

M.tech thesis

Education

Transcript of M.tech thesis