Mechanical Properties of Ultra High Performance Fiber ...library.iugaza.edu.ps/thesis/110330.pdf ·...

The Islamic University of Gaza الجــــبمعة اإلســالمــــــــية بـــــغزة

Higher Education Deanship عــــــــــمبدة الذراســـــبت العلــــــيب

Faculty of Engineering كـــــلــــــــــية الـــهـــــــــنــــذســــة

Civil Engineering Department ــــــــسم الهــــــــنذسة الـــــمذنـيةقـ

Design and Rehabilitation of Structures برنــبمج تصمــيم و تأهيل المنشئبت

Mechanical Properties of Ultra High Performance

Fiber Reinforced Self-Compacting Concrete

By:

AbdUlla Taisir Al Madhoun

Supervised by:

Prof. Samir Shihada

Dr. Mohammed Arafa

A Research Submitted in Partial Fulfillment of the Requirements for the Degree of Master

of Science in Civil Engineering – Design and Rehabilitation of Structures

2013 - 1434

I

ABSTRACT

The usage of ultra-high strength concrete with high compressive strength in construction

applications has been increasing worldwide and will make an impact in Gaza Strip due to

the limited land area available for construction, the fast growing population and due to bad

and unstable political conditions and the continuing wars in Gaza Strip, strong, relatively

cheap, easy to use and locally available repairing and strengthening material should be

produced for that purposes as well.

The main goal of this research is to produce Ultra High Performance Fiber Reinforced Self

Compacting Concrete in Gaza strip, using materials that are available at the local markets.

Different trial mixes were used to obtain the acceptable fresh properties of self-compacting

concrete with a compressive strength exceeding 177 MPa. The research includes also the

use of a recognized manufacturer mineral admixture, steel fibers, quartz sand,

superplasticizers and without using any type of aggregates other than the quartz sand.

The fresh and hardened mechanical properties of Ultra High Performance Fiber Reinforced

Self Compacting Concrete were studied, such as, workability, self-compacting properties,

compressive strength, split cylinder strength, and flexural strength. The effects of using

different steel fibers and silica fume doses on these properties are obtained within the

research work.

The effect of adding different amounts of Polypropylene fibers (0.45 kg/m3, 0.9 kg/m

3 and

1.8 kg/m3) on the fresh and hardened properties of Ultra High Performance Fiber

Reinforced Self Compacting Concrete is also investigated.

Results show that it is possible to produce Ultra High Performance Fiber Reinforced Self

Compacting Concrete in Gaza strip using materials that are available at the local markets if

they are carefully selected and will achieve a minimum compressive strength of 177 MPa at

the age of 28 days. Such concretes can be produced with cement, Water/Cement ratoi of

0.24, steel fibers (16% by the weight of cement), polypropylene fibers (0.9 kg/m3), quartz

sand (125% by the weight of cement), and silica fume (15% by the weight of cement) as

the mineral admixture (3% superplasticizer by the weight of cement.

II

الملخص

إ إسزخذاو انخشسبخ فبئمخ األداء زضاذ ثشكم كجش عه يسز انعبنى، ي انؤكذ أ ك ن أصش ف

لطبع غضح، خصصب ثسجت ضك يسبحبد األساض انزبحخ نهجبء، انزضاذ انكجش ف أعذاد انسكب،

حشة، األيش انز سزذع إسزخذاو يضم ز ثبإلضبفخ عه األضبع األيخ انغش يسزمشح ركشاس حذس ان

اناد انشخصخ سجب يادب انزفشح يحهب كاد رمخ رشيى نهشئبد انزضشسح.

غضح لطبع ف األداء فبئمخو انذيك رارخ ،يسهحخ ثبألنبف خشسبخ إزبط انجحش زا ي انشئس انذف إ

انزغشجخ انخهطبد ي انعذذ رفز انجحش زا ف رى حش انحهخ، ألساقا ف انزفشح اناد ثئسزخذاو

.ثبسكبل يغب 177 فق كسش ضغط رزحم انلذ فس ف انذيك رارخ انخشسبخ عه نهحصل

دذبانه ثعض انسهكب غجبس، انكاسرض سيم أنبف انحذذ، يضم انخهطبد، ز ف خبصخ ياد اسزخذاو رى

د إسزخذاو أ ع ي انشكبو ر انزذسط انحجج انكجش. خانضبف

انصهجخ، انحبنخ انطبصعخ انحبنخ ف األداء فبئمخو انذيك رارخالمسلحة باأللياف، انخشسبخ خاص دساسخ ذر

ذر .االحبء يمبيخ انمبسخ االسطاخ ثبسزخذاو انشذ يمبيخ انكسش انضغط يمبيخ انزشغهخ يضم

على هذه الخواص. انسهكب غجبسأنبف انحذذ ي يخزهفخ ست اضبفخ رأصش دساسخ اضب

كغى/و 0.45كب رذ دساسخ رأصش إضبفخ ست يخزهفخ ي أنبف انجن ثشثه )3

كغى/و 0.0، 3

،1.1

كغى/و3

.االداء فبئمخو انذيك رارخانسهحخ ثبألنبف، نهخشسبخ انزصهجخ انطبصعخ انخاص( عه

أظشد انزبئظ أ ك إزبط خشسبخ يسهحخ ثبألنبف، رارخ انذيك فبئمخ األداء ف لطبع غضح ثئسزخذاو اناد

انزفشح ف األساق انحهخ، إرا رى إخزبس ز اناد ثعبخ، ك انحصل عه خشسبخ راد لذسح رحم نهضغط

% ي ص األسذ، أنبف 16، أنبف حذذ ثسجخ 0.24بسكبل، ثئسزخذاو سجخ يب نألسذ يغب ث 177انكسش رفق

كغى/و 0.9ثن ثشثه ثسجخ 3

% ي ص 15% ي ص األسذ، غجبس انسهكب ثسجخ 125، سيم كاسرض ثسجخ

% ي ص األسذ.3األسذ يهذبد ثسجخ

III

DEDICATIONS

To my Father Eng. Taiseer, My mother’s soul, Aunt Em Mohammed, brothers

Mohammed and Abdel Rahman, sisters Abeer, Nirmeen, Nisreen, Eman, Rana

Yasmin and Marah, and to my wife Nour and my son Taiseer.

To my friends, and to whom I belong.

IV

ACKNOWLEDGMENT

I would like to express my sincere appreciation to Prof. Samir Shihada and Dr. Mohamed

Arafa, Department of Civil Engineering, Faculty of Engineering, The Islamic University of

Gaza, for their help and guidance in the preparation and development of this work. The

constant encouragement, support and inspiration they offered were fundamental to the

completion of this research.

Special thanks go to Consulting Center for Quality & Calibration, and to the material and

soil lab of the Islamic University of Gaza, for their logistic facilitations and their

continuous support. Finally I would like to thank everyone who gave advice or assistance

that contributed to complete this research.

V

ABBREVIATIONS

ACI American Concrete Institute

ASTM American Society for Testing and Materials

DIN German Institute for Standardization (Deutsches Institut für Normung)

fct Concrete compressive strength at age = t

FRC Fiber Reinforced Concrete

GFRC Glass Fibers Reinforced Concrete

GFRP Glass Fibers Reinforced Plastic

HRWRA High-Range Water-Reducing Admixture

HSC High Strength Concrete

ITZ Interfacial Transition Zone

NSC Normal Strength Concrete

SCC Self-Compacting Concrete

SFRC Steel Fibers Reinforced Concrete

SHSC Super High Strength Concrete

UHPC Ultra High Performance Concrete

UHPFRC Ultra High Performance Fiber Reinforced Concrete

UHPFRSCC Ultra High Performance Fiber Reinforced Self-Compacting Concrete

UHSC Ultra High Strength Concrete

VHSC Very High Strength Concrete

W/C Water / Cement ratio

VI

TABLE OF CONTENTS

ABSTRACT …………………………………………………………………………………………. I

II .………………………………………………………………………………...................... الملخص

DEDICATIONS ……………………………………………………………………………………... III

ACKNOWLEDGMENT …………………………………………………………………………….. IV

ABBREVIATIONS …………………………………………………………………………………..

TABLE OF CONTENTS …………………………………………………………………………….

V

VI

LIST OF TABLES …………………………………………………………………………………... IX

LIST OF FIGURES …………………………………………………………………………………. X

CHAPTER 1- INTRODUCTION …….…………………………………………………............... 1

1.1 General Background ……………………………..…………………………….................. 1

1.2 Statement of the Problem ………………………………………………………..…….... 2

1.3 Objectives …………………………………………………………................................... 2

1.4 Methodology …………………………………………………………................................ 3

1.5 Scope of Work …………………………………………………………............................ 3

1.6 Thesis Structure …………………………………………………………............................ 4

CHAPTER 2- LITERATURE REVIEW…………………………………………………….......... 5

2.1 General Definition of Ultra High Performance Fiber Reinforced Self-Compacted

Concrete ( UHPFRSSC ) …..……………………………………………..........................

5

2.1.1 Ultra High Performance Concrete ( UHPC ) .……………………......................... 5

2.1.2 Fiber Reinforced Concrete ( FRC ) ………………………….................................... 5

2.1.3 Self-Compacted Concrete ( SCC ) …………………………..................................... 6

2.1.4 Ultra High Performance Fiber Reinforced Concrete ( UHPFRC ) ..................

6

2.2 History of Using Fibers as a Reinforcement …………………........................................ 6

2.3 Advantages of UHPFRSCC ..……………………………………………........................ 6

2.4 Large Scale Applications ………………………………………………............................. 9

2.4.1 Sherbrooke Footbridge ….……………………………………............................. 9

2.4.2 Glenmore/Legsby Pedestrian Bridge ..…………………………........................ 9

2.4.3 Wapello County Bridge …………………………………………....................... 10

VII

2.4.4 Rainy Lake – CN Rail Overhead Bridge……………………….......................... 10

2.5 Materials of UHPFRSCC ………………………………………................................... 11

2.5.1 Portland Cement ..…………………………………............................................. 11

2.5.2 Silica Fume ………………………………………..................................................... 14

2.5.3 Steel Fibers ………………………………………..................................................... 18

2.6 Mixing of fresh UHPFRSCC ………………………...................................................... 19

2.7 Concluding Remarks ………………………………...................................................... 19

CHAPTER 3- CONSTITUENT MATERIALS AND EXPERIMENTAL PROGRAM …...... 21

3.1 Introduction ……………………………………….......................................................... 21

3.2 Characterizations of constituent Materials ……........................................................... 21

3.2.1 Cement ……...…………………………………......................................................... 22

3.2.2 Aggregates (quartz sand) …………………..…........................................................ 22

3.2.3 Water ……...…………………………………............................................................. 24

3.2.4 Admixture ...………………………………….............................................................. 25

3.2.5 Silica Fume …………………………………............................................................... 26

3.2.6 Steel Fibers ………………………………….............................................................. 26

3.2.7 Polypropylene Fibers ……………………….............................................................. 27

3.3 Mix Design of UHPFRSCC …………………................................................................ 27

3.4 Preparation of UHPFRSCC …………………................................................................ 28

3.5 Test Program …………………........................................................................................ 28

3.6 Equipment and Testing Procedure ................................................................................ 29

3.6.1 Tests applied on Fresh Concrete ........................................................................... 29

3.6.2 Tests applied on Hardened Concrete ..................................................................... 32

3.6.3 Curing Procedure ............................................................... ..................................... 37

CHAPTER 4- TEST RESULTS AND DISCUSSION …………………………………................ 38

4.1 Introduction …………………........................................................................................... 38

4.2 Fresh Properties Tests Results …...................................................................................... 39

4.2.1 Effect of Silica Fume and Steel Fibers on Slump Test Results .......................... 41

4.2.2 Effect of Silica Fume and Steel Fibers on V-Funnel Test Results .................... 41

4.2.3 Segregation in the Trial Mixes ................................................................................ 42

4.3 Hardened Properties Tests Results .................................................................................. 43

VIII

4.3.1 Effects of Silica Fume and Steel Fibers on UHPFRSCC Unit Weight .............. 44

4.3.2 Effects of Silica Fume and Steel Fibers on UHPFRSCC Compressive Strengt.. 44

4.3.3 Compressive Strength – Time Relationship ........................................................... 47

4.3.4 Effects of Silica Fume and Steel Fibers on UHPFRSCC Splitting Strength….. 49

4.3.5 Effects of Silica Fume and Steel Fibers on UHPFRSCC Flexural Strength …. 51

4.4 Effect of Polypropylene Fibers Content ........................................................................ 52

4.4.1 Effect of Polypropylene Fibers Conclusion ........................................................... 57

CHAPTER 5- CONCLUSIONS AND RECOMMENDATIONS …...………………................. 58

REFERENCES …………………………………….…..………………………………................. 63

APPENDIXES ……………………….................…………………………………….................... 66

IX

LIST OF TABLES

Table 2.1: Classification of concrete strength ………………...………………………… 5

Table 3.1: Cement characteristics according to manufacturer sheet tests …………… 22

Table 3.2: Physical property of quartz sand ………………...………………………… 24

Table 3.3: Water absorption of quartz sand ………………...………………………….. 24

Table 3.4: Technical data for the "Sika ViscoCrete – 5930" .………………………… 25

Table 3.5: The technical data for the "Sika – Fume” ……...…………………………… 26

Table 3.6: Self-compacting criteria (Slump flow, T500 test) ………………………… 31

Table 3.7: Self-compacting criteria (V-funnel) ………………………………..……… 31

Table 4.1: Best mixture proportions of UHPFRSCC by weight of cement …………… 38

Table 4.2: One cubic meter components of UHPFRSCC mixture …………………….. 38

Table 4.3: Different mixes proportions ………………………………………………... 39

Table 4.4: Fresh properties tests results ………………………………..……………… 40

Table 4.5: Hardened properties tests results …………………………………………… 43

Table 4.6: Mean ratio of ( fct / fc28) for UHPFRSCC ………………………………… 48

Table 4.7: Additional mixture proportions of UHPFRSCC by weight of cement ……... 52

Table 4.8: One cubic meter components of additional UHPFRSCC mixture ………… 53

Table 4.9: Effect of Polypropylene fibers on fresh and hardened properties …………. 53

Table 5.1: Best mixture proportions of UHPFRSCC by weight of cement ……….. 58

X

LIST OF FIGURES

Figure 2.1: UHPFRSCC advantages ………………………...………………………………… 8

Figure 2.2: Sherbrooke footbridge ………………………………………….…………………. 9

Figure 2.3: Glenmore/legsby pedestrian bridge …………...……………………………….… 9

Figure 2.4: Wapello County Bridge ……………………………………….……………….…. 10

Figure 2.5: Joints of CN Overhead Bridge ………………………………….………………... 11

Figure 2.6: Microstructure development in Portland cement pastes ………………………..... 12

Figure 2.7: Effect of micro silica in densifying the concrete mix - comparison between

conventional and micro silica concretes ..…………………………………............

15

Figure 2.8: Amount of calcium hydroxide (as CaO) in cement pastes containing different

amounts of silica fume ………………………………………………………..........................

16

Figure 2.9: The boundary zone and the bulk zone between the aggregates ……...…………... 17

Figure 3.1: Aggregate used in mixes: Quartz sand ………………………………………….... 23

Figure 3.2: The chemical admixture (Superplastisizer) …………………………………….... 25

Figure 3.3: Steel fibers …………..………………………………………………………….... 26

Figure 3.4: Polypropylene fibers ……………………………………………………………... 27

Figure 3.5: Mix design process …………………………………………………………….… 27

Figure 3.6: Test Program ………………………………………………………...................... 29

Figure 3.7: Slump cone and base plate …………...………………………………………….. 30

Figure 3.8: Self-compacted concrete at the lab ………...……………………………………. 30

Figure 3.9: V-Funnel apparatus dimensions ………………………………………..………... 31

Figure 3.10: Cube specimens …………………………………..……………………………. 32

Figure 3.11: Cube specimens at curing basin ……………………...………………………… 32

Figure 3.12: Split cylinder test ……………………………………………………………… 34

Figure 3.13: cylinders damages after test …………………………………………………… 34

Figure 3.14: Beam dimensions used for flexural prism tests….……………………………… 35

Figure 3.15: Diagrammatic view for flexure test of concrete by center-point loading … 35

Figure 4.1: Effect of silica fume and steel fibers on slump test results …………………... 41

Figure 4.2: Effect of silica fume and steel fibers on V-funnel time results ………………. 42

Figure 4.3: Effect of silica fume and steel fibers on UHPFRSCC unit weight ……………. 44

Figure 4.4: Effect of silica fume and steel fibers on UHPFRSCC compressive strength

XI

(7days) ……..…………………………………………………………………… 44


(14days) …...…………………………………………………………………….

45


(28days) ……………………………...………………………………………….

45

Figure 4.7: Mean compressive strength Vs. age of mix #11 …………………………………. 47

Figure 4.8: Mean compressive strength Vs. age ……………………………………………… 48

Figure 4.9: Comparison of (fct / fc28 ) between NSC and UHPFRSCC at different ages ….. 49

Figure 4.10: Effect of silica fume and steel fibers on UHPFRSCC splitting tensile strength @

age of 28 Days. …………………………………………......................................

50

Figure 4.11: Effect of silica fume and steel fibers on UHPFRSCC Flexural strength @ age

of 28 Days. ……………………………………………………………………….

51

Figure 4.12: Effect of Polypropylene fibers on slump test ……………………………………… 54

Figure 4.13: Effect of Polypropylene fibers on V-funnel test ………………………………….. 54

Figure 4.14: Effect of Polypropylene fibers on unit weight ……………………………………. 55

Figure 4.15: Effect of Polypropylene fibers on compressive strength ……………………...... 55

Figure 4.16: Effect of Polypropylene fibers on splitting tensile strength at the age of 28 days. 56

Figure 4.17: Effect of Polypropylene fibers on flexural strength at the age of 28 days. …….. 56

nuctioChapter 1 Introd

1

Chapter (1)

Introduction

1.1 General Background:

Concrete is a widely used construction material dominating the construction industry

worldwide and the use of cementitious material can be traced back thousands of years ago.

Concrete has been used since ancient times. Regular Roman concrete for example was

made from volcanic ash (pozzolana), and hydrated lime. Roman concrete was superior from

other concrete recipes (for example, those consisting of only sand and lime).

(Richards, 2012)

But up to now mankind has been searching for construction materials with higher and

higher strength to construct taller and larger structures and to use for rehabilitation works.

As construction materials cost escalates, demand has been increased for stronger materials

with acceptable cost like concrete.

Building element made of high strength concrete are usually densely reinforced. The small

distance between reinforcing bars may lead to defects in concrete. If the ultra-high

performance concrete is self-compacting, the production of densely reinforced building

element from ultra-high performance concrete with high homogeneity would be easy work

(Jianxin and Jorg, 2002)

Modern concrete mix designs can be complex. The choice of concrete mix depends on the

need of the project both in terms of strength and appearance and in relation to local

legislation and building codes.


2

1.2 Statement of the Problem:

The usage of ultra-high strength concrete with high compressive strength in construction

applications has been increasing worldwide and will make an impact in Gaza Strip due to

the limited land area available for construction and the fast growing population as well.

High-rise reinforced concrete multistory buildings are being increasingly used. The large

loads in high rise buildings lead to the design of large sections when normal strength

concrete is used, but when ultra-high performance fiber reinforced concrete is to be used,

small cross sections can be obtained.

Moreover; finally yet importantly, due to bad and unstable political conditions and the

continuing wars in Gaza Strip, strong, relatively cheap, easy to use and locally available

repairing and strengthening material should be produced for that purposes.

1.3 Objectives:

The aim of this research is to produce Ultra High Performance Fiber Reinforced Self

Compacted Concrete (UHPFRSCC) in Gaza Strip using local available materials, and to

study the mechanical properties and the influence of key mix design parameters on

compressive strength, tensile strength and ductility of UHPFRSCC. This can be achieved

by the followings:

1. Produce UHPFRSCC by using materials available at local markets.

2. Obtain the fresh mechanical properties of UHPFRSCC.

3. Obtain the mechanical properties of hardened UHPFRSCC including, compressive

strength, splitting tensile strength, density and flexural strength.


3

1.4 Methodology:

In general, the following methodology was followed:

1. Conduct comprehensive literature review related to subject of UHPFRSCC.

2. Selection of suitable local available materials required for producing UHPFRSCC,

including cement, silica fume, steel fibers, polypropylene and plasticizers.

3. Determine mix proportions to produce UHPFRSCC.

4. Performing physical and mechanical laboratory tests on UHPFRSCC samples.

5. Analyze results and draw conclusions.

1.5 Scope of work:

The work program is summarized below:

1.5.1 Characteristics of fresh UHPFRSCC

In order to assess the characteristics of fresh UHPFRSCC, the following aspects

are considered:

Mix design.

Workability.

Homogeneity.

1.5.2 Characteristics of hardened UHPFRSCC

The following tests were carried out in order to establish the mechanical

properties of UHPFRSCC:

Compressive strength.

Splitting tensile strength.

Flexural strength.

Hardened density.


4

1.6 Thesis structure:

The research consists of seven chapters arranged as shown below. This section presents a

brief description of these chapters.

Chapter 1 (Introduction)

This chapter gives general background about UHPFRSCC, statement of

problem, goals and objectives of the research, scope of work, and the

methodology adopted.

Chapter 2 (Literature Review)

This chapter gives general review of previous research related to UHPFRSCC

and the main materials used, advantages, disadvantages and applications.

Chapter 3 (Constituent Materials and experimental program)

This chapter discusses types of laboratory tests, standards, adopted procedures,

materials properties, curing condition and schedules of the testing program.

Chapter 4 (Results and discussion)

Test results, analysis of these results and discussion are included.

Chapter 5 (Conclusion and Recommendations)

General conclusion and recommendations from this research work are stated.

(References)

(Appendices)

eviewLiterature R Chapter 2

5

Chapter (2)

Literature Review

2.1 General Definition of Ultra High Performance Fiber Reinforced

Self-Compacted Concrete ( UHPFRSSC )

2.1.1 Ultra-high-performance concrete ( UHPC )

Ultra-high-performance concrete is a new type of concrete which is also characterized by

its constituent material make-up: typically fine-grained sand, silica fume, small steel fibers

or basalt aggregates, and Portland cement, with a low water/cement ratio, high cement

content and mineral admixtures that are selected to increase the bond between the

aggregates and the cement paste. Note that there is no large aggregate.

From the strength point of view, the classification of concrete strength may be made as

shown in Table 2.1. (ACI 363R-92, 2003), (DIN 1045-1), (SETRA – AFGC, 2002):

Table 2.1: classification of concrete strength

Type From (MPa) To (MPa)

Normal Strength Concrete ( NSC) - B 41/60

High Strength Concrete (HSC) B41/60 B70/90

Very High Strength Concrete (VHSC) B70/90 B120/150

Ultra High Strength Concrete (UHSC) B120/150 B200/250

Super High Strength Concrete (SHSC) B200/250 No limits

2.1.2 Fiber Reinforced Concrete ( FRC )

FRC is a concrete containing fibrous material which increases its structural integrity. It

contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers

include steel fibers, glass fibers, synthetic fibers and natural fibers – each of which lend

varying properties to the concrete. In addition, the character of fiber-reinforced concrete

changes with varying concretes, fiber materials, geometries, distribution, orientation, and

densities.


6

2.1.3 Self-Compacted Concrete ( SCC )

Self-Compacting Concrete has properties that differ considerably from conventional

slump concrete. SCC is highly workable concrete that can flow through densely reinforced

and complex structural elements under its own weight and adequately fill all voids without

segregation, excessive bleeding, excessive air migration (air-popping), or other separation

of materials, and without the need for vibration or other mechanical consolidation.

(Technical Bulletin TB-1500, 2005)

2.1.4 Ultra High Performance Fiber Reinforced Concrete ( UHPFRC )

UHPFRC (Ultra High Performance Fiber Reinforced Concrete) is a material that allows

reaching high compressive strength even at short term, and a considerable tensile strength

associated to high strains. Thanks to the low Water/Cement ratio as long as high steel fiber

content, dense matrix, cracking distribution ability and as consequence high durability and

marked ductility are achieved. These characteristics and the high control requirements

make this material suitable for the design of precast prestressed elements.

(Camacho, et al., 2010)

2.2 History of Using Fibers as a Reinforcement

The concept of using fibers as reinforcement is not new. Fibers have been used as

reinforcement since ancient times. Historically, horsehair was used in mortar and straw in

mud bricks. In the 1900s, asbestos fibers were used in concrete. In the 1950s, the concept

of composite materials came into being and fiber-reinforced concrete was one of the topics

of interest. Once the health risks associated with asbestos were discovered, there was a

need to find a replacement for the substance in concrete and other building materials. By

the 1960s, steel, glass (GFRC), and synthetic fibers such as polypropylene fibers were

used in concrete. Research into new fiber-reinforced concretes continues today.

2.3 Advantages of UHPFRSCC

Fiber reinforced concrete (FRC) is a new material opening new ways for concrete

structures. Fibers added to concrete improve its mechanical resistance and ductility,

reduce its plastic shrinkage and improve its resistance to abrasion, to fire or to impact.

With such material, engineers are able to design new structures, original in their design or

http://en.wikipedia.org/wiki/Steel

http://en.wikipedia.org/wiki/Glass

http://en.wikipedia.org/wiki/Glass_Fiber_Reinforced_Concrete_(GFRC)

http://en.wikipedia.org/wiki/Polypropylene


7

their ability to resist to severe conditions. In ultra-high performance fiber reinforced

concrete (UHPFRC), fibers contribute to the material strength. The tensile strength is

accounted for when designing a UHPFRC component structure.

It is now well established that one of the important properties of steel fiber reinforced

concrete (SFRC) is its superior resistance to cracking and crack propagation. As a result of

this ability to arrest cracks, fiber composites possess increased extensibility and tensile

strength, both at first crack and at ultimate, particular under flexural loading; and the

fibers are able to hold the matrix together even after extensive cracking. The net result of

all these is to impart to the fiber composite pronounced post – cracking ductility which is

unheard of in ordinary concrete. The transformation from a brittle to a ductile type of

material would increase substantially the energy absorption characteristics of the fiber

composite and its ability to withstand repeatedly applied, shock or impact loading.

(Johnston, 2001).

Over the last 10 years, considerable efforts to improve the behavior of cementitious

materials by incorporating fibers have led to the emergence of Ultra-High Performance

Fiber Reinforced Concretes (UHPFRC). These novel building materials provide the

structural engineer with a unique combination of:

(1) Extremely low permeability: which prevents the ingress of detrimental substances such

as water and chlorides (Charron et al., 2006);

(2) Very high strength: i.e., compressive strength higher than 150 MPa, tensile strength

higher than 10 MPa and with considerable tensile strain hardening and softening

behaviour (Denarié & Brühwiler, 2011).

UHPFRSCC holds the advantages of the UHPC, SCC and the FRC as shown in Figure

2.1. UHPFRSCC has found application in the storage of nuclear waste, bridges, roofs,

piers, precast structural elements, seismic-resistant structures and structures designed to

resist impact loading. UHPFRSCC construction requires lower maintenance costs in its

service life than conventional concrete. UHPFRSCC may incorporate larger quantities of

steel or synthetic fibers and has enhanced ductility, high temperature performance and

improved impact resistance.


8

UHPFRSCC enables structural members to be built entirely without the use of

conventional transverse reinforcement, relying on the UHPFRSCC without traditional

reinforcement because of its advantageous flexural strength.

UHPFRSCC is an innovative concrete that does not require vibration for palcing and

compaction due to its own high workability.

Figure 2.1: UHPFRSCC advantages

SCC

1- No need for vibration;

2- easy to be casted;

3- Low sensitivity to temp. changes;

4- Homogenous;

5- Durable.

UHPFRSCC

A mix of all above advantages;

1- High Compressive and tensile strengths;

2- Low porosity;

3- Superior freeze/thaw resistance;

4- Durable;

5- Homogenous;

6- Low shrinkage possibility;

7- High resistance to abrasion, fire and impact;

8- Ease of casting without need for vibration.


9

2.4 Large scale applications

2.4.1 Sherbrooke footbridge

The Sherbrooke Pedestrian Bridge in Quebec, Canada (Figure 2.2) was constructed in

1997 and spans 60 m across the Magog River with a space truss, precasted in 6 segments

(10 m each). The top deck is 30 mm thick and the diagonals are formed with leave-in-

place stainless steel tubes containing tri-axially confined UHPFRC with post-tensioning.

(Behloul, et al, 1998).

Figure 2.2: Sherbrooke footbridge

2.4.2 Glenmore/Legsby Pedestrian Bridge

The Glenmore/Legsby Pedestrian Overpass in Calgary, Alberta, Canada (Figure 2.3), is a

single span, 53 m bridge that stretches across 8 lanes of traffic. It consists of two

cantilevered, high performance concrete abutments and a drop-in, “T-section” UHPFRC

girder with an arch. The girder is 33.6m long, 1.1m deep at mid-span with a 3.6m wide

deck and weighs approximately 100 tons. It is constructed with 13 mm steel fibers and

post-tensioned with 42 – 15 mm strands. GFRP (Glass fiber-reinforced plastic) bars were

also utilized as a redundant, passive reinforcing system. (Perry and Seibert, 2008)

Figure 2.3: Glenmore/legsby pedestrian bridge


10

2.4.3 Wapello County Bridge

In 2006, the first UHPFRC highway bridge in North America was completed in Wapello

County, Iowa with three 33.5 m UHPFRC girders that do not have any rebar for shear

stirrups. (Perry and Seibert, 2008)

Figure 2.4: Wapello County Bridge

2.4.4 Rainy Lake – CN Rail Overhead Bridge

The original CN Overhead Bridge was constructed in 1962. The existing bridge deck had

reached its useful life and in need of major reconstruction, and a staged method of

construction was utilized to maintain one lane of traffic during deck reconstruction, The

material supplier, consultant and owner worked together to develop an innovative solution

for reconstructing the bridge deck. The existing deck was removed transversely, one half

at a time, while maintaining full traffic volume and replaced with a new precast deck panel

system (one lane at a time). A challenge facing highway authorities is durability of the

joints due to constant flexing from truckloads and corrosion from salt of the rebar crossing

the joints. To minimize corrosion potential, a noncorrosive rebar (GFRP) was used in the

top mat and joint size was minimized to provide the least possible shrinkage across the

joint and the joints (Figure 2.5) were filled with the-self leveling UHPFRC materials.

After a 4-day field cure, the UHPFRC material was ground smooth in the area of any high

spots. Traffic was transferred onto the new deck and the second phase was started with the

same system.


11

Figure 2.5: Joints of CN Overhead Bridge

2.5 Materials of UHPFRSCC

Materials used for producing UHPFRSCC are those used for producing UHPC and

UHPSCC, except that UHPFRSCC contain no large aggregates, although containing large

amounts of binder (i.e. cement). Silica fume, quartz powder …etc. are used as filler

materials. Fibers added to improve the mechanical properties.

To ensure and improve the self-leveling and high workability properties, without causing

segregation; Large amounts of superplasticizers are to be used.

2.5.1 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 life

2.5.1.1 Hydration of Portland cement

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 2.6) shows schematically the


12

sequence of structure formation as hydration proceeds. This involves the replacement of

water that separates individual cement grains in the fluid paste (Figure 2.6.a) 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 2.6 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 (Mindess, et al., 2002).

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.

2002).

2C3S + 11 H2O → C3S2H8 + 3 CH

tricalcium silicate water calcium silicate hydrate calcium hydroxide

Figure 2.6: Microstructure development in Portland cement pastes (Mindess, et al. 2002)

2C2S + 9 H2O → C3S2H8 + CH

dicalcium silicate water C – S – H calcium hydroxide

Unhydrated material C-S-H

Water filled capillarity pores C-H


13

C-S-H 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 + 3 CSH2 + 26 H2O → C6AS 3H32

tricalcium aluminate gypsum water ettringite

Where S is equivalent to SO3 and ettringite is a stable hydration product only while there

is an ample supply of sulfate available.

2.5.1.2 Cement grains Size Distribution, Packing and Dispersion

Portland cements are ground to a rather narrow range of particle sizes, varying only from

about 1μ m to about 10 μm, with a mean size of the order of 12 to 15 μm. Cements are

ground slightly finer, but not much. the mean size being of the order of 0 to 10 μm. In

visualizing the state of the flocculated mass of cement grains in fresh Portland cement

mixes, it appears that the variation in particle size between larger and smaller cement

particles does not result a dense packing. To a considerable extent this is due to the

flocculated character particles once bumped together are "stuck" together by forces of

attraction cannot readily slide to accommodate each other better. However, even if they

could, they are far too close to being of the same order of size to be able to form dense

local mixes. Water filled pockets of roughly the same size as the cement particles exist

throughout the mass (Neville, 1993).

It is obvious that what is needed is an admixture of much finer particles to pack into the

water filled pockets between the cement grains. Silica fume (or micro silica) provides such

particles, the mean particle size of commercial silica fume being typically less than 0.2

μm. When micro silica is added to ordinary cement paste a denser packing that may be

ensued. In order to get the desired state of dense particle packing, not only must the fine

particles be present, but must be effectively deflocculated during the mixing process. Only


14

then can the cement particle move around to incorporate the fine micro silica particles.

The fine micro silica particles must themselves be properly dispersed so that they can

separate from each other and pack individually between and around the cement grains.

Another requirement for best packing is that the mixing used be more effective than the

relatively usual mixing done in ordinary concrete production. High shear mixers of several

kinds have been explored. Proper dispersion and incorporation of fine micro silica

particles thus can results in a dense local structure of fresh paste with little water-filled

space between the grains. When the cement hydrates, the overall structure produced in the

groundmass is denser, tighter, and stronger (Young and Menashi, 1993).

2.5.2 Silica Fume

Silica fume, also known as microsilica, which is an amorphous (non-crystalline)

polymorph of silicon dioxide, silica. It is an ultrafine powder collected as a by-product of

the silicon and ferro-silicon alloy production and consists of spherical particles with an

average particle diameter of 150 nm. The main field of application is as pozzolanic

material for high performance concrete.

2.5.2.1 The pozzolanic reactions

In the presence of hydrating Portland cement, silica fume will react as any finely divided

amorphous silica-rich constituent in the presence of (CH) the calcium ion combines with

the silica to form a calcium-silicate hydrate through the pozzolanic reaction. (Figure 2.7)

(C3S + C2S) + H2O → C-S-H + CH + S → C-S-H

Portland cement Water Silica

The simplest form of such a reaction occurs in mixtures of amorphous silica and calcium

hydroxide solutions.

Buck and Burkes (1981) studied the reactivity of silica fume with calcium hydroxide in

water at 38 oC. Silica fume to calcium hydroxide ratios (SF:CH) 2:1, 1:1 and 1:2.25 were

included. They found that a well-crystallized form of CSH was formed by 7 days of


15

curing. For the 2:1 mixtures, all CH was consumed by 7 days; for the 1:1 mixtures, 28

days was required to consume the CH.

Figure 2.7: Effect of micro silica in densifying the concrete mix - comparison between

conventional and micro silica concretes

Grutzeck et al. (1995) suggest a gel model of silica fume-cement hydration. According to

this model, silica fume contacts mixing water and forms a silica-rich gel, absorbing most

of the available water. Gel then agglomerates between the grains of unhydrated cement,

coating the grains in the process. Calcium hydroxide reacts with the outer surface of this

gel to form C-S-H. This silica-fume gel C-S-H forms in the voids of the C-S-H produced

by cement hydration, thus producing a very dense structure.

Ono et al. (1985) studied the cement-silica fume system in low water-cement ratio (0.23)

pastes at 20 C. The amounts of CH present after various periods of hydration at Portland

cement: silica fume ratios of 100:0, 90:10, 80:20, and 60:40 are shown in Figure 2.8. At

very high levels of silica fume, almost all CH are consumed by 28 days. At lower levels of

Hydration

crystals

growing from

cement grains.

Hydration

complete voids

left between

crystal

structures.

Conventional concrete

Hydration

crystals

growing from

cement grains

and form

nucleation

centers of

micro silica

Crystals from

micro silica

and cement

grains

interacting to

form a

complete and

dense structure

with no voids

Micro silica concrete


16

silica fume, e.g., 10 percent, typical of those used in practice, CH is reduced by almost 50

percent at 28 days. These results are supported by those of Huang and Feldman who found

that while silica fume accelerates early hydration and leads to increased production of CH

at times up to 8 hours, at later ages CH is consumed, and for a mixture containing 50

percent silica fume, no CH is detectable after 14 days.

Figure 2.8: Amount of calcium hydroxide (as CaO) in cement pastes containing different

amounts of silica fume

2.5.2.2 The physical effects

Mindess S., (1988) silica fume increases the strength of concrete largely because it

increases the strength of the bond between the cement paste and the aggregate particles.

Wang et al. (1986) found that even small additions (2 to 5 percent) of silica fume

produced a denser structure in the transition zone with a consequent increase in micro

hardness and fracture toughness.

Monteiro and Mehta, (1986) stated that silica fume reduces the thickness of the

transition zone between cement paste and aggregate particles. One reason for this is the

reduction in bleeding. The presence of silica fume accelerates the hydration of cement

during the early stages.


17

Sellevold et al. (1982) found that equal volumes of inert filler (calcium carbonate)

produced the same effect. They concluded that the mere presence of numerous fine

particles whether pozzolanic or not has a catalytic effect on cement hydration.

Wang et al. (1986) also found that the mean size and orientation index of the CH crystals

within the transition zone were reduced by the addition of silica fume. At the interface

itself, the CH crystals will be oriented parallel to the aggregate surface whether silica fume

is present or not, in a study of the texture (preferred orientation) of CH crystals in the

transition zone.

Bache (1981) explained the theory of the packing of solid particles and its effect on the

properties of the material. Because it is a composite, concrete is affected not only by the

packing of particles in the cement paste, but also by their packing near the surfaces of

aggregate particles. Figure 2.9 illustrates how the minute silica fume particles can improve

packing in the boundary zone. Since this is frequently weakest part of a concrete, it is

especially important to improve packing in this region.

Figure 2.9: The boundary zone and the bulk zone between the aggregates

Bache also showed that addition of silica fume could reduce water demand because the

silica-fume particles were occupying space otherwise occupied by water between the

cement grains. This reduction only applies for systems with enough admixtures to reduce

surface forces.


18

It is worth emphasizing here that all of these physical mechanisms depend on thorough

dispersion of the silica-fume particles in order to be effective. This requires the addition of

sufficient quantities of water-reducing admixtures to overcome the effects of surface

forces and ensure good packing of the solid particles. The proper sequence of addition of

materials to the mixer as well as thorough mixing is also essential.

2.5.3 Steel Fibers

Steel fibers are manufactured fibers composed of stainless steel. Composition may include

carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), and other elements.

Hoang et al. (2008) studied the influence of types of steel fiber on properties of ultra-high

performance concrete and self-compacting ultra-high strength concrete has been

manufactured, short steel fiber (straight fiber) with length/diameter = 17/0.2 and long

steel fiber (hooked ends) with length/diameter = 35/0.5 have been added, in order to

improve ductility. By a reasonable combination of two steel fiber types guarantee for high

flowability, flexural strength of over 20 MPa and compressive strength of over 150 MPa.

Kang et al. (2010) studied the tensile fracture properties of Ultra High Performance Fiber

Reinforced Concrete (UHPFRC) considering the effects of the fiber content, they found

that flexural tensile strength of UHPFRC linearly increases with increasing fiber volume

ratio.

Koksal et al. (2008) conducted an experimental study to understand combined effect of

silica fume and steel fiber on the mechanical properties of high strength concretes, Results

show that the use of silica fume increased both the mechanical strength and the modulus

of elasticity of concrete. On the other hand, the addition of steel fibers into concrete

improve toughness of high strength concrete significantly. As the steel fiber volume

fraction increases, the toughness increases, and high values of aspect ratios give higher

toughness. The toughness of high strength steel fiber concrete depends on silica fume

content, the fiber volume fraction and the fiber aspect ratio.


19

2.6 Mixing of fresh UHPFRSCC

Shihada and Arafa, (2010) found that changing the mixing sequences affect the main

properties of UHPC, including density, slump and compressive strength.

Chopin et al., (2004) completed a study to find out the mix-design peculiarities of high-

performance concrete (HPC) and by the way ultra-high performance concrete and self-

consolidating concrete (SCC) that could be responsible for the long mixing time. To

compare the behavior of various mixes, a mathematical model was proposed to fit the

power consumption curve of the mixer and to choose a criterion to determine the

stabilization time of the curve. The parameters studied were the paste content, its

components (silica fume, limestone filler, etc.), the high-range water reducing admixture

(HRWRA) type and dosage and the water/cement (w/c) ratio. The comparison of

stabilization time for 36 different HPC and SCC mixes allowed to highlight the major

influence of w/c ratio, on the stabilization time. The higher the w/c ratio, the lower the

stabilization time. It also appeared that fine content, HRWRA dosage and the use of silica

fume have significant effects on the time necessary to homogenize the material.

2.7 Concluding Remarks

Ultra High Performance Fiber Reinforced Self Compacted Concrete is one of the latest

developments in concrete technology. UHPFRSCC refers to materials with a cement

matrix and a characteristic compressive strength in excess of 120 MPa, possibly attainting

200 MPa.

The hardened concrete matrix of Ultra High Performance Fiber Reinforced Self

Compacted Concrete shows extraordinary strength and durability properties. These

features are the result of using very low amounts of water, high amounts of cement, fibers,

fine aggregates and micro fine powders. These materials are characterized by a dense

microstructure. The sufficient workability is obtained by using superplastisizers.

Silica fume is an essential ingredient of UHPFRSCC. This material comprises extremely

fine particles and not only fills up the space between the cement grains, but also reacts

with the cement, which increasing the bond between cement matrix and amal aggregate

particles.


20

As a result of its superior performance, UHPFRSCC has found application in the storage

of nuclear waste, bridges, roofs, piers, long span girders, shell and seismic-resistant

structures and rehabilitation works of mega structures.

aterial M Chapter 3

21

Chapter (3)

Constituent Materials and Experimental Program

3.1 Introduction

This chapter presents the experimental program and the constituent materials used to

produce UHPFRSCC associated with this research work.

The laboratory investigation consisted of tests for both fresh and hardened concrete

properties. Fresh concrete was tested for slump flow and V-funnel to ensure reasonable

workability and self-compacting ability in the plastic state. The tests for hardened concrete

included compression tests for strength and indirect tensile tests (split cylinder and flexural

strength tests)

The influence of the silica fume dosages, cement/ultra-fine ratio, steel fibers and

polypropylene fibers amounts on the compressive strength concrete together with the

workability and density of UHPFRSCC was studied by preparing several concrete mixes.

The properties of different constituent materials used to produce UHPFRSCC are also

discussed such as moisture content, unit weight, specific gravity and the grain size

distribution. The test procedures, details and equipment used to assess concrete properties

are illustrated in the following sections.

3.2 Characterizations of constituent Materials

UHPFRSCC constituent materials used in this research include ordinary Portland cement,

grey silica fume, steel fibers and polypropylene fibers. Silica fume and cement was used as

micro filler and binder. Quartz sand, in addition to superplastisizers, are used to ensure

suitable workability. Steel and Polypropylene fibers used to improve the strength and

ductility. Proportions of these constituent materials have been chosen carefully in order to

optimize the packing density of the mixture.

aterial M Chapter 3

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3.2.1 Cement

Cement paste is the binder in UHPFRSCC that holds the aggregate (fine, micron fine)

together and reacts with mineral materials in hardened mass. The property of UHPFRSCC

depends on the quantities and the quality of its constituents. Because cement is the most

active component of UHPFRSCC and usually has the greatest unit cost, its selection and

proper use is important in obtaining most economically the balance of properties desired of

UHPFRSCC mixture.

In this research ordinary Portland cement CEM I 42.5R was used for the production of

Ultra High Performance Fiber Reinforced Self Compacting Concrete. The cement met the

requirements of ASTM C 150 specifications. The results of physical and mechanical

analyses of the cements are summarized in Table 3.1 along with the requirements of

relevant ASTM specifications for comparison purposes.

Table 3.1: Cement characteristics according to manufacturer sheet tests

Type of test

Ordinary Portland Cement

Results ASTM C 150

Setting time ( Vicat test ) hr : min Initial 1 hr 30 min > 60 min

Final 4 hr 40 min < 6 hrs 15 min

Mortar compressive strength (MPa)

3-Days 25.7 Min. 12

7-Days 36.9 Min. 19

28-Days 53.4 No limit

Blain Fineness (cm2/gm) 3005 Min. 2800

Water demand 27.5 % No limit

3.2.2 Aggregates (quartz sand)

Aggregate is relatively inexpensive and strong making material for concrete. It is treated

customarily as inert filler. The primary concerns of aggregate in mix design for Ultra High

Performance Fiber Reinforced Self Compacted Concrete are gradation, maximum size, and

strength. Providing that concrete is workable, the large particles of aggregate are

aterial M Chapter 3

23

undesirable for producing UHPFRSCC. For producing UHPFRSCC, the nominal size

ranges from 0.15 to 0.6 mm for quartz sand (fine aggregate) which are locally available in

Gaza markets. In addition, it is important to ensure that the aggregates are clean, since a

layer of silt or clay will reduce the cement aggregate bond strength, in addition to

increasing the water demand.

Figure 3.1: Aggregate used in mixes: Quartz sand.

3.2.2.1 Specific gravity and Unit weight:

The density of the aggregate is required in mix proportions to establish weight volume

relationships. The density is expressed as the specific gravity, which is dimensionless

relating the density of the aggregate to that of water. The determination of specific gravity

of quartz sand was according to ASTM C128. The specific gravity was calculated at two

different conditions which are the dry condition and the saturated surface dry condition.

Table 3.2 shows the physical properties of quartz sand.

The unit weight or the bulk density of the aggregate is the weight of the aggregate per unit

volume. The unit weight is necessary to select concrete mixtures proportions in

UHPFRSCC .The determination of unit weight was according to ASTM C556. Table 3.2

illustrate the unit weight of quartz sand.

aterial M Chapter 3

24

Table 3.2: Physical property of quartz sand

Unit Weight

(kg/m3) (SSD)

Unit Weight

(kg/m3) (dry)

Specific

Gravity(SSD)

Specific

Gravity(dry)

Aggregate

Size(mm)

1672.588 1662.15 2.675 2.658 0.6

1673.002 1662.64 2.68 2.663 0.5

1673.416 1663.130 2.685 2.668 0.4

1674.100 1663.950 2.697 2.680 0.3

1674.614 1664.000 2.697 2.680 0.15

1673.544 1663.174 2.687 2.670 average

3.2.2.2 Moisture content:

The aggregate moisture is the percentage of the water present in the sample aggregate,

either inside pores or at the surface. Moisture content of the fine aggregate was done

according to ASTM C128, but the final moisture content was zero because fine aggregates

were dried in an oven at temperature (110o C±5). Table 3.3 illustrates the absorption

percentages of quartz sand.

Table 3.3: Water absorption of quartz sand

Water Absorption (%) Aggregate Size(mm)

0.620 0.6

0.625 0.5

0.628 0.4

0.636 0.3

0.639 0.15

0.629 average

From the previous results, it can be observed that the specific gravity ranges from 2.658 to

2.697 for quartz sand, and the water absorption tends to increase with the size reduction.

3.2.3 Water

Drinkable water was used in all concrete mixtures and in the curing of specimens.

aterial M Chapter 3

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3.2.4 Admixture

The chemical admixture used is superplasticizer manufactured to confirm to ASTM-C-494

specifications (Type G and F) see Table 3.4 and Figure 3.2. When superplasticizer is added

to concrete mix, it shows a strong self-leveling behavior therefore suitable for the

production of self-compacting concrete and improves the properties of fresh and hardened

concrete. This plasticizing effect can be used to increase the workability of fresh concrete

without causing segregation, water reduction (resulting in high density, durability and

strength), high flowability, improve shrinkage and creep behavior and finally improve

water impermeability.

Table 3.4: Technical data for the "Sika ViscoCrete – 5930"

Type Property

Appearance Turbid liquid

Density (kg/l) 1.08 ± 0.005

Basis Aqueous solution of modified polycarboxylate

Toxicity Non-Toxic under relevant health and safety codes

Figure 3.2: The chemical admixture (Superplastisizer).

aterial M Chapter 3

26

3.2.5 Silica Fume

Silica fume is a byproduct resulting from the reduction of high-purity quartz with coal or

coke and wood chips in an electric arc furnace during the production of silicon metal or

ferrosilicon alloys. The silica fume which condenses from the gases escaping from the

furnaces has a very high content of amorphous silicon dioxide and consists of very fine

spherical particles. (ACI 548.6R - 96).

The silica fume "Sika -Fume" was supplied from SIKA Company. Table 3.5 shows the

technical data supplied from the SIKA Company.

Table 3.5: The technical data for the "Sika – Fume”

Type Property

Appearance Grey powder

Specific gravity 2.20

Chloride Content Nil

Toxicity Non-Toxic

3.2.6 Steel fibers

Straight stainless steel fibers with length/diameter ≈ 60, Tensile strength ≈ 650 MPa, and

density of 7.8 g/cm3, have been added, to improve hardened concrete properties especially

the ductility.

Figure 3.3: Steel fibers

aterial M Chapter 3

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3.2.7 Polypropylene fibers

Polypropylene fibers are thermoplastic polymers, meet the requirements of ASTM C-1116,

with a specific gravity of 0.9 g/cm3 and length of 1.5 cm, added to improve the

UHPFRSCC shrinkage and ductility properties.

Figure 3.4: Polypropylene fibers

3.3 Mix Design of UHPFRSCC

Mix design process is summarized in Figure 3.5.

1. What is Required !! based on related specifications

2. Select needed materials

3. Design mix proportions

4. Laboratory testing

5. Adjust proportions or verify.

Figure 3.5: Mix design process

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3.4 Preparation of UHPFRSCC

After selection of all needed constituent materials and amounts to be used (mix designs); all

materials are weighed properly. Then mixing with a power-driven tilting revolving drum

mixer started to ensure that all particles are surrounded with cement paste and silica fume

and all the materials and fibers (i.e. steel and polypropylene fibers) should be distributed

homogeneously in the concrete mass.

Mixing procedure was according following steps: (Arafa et al., 2010):

1) Adding 40 % of superplasticizer to the mixing water.

2) Placing all dry materials (cement, silica fume, quartz sand, steel fibers and

polypropylene fibers) in the mixer pan, and mixing for 2 minutes.

3) Adding water (with 40% of superplasticizer) to the dry materials, slowly for 2 minutes.

4) Waiting 1 minute then adding the remaining superplasticizer to the mixture for 30

seconds.

5) Continuation of mixing as the UHPFRSCC changes from a dry powder to a thick paste.

After final mixing, the mixer is stopped, turned up with its end right down, and the fresh

homogeneous concrete is poured into a clean plastic pan.

The casting of all UHPFRSCC specimens used in this research completed within 20

minutes after being mixed. All specimens were cast and covered to prevent evaporation.

3.5 Test Program

As stated in the first chapter of this research, the aim of this research is to produce Ultra

High Performance Fiber Reinforced Self Compacted Concrete (UHPFRSCC) in Gaza Strip

by using local available materials. The test program adopted to achieve this objectives is

summarized in Figure 3.6.

aterial M Chapter 3

29

Figure 3.6: Test Program

3.6 Equipment and testing procedure

The laboratory testing consists of tests for both fresh and hardened concrete. Fresh concrete

tested for slump and V-funnel. Hardened concrete tested for compressive strength, indirect

tensile tests (split cylinder test and flexural test).

3.6.1 Tests Applied On Fresh Concrete

Based on previous experiences, as for site quality control, two test methods are generally

sufficient to monitor production quality, and typical combinations are slump flow and V-

funnel (EFNARC, 2005), this combination is adopted in this research.

Best mix

Steel fibers

Silica fume

Test the effect of

Polypropylene

aterial M Chapter 3

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3.6.1.1 Slump flow, T500 tests

The slump-flow and T500 time is a test to measure the flowability and the flow rate of self-

compacting concretes in the absence of obstructions. It is based on the slump test to

measure two parameters, the flow speed and the flow time. The result is an indication of the

filling ability of self-compacting concrete. The T500 time is also a measure of the speed of

flow and hence the viscosity of the self-compacting concrete, also the test is not suitable

when the maximum size of the aggregate exceeds 40 mm.

The fresh concrete is placed into a cone as for the normal slump test as shown in Figure

3.7. When the cone is left upwards, the time from commencing upward movement of the

cone to when the concrete has flowed to a diameter of 500 mm is measured; this is the

T500 time. The largest diameter of the flow spread of the concrete and the perpendicular

diameter are then measured and the mean is the slump-flow, Figure 3.8.

Don‟t forget to check the concrete spread for segregation. The cement paste/mortar may

segregate from the aggregate and steel fibers to give a ring of paste/mortar extending

several millimeters beyond them.

Figure 3.7: Slump cone and base plate

Figure 3.8: Self-compacted concrete at the lab.

aterial M Chapter 3

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Table 3.6: Self-compacting criteria (Slump flow, T500 test)

Test Unit Min. Max.

Slump flow mm 550 850

T500 mm Slump flow Sec. 2 9

3.6.1.2 V-funnel test

The V-funnel test is used to assess the viscosity and filling ability of self-compacting

concrete with a maximum size aggregate of 20mm. The V shaped funnel as shown in

Figure 3.9 is filled with fresh concrete and the time taken for the concrete to flow out of the

funnel is measured and recorded as the V-funnel flow time.

Figure 3.9: V-Funnel

Table 3.7: Self-compacting criteria (V-funnel)

Test Unit Min. Max.

V-funnel Sec. 6 12

aterial M Chapter 3

32

3.6.2 Tests Applied On Hardened Concrete

3.6.2.1 Compression Test

A significant portion of this research focused on the behaviors of UHPFRSCC cube

specimens under compressive loading. The compressive tests discussed in this section were

all completed nominally according to (ASTM C109. 2004) standard test method for cubes.

Total number of 126 cubes were manufactured. For each batch of UHPFRSCC made,

100x100x100 mm cube specimens were prepared, as shown in Figure 3.10. The cubes were

filled with fresh concrete without compacting, after preparing the specimens, cubes were

covered with plastic sheets for about 24 hours to prevent moisture loss.

Figure 3.10: Cube specimens Figure 3.11: Cubes at curing basin

After 24 hours; Cubes extracted from forms and stored in water (curing phase) up to the

time of test. Before testing, specimens were air dried for 10 to15 minutes and any loose

sand grains or incrustations from the faces that will be in contact with the bearing plate of

the testing machine are removed. The cubes then placed in the testing machine so that the

load is applied through flat and parallel sides.

The compressive strength of the specimen, σcomp (in MPa), is calculated by dividing the

maximum load carried by the cube specimen during the test by the cross sectional area of

the specimen.

The compressive strength was determined at different ages 7, 14, and 28 days. At least

three of these cubes were tested for each period the mean value of the specimens was

considered as the compressive strength of the experiment.

aterial M Chapter 3

33

3.6.2.2 Splitting Cylinder Test

Total number of 42 cylinders were manufactured. The splitting tensile strength of

UHPFRSCC was measured based on (ASTM C496. 2004) Standard test Method for

Splitting Tensile Strength of Cylindrical Concrete Specimens.

This test often referred to as the split cylinder test, indirectly measures the tensile strength

of concrete by compressing a cylinder through a line load applied along its length. The

failure of concrete in tension is governed by micro-cracking, associated particularly with

the interfacial region between the aggregate particles and the cement, also called interfacial

transition zone (ITZ). The load applied (compressive force) on the cylindrical concrete

specimen induces tensile and shear stresses on the aggregate particles inside the specimen,

generating the bond failure between the aggregate particles and the cement paste. Usually,

splitting tensile strength test is used to evaluate the shear resistance provided by concrete

elements. However, the most important advantage is that, when applying the splitting

procedure, the tensile strengths are practically independent of either the test specimen or of

the test machine sizes, being only a function of the concrete quality alone. Thus, much

inconvenience is eliminated, particularly with respect to the scale coefficient, which is

involved in direct tensile tests. For this reason, this procedure is considered to reproduce

more exactly the real concrete tensile strength.

The tensile strength of concrete is evaluated using a split cylinder test, in which a

cylindrical specimen is placed on its side and loaded in diametrical compression, so to

induce transverse tension. Practically, the load applied on the cylindrical concrete specimen

induces tensile stresses on the plane containing the load and relatively high compressive

stresses in the area immediately around it. When the cylinder is compressed by the two

plane-parallel face plates, situated at two diametrically opposite points on the cylinder

surface then, along the diameter passing through the two points, as shown in Figure 3.15,

the major tensile stresses are developed which, at their limit, reach the fracture strength

value ASTM C496 indicates that the maximum fracture strength can be calculated based on

the following equation.

aterial M Chapter 3

34

DL

2P Fsp

Where: P is the fracture compression force acting along the cylinder;

D is the cylinder diameter;

π = 3.14;

L is the cylinder length.

The load and stress distribution pattern across the cross section if it is assumed that the load

is concentrated at the tangent points then, over the cross section, only tensile stresses would

be developed. In practice, however, the load is distributed over a finite width owing to

material deformations. So, over the cross section, horizontal compressive stresses are

developed too, in the close vicinity of the contact point between the press platens and the

material. Since the compressive stresses only develop to a small depth in the cross section,

it may be assumed that the tensile stresses are distributed evenly along the diameter where

the splitting takes place, see Figure 3.12.

Figure 3.12: Split cylinder test

Figure 3.13: Cylinders damages after test

aterial M Chapter 3

35

All cylinder specimens were tested after 28 days from casting. Three cylinders were tested

for each patch, the mean values of the specimens were considered as split cylinder strength.

3.6.2.3 Flexural Prism Test

Total number of 42 prisms were manufactured. The flexural strengths of concrete

specimens are determined by the use of simple beam with center point loading in

accordance to (ASTM C293. 1994) as shown in Figure 3.14. The specimens are prisms 100

x 100 x 500 mm.

The mold is filled with the concrete in one layer, without compacting. After preparing the

specimens, they are covered with plastic sheets for about 24 hours to prevent moisture loss.

After 24 hours, the specimens are extracted from the molds and placed in water for curing

up to time of test.

Figure 3.14: Beam dimensions used for flexural prism tests

At the time of testing, and because the flexural strengths of the prisms are quickly affected

by drying which produces skin tension, they are tested immediately after they are removed

from the curing basin.

The casted beam specimens to be tested, turned on their sides with respect to their position

as molded. This should provide smooth, plane and parallel faces for loading. See Figure

3.15.

100 mm

250 mm P 250 mm

aterial M Chapter 3

36

Figure 3.15: Schematic view for flexure test of concrete by center-point loading

The pedestal on the base plate of the machine is centered directly below the center of the

upper spherical head, and the bearing plate and support edge assembly are placed on the

pedestal. The center loading device is attached to the spherical head. The test specimen is

turned on its side with respect to its position as molded and it is placed on the supports of

the testing device. This provides smooth, plane, and parallel faces for loading. The

longitudinal center line of the specimen is set directly above the midpoint of both supports.

The center point loading device is adjusted so that its bearing edge is at exactly right angles

to the length of the beam and parallel to its top face as placed, with the center of the bearing

edge directly above the center line of the beam and at the center of the span length. The

load contacts with the surface of the specimen at the center. If full contact is not obtained

between the specimen and the load applying or the support blocks so that there is a gap, the

contact surfaces of the specimen are capped.

The specimen is loaded continuously and without shock at until rupture occurs. Finally, the

maximum load indicated by the testing machine is recorded.

The flexural strength of the beam, Fr (in MPa), can be calculated by using the following

equation:

Where: P = maximum applied load indicated by the testing machine;

L = span length;

B = average width of specimen, at the point of fracture;

D = average depth of specimen, at the point of fracture)

All beam specimens were tested after 28 days from casting. Three beams were tested for

each patch, the mean values of the specimens were considered as flexural strength of the

beam.

22BD

3PLFr

aterial M Chapter 3

37

3.6.2.4 Unit weight

In this research, the unit weight of the concrete cube specimen is the theoretical density.

The density is calculated by dividing the weight of each cube by the volume. The same

cube specimens which are used to determine the compressive strength was used to

determine the density and the tests were carried out according to ASTM C642. (2004).

3.6.3 Curing Procedure

Curing is an important process to prevent the concrete specimens from losing of moisture

while it is gaining its required strength. Lack of curing will tend to lead the concrete

specimens to perform less well in its strength required.

All concrete samples were placed in curing basin after 24 hours from casing. All samples

remained in the curing basin up to time of testing at the specified age. The curing condition

of lab basin followed the ASTM C192, (2004). Curing water temperature is around 25oC.

Discussionand sesultRTest 4Chapter

38

Chapter (4)

Test Results and Discussion

4.1 Introduction

Series of tests were carried out on the concrete specimens to develop, study and evaluate

the mechanical properties of fresh and hardened Ultra High Performance Fiber Reinforced

Self Compacted Concrete. This chapter discusses the results obtained from 14 different

tests adopted in the testing program. Results include slump flow test, V-funnel, unit weight,

compressive strength and indirect tensile strength tests.

Table 4.1 and Table 4.2 show the mixture proportions and one cubic meter ingredient of the

best results obtained mixture of UHPFRSCC. All mixtures details and average results are

presented in appendix (A).

Table 4.1: Best mixture proportions of UHPFRSCC by weight of cement

ingredient / cement content Material

1.00 Cement CEM I 42.5R

0.24 Water cement ratio (w/c)

0.15 Silica fume to cement (s/c)

1.25 Quartz sand to cement (q/c)

0.03 Superplastisizer to cement

≈ 0.16 (2% of total volume) Steel Fibers to cement

0.001

Polypropylene fibers to cement

Table 4.2: One cubic meter components of UHPFRSCC mixture

Materials Proportion (kg/m3)

Cement CEM I 42.5R 900

Water 216

Silica fume 135

Quartz sand 1125

Superplastisizer 27

Steel Fibers 144

Polypropylene fibers 0.9


39

All mixtures were subjected to fresh and hardened concrete tests in order to be classified as

UHPFRSCC, some mixing ingredients were fixed and the other were variable. Table 4.3

summarizes the different mixes proportions.

Table 4.3: Different mixes proportions

Material / C Mix No.

1 2 3 4 5 6 7 8 9 10 11 12

Cement 1 1 1 1 1 1 1 1 1 1 1 1

Water 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24

Silica fume 10% 15% 20% 10% 15% 20% 10% 15% 20% 10% 15% 20%

Quartz sand 125% 125% 125% 125% 125% 125% 125% 125% 125% 125% 125% 125%

Superplastisizer 3% 3% 3% 3% 3% 3% 3% 3% 3% 3% 3% 3%

Steel fibers 4% 4% 4% 8% 8% 8% 12% 12% 12% 16% 16% 16%

Polypropylene 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1%

4.2 Fresh properties tests results

By conducting the test methods on the fresh concrete mixtures, Table 4.4 shows all results

obtained in the lab. The results showed that eight mixtures out of twelve satisfy the fresh

properties standards developed by the European Guidelines for self-Compacting Concrete,

2005 and concrete strength classification of Ultra high strength concrete, shown in chapter

2 of this research. These mixtures were called UHPFRSCC; On the other hand, three other

mixtures did not satisfy the fresh properties standards but satisfy the concrete strength

classification of Ultra high strength concrete and these mixtures were called UHPFRC. The

remaining mixture did not satisfy the fresh properties standards but satisfy the concrete

strength classification of very high strength concrete and this mixture was called HPFRC.


40

Table 4.4: Fresh properties tests results

a. 0.5% steel fiber (by total volume), (i.e. 4% steel fibers (by cement content) )

Mix # Slump test (mm) V-funnel test

(sec.)

Compressive

strength 28D (MPa) Classification

1 770 OK SF3 9.7 OK 120.7 OK UHPFRSCC


3 745 OK SF2 13.15 N.OK 116.2 N.OK HPFRC

b. 1.0% steel fiber (by total volume), (i.e. 8% steel fibers (by cement content) )


(sec.)

Compressive




6 743 OK SF2 13.2 N.OK 130.4 OK UHPFRC

c. 1.5% steel fiber (by total volume), (i.e. 12% steel fibers (by cement content) )


(sec.)

Compressive





d. 2.0% steel fiber (by total volume), (i.e. 16% steel fibers (by cement content) )


(sec.)

Compressive






41

4.2.1 Effect of silica fume and steel fibers on slump test results

Three different doses of silica fume added, (10%, 15% and 20%) by mass of the Portland

cement and four different percentages of steel fibers (by the total volume) (0.5%, 1.0%,

1.5% and 2%) have been used to study the influence on fresh UHPFRSCC properties. The

water/cement ratio 0.24 was kept constant for all mixtures and superplastisizer/cement also

kept to 0.03.

Figure 4.1, shows that the larger is the silica fume amount, the smaller is the slump flow

results, this can be justified because silica fume is a very fine materials need much more

amount of water to break the flocculation forces. And as the steel fibers increases, the

slump flow results decreases. Results agree with that of previous research of Abu Shaban,

(2012).

Figure 4.1: Effect of silica fume and steel fibers on slump test results

4.2.2 Effect of silica fume and steel fibers on V-Funnel test results

Table 4.4 Shows the V-Funnel test time results for the mixes, these results also reflect the

concrete viscosity ratio which is inversely proportional with the V-Funnel time, in other

words when the V-Funnel time increases the concrete loses its viscosity.


42

Figure 4.2 shows the effect of adding 10%, 15% and 20% silica fume, by the mass of

Portland cement and four different percentages of steel fibers (by the total volume) (0.5%,

1.0%, 1.5% and 2%) on the UHPFRSCC V-Funnel time.

It was shown that the larger is the amount of the silica fume and steel fibers, the lower is

the viscosity of mixtures. And, when the silica fume percentage equal or above 20%,

mixtures cannot be considered as a self-compacting concrete any more. High percentage of

silica fume as a fine Pozzolanic material fill all the spaces between cement particles and

need much more high range water reducer superplasticizer, that would led to a very rigid

and not self-compacted concrete.

Figure 4.2: Effect of silica fume and steel fibers on V-funnel time results

The obtained results agree with that of previous research of Abu Shaban, (2012).

4.2.3 Segregation in the trial mixes

In all trial mixtures, where the W/C was constant and equal to 0.24, no segregation was

observed and all mixtures were homogenous and fibers were well distributed through every

batch.


43

4.3 Hardened properties tests results

Laboratory tests were conducted to evaluate and study the hardened properties of

UHPFRSCC. Results are the unit weight, compressive strength test and indirect tensile

tests. Mean results are summarized in Table 4.5.

Table 4.5: Hardened properties tests results

a. 0.5% steel fiber (by total volume), (i.e. 4% steel fibers (by cement content) )

Mix # Unit weight

Kg/m3

Compressive strength MPa Splitting tensile

strength 28days

MPa 7 days 14 days 28 days

1 2554 85.3 104.9 120.7 12.5

2 2542 95.5 117.4 134.9 14.2

3 2539 82.2 101.1 116.2 12.1

b. 1.0% steel fiber (by total volume), (i.e. 8% steel fibers (by cement content) )

Mix # Unit weight

Kg/m3


strength 28days


4 2587 101.3 124.6 143.2 15.1

5 2577 111.1 136.3 156.7 16.4

6 2565 92.2 113.4 130.4 13.7

c. 1.5% steel fiber (by total volume), (i.e. 12% steel fibers (by cement content) )

Mix # Unit weight

Kg/m3


strength 28days


7 2590 106.1 130.2 149.7 15.7

8 2581 114.6 141 162.1 17.1

9 2574 100.2 122.9 141.3 14.8

d. 2.0% steel fiber (by total volume), (i.e. 16% steel fibers (by cement content) )

Mix # Unit weight

Kg/m3


strength 28days


10 2601 112.9 140.3 159.4 16.1

11 2592 125.7 156.2 177.5 18.7

12 2583 105.1 130.6 148.4 15.6


44

4.3.1 Effects of silica fume and steel fibers on UHPFRSCC unit weight

Figure 4.3: Effect of silica fume and steel fibers on UHPFRSCC unit weight

Figure 4.3 summarizes the effect of silica fume and steel fibers on the UHPFRSCC unit

weight, the results show that the density of concrete decreases when increasing the silica

fume content, but increases when the amount of steel fibers increases.

4.3.2 Effects of silica fume and steel fibers on UHPFRSCC compressive strength

Figure 4.4: Effect of silica fume and steel fibers on UHPFRSCC compressive strength (7days)


45


(14days)


(28days)


46

Results shown in Table 4.5, Figure 4.4, Figure 4.5 and Figure 4.6 demonstrate that it is

possible to develop UHPFRSCC with different silica fume and steel fibers amounts.

It can be observed that increasing the silica fume content from 10% to 15% effectively

increases the compressive strength of concrete. But increasing the silica fume content from

15% to 20% decreases the compressive strength. Results agree with that of Abu Shaban,

(2012).

This can be explained according to what have been mentioned in EFNARC, that the silica

fume works in two levels, the Pozzolanic reaction and the physical function. The hydration

of Portland cement produces many compounds; including calcium silicate hydrates (C-S-H)

and calcium hydroxide (CH). When silica fume is added to fresh concrete, it chemically

reacts with the CH to produce additional C-S-H which improve the bond between the

cement and the surface of the aggregate, more ever the silica fume particle can fill the voids

creates by free water in the matrix. This function is called particle packing refines the

microstructure of the concrete, thus creating a much denser pore structure the benefit of this

reacts is twofold; increasing compressive strength and decreasing total pores volume

(EFNARC, 2005). But when silica fume percent increased significantly, the strength

decreases, this can be explained that the silica fume can react to a certain level, after that

the silica fume did not participate in the hydration reaction and remain inert in concrete as

the weakest point.

On the other hand, when the steel fibers amount increases, the compressive strength

increases also.

The maximum compressive strength of the concrete specimens was achieved by using 15 %

silica fume by the mass of cement, and addition of 2% of steel fibers of the total volume.

where a compressive strength up to 177.5 MPa, which met the target compressive strength

for the UHPFRSCC and agree with results obtained by Hoang K. et al., (2008).


47

4.3.3 Compressive strength – Time relationship

Figures 4.4 through 4.6 show the compressive strength results at several ages of the

concrete mixtures.

For the mixture #11 with the best results, Figure 4.7 shows the variation of mean

compressive strength with age.

Figure. 4.7: Mean compressive strength Vs. age of mix #11

Results of Figure 4.7 show that this mixture can achieve a mean compressive strength of

concrete specimens near 177.5 MPa at an age of 28 days. Where the curing was done at

room temperature by immersion in water without any heat treatment.

Figure 4.8 shows the mean compressive strength Vs. age of the mix.


48

Figure 4.8: Mean compressive strength Vs. age.

ACI Committee 209, 2033 recommends the following expressions to predict the

compressive strength (fc‟) of Normal Strength Concrete (NSC) with strengths up 41 MPa at

any time:

Where a = 4 (cement type I), β = 0.15 (moist curing), fc28 = 28 days strength and t is the age

of concrete.

Ratios for compressive strengths at different ages of UHPFRSCC concrete fct (7, 14, and 28

days), and that of ACI Committee 209, 2033 expressions are summarized in Table 4.6

shown below.

Table 4.6: Mean ratio of ( fct / fc28) for UHPFRSCC

Age of Cubes (days) Mean ratio of ( fct / fc28)

“Results”

Mean ratio of ( fct / fc28)

“ACI 209, 2033”

7 0.71 0.7

14 0.87 0.88

28 1 1

(MPa) )( t

)( 28ctc fta

f


49

Table 4.6 and Figure 4.9, show results very close to that of ACI Committee 209, 2033

expressions, and that expression can be used for concrete with strength up to 177 MPa.

Figure 4.9: Comparison of (fct / fc28 ) between NSC and UHPFRSCC at different ages .

4.3.4 Effects of silica fume and steel fibers on UHPFRSCC splitting strength

Figure 4.10 shows the effect of adding silica fume 10%, 15% and 20% by mass of cement,

and the addition of steel fibers with 0.5%, 1.0%, 1.5% and 2% by total volume on the

UHPFRSCC splitting tensile strength.


50

Figure. 4.10: Effect of silica fume and steel fibers on UHPFRSCC splitting tensile strength @

age of 28 Days.

From figure 4.10, it can be stated that the larger is the steel fiber amount, the larger is the

splitting tensile strength, and when silica fume increased from 10% to 15% the strength

increased, but when the amount is above 15%, the splitting tensile strength decreased.

The obtained results can be justified as, the addition of steel fibers with the tensile strength

of 650 MPa, distributed homogenously within every batch will sustain the developed

tensile stresses, thus increase the splitting tensile strength of specimens.

Finally, the above results show that mixtures can achieve a mean splitting tensile strength

of concrete specimens of 18.7 MPa at an age of 28 days. Curing was at 25oC by immersion

in water without heat treatment. The standard deviation value was very low ≈ 0.3 MPa.


51

4.3.5 Effects of silica fume and steel fibers on UHPFRSCC flexural strength

Figure 4.11: Effect of silica fume and steel fibers on UHPFRSCC Flexural strength @ age

of 28 Days.

From figure 4.11, it can be concluded that the larger is the steel fiber amount, the larger is

the flexural strength, and when silica fume increased from 10% to 15% the strength

increased, but when the amount is above 15%, the flexural strength decreased. Results

agree with that obtained by Hoang K. et al., (2008).

Obtained results can be justified as a better bonding developed due to the use of silica

fume, which is the most effective way to get the Interface Transition Zone (ITZ) denser, it

eliminates many of the large pores in this zone and increases the strength of the bond

between the cement paste and the fibers, thus reducing the pores in cement paste. And the

addition of steel fibers with the ultimate tensile strength of 650 MPa, distributed

homogenously within every batch and work as a reinforcement, will sustain the developed

tensile stresses, thus increase the flexural strength of specimens.


52

Finally, The above results show that mixtures can achieve a mean rupture flexural strength

of concrete specimens of 22.1 MPa at an age of 28 days. Curing was at 25oC by immersion

in water without heat treatment. The standard deviation value was very low ≈ 0.4 MPa.

4.4 Effect of Polypropylene fibers content

Another series of tests were carried out to study the effect of polypropylene fibers content

on concrete cubes, cylinders, and beams by evaluating the fresh and hardened properties of

Ultra High Performance Fiber Reinforced Self Compacting Concrete. Two new mixes were

developed after choosing the best mixture from the previous twelve UHPFRSCC mixtures.

Table 4.7 and table 4.8 show the new mixture proportions and one cubic meter components

of UHPFRSCC, and all test results of the new two mixes are presented in appendix (A).

All the new mixtures were subjected to fresh and hardened tests in order to be classified as

UHPFRSCC, some mixing proportions were fixed such as cement, water, silica fume,

quartz sand, steel fibers and superplasticizer and the polypropylene fibers content were

varied, to study its effect on fresh and hardened concrete.

Table 4.7: Additional mixture proportions of UHPFRSCC by weight of cement

Material Unit Mix 11 (a) Mix 11 (b)

Cement

Pro

port

ion (

% /

Cem

ent)

1 1

Water 0.24 0.24

Silica fume 15% 15%

Quartz sand 1.25 1.25

Superplastisizer 0.03 0.03

Steel fibers 0.16 0.16

Polypropylene fibers 0.0005 0.002


53

Table 4.8: One cubic meter components of additional UHPFRSCC mixture


Cement

Kg/m

3

900 900

Water 216 216

Silica fume 135 135

Quartz sand 1125 1125

Superplastisizer 27 27

Steel fibers 144 144


Test results for the new mixes are summarized in Table 4.9 shown below.

Table 4.9: Effect of Polypropylene fibers on fresh and hardened properties

Material Unit Mix 11 Mix 11 (a) Mix 11 (b)

Cement

Kg/

m3

900 900 900

Water 216 216 216

Silica fume 135 135 135

Quartz sand 1125 1125 1125

Superplastisizer 27 27 27

Steel fibers 144 144 144

Polypropylene fibers 0.9 0.45 1.8

Slump flow test mm 742 748 739

T500 test sec. 6.4 5.9 6.7

V-funnel test sec. 11.4 10.4 11.9

Density kg/m3 2592 2590 2588

Compressive strength - 7 days Mpa 125.7 124 126.9

Compressive strength - 14 days MPa 156.2 148.6 155.8

Compressive strength - 28 days MPa 177.5 165.1 175.4

Splitting tensile strength - 28 days MPa 18.7 17.9 19.1

Flexural Strength - 28 days MPa 22.1 20.8 23.2


54

Figure 4.12: Effect of Polypropylene fibers on slump test

Figure 4.12 shows the effect of adding 0.45, 0.90 and 1.80 kg/m3

polypropylene fibers by

the total volume of batch. It shows that the mixtures lose some of its flowability when the

polypropylene fibers percentage increases, but still classified as self-compacting concrete.

Figure 4.13: Effect of Polypropylene fibers on V-funnel test

Figure 4.13 shows the effect of adding 0.45, 0.90 and 1.80 Kg/m3


the total volume of batch on the V-Funnel test. It also shows that the mixtures lose some of

its viscosity when the polypropylene fibers percentage increases, but still classified as self-

compacting concrete


55

Figure 4.14: Effect of Polypropylene fibers on Unit weight

Figure 4.14 shows the effect of adding 0.45, 0.90 and 1.80 Kg/m3


the total volume of batch on the unit weight of hardened concrete. It can be observed that

the difference is very small, it could be because of the small amount of Polypropylene

fibers when compared with other contents.

Figure 4.15: Effect of Polypropylene fibers on compressive strength



the total volume of batch on the compressive strength at different ages. It can be observed

that the optimum amount is 0.9 kg/m3 for all ages.


56

Figure 4.16: Effect of Polypropylene fibers on splitting tensile strength at the age of 28 days.



the total volume of batch on the splitting tensile strength at the age of 28 days. It can be

observed that the optimum amount is 1.8 kg/m3. This is because the added polypropylene

fibers, works as a secondary reinforcement sustain some of the tensile loads developed by

the test.

Figure 4.17: Effect of Polypropylene fibers on flexural strength at the age of 28 days.


57



the total volume of batch on the flexural strength at the age of 28 days. It can be observed

that the optimum amount is 1.8 kg/m3. This is because the added polypropylene fibers,

works as a secondary reinforcement sustain some of the tensile loads developed by the test.

4.4.1 Effect of Polypropylene fibers conclusion

From the above results, it can be observed that all polypropylene fibers contents, do not

affect the classification of mixes from being UHPFRSCC.

The optimum content of Polypropylene fibers from the compressive strength point of view

is 0.9 kg/m3, with cement content of 900 kg/m

3, W/C of 0.24, Silica fume of 15% by

cement weight, sand with 125% of weight of cement, 3% plasticizer and 16% of steel

fibers. However, if the polypropylene fibers increased up to 1.8 kg/m3, the decrease in

compressive strength is not significant and the tensile and flexural strengths are improved.

s and RecommendationsConclusion Chapter 5

58

Chapter (5)

Conclusions and Recommendations

UHPFRSCC is a relatively new form of concrete, which can be used for general

applications and especially for rehabilitation works. The main advantages that UHPFRSCC

has over standard concrete are its high compressive strength, relatively high tensile and

flexural strength, low porosity and high durability and self-compacting properties.

The objective of this research was to produce UHPFRSCC using local available materials

in Gaza Strip. The experimental phase of this research focused on developing UHPFRSCC

and determining the mechanical behavior for fresh and hardened statuses. The laboratory

tests determined the different fresh properties, compressive, flexural and indirect tensile

strength of the developed UHPFRSCC. The analytical phase of this research focused and

elaborated on the results obtained from the experimental phase.

The following paragraphs discuss conclusions and recommendations for this material

applications, and recommendations for future researches.

5.1 Conclusion

Results of this research show that it is possible to produce UHPFRSCC in Gaza strip using

materials that are available at the local markets if they are carefully selected and will

achieve a minimum compressive strength of 177 MPa at the age of 28 days. Such concretes

can be produced with cement, W/C of 0.24, steel fibers (16% by the weight of cement),

polypropylene fibers (0.9 Kg/m3), quartz sand, and silica fume (15% by the weight of

cement) as the mineral admixture (3% superplasticizer by the weight of cement).

For the fresh properties of UHPFRSCC, we can notice that;

Increasing silica fume content from 10% to 15% and then to 20% leads to a

decrease in the slump values and the filling ability of the UHPFRSCC.


59

Increasing the steel fibers content will slightly decrease the slump flow and the

filling ability of the UHPFRSCC.

Increasing silica fume content from 10% to 15% leads to a slight increase in the V-

funnel time which results in decreasing the UHPFRSCC viscosity, but concrete still

being classified as self-compacted concrete.

Increasing silica fume percent up to 20% leads to an increase in the V-funnel time

which results in decreasing the UHPFRSCC viscosity, and concrete cannot be

classified as self-compacted concrete any more.

In all trial mixtures, where the W/C was constant and equal to 0.24, no segregation

was observed and all mixtures were homogenous and fibers were well distributed

through every batch.

Adding 0.45, 0.9 and 1.8 kg/m3 polypropylene fibers to the UHPFRSCC, shows

that the mixtures loses some of its flowability when the polypropylene fibers

increased, where other contents are constant, but not affecting the concrete from

being self-compacted.

Adding 0.45, 0.9 and 1.8 Kg/m3 polypropylene fibers to the UHPFRSCC, shows

that the mixtures loses some of its viscosity when the polypropylene fibers

increased, where other contents are constant, but not affecting the concrete from

being self-compacted.

On the other hand; For the hardened properties, we can notice that;

Because of the large amount of Type I cement plus silica fume used in the UHPC

concrete mixtures with a relatively low W/C ratio, the strength of the concretes

develops more rapidly at the first 7 days than predicted by the current

recommendation of ACI Committee 209 (1993a) for normal conventional concrete.


60

The subsequent rate of strength growth is greatly decreased and is comparable to

that predicted by the ACI method.

The densities of concrete decreases as silica fume content increases, while keeping

other contents constant.

The densities of concrete increases as steel fibers content increases, while keeping

other contents constant.

It is possible to develop UHPFRSCC with different silica fume and steel fibers

contents. For 10 %, 15% and 20% silica fume, very high strength concrete with

159.4 MPa, 177.5 MPa, 148.4 MPa respectively can be achieved as steel fibers

content is 2% by the total volume.

Increasing the silica fume content from 10% to 15% effectively increases the

compressive strength of concrete. But increasing the silica fume content from 15%

to 20% decreases the compressive strength.

When the steel fibers amount increases, the compressive strength increases also.

As the compressive strength increases the splitting cylinder strength also increases

at certain cases of contents for the UHPFRSCC and as known in the normal

concrete.

The larger the steel fiber content, the larger the splitting tensile strength.

When silica fume increased from 10% to 15% the splitting tensile strength

increased, but when the content is above 15%, the splitting tensile strength

decreased.

The larger the steel fiber content, the larger the flexural strength.

When silica fume increased from 10% to 15% the flexural strength increased, but

when the content is above 15%, the flexural strength decreased.


61

The optimum amount of polypropylene fibers for the largest compressive strength is

0.9 Kg/m3 for all ages.

Splitting tensile strength increases as the polypropylene fibers content increases,

because the added polypropylene fibers, works as a secondary reinforcement

sustaining some of the developed tensile stresses.

Flexural strength increases as the polypropylene fibers content increases, because

the added polypropylene fibers, works as a secondary reinforcement sustaining

some of the developed tensile stresses.

5.1 Recommendations

The following recommendations are proposed for further research.

The effect of Material Property

The influences of cement type and steel fibers shape on the mechanical property of

UHPFRSCC need to be taken into consideration.

The effect of other types of fibers (Carbon, Glass …etc.) and polymers (Epoxy, SPR)

addition on the mechanical properties of UHPFRSCC need to be taken into

consideration for further research.

The influences of superplastisizer type on the mechanical property of UHPFRSCC

need to be taken into consideration.

Durability of UHPFRSCC

Further investigations have to be carried out on the following:

Performance under high-temperatures.

Pore structure and permeability.

Mechanism of strength development.


62

Chemical resistance.

Fire resistance.

Short term mechanical properties

Further testing and studies on short term mechanical properties of UHPFRSCC have to be

carried out on the following:

Drying Shrinkage and creep.

The stress – strain behavior in compression.

The stress – strain behavior in tension.

Static and dynamic modulus.

Using UHPFRSCC in the Rehabilitation Works

Further testing and studies needed to be carry out, to test the behavior of UHPFRSCC when

used as a repair material, and derive a proper equations when we use it to repair the

different deteriorated structural elements such as beams, columns, slabs, footings, shear

walls … etc.

References

63

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ASTM C109, 2004, “Standard Test Method for Compressive Strength of cube Concrete

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ASTM C127, 2004, “Standard Test Method for Specific gravity and absorption of coarse

aggregate”, American Society for Testing and Materials Standard Practice C127,


ASTM C150, 2004, “Standard specification of Portland cement American Society for Testing

and Materials Standard Practice C150”, Philadelphia, Pennsylvania.

ASTM C28, 2004, “Standard Test Method for Specific gravity and absorption of fine

aggregate”, American Society for Testing and Materials Standard Practice C128,


ASTM C293, 1994, “Standard Test Method for Flexural Strength of Concrete (Using Simple

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Practice C293, Philadelphia, Pennsylvania.

References

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ASTM C496, 2004, “Standard Test Method for Splitting Tensile Strength of Cylindrical

Concrete Specimens”, American Society for Testing and Materials Standard Practice

C496, Philadelphia, Pennsylvania.

ASTM C642, 2004, “Standard Test Method for density, absorption, and voids in hardened

concrete”, American Society for Testing and Materials Standard Practice C642,


Bache H., 1981, “Densified Cement/Ultra-Fine Particle-Based Materials” Presented at the

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Charron, J.-P., Denarié, E. & Brühwiler, E. 2006. "Permeability of Ultra High Performance

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40(3): 269–277.

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Appendixes

66

APPENDIX I : Results

ingredient / cement content

Material Unit Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 Mix 7 Mix 8 Mix 9 Mix 10 Mix 11 Mix 12

Cement

% i

ngr

edie

nt

/ C

emen

t

1 1 1 1 1 1 1 1 1 1 1 1

Water 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24 0.24

Silica fume 0.1 0.15 0.2 0.1 0.15 0.2 0.1 0.15 0.2 0.1 0.15 0.2

Quartz sand 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25

Superplastisizer 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03

Steel fibers 0.04 0.04 0.04 0.08 0.08 0.08 0.12 0.12 0.12 0.16 0.16 0.16

Polypropylene fibers 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001 0.001

Appendixes

67

ingredient (Kg/m3)

Material Unit Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 Mix 7 Mix 8 Mix 9 Mix 10 Mix 11 Mix 12

Cement K

g/m

3 900 900 900 900 900 900 900 900 900 900 900 900

Water 216 216 216 216 216 216 216 216 216 216 216 216

Silica fume 90 135 180 90 135 180 90 135 180 90 135 180

Quartz sand 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125

Superplastisizer 27 27 27 27 27 27 27 27 27 27 27 27

Steel fibers 36 36 36 72 72 72 108 108 108 144 144 144


Appendixes

68

Average test results

Material Unit Mix

1 Mix

2 Mix

3 Mix

4 Mix

5 Mix

6 Mix

7 Mix

8 Mix

9 Mix 10

Mix 11

Mix 12

Cement

Kg/

m3

900 900 900 900 900 900 900 900 900 900 900 900

Water 216 216 216 216 216 216 216 216 216 216 216 216

Silica fume 90 135 180 90 135 180 90 135 180 90 135 180

Quartz sand 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125 1125

Superplastisizer 27 27 27 27 27 27 27 27 27 27 27 27

Steel fibers 36 36 36 72 72 72 108 108 108 144 144 144


Slump test mm 770 754 745 768 756 743 760 748 739 757 742 733

T500 test sec. 4.9 5.6 8.2 5.1 6 8.4 5.4 6.2 8.7 5.5 6.4 9.1

V-funnel test sec. 9.7 10.2 13.15 9.85 10.4 13.2 10.1 10.8 13.35 10.55 11.4 14.9

Density kg/m3 2554 2542 2539 2587 2577 2565 2590 2581 2574 2601 2592 2583

Compressive strength - 7 days Mpa 85.3 95.5 82.2 101.3 111.1 92.2 106.1 114.6 100.2 112.9 125.7 105.1

Compressive strength - 14 days MPa 104.9 117.4 101.1 124.6 136.3 113.4 130.2 141 122.9 140.3 156.2 130.6

Compressive strength - 28 days MPa 120.7 134.9 116.2 143.2 156.7 130.4 149.7 162.1 141.3 159.4 177.5 148.4

Splitting tensile strength - 28 days MPa 12.5 14.2 12.1 15.1 16.4 13.7 15.7 17.1 14.8 16.1 18.7 15.6

Flexural Strength - 28 days MPa 15.4 16.9 15.2 16.7 18.1 15.8 17.1 18.9 16.7 17.4 22.1 16.9

Appendixes

69

ingredient / cement content


Cement

Pro

po

rtio

n (

% /

Cem

ent)

1 1

Water 0.24 0.24

Silica fume 15% 15%

Quartz sand 1.25 1.25

Superplastisizer 0.03 0.03

Steel fibers 0.16 0.16

Polypropylene fibers 0.0005 0.002 ingredient (Kg/m3)


Cement

Kg/

m3

900 900

Water 216 216

Silica fume 135 135


Superplastisizer 29.7 27



Average test results


Cement

Kg/

m3

900 900

Water 216 216

Silica fume 135 135


Superplastisizer 27 27



Slump test mm 748 739

T500 test sec. 5.9 6.7

V-funnel test sec. 10.4 11.9

Density kg/m3 2590 2588

Compressive strength - 7 days Mpa 124 126.9

Compressive strength - 14 days MPa 148.6 155.8

Compressive strength - 28 days MPa 165.1 175.4

Splitting tensile strength - 28 days MPa 17.9 19.1

Flexural Strength - 28 days MPa 20.8 23.2

Appendixes

70

APPENDIX II : Concrete Specimen Results and average

Test

Unit Mix 1 Mix 2 Mix 3

#1 #2 #3 Avg. #1 #2 #3 Avg. #1 #2 #3 Avg.

Density kg/m3 2558 2549 2555 2554 2534 2551.2 2540.8 2542 2530 2545.9 2541.1 2539

Compressive strength - 7 days Mpa 83.1 86.2 86.6 85.3 93.1 94.7 98.7 95.5 79.4 81.3 85.9 82.2

Compressive strength - 14 days MPa 101.4 105.7 107.6 104.9 110.3 124 117.9 117.4 98.7 104.5 100.1 101.1


Splitting tensile strength -28 days MPa 12.3 12.4 12.8 12.5 13.9 14.4 14.3 14.2 11.9 12.1 12.3 12.1

Flexural Strength - 28 days MPa 15.7 15.2 15.3 15.4 15.4 17.2 18.1 16.9 14.8 15.3 15.5 15.2

Test Unit Mix 4 Mix 5 Mix 6

#1 #2 #3 Avg. #1 #2 #3 Avg. #1 #2 #3 Avg.

Density kg/m3 2561 2630 2570 2587 2590 2560 2581 2577 2579 2530 2586 2565

Compressive strength - 7 days Mpa 98.1 102.7 103.1 101.3 103.4 116 113.9 111.1 94.1 89.3 93.2 92.2



Splitting tensile strength - 28 days MPa 15.3 14.8 15.2 15.1 16.3 16.5 16.4 16.4 13.4 13.9 13.8 13.7

Flexural Strength -28 days MPa 16.4 16.9 16.8 16.7 17.9 18.1 18.3 18.1 15.6 15.7 16.1 15.8


#1 #2 #3 Avg. #1 #2 #3 Avg. #1 #2 #3 Avg.

Density kg/m3 2602 2581 2587 2590 2600 2566 2577 2581 2591 2561 2570 2574

Compressive strength - 7 days Mpa 104.2 110.6 103.5 106.1 119.1 115 109.7 114.6 98.4 102.4 99.8 100.2

Compressive strength -14 days MPa 127.1 133.6 129.9 130.2 137.5 145.2 140.3 141 124.6 125.4 118.7 122.9


Splitting tensile strength - 28 days MPa 15.6 16.1 15.4 15.7 16.9 16.8 17.6 17.1 14.6 15 14.8 14.8

Flexural Strength - 28 days MPa 16.8 17.3 17.2 17.1 18.7 18.9 19.1 18.9 16.5 17 16.6 16.7

Appendixes

71


#1 #2 #3 Avg. #1 #2 #3 Avg. #1 #2 #3 Avg.

Density kg/m3 2603 2594 2606 2601 2598 2584 2594 2592 2561 2593 2595 2583

Compressive strength - 7 days Mpa 110.1 113.4 115.2 112.9 127.2 129.4 120.5 125.7 100.9 106.4 108 105.1

Compressive strength - 14 days

MPa 142 138.1 140.8 140.3 158.9 153.1 156.6 156.2 127.1 128.7 136 130.6

Compressive strength - 28 days

MPa 161.5 154.2 162.5 159.4 170.8 180.4 181.3 177.5 140.9 151.2 153.1 148.4

Splitting tensile strength - 28 days

MPa 15.7 16.2 16.4 16.1 18.6 19 18.5 18.7 15.7 16 15.1 15.6

Flexural Strength - 28 days MPa 17.6 17.5 17.1 17.4 22 21.8 22.5 22.1 16.9 17.1 16.7 16.9

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