Roy Belton: M.Sc. Dissertation - The Rheological and Empirical Characteristics of Steel Fibre...

The Rheological Characteristics of Steel Fibre

Reinforced Self-Compacting Concrete with PFA and

GGBS

A thesis submitted to Trinity College Dublin

for the Degree of Master of Structural and Geotechnical Engineering

By

Roy Belton

Department of Civil, Structural and Environmental Engineering

Trinity College Dublin

August 2014

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DECLARATION

I hereby certify that this dissertation I submit for examination for the Degree of Master of

Structural and Geotechnical Engineering in Trinity College Dublin, is wholly my own

work. No work has been taken from others; any such work that has been used is correctly

cited and acknowledged throughout this text. It has not been submitted for any degree or

examination in any other University or Institution. TCD has my full permission to keep,

lend or copy my work presented here on the condition that any work used in this thesis be

accordingly acknowledged.

Signed: Date:

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ABSTRACT

When testing steel fibre reinforced self-compacting concrete (SFRSCC) on-site, it is not

practical to determine the fundamental properties (yield stress and plastic viscosity) of

SFRSCC by means of rheological testing. Therefore, various empirical tests have been

developed to overcome this rheological shortcoming. These tests attempt to evaluate the

workability of SFRSCC for its successful placement concerning the ability of SFRSCC to

fill and flow into all the areas within the formwork, under its own weight, while maintain

a uniform distribution of constituent materials throughout the composite.

Within this study, the focus is on evaluating both the rheological and empirical parameters

of SFRSCC with both pulverised fly ash (PFA) and ground granulated blast furnace slag

(GGBS) for the partial replacement of cement (CEM II/A-L). By considering both the

rheological and empirical aspects of SFRSCC with 30% PFA and 50% GGBS cement

replacements, a correlation between concrete rheology and concrete workability could be

determined.

The results show that the use of PFA and GGBS caused an overall reduction in g and an

increase in h. Intuitively, a reduction in the relative parameter g means a reduction in yield

stress, while an increase in the relative parameter h means an increase in plastic viscosity.

Therefore, the use of PFA and GGBS for the partial replacement of CEM II/A-L caused an

overall reduction in yield stress and an increase in plastic viscosity. In addition, the GGBS

degraded the passing ability of SFRSCC and the workability of SFRSCC is retained for

longer periods after the addition of water when incorporating 30% PFA and 50% GGBS

cement replacements.

Both the slump flow and slump flow t500 time showed a reasonably good correlation with,

respectively, g and h, 15 minutes after the addition of mixing water. Therefore, quick and

easy empirical tests (such as the inverted slump flow test) could be used onsite instead of

rheology to determine, once suitable calibration has been carried out, the fundamental

parameters of yield stress and plastic viscosity. In addition, the inverted slump flow test

could be used to determine the actual steel fibre content, when using the relationships of g

to slump flow, h to slump flow t500 time and the variation of g and h with an increase in

steel fibre content as proxy.

In addition, a good correlation was shown to exist between the L-box blocking ratio and

the J-ring step of blocking for all the mixtures.

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ACKNOWLEDGEMENTS

I would like to thank Dr Roger P West of Trinity College Dublin, for his outstanding

supervision, guidance, patience, and steadfast encouragement throughout the course of my

study.

Thanks are also extended to the staff of the Department of Civil, Structural and

Environmental Engineering, TCD for their expertise and assistance. In particular, Dr

Kevin Ryan, Michael Grimes, Mick, Dave and, Owen.

Thanks are also extended to Tom Holden of Roadstone for the constituent materials used

in this study.

Finally, my special thanks go to my family and friends for their never-ending love,

support and encouragement.

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TABLE OF CONTENTS

DECLARATION ....................................................................................................................................... ii

ABSTRACT .............................................................................................................................................. iii

ACKNOWLEDGEMENTS ...................................................................................................................... iv

Table of contents .........................................................................................................................................v

Chapter 1 – Introduction and motivation ..................................................................................................1

1.1. Self-compacting concrete...................................................................................................................1

1.2. Benefits of using self-compacting concrete ........................................................................................1

1.3. Concrete workability .........................................................................................................................2

1.4. Objectives and Scope .........................................................................................................................3

1.5. Limitations ........................................................................................................................................4

1.6. Methodology .....................................................................................................................................5

1.7. Layout of the Thesis ..........................................................................................................................6

Chapter 2 – Review of the literature ..........................................................................................................7

2.1. Introduction .......................................................................................................................................7

2.2. Constituent Materials .........................................................................................................................8

2.2.1. Aggregates .................................................................................................................................8

2.2.2. Fine and Coarse Aggregates .......................................................................................................8

2.2.3. Cements and additions ...............................................................................................................9

2.2.4. Pozzolanic materials................................................................................................................. 10

2.2.5. Superplasticisers ...................................................................................................................... 13

2.2.6. Viscosity modifying admixtures ............................................................................................... 13

2.2.7. Steel fibres ............................................................................................................................... 14

2.3. Mechanism for achieving self-compactability .................................................................................. 15

2.3.1. Filling Ability .......................................................................................................................... 16

2.3.2. Passing Ability ......................................................................................................................... 16

2.3.3. Resistance to Segregation ......................................................................................................... 17

2.4. Rheology ......................................................................................................................................... 17

2.4.1. Principles and measurement of rheology .................................................................................. 17

2.4.2. Thixotropy ............................................................................................................................... 23

2.5. Constituent materials and effects on SCC workability and rheology................................................. 25

2.5.1. Influence of coarse and fine aggregates .................................................................................... 25

2.5.2. Cementitious materials ............................................................................................................. 27

2.5.3. Influence of PFA on rheology and workability ......................................................................... 28

2.5.4. Influence of GGBS on rheology and workability ...................................................................... 30

2.5.5. Blended cementitious materials ................................................................................................ 30

2.5.6. Steel fibres ............................................................................................................................... 31

2.5.7. Effect of delaying SP on rheology ............................................................................................ 32

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2.5.8. Influence of superplasticiser on rheology ................................................................................. 33

2.6. Concrete rheometers ........................................................................................................................ 33

2.7. Mixer and mix procedure ................................................................................................................. 37

Chapter 3 – Empirical and Rheological tests ........................................................................................... 39

3.1. Rheological and workability tests .................................................................................................... 39

3.2. Passing ability tests .......................................................................................................................... 41

3.2.1. J-ring ....................................................................................................................................... 41

3.2.2. L-box test ................................................................................................................................. 43

3.2.3. U-test ....................................................................................................................................... 44

3.3. Filling ability tests ........................................................................................................................... 45

3.3.1. Slump Flow Test ...................................................................................................................... 45

3.3.2. V-funnel test ............................................................................................................................ 47

3.3.3. Orimet test ............................................................................................................................... 47

3.4. Segregation tests .............................................................................................................................. 48

3.4.1. Visual Inspection ..................................................................................................................... 48

3.4.2. Sieve Stability test .................................................................................................................... 48

3.4.3. Penetration Test ....................................................................................................................... 49

3.4.4. Review of empirical tests for SCC ............................................................................................ 50

3.4.5. Two point workability test........................................................................................................ 52

3.4.6. Summary.................................................................................................................................. 55

Chapter 4 – Parametric study on constituent materials and tests........................................................... 56

4.1. Introduction ..................................................................................................................................... 56

4.2. Coarse and fine aggregates .............................................................................................................. 56

4.2.1. Particle size distribution of aggregates...................................................................................... 57

4.3. Powders ........................................................................................................................................... 57

4.3.1. Particle size distribution of powders ......................................................................................... 58

4.4. Water............................................................................................................................................... 59

4.5. Chemical admixtures ....................................................................................................................... 59

4.6. Fibres .............................................................................................................................................. 59

4.7. Rheological study of trial mixes ....................................................................................................... 60

4.8. Proposed mix design, mixes and testing procedure........................................................................... 68

4.8.1. Mixing sequence and mixer ...................................................................................................... 69

4.8.2. Testing methods ....................................................................................................................... 70

4.8.3. Trial SCC mixes ....................................................................................................................... 72

4.8.4. Summary.................................................................................................................................. 74

chapter 5 - Rheological study on SFRSCC with PFA and GGBS. .......................................................... 75

5.1. Introduction ..................................................................................................................................... 75

5.2. Testing sequence ............................................................................................................................. 75

5.3. Experimental program on SFRSCC with GGBS and PFA ................................................................ 76

5.3.1. Rheological analysis of SFRSCC with PFA and GGBS ............................................................ 77

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5.3.2. Empirical tests ......................................................................................................................... 82

5.3.3. Correlation of empirical tests with rheological parameters ........................................................ 86

5.3.4. Influence of time on the parameters .......................................................................................... 88

5.3.5. Summary.................................................................................................................................. 94

6. Conclusion and Recommendations ....................................................................................................... 96

6.1. Objective Number One: Conclusion................................................................................................. 96

6.2. Objective Number Two: Conclusion ................................................................................................ 96

6.3. Objective Number Three: Conclusion .............................................................................................. 97

6.4. Objective Number Four: Conclusion: ............................................................................................... 98

7. References............................................................................................................................................ 100

Appendix A – Mix design ........................................................................................................................ 109

A.1 – Mix Design for SCC-1 to SCC-7. ........................................................................................ 110

A.2 – Mix design for SCC-8 to SCC-14. ....................................................................................... 111

A.3 – Mix design for SCC-15 to SCC-21. ..................................................................................... 112

Appendix B – Rheological data .............................................................................................................. 113

B.1 - Rheological data ................................................................................................................... 113

Appendix C – Time evolution relationships ........................................................................................... 114

C.1 – Time evolution relationship of torque versus speed for SCC-1 to SCC-7.............................. 115

C.2 – Time evolution relationship of torque versus speed for SCC-8 to SCC-14. ........................... 116

C.3 – Time evolution relationship of torque versus speed for SCC-15 to SCC-21. ......................... 117

C.4 - Hershel-Bulkley Rheological parameters for SCC-1 to SCC-21. ........................................... 118

Appendix D – Compressive strengths .................................................................................................... 120

D.1 - Cube Strengths ..................................................................................................................... 120

Appendix E – Correlation between empirical and rheological parameters .......................................... 121

E.1 - Correlations between empirical and rheological parameters for SCC-1 to SCC-7.................. 122

E.2 - Correlations between empirical and rheological parameters for SCC-8 to SCC-14. ............... 123

E.3 - Correlation between empirical and rheological parameters for SCC-15 to SCC21. ............... 124

E.4 - Correlation between empirical and rheological parameters ................................................... 125

E.5 - Time evolution of empirical tests.......................................................................................... 127

E.6 - Time evolution correlation between empirical and rheological parameters............................ 128

Appendix F – Two-point theory and calibration ................................................................................... 131

F.1 - Theory of the Two-point method .......................................................................................... 132

F.2 - Calculation of results and Calibration ................................................................................... 136

Appendix G – Technical data sheets ...................................................................................................... 139

G.1 – Steel fibres........................................................................................................................... 139

G.2 – Admixtures .......................................................................................................................... 139

CHAPTER 1 - INTRODUCTION

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CHAPTER 1 – INTRODUCTION AND MOTIVATION

1.1. Self-compacting concrete

In general, the construction of traditional concrete requires compaction to remove the

trapped air and densify the concrete. This type of concrete composite is known as

traditional vibrated concrete (TVC). On the other hand, self-compacting concrete (SCC)

possesses both superior flowability and a high segregation resistance, which consolidates

under its own weight without the need for conventional vibrating techniques (Goodier,

2003; Kuroiwa, et al, 1993).

1.2. Benefits of using self-compacting concrete

The use of SCC eliminates the need for conventional concrete vibrators, which improves

on-site health and safety by reducing serious health hazards, such as vibration white finger

and deafness. It can also be stated that the use of SCC reduces the potential for human

error in relation to compaction, as over-compacting and under-compacting the concrete

can lead to internal segregation and surface defects (such as honeycombing). Fewer

operatives are needed, but more time is required to test the concrete before placing. The

high binder content and the need for well-graded aggregates improves the concrete, which

produces a dense pore structure between the aggregate and the cement matrix and,

consequently improves concrete strength and durability.

The use of SCC leads to lower overall costs. However, it can lead to an increase and

decrease in direct costs, which are:

significant reductions in labour costs due to eliminating the need for operatives to

place and vibrate the concrete (See Fig 1.1 – 1.2);

reduced electrical energy requirements as concrete vibrators are not required,

which reduces the costs associated with SCC placement;

reduced placing times as conventional concrete vibrating techniques are not

required, which can increase productivity;

a more durable concrete due to its denser microstructure, particularly within the

concrete cover zone.


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Fig 1. 1: A team of eight operatives placing and

finishing TVC (after De Schutter et al. 2008).

Fig 1. 2: A team of two operatives placing and

finishing SCC (after De Schutter et al. 2008).

According to Goodier (2003), the Lafarge Group investigated the overall cost savings

associated with using SCC. In this study, the Lafarge Group constructed two identical

concrete building; one from TVC and the other from SCC. The building constructed using

SCC materials was completed 2.5 months before the traditionally constructed building and

with an overall project saving of 21.4%.

1.3. Concrete workability

The term workability is described as “that property of freshly mixed concrete or mortar

that determines the ease at which it can be mixed, placed, consolidated, and finished to a

homogenous condition” (Koehler and Fowler, 2003). According to Tattersall (1991),

workability test methods can be placed into categories based on different classifications

(See Table 1.1).

Table 1. 1: Classes of workability measurement (after Tattersall 1991).

Concerning concrete workability test methods, most of the test methods fall into Class II

and Class III. Most test methods for concrete workability have been divided between

single-point tests (Class II) and multi-point tests (Class III). A single-point test measures

only one point on the flow curve relating shear stress to shear strain rate, whereas multi-

point tests measure multiple points on the flow curve and, therefore, provides a more


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complete description of workability by the use of two parameters, namely, the yield stress

and plastic viscosity. For example, a single point test, such as the slump test only provides

one point on the flow curve, namely, the yield stress.

According to Tanner (2009), rheology plays a crucial role in understanding the material

behaviour of fresh concrete. Furthermore, rheology as a science allows one to determine

and evaluate the correct proportions of constituents within the mix. Therefore, the use of

this science, when applied to concrete in its fresh state, allows one to measure and

quantify the rheological properties of fresh concrete and thus provides a better

understanding of the rheological influence of various constituent materials on the fresh

state of concrete (Roussel, 2011).

Fresh concrete is considered a multiphase material, whereby complex interactions between

the paste and the aggregate control the flow of concrete and hence provide a certain level

of workability (De Schutter, et al., 2008). In general, the slump test is used to evaluate

concrete workability. However, different concrete mixtures possessing the same slump

may behave differently concerning flowability and workability (Ferraris, et al., 2001).

Consequently, evaluating concrete flow requires two parameters and not one, as in the

case of the slump test.

According to Ferraris et al. (2001), the slump flow test evaluates concrete yield stress and

shows reasonably good correlations with this parameter; however, the slump flow test

does not evaluate the plastic viscosity; that is, its continual flowability after flow has

initiated. It is important to recognise that evaluating the plastic viscosity allows one to

determine why different concrete mixtures possessing the same slump value differ in

terms of flowability and workability.

1.4. Objectives and Scope

This study presents a review of the constituent requirements for the successful placement

of SCC as well as the influence of these constituent materials on both the rheological and

workability aspects of SCC. In addition, both the importance and fundamental principles

of rheology are highlighted and discussed as well as the various empirical and rheological

test methods. In addition, the physical appearance and the particle size distributions of the

constituent materials used in this study are presented.

The research described in this dissertation had the broad objective of evaluating both the

rheological and empirical parameters of steel fibre reinforced self-compacting concrete


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(SFRSCC) with both the use of pulverised fuel ash (PFA) and ground granulated blast

furnace slag (GGBS) for the partial replacement of cement (CEM II/A-L). Therefore, it is

possible that, by considering both the rheological and empirical aspects of SFRSCC with

PFA and GGBS cement replacements, a correlation between concrete rheology and

concrete workability could be determined. To achieve this objective, rheology was used to

determine the rheological parameters g and h, which are, respectively, related to the

fundamental parameters of yield stress and plastic viscosity. In addition, the workability

aspects were evaluated by using current empirical tests, such as the slump flow, L-box and

J-ring.

Various steel fibre reinforced self-compacting (SFRSCC) mixtures were used to determine

the effect of both pulverised fuel ash (PFA) and ground granulated blast furnace slag

(GGBS) on both the rheological and empirical parameters of these mixtures. In addition,

the influence of various steel fibre contents on both the rheological and empirical

parameters of SCC were investigated. The workability retention of the different

supplementary cementitious materials (PFA and GGBS) used in this study was also

investigated.

Evaluating the rheological properties of SCC is no easy task; these properties change as

concrete progresses through its various transitional stages of development. The reason for

this is due to progressive chemical changes/reactions occurring within the mix (De

Schutter, et al., 2008). Furthermore, according to De Schutter et al. (2008) the rheological

characteristics behave in a nonlinear manner. Therefore, the influence of time, after the

addition of mixing water, on both the rheological and empirical values was investigated in

this study.

1.5. Limitations

In this study, the main focus was on evaluating the rheological parameters g and h, which

are related and, consequently, used to obtain the fundamental parameters of yield stress

and plastic viscosity. Therefore, this study concentrated on the rheology and workability

of SFRSCC with PFA and GGBS cement replacements. Only one type of steel fibre was

used: Dramix R-65/35 hooked steel fibres. One sand was used in all the mixtures and the

fillers used in this study (i.e. limestone, pulverised fuel ash and ground granulated blast

furnace slag) were each restricted to a single source and, therefore, each one possessed the

same physical and chemical properties.


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1.6. Methodology

A comprehensive review of the literature was undertaken to better understand the

development and production of SCC as well as the rheology and workability of concrete.

In this undertaking, information was compiled on SCC mix design and SCC testing as

well as various rheological models.

Initially, the laboratory technicians constructed the equipment for the empirical tests, i.e.,

slump flow, L-box and J-ring. Shortly after, the required constituents for all the mixtures

were quantified and ordered. To determine the influence of PFA and GGBS on the

rheological and workability parameters of SFRSCC, the constituent materials were each

acquired from a single source and hence each possessed the same physical and chemical

properties.

The Tattersall two-point apparatus was used to evaluate the rheological parameters g and h

for each mixture. Furthermore, these obtained parameters were not converted into their

fundamental units of shear stress and plastic viscosity by using both Newtonian and non-

Newtonian fluids of known flow properties. However, Appendix F gives the theory of the

Tattersall two-point method along with the calibration theory.

Since the author had not previously used the two-point apparatus, it was necessary to

perform tests on trial mixtures. This was done to assess the variability associated with

recording the resulting pressures and, therefore, the obtained torques as well as finding out

if the two-point apparatus was actually working. Also, various functional torque-speed

relationship were investigated and, therefore, their associated correlation coefficients were

investigated.

The workability of the mixtures was measured using the slump flow, L-box and J-ring

tests. The filling ability and segregation resistance were assessed with the slump flow test,

while the passing ability and segregation resistance were assessed with the L-box and J-

ring tests.

To verify the obtained rheological and empirical parameters, cubes were cast for each

mixture and tested at seven-day for their compressive strengths.


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1.7. Layout of the Thesis

Chapter One presents the introduction and motivations, elaborating on the benefits of SCC

and the importance of concrete rheology and concrete workability.

Chapter Two presents the development of SCC, constituent materials and their influence

on concrete rheology and concrete workability, mechanisms for achieving self-

compactability, rheology, concrete rheometers and mix procedure.

All the empirical and rheological tests are described in Chapter Three. This chapter

involves describing the procedures for these tests, their limitations and the expression of

the obtained results. In addition, minimum and maximum criteria for the various empirical

tests are presented.

Chapter Four involves a parametric study on both the constituent material and tests used in

this study as well as a rheological study on trial mixes, the proposed mix design, mixes

and testing procedures.

The experimental program on SFRSCC with PFA and GGBS cement replacements is

presented in Chapter Five. This includes all the test results for all the mixtures that

underwent rheological and workability testing at different times after the addition of

mixing water.

Finally, the last chapter (Chapter Six) summarises the findings and conclusions of this

study. In addition, recommendations are given.

CHAPTER 2 – REVIEW OF THE LITERATURE

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2.1. Introduction

During the late 1980s, and due to the gradual decline of skilled operatives in Japan’s

construction industry, Professor Okamura of the University of Tokyo proposed and

developed various concepts for self-compacting concrete, and during 1988 the first

prototype was developed. The constituent materials used in SCC are the same as in

traditional concrete except that an increased amount of both fine materials (sand and

binders) and admixtures are needed combined with a reduction in coarse aggregates (See

Fig 2.1). These material requirements are essential in achieving self-compactability. Due

to its higher binder and chemical admixture content, the material costs associated with

SCC are usually 20 - 50% higher than traditional concrete (Nehdi, et al., 2004).

Fig 2. 1: Constituent requirements for TVC and SCC (after Okamura and Ouchi 2002).

In the mid to late 1990s, the development and use of SCC spread from Japan to Europe.

Some of the first research work to be published from Europe was at an International

RILEM (International Union of Laboratories and Experts in Construction Materials and

Structures) Conference held in Glasgow in 1996 (Bartos, et al., 1996; Goodier, 2003).

Domone and Chai (1996) produced some of the very first European scientific papers on

the design and testing of SCC, which involved an experimental programme in producing

and evaluating SCC with indigenous UK materials.

In 2000, the first European guidelines on SCC appeared in France and in the Nordic

countries. In 2001, the European Commission approved a SCC testing programme, known

as the Testing-SCC project, which was led by the ACM Centre, the University of Paisley,

W=Water

C = Cement

S = Sand

G = Gravel


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Scotland. The project set out to evaluate existing testing methods in order to recommend

appropriate tests for international standardisation.

2.2. Constituent Materials

Concrete is considered a three-phase material, namely, cement, water and aggregates, with

the addition of admixtures. This section will briefly describe the constituents used to

produce SCC.

2.2.1. Aggregates

The choice of aggregates has a significant impact on the fresh and hardened properties of

concrete. In traditional concrete, the inherent characteristics of aggregates (such as shape,

surface morphology, size, grading and type) are known to significantly influence the

hardened properties of concrete (such as strength, robustness, durability, toughness,

shrinkage, creep, density and permeability) and the fresh properties of concrete (such as

workability, segregation, bleeding, finishability and pumpability (Dhir and Jackson, 1996;

Nanthagopalan and Santhanam, 2011). According to De Schutter et al. (2008), the use of

lightweight aggregates is feasible with special attention towards mix design.

According to the European specifications and guidelines for SCC, all constituent materials

shall conform and comply with the requirements set out in IS EN 206 (EFNARC, 2002).

2.2.2. Fine and Coarse Aggregates

In SCC, a sufficiently low coarse aggregate content is required to avoid aggregate bridging

and hence blocking of concrete in and around confined spaces (reinforcement) (De

Schutter, et al., 2008). However, reducing the coarse aggregate content can also cause a

decrease in particle packing, which if overdone can affect the overall performance of the

concrete (Fung and Kwan, 2014). Consequently, one should expect the coarse aggregate

content to affect both the fresh and hardened properties of concrete. Coarse aggregate

content normally ranges from 28 to 35 per cent per cubic meter of SCC (EFNARC, 2002).

Domone (2006) analysed 68 case studies on the use of SCC in many countries, published

during the period 1993 – 2003. The author stated that crushed rocks were used in over 75

per cent of these in relation to natural gravel deposits. In addition, maximum aggregate

sizes ranged from 16 – 20 mm, however in some cases larger aggregates of up to 40 mm

were used; it is possible that overall grading plays a more important role than aggregate

size (Domone, 2006). Furthermore, EFNARC (2002) states that consistency of grading is


9

critical for successfully placing SCC. Concerning aggregate conformity, EFNARC (2002)

recommends a limited aggregate size of 20 mm. According to EFNARC (2002), either

crushed or rounded sands are suitable for SCC. The quantity of fine aggregates provides

both lubrication between the coarse aggregates and overall concrete stability, while a

lower coarse aggregate content reduces interparticle friction. It is important to recognise

that fine aggregates below 0.125 mm should be considered as being part of the powder

fraction in SCC mix design (De Schutter, et al., 2008).

Fig 2. 2: Overall aggregate gradings for SCC mixes from testing SCC project partners (after Aarre and

Domone 2003).

In producing SCC, a well distributed overall grading is desirable. However, SCC has been

produced with aggregates of significantly different gradings. Fig 2.2 adapted from

Domone (2003) shows 11 aggregate gradings considered suitable for SCC, originally

compiled by a consortium of twelve partners, known as SCC project partners.

Furthermore, the need for a higher fine aggregate content in SCC is clear (Fig 2.2). In

addition, all aggregates in SCC shall conform to IS EN 12620 (EFNARC, 2002).

2.2.3. Cements and additions

In concrete, powders are the smallest solid particles with sizes less than 250 or 125 µm

(Liu, 2009). The powder part of SCC consists of ordinary Portland Cement (OPC) and

fillers, which can be nearly inert or latent hydraulic (De Schutter, et al., 2008). SCC

requires a high powder content and a low water/cement ratio, which increases the

exothermic reaction during cement hydration and, therefore, increases the risk of cracking

from thermal effects. As mentioned previously, SCC requires a high cement content,

which results in high costs and thermal cracking (De Schutter, et al., 2008). It is therefore

necessary to reduce the cement content by additions such as limestone filler, fly ash or


10

GGBS. Additions are used in order to control, reduce, improve and/or extend certain

concrete properties. Additions of all types have been previously incorporated into

concrete, of which three types exist; which are: (i) nearly inert (Type I), such as limestone

filler (ii) pozzolanic (Type II), such as fly ash or microsilica, and (iii) latent hydraulic

(Type II), such as ground granulated blast furnace slag (De Schutter, et al., 2008; IS EN

206 – 1, 2000; EFNARC, 2002).

The performance of SCC in its fresh state is influence by cement composition. This

influence depends on the content of tricalcium aluminate (C3A) and tetracalcium

aluminoferrite (C4AF). Immediately after mixing, the superplasticisers are first absorbed

by the C3A and C4AF; therefore, the effect of a superplasticiser depends on the content of

C3A and C4AF (Liu, 2009). In addition, the C3A content influences the setting rate of

concrete; put simply, a large amount of C3A will cause an increase in concrete setting,

known as flash set. All cements that conform to IS EN 197-1 can be incorporated in SCC

(EFNARC, 2002).

2.2.4. Pozzolanic materials

A pozzolana is defined “as a natural or artificial material containing silica in a reactive

form which by themselves possesses little or no cementitious value” (Newman and Choo,

2003). However, in finely divided form and in the presence of water/moisture, SiO2

(silica) and Al2O3 (alumina) react with calcium hydroxide (Ca(OH)2) (lime) to form

compounds possessing cementitious properties, mainly calcium silica hydrates (C-S-H)

and calcium silica alumina hydrates (C-S-A-H) (Newman and Choo, 2003). These

cementitious compounds fill the voids in the concrete thus producing a dense impermeable

concrete, while also reducing the thickness of the transitional zone between coarse

aggregate and paste thus improving bond strength, long-term strength development and

durability. In addition, the use of pozzolanic materials for the partial replacement of

cement dilutes the overall C3A content, which reduces the rate of hydration, heat of

hydration and early strength development. It is important to acknowledge that reducing the

C3A content and hence the high heat rate of hydration will reduce the likelihood of

thermal cracking. In addition, the occurrence of shrinkage and creep is a notable factor as

SCC contains a much higher fraction of powder than traditional concrete mixes

(EFNARC, 2002).


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The definition and effects of some frequently used additions in SCC are listed as follows:

Blast furnace slag is produced by rapid cooling of slag particles as obtained during

the smelting of iron ore (IS EN 197-1:2001). Once cooled, the slag particles are

ground into a fine cementitious powder, known as ground granulated blast furnace

slag (GGBS). As mentioned previously, GGBS possesses latent hydraulicity, i.e.,

the hydraulicity of the slag is locked within its glassy structure (Newman and

Choo, 2003). Details on the acceptable proportions of GGBS and cement clinker

are shown in Table 2.1 as given in IS EN 197-1:2011.

Table 2. 1: Composition for slag cements.

Constituents (%)

CEM II

CEM III

Portland-slag cement

Blast furnace cement

Type A Type B Type A Type B Type C

PC Clinker

80-94 65-79

35-64 20-34 5-19

GGBS

6-20 21-35

36-65 66-80 81-95

Minor constituents 0-5 0-5

0-5 0-5 0-5

It should be noted, that replacements of cement clinker are possible up to 95 per

cent. Typically speaking, however, replacement levels between 50-70 per cent are

suited for structural concrete purposes (Newman and Choo, 2003).

Kim et al. (2007) studied the effects of GGBS on concrete strength (tensile) and

fibre bonding; the authors reported that GGBS for the partial replacement of

cement increased the strength and improved fibre bonding.

Fly ash is produced when pulverised coal burns in a power station. It is a fine

powder of mostly spherical glassy particles of silica (SiO2), alumina (Al2O3), iron

oxide (Fe2O3) and other minor compounds, ranging from 1 to 150 µm in diameter,

of which the most of it passes the 45 µm sieve (IS EN 197-1:2011; Newman and

Choo, 2003; Tattersall, 2003).

It is well known that the use of fly ash for the partial replacement of cement

increases the workability and contributes towards long-term strength development.

According to Khatib (2008), the use of fly ash in SCC reduces the amount of

superplasticiser needed to achieve a similar flow spread value compared to SCC

containing only Portland cement and/or Portland cement + Limestone filler.


12

Siddique (2011) stated using fly ash reduces the need for stability admixtures such

as viscosity modifying agents. The authors (Khatib, 2008; Xie, et al., 2002;

Gesoğlu, et al., 2009) reported a reduction in drying shrinkage with increasing

amounts of fly ash, while Khatib (2008) stated that fly ash replacement levels of 80

per cent can reduce drying shrinkage by two thirds compared with binders

comprised of only Portland cement. Details on the acceptable proportions of PFA

and cement clinker are shown in Table 2.2 as given in IS EN 197-1:2011.

Table 2. 2: Composition of fly ash cements.

Constituents (%)

CEM II

CEM IV

Portland-fly ash cement

Pozzolanic cement

Type A Type B Type A Type B

PC Clinker

80-94 65-79

65-89 45-64

Fly ash

6-20 21-35

11-35 36-55

Minor constituents 0-5 0-5

0-5 0-5

Limestone powder is frequently used in SCC. IS EN 197-1:2011 states that

limestone can replace up to 35 per cent of the cement by mass. According to Pera

et al. (1999) and Ye et al. (2007), additions of limestone powder exceeding 30 per

cent replacement of cement increases the rate of hydration and contributes towards

strength development. This is because the calcium carbonate (CaCO3) increases

the acceleration rate of C3S (tricalcium silicate) and hence increases the rate of

cement hydration, which contributes towards early strength development. Zhu and

Gibbs (2005) stated that incorporating fine limestone powder in SCC could lead to

a reduction in superplasticiser dosage compared to SCC containing only Portland

cement because of improved particle packing, water retention and possible

chemical reactions.

The use of limestone as a filler in SCC is more effective than fly ash in terms of

early strength development. However, beyond 28 days, the use of fly ash achieves

higher strengths when compared to binders consisting of Portland cement and

limestone filler (Felekoğlu, et al., 2006).

Limestone filler is not a chemically active material; this means that the water

content is fully available for cement hydration (De Schutter, 2011). For example, if

using limestone filler for the partial replacement of CEM II to counteract the

negative effects of just using only CEM II (such as high heat of hydration) then the


13

overall water/cement ratio is available for the CEM II addition and not the

limestone filler. Therefore, it is important to recognise that increasing the

water/cement ratio will significantly influence workability and strength.

2.2.5. Superplasticisers

Superplasticisers improve the deformation capacity of concrete by keeping the

cementitious particles apart, which reduces interparticle friction forces between the

cement particles. However, increasing the dosage beyond the norm can give rise to

decreased stability and hence increased segregation (Tattersall, 2003). Furthermore, the

type and dosage of superplasticiser affects the deformation capacity of SCC. It is

important to recognise that certain types of superplasticisers can give rise to an excessive

air content within the paste; therefore, the volume of air should be added to the volume of

paste within the mix design.

In general, they work in two ways. First, they attach themselves to the individual

cementitious particles which temporarily neutralises the forces of attraction between the

cement particles (provides a negative charge on a once positive charged cement particle)

and this gives the concrete a much more liquid consistency (De Schutter, et al., 2008). In

addition, polycarboxylate ether based superplasticisers bind themselves around the cement

particles by the presence of long neutral molecules (chains and links) which allows the

free water to completely encapsulate the cement particles and hence improves fluidity, this

is known as steric repulsion (De Schutter, et al., 2008; Łaźniewska-Piekarczyk, 2014). In

general, superplasticisers improve SCC fluidity by repelling the cement particles and

decreasing particle flocculation (Roussel, 2011).

Łaźniewska-Piekarczyk (2014) reported that lignosulfonate, sulfonated naphthalene

formaldehyde and sulfonated melamine formaldehyde superplasticisers work by

neutralising the forces of attraction between the cement particles, thus improving concrete

fluidity. Broadly speaking, superplasticisers used in SCC are comprised of a

polycarboxylate ether or a modified acrylic polymer (West, 2009).

2.2.6. Viscosity modifying admixtures

SCC requires a high resistance against segregation while maintaining and/or improving a

uniform suspension of constituent materials. Viscosity modifying agents (VMA) are

water-soluble polymers or inorganic substances that increase the viscosity and cohesion of

the mixture, therefore enhancing concrete stability (Lachemi, et al., 2004). In addition,


14

providing adequate stability will allow the constituents to remain in suspension, which is

important for high segregation resistance. It should be noted, that the combined use of a

VMA with a high range water reducer (superplasticiser) would produce a highly flowable

yet cohesive cementitious material. According to Roussel (2011) the use of a VMA can

enhance the hardened properties of concrete; that is, enhance the bond strength between

reinforcing elements and the aggregates.

One should be cautious when selecting combinations of VMAs and SPs as certain types of

SPs can counteract the performance of the VMA; one of which is a methyl cellulose-based

VMA combined with a naphthalene-based SP (De Schutter, et al., 2008).

2.2.7. Steel fibres

IS EN 14889-1 (2006) defines steel fibres as “straight or deformed pieces of cold-drawn

steel wire, straight or deformed cut sheet fibres, melt extracted fibres, shaved cold drawn

wire fibres and fibres milled from steel blocks which are suitable to be homogeneously

mixed into concrete or mortar”. There are various types of steel fibres available, which

differ in shape and size. Furthermore, their pull out behaviour can be modified by

optimising the fibre anchorage properties and/or enhancing the chemical and physical

bond between the fibre surface and the cement paste (Cunha, et al., 2009). It was reported

that fibre strength, geometry and orientation have a direct influence on the load bearing

capacity of fibre-reinforced composites without traditional tensile reinforcement

(Holschemacher, et al., 2010). El-Dieb (2009) stated the inclusion of steel fibres improves

the compressive strength of concrete. However, Kayali et al. (2003) reported the opposite;

that is, the addition of steel fibres did not significantly affect the compressive strengths. In

both cases, different constituent (coarse aggregates) materials were used along with

varying amounts of constituents and steel fibres of different geometrical proportions.

Therefore, it is important to recognise that the compressive strength of fibre reinforced

concrete depends on the amount, type and quality of constituents in the mixture. Some

typical profiles of steel fibres used in concrete are presented in Table 2.3.


15

Table 2. 3: Steel fibre profiles (after Cunha et al. 2009).

As mentioned previously, SCC requires a high cement/paste content and a low

aggregate/cement ratio, which can affect the rate of shrinkage and can cause the formation

of cracks and crack development. The use of steel fibres improves cracking resistance thus

reducing the development of cracks. Furthermore, increasing amounts of fibres can be

added in SCC due to its high fine content and low aggregate/cement ratio (Grünewald and

Walraven, 2001). However, fibres all lead to a reduction in filling ability and an increase

in blocking. In 2002, researchers at the Polytechnical University in Italy (Corinaldesi and

Moriconi, 2004) reported that fibre addition in SCC proved very effective in counteracting

the effects of drying shrinkage. In this study, 50 kg/m3 of steel fibres were incorporated in

the mix design.

2.3. Mechanism for achieving self-compactability

SCC is not a new composite material. However, not many understands its complex

behaviour both in its fresh and hardened state (De Schutter, et al., 2008). De Schutter et al.

(2008) defines self-compacting concrete as “its ability to flow under its own weight, fill

the required space or formwork completely and produce a dense and adequately

homogeneous material without the need for compaction”. Therefore, it is widely

understood that SCC has three characteristics, which are required for the successful

casting of SCC. These three characteristics are:

filling ability;

passing ability;

resistance to segregation.


16

Broadly speaking and according to EFNARC (2002), there are numerous methods to

assess and characterise SCC workability.

2.3.1. Filling Ability

The filling ability of SCC is defined as its ability to flow into and fill all spaces within the

formwork, under its own weight, while passing through openings of heavily congested

reinforcement (Sonebi and Bartos, 2002). Broadly speaking, the main factor affecting

concrete workability is the water to cement ratio (w/c). Increasing the w/c will improve

concrete workability, which will reduce the yield stress. However, increasing the w/c will

reduce the plastic viscosity, which can give rise to segregation.

2.3.2. Passing Ability

During the placement of SCC, the concrete must pass freely through reinforcement

without blocking. As SCC passes through constricted spaces or narrow openings or

reinforcement, it causes an increase in internal stresses between the aggregates (RILEM

TC 7 SCC, 1999). When SCC flows through restricted openings, the energy required for

adequate flowability is consumed by increasing internal particle stresses, consequently

leading to an increased coarse aggregate content around the reinforced areas and,

therefore, blocking (See Fig 2.3).

Fig 2. 3: Blocking due to increased coarse aggregate content (after Von Selbstverdichtendem and Frais

2003).

Okamura and Ouchi (2003) states that a high deformation capacity can only be achieved

by the use of a superplasticiser, while ensuring a low water-cement ratio. West (2003)

stated it is difficult to achieve superior flowability by just altering the grading of

aggregates. Furthermore, the author suggests the need for a supplementary cementitious

material.


17

2.3.3. Resistance to Segregation

In SCC, good segregation resistance involves the uniform distribution of constituent

materials. Consequently, this means in all directions, both horizontal and vertical. De

Schutter et al. (2008) considered segregation of fresh concrete as a “phenomenon related

to the plastic viscosity and density of the cement paste”. In addition, the author stated that

when the density of the solid particles are greater than the cement paste, the solid particles

tend to sink or segregate. Furthermore, segregation can occur during the placement stage

(dynamic segregation) and after the placement stage (static segregation). Static

segregation occurs when the water separates from the mix and rises to the upper region of

formwork, also known as bleeding. Another form of dynamic segregation is pressure

segregation, which can occur during the pumping of concrete (De Schutter, et al., 2008).

When transporting and placing SCC, the fresh mix must maintain its original distribution

of constituent materials (aggregates). This is known as resistance to segregation.

Furthermore, De Schutter et al. (2008) suggest that segregation can occur in SCC, which

possesses adequate filling and passing abilities. It is important to recognise that inadequate

segregation resistance can cause poor deformability and blocking in and around

reinforcement areas, which will reduce the compressive strength of SCC (Bui, et al.,

2002).

2.4. Rheology

Tattersall and Banfill (1983) define rheology as the “science of deformation and flow of

matter”. Rheology is of Greek origin, referring to panta rei, everything flows. Rheology is

used to describe the behaviour of materials, which do not conform to the deformation of

simple elastic Newtonian gases, liquids and solids. In essence, rheology is concerned with

relationships between stress, strain, rate of strain and time. According to De Schutter et al.

(2008), rheology allows one to assess the properties of concrete in its fresh and transitional

states of development. Concrete possesses a certain resistance to flow, therefore the

application of a certain force is required for concrete to flow, and that force is known as a

shear stress.

2.4.1. Principles and measurement of rheology

In order to understand the rheology of cementitious materials, an understanding of the

simplest case is required; the simplest case is described by Hooke’s law. This law states

that the deformation of an ideal elastic material depends only on the applied force, which

means that the strain is proportional to the stress. For example, if a rectangular prism is


18

deformed by equal and opposite forces applied tangentially to opposite faces, then the area

A is deformed under shear stress, τ = F/A and the angle γ represents the deformation or

shear strain (See Fig 2.4). Therefore, shear stress is proportional to shear strain and,

therefore, expressed by the following equation:

τ = nγ (2. 1)

where n is the constant of proportionality, also known as the rigidity modulus or shear

modulus.

Fig 2. 4: Hooke’s law for a material in shear (F/A

= nγ).

Fig 2. 5: Hookean solid in shear.

Fig 2.5 illustrates a straight-line relationship if τ is plotted as a function of γ whose slope

is equal to n. If a particular shear stress could be applied to a rectangular prism made of

simple fluid, the deformation of the fluid will not result in a definite deformation or shear

strain, but the fluid would deform and continue deforming once the initial shear stress is

applied. This constant deformation depends on the shear stress, τ and is measured by the

time differential of shear strain. Therefore, the time differential of γ is proportional to τ

and is represented by the following equation:

τ = ndϒ

dt . (2. 2)

This equation is similar to Hooke’s law except that the shear strain rate replaces the shear

strain and in this case n represents the constant of proportionality and is known as the

coefficient of viscosity. According to Tattersall and Banfill (1983), a fluid can be

considered as moving in laminar motion relative to two parallel solid planes, which move

relative to each other along one of their directions (See Fig 2.6). Therefore, this represents

Newton’s law of viscous flow, which states that shear stress is proportional to the velocity

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8

Shea

r st

ress

, τ

Shear strain, γ

Slope = n


19

v and inversely proportional to the distance L between the planes, and is expressed by the

following:

τ = ndv

dL (2. 3)

dv/dL is known as the velocity gradient, which can be shown to be the same as dγ/dt and,

therefore Newton’s law of viscous flow can be expressed as:

τ = nγ (2. 4)

where γ is the rate of shear and n is the constant of proportionality.

Fig 2. 6: Newton’s law of viscous flow.

For a Newtonian fluid at a constant temperature, which behaves according to laminar

flow, only one constant n is required to describe the flowing properties. In addition, the

relationship between rate of shear and shear stress passes through the origin (See Fig 2.7)

and the slope is equal to the coefficient of viscosity n.

Fig 2. 7: Newtonian fluid.

In the case of a Newtonian fluid, the relationship between the rate of shear and shear stress

is constant, which does not depend on the shear rate and the length of time for which the

Shea

r st

ress

, τ

Rate of shear, γ

Slope = n

τ = nγ


20

shear stress is applied. This is the simplest form to describe the behaviour of a fluid.

Actually the behaviour of most materials (such as concrete) do not conform to this model,

but depend on shearing resistance and, therefore, at least two different shear deformation

rates are required to describe its flow properties. Figure 2.8 illustrates this requirement,

while it can be seen that the straight-line relationship of shear stress to shear strain rate

does not pass through the origin and, therefore the relationship between shear and stress is

not constant, i.e., it intercepts the stress axis. Many authors (Tattersall and Banfill, 1983;

De Schutter, et al., 2008; Gram, 2009; Sheinn, et al., 2002) state that the strain-stress

relationship is described by the two parameters of the Bingham model, the yield stress and

plastic viscosity in the form of

τ = τo + µγ (2. 5)

where the term µ is the plastic viscosity, γ is the rate of shear and τo is the distance from

the intercept to the origin, known as the yield value. It is clear that a material that follows

this equation needs two constants to characterise its rheological properties.

Fig 2. 8: Bingham model.

For non-Newtonian materials (such as concrete), their behaviour is slightly more

complicated than Newtonian materials. Their behaviour is more complex and may behave

in a non-linear manner (See Fig 2.9). If the flow curve is concave towards the shear rate

axis, it is described as shear thinning because the stress is increasing less rapidly than the

shear rate and at higher strain rates the material flows much easier compared to a shear

thickening material, i.e., the structure of a shear thinning material is broken down by an

Shea

r st

ress

, τ

Rate of shear, γ

Slope = µ

τ = τo + µγA

B

τo


21

increasing shear strain rate. The following equation represents this and is known as a

power law fluid in the form of

τ = kγn. (2. 6)

Fig 2. 9: Linear and nonlinear flow curves.

On the other hand, if the flow curve is concave towards the stress axis, it is described as a

shear thickening material, where the shear stress is increasing more rapidly than the rate of

shear strain, which causes the material to become less workable at higher rates of shear

strain.

Feys et al. (2008) investigated the rheological properties of SCC and compared their

finding with the Bingham model. The authors reported that the rheological behaviour is

non-linear (due to negative values of yield stress) and shows shear thickening behaviour,

which can be described by the Herschel-Bulkley model. De Schutter et al. (2008) supports

this nonlinear behaviour. However, the authors do not suggest whether it shows shear

thickening or shear thinning behaviour. The Hershel-Bulkley model can be represented by

the following equation (Feys, et al., 2008):

τ = τo + kγn (2. 7)

where the term τ is the shear stress, k is a constant related to the consistence of the fluid

(consistency factor), γ is the imposed shear rate, n is the flow index which represents shear

thickening (n>1) or shear thinning (n<1) and τo is the yield stress. When n is equal to 1,

the model takes the form of a Bingham model. In addition, the term k is related to plastic

γ


22

viscosity, where a high k means a greater viscosity. This model is similar to the power law

model but with the addition of a yield value.

The relationship between torque and the angular velocity in a rheometer is similar to the

Hershel-Bulkley model, which can be calculated by integrating the function relating the

velocity and torsional motion imposed by the geometry of the apparatus. This relationship

is in the following form:

T = To + ANb (2. 8)

where the term T is the torque, A and b are parameters that depend on both the geometry

of the apparatus and the concrete, N is the angular velocity and To is the amount of torque

needed to shear the concrete.

Zerbino et al. (2009) assessed the rheological properties of SCC; they stated that in most

cases the yield stress of SCC would be close to zero, while the plastic viscosity can vary.

It is important to recognise that non-Newtonian fluids, which exhibit a zero yield stress,

are generally called pseudoplastic materials. As previously stated, the yield stress and

plastic viscosity are important rheological parameters, which describe the behaviour of

fresh concrete. However, these parameters can vary depending on various factors, such as

the exposure conditions, the mixing and testing procedures, the constituents in the mix, the

equipment used in establishing the parameters and the idle time following the mixing

procedure.

As previously mentioned, the flow curve which describes shear thinning is concave

towards the shear rate axis; that is, the slope of the nonlinear relationship of strain to shear

increases as the shear rate increases, which means that the reciprocal of the slope

decreases, which means that the viscosity decreases (See Fig 2.10). The reason for this

decrease in viscosity is that the shearing forces are breaking down the structure that

existed in the material when it was at rest (up-curve). The longer the material is sheared

and until a maximum shear rate (γ1) is reached, then decreasing the rate of shear strain will

allow the structure to rebuild. In Fig 2.10, the down-curve illustrates this reduction in

shearing due to structural breakdown. Rheometers are normally used to measure this down

curve.


23

Fig 2. 10: Hysteresis loop for material suffering structural breakdown under shear.

2.4.2. Thixotropy

The area between the up-curve and the down-curve is known as the hysteresis loop or the

degree of thixotropy and, therefore, the greater the area the more thixotropic the material

is (See Fig 2.10). A material that exhibits a hysteresis loop is known as a thixotropic

material; that is, a material becomes thinner, which occurs in pseudoplastic systems under

increased shearing or when a material becomes thicker, which occurs in dilatant systems

under increased shearing. Thixotropy is reversible and time-dependent, which means that

when concrete is at rest, the viscosity increases, and when concrete is sheared, the

viscosity decreases. These changes in viscosities are time-dependent as it takes time to

build up or break down this thixotropic structure. Furthermore, thixotropy only occurs in

non-Newtonian fluids and not Newtonian fluids, as Newtonian fluids will revert to their

original shape, that is, they have identical upward and downward curves. This is because

their viscosity is constant. It is important to recognise that thixotropy is not the same as

shear thinning or shear thickening as these are not time dependent, but is mainly due to the

flocculation of cement particles when at rest, which results in an increase in viscosity,

while then breaking apart the flocs under shearing reduces the viscosity. Furthermore,

SCC is considered highly thixotropic in relation to traditional concrete (Loukili, 2013).

Shea

r ra

te, γ

Shear stress, τ

Down-curve

Up-curve

Hysteresis loop area

γ1

τo(s) = Static yield stress

τo = Dynamic yield stress

Shear thickening

Shear thinning

1

µ


24

Fig 2. 11: Apparent viscosity napp as a function of shear rate.

Another important term is used to define thixotropy is the apparent viscosity napp, which

passes through the origin and is the shear stress divided by the shear rate (See Fig 2.11). In

addition, napp is the viscosity of a Newtonian fluid that would behave in a similar manner

as a non-Newtonian fluid at similar shear rates or similar speeds under identical testing

conditions.

Fig 2.11 illustrates shear thickening behaviour, which is represented by the Hershel-

Bulkley curve, it be clearly seen that the apparent decreases with an increase in shear

strain rate until a certain shear is reached γ2, once this shear is exceeded, the apparent

viscosity increases. This increase in apparent viscosity (after a certain rate of shear)

suggests shear thickening behaviour because as the apparent viscosity increases, a larger

amount of energy is required to further increase the flow rate. The opposite holds true for

a Bingham material, in that, the apparent viscosity decreases with increasing shear rates

and for a shear thinning material the apparent viscosity decreases at larger increments

relative to a Bingham material at incremental shear rates.

In SCC, thixotropy is important as it creates a higher viscosity when concrete is at rest

than when it is flowing and that higher viscosity is critical for formwork pressure

reduction and segregation resistance. On the other hand, placing SCC, which has a high

degree of thixotropy or a high rate of flocculation, will result in “distinct layer casting”

which produces a weak interface between the concrete layers (See Figure 2.12).

Shea

r ra

te,

γ

Shear stress, τ

Bingham Modelτ = τo + µγ

napp1

µ1

τo = dynamic yield stress

γ2

γ1

Hershel Bulkley Modelτ = τo + kγb


25

Fig 2. 12 Distinct layer casting caused by a high degree of SCC thixotropy.

2.5. Constituent materials and effects on SCC workability and rheology

In general, SCC can be produced with a wide variety of constituent materials. However,

these constituent materials influence the workability and rheology of fresh concrete.

Therefore, this section is aimed at evaluating the effect of constituent materials on both the

workability and rheological parameters of SCC.

2.5.1. Influence of coarse and fine aggregates

Incorporating coarse or fine aggregates into a concrete, mortar or cement mix, “then

irrespective of their shape or surface texture, the workability of the mix will be reduced

because of the increase viscous drag provided by the particles” (Bartos, 1993). Hu and

Wang (2011) stated that concrete rheology is influenced by various aggregate

characteristics such as gradation, size, shape, surface texture, volume fraction and

variability. Furthermore, as the aggregate volume fraction increases so will the

pseudoplastic parameters; that is, the yield stress and plastic viscosity. Fig 2.13 adapted

from Wallevik and Wallevik (2001) shows the influence of different aggregate shapes and

sand contents on the rheological parameters. Rheologically speaking, the use of rounded,

uncrushed aggregates would be preferable to crushed or flaky aggregates, while

incorporating different quantities of fine aggregates within the mix will influence its

rheological nature.


26

Fig 2. 13: Effect of aggregate shape and sand content (after Wallevik and Wallevik 2011).

The water requirements within SCC decrease as the aggregate particle size increases.

Therefore, fine aggregates require an increased water content for desired consistencies. It

is important to recognise that a high degree of particle packing will require less paste for a

given consistency, where a high degree of particle packing is achieved by sufficient

aggregate grading (Hu and Wang, 2011).

In SCC, achieving near optimum particle packing relative to low particle packing has

proven to increase the rheological performance of the mix, which provides an increased

filling capacity and better stability, when flowing (dynamic segregation). Ghoddousi et al.

(2014) reported that with a higher packing density, more free water is available to act as a

lubricant between the solid particles and, therefore, provides better fluidity; this statement

suggests that there is a connection between the rheological parameters and particle

packing. Figure 2.14 – 2.15 adapted from Fung et al. (2014) illustrates the importance of

particle packing. Providing a sufficient amount of fine materials reduces interlocking

between the coarse particles, which consequently improves the fundamental characteristics

(yield and viscosity) of SCC.

Fig 2. 14: Maximum packing density (after Fung

et al. 2014).

Fig 2. 15: Maximum mass flow rate (after Fung et

al. 2014).


27

Many authors (Zhao, et al., 2012; Mahaut, et al., 2008; Okamura and Ouchi, 2003;

Grunewald and Walraven, 2001) discuss the influence of coarse aggregate content and

grading on the properties of self-compacting concrete. Zhao et al. (2012) assessed four

SCC mixes comprised of different coarse aggregate ratios. In this study, the water-cement

ratio and fine aggregate content remained constant. They stated that the coarse aggregate

content, which ranged from 5 – 20 mm, had an influence on the workability of SCC.

Consequently, high volumes of 10 – 20 mm coarse aggregate content relative to high

volumes of 5 – 10 mm coarse aggregate caused a decrease in the passing ratio (See Table

2.4).

Table 2. 4: Properties of SCC with various A/B ratios (after Zhao et al. 2012).

A/B

ratio

Coarse aggregate (kg/m3)

Initial slump

flow (mm)

L Box test

5-10mm

(A)

10-20mm

(B)

Ratio

(%)

Time

(s)

4/6 434.4

651.6 826 0.96 18.2

5/5 544

544 802 0.95 18.3

6/4 651.6

434.4 786 0.92 18.5

7/3 760.2 325.8 775 0.9 18.7

2.5.2. Cementitious materials

SCC has a much higher paste volume relative to traditional concrete; this increase in paste

volume decreases the yield stress, while increasing the viscosity. Simply put, increasing

the paste will increase the flowability of the mix, while increasing its cohesion, a

characterisation known as ‘rich’ or ‘fatty’ (Newman and Choo, 2003). It is important to

recognise that binders incorporated in SCC comprised of just Portland cements will result

in inadequate cohesion, poor segregation resistance and an increase in hydration

temperatures, therefore supplementary cementitious materials (SCM) (fillers) and/or

admixtures are needed to counteract these effects (Domone and Chai, 1996; Yahia, et al.,

2005). In other words, self–compacting concrete can be produced by simply increasing the

amount of fine materials, either pozzolanic or non-pozzolanic, without altering the water

content relative to traditional concrete. Another alternative is to incorporate a VMA into

the mix, which will provide sufficient stability (Lachemi, et al., 2004; Bosiljkov, 2003).

Domone and Chai (1996) stated that SCC binder contents are relatively high and typically

range between 450 – 550 kg per cubic meter.

Newman and Choo (2003) illustrated the rheological effects of replacing cement with

SCM, which causes a reduction in yield stress for both pulverised fuel ash (PFA) and


28

ground granulated blast furnace slag (GGBS) with an increase in viscosity for GGBS and

a decrease in viscosity for PFA. Fig 2.16 adapted from Newman and Choo (2003)

illustrates that an increase in paste volume will increase both the yield stress and plastic

viscosity. It is important to recognise that the appropriate usage of a superplasticisers will

decrease the yield stress, while not affecting the plastic viscosity or concrete stability.

Fig 2. 16: Illustration of the effects on the viscoplastic parameters by replacing cement with SCM (after

Newman and Choo 2003).

2.5.3. Influence of PFA on rheology and workability

It is well known that the inclusion of fly ash (FA) in concrete increases the workability

and enhances long-term strength development. Felekoğlu et al. (2006) reported that SCC

incorporated with SCMs, such as fly ash, will reduce the water content and enhance

concrete workability. Furthermore, the improvement is most likely due to the spherical

shape of the fly ash particles and possibly its surface texture; this improvement allows the

particles to pass easily around each other and, therefore, reduces the internal particle

stresses between the aggregate particles and the paste. It should be noted that the physical

properties of powders play an important role in rheology, i.e., the shape, surface texture,

fineness, particle size distribution and particle packing (Felekoğlu, et al., 2006). Indeed,

these physical properties are all equally important concerning rheology.

More recently, in 2014, researchers at the University of Petroleum and Minerals (Rahman,

et al., 2014) investigated the thixotropic behaviour of SCC with different mineral

admixtures; they concluded that the inclusion of fly ash, up to 15% cement replacement,

increased the flocculation rate considerably. In the field, flocculation rates are very


29

important, as SCC is required to flow into and fill all spaces within the formwork, under

its self-weight.

Over the last two decades, many researchers (Xie, et al., 2002; Monosi and Moriconi,

2007; Naik et al., 2012; Siddique, 2011; Bouzoubaa and Lachemi, 2001; Liu, 2010) have

studied the performance of SCC containing SCM, such as, Class C fly ash, Class F fly ash

and ultrafine pulverised fly ash (UPFA). Xie et al. (2002) studied the use of UPFA in

SCC. They stated that the appropriate viscosities could be achieved by replacing VMA

with UPFA. Siddique (2011) and Bouzoubaa and Lachemi (2001) studied the properties of

SCC with various levels of Class F fly ash. Siddique (2011) concluded that it is possible to

incorporate fly ash contents of up to 35% replacement of cement, whereas Bouzoubaa and

Lachemi (2001) stated fly ash contents ranging between 40 – 60% were achievable. In all

mixtures, both Siddique (2011) and Bouzoubaa and Lachemi (2001) used various

superplasticisers, while Bouzoubaa and Lachemi (2001) also used an air entraining

admixture (AEA). Furthermore, the differences in SCC Class F fly ash usage were most

likely due to a number of factors, mainly, the different chemical admixtures, and various

levels of constituent materials within the mixtures. Nevertheless, it is important to

recognise that fly ash, in general, will improve the rheological parameters, while reducing

the need for chemical admixtures and the level of fly ash usage depends on the types of

chemical admixtures and/or the quality, type, size, grading and quantities of constituent

materials within the mix.

According to Krishnapal et al. (2013), the inclusion of fly ash for cement replacement

levels of up to 30% improves the slump flow value, decreases the V-funnel time and

shows no significant variation in blocking ratio (L-box) when compared to SCC

comprised of only Portland Cement (PC). In this study Class F Fly ash replacements were

used, while various dosages of superplasticiser were used (Polycarboxylic ether based).

The authors reported that the addition of fly ash reduced the need for a superplasticiser in

achieving the same workability. It is important to recognise that reducing the V-funnel

time and increasing the spread capacity allows one to achieve a more workable mix.

However, its workability in terms of abilities must comply with known criteria set out by

EFNARC.

When using fly ash in SCC a reduction in superplasticiser dosage is needed along with an

increase in water/cement ratio in order to keep the slump flow and V-funnel time constant

when compared with zero replacement of fly ash (Liu, 2010).


30

2.5.4. Influence of GGBS on rheology and workability

As mentioned previously, the inclusion of GGBS within SCC mixes reduces the yield

stress and increases the viscosity. Indeed, GGBS can be used as a supplementary

cementitious cement replacement (SCCR) to improve SCC workability and provide long-

term strength development (Boukendakdji, et al., 2009). In 2009, Boukendakdji et al.

studied the effect of GGBS upon SCC rheology. A polyether-polycarboxylate based

superplasticiser and various levels of constituent materials were used in this study. In all

the mixtures, the authors concluded that the use of GGBS was found to improve the

workability, with an optimum slag content of 15%. (See Fig 2.17 – 2.18).

Fig 2. 17: Influence of slag content on filling

ability (after Boukendakdji et al. 2012).

Fig 2. 18: Influence of slag content on passing

ability (after Boukendakdji et al. 2012).

2.5.5. Blended cementitious materials

More recently, in 2009, researchers (Gesoğlu, et al., 2009) at the University of Gaziantep

studied the properties of SCC made with various blends of SCM. Table 2.5 summarises

the rheological effects of incorporating binary and ternary blends of SCM in SCC. The

authors reported that in all mixtures, relative to a reference mix (Control-PC), L-box

H2/H1 ratios increased, thus improving the passing and filling abilities of SCC. A

Polycarboxylic-ether type superplasticiser and various levels of constituent materials were

used in this study. In all mixtures, the authors reported that only the ternary use of

Portland cement (PC), fly ash (FA) and slag (GGBS) satisfied the acceptable criteria of

EFNARC.


31

Table 2. 5: Fresh properties of SCC with various level of SCM (after Gesoğlu et al. 2009).

Slump flow L-Box V-funnel

flow time (s)

Mix no Mix ID T50 D (cm) H2/H1

M1 Control-PC 1.0 67.0 0.706 3.2

M2 20FA 2.0 67.5 0.706 10.4

M3 40FA 2.0 73.0 0.800 6.0

M4 60FA 1.0 72.0 0.950 4.0

M5 20GGBS 3.0 67.0 0.704 10.0

M6 40GGBS 3.0 71.0 0.706 14.0

M7 60GGBS 3.0 70.5 0.732 12.0

M8 10FA10GGBS 3.0 70.5 0.854 9.9

M9 20FA20GGBS 2.2 69.0 0.859 6.6

M10 30FA30GGBS 3.0 73.0 0.904 6.2

Acceptable criteria of SCC suggested by EFNARC

Minimum 2.0 65.0 0.800 6.0

Maximum 5.0 80.0 1.000 12.0

2.5.6. Steel fibres

The benefits of using steel fibres in concrete are well known and established. In relation to

traditional concrete, the use of steel fibres enhances the structural performance of

concrete, mainly, improved structural rigidity and resistance to impact. (Holschemacher, et

al., 2010). Intuitively, these structural enhancements can be achieved in SCC, with

significant benefits due to its flowable nature. Cunha et al. (2009) stated that after the

occurrence of matrix cracking, the fibres bridge the crack, which providing a resistance

against increased cracking widths. In essence, the rheological characteristics of SFSCC

will ultimately dictate its performance in its fresh state.

Grünewald and Walraven (2001) investigated the influence of various fibre types and

volumetric proportions on the workability of SCC. In all the mixtures, the authors stated

that both the fibre type and fibre content affects the deformation of SCC. However, mixes

with fibre contents up to 120 kg per cubic meter produced satisfactory flow regimens, but

with some reduction in passing ability. It is important to recognise that incorporating

relatively high fibre content is dependent upon the geometrical proportions of the fibres in

question, i.e., aspect ratio and shape. Fig 2.19 adapted from Grünewald and Walraven

(2001) illustrates the maximum steel fibre content relative to fibre type.


32

Fig 2. 19: Maximum fibre content relative to fibre type for SCC (after Grünewald and Walraven 2001).

Similarly, Ponikiewski (2009) reported that increased fibre content and different aspect

ratios affected concrete workability. Furthermore, they showed that fibre type, volume

fraction, shape and length significantly influence the fresh properties of SCC.

Rheologically speaking, they recommended a fibre volume fraction of 2.0%,

approximately 45kg per cubic meter, while recommending the feasible use of high fibre

contents with short fibre lengths. Hossain et al. (2012) discussed the influence of steel

fibres on the fresh and rheological properties of SCC. They concluded that increasing fibre

content increases the plastic viscosity and yield stress, while the use of short fibres relative

to long fibres enhances flowability.

Grünewald and Walraven (2001) stated that for a required fibre content a lower aspect

ratio would achieve a more workable mix relative to the same fibre content with a higher

aspect ratio. However, its performance in its hardened state would be slightly

compromised as a higher aspect ratio performs somewhat better in its elastic state. The

authors also reported that increasing the amount of fibres decreases the slump flow and

hence decreases the deformation capacity of SCC. Furthermore, increasing the fibre

content while also increasing their aspect ratio increases V-funnel times. Therefore, both

higher fibre contents and aspect ratios will reduce workability in terms of abilities.

2.5.7. Effect of delaying SP on rheology

Aiad et al. (2002) assessed whether the addition of certain admixtures would affect the

rheological properties of cement pastes. More importantly, the authors suggested that


33

delaying certain admixtures, after the addition of water, could significantly reduce the

shear stress, while not greatly altering the relative viscosity.

2.5.8. Influence of superplasticiser on rheology

The use of a superplasticiser improves the ability of concrete to deform under its own

weight therefore improving its deformation capacity and reducing the yield value.

However, superplasticisers should be used with caution as increasing its dosage above the

norm can result in an unstable mix, which can compromise its segregation resistance.

2.6. Concrete rheometers

As previously mentioned, a single parameter such as yield stress does not adequately

describe the behaviour of fresh concrete. Therefore, concrete rheometers can be used to

evaluate the workability of SCC in terms of two parameters. Furthermore, they apply

physical measurements to rheology to measure the flow of concrete. i.e., measure the

resistance of concrete (shear stress) to flow at varying shear rates (Ferraris, et al., 2001).

According to Feraris et al. (2001), various rotational rheometers for concrete are available

and are as follows:

BML (coaxial cylinder)

BTRHEOM (parallel plate)

CEMAGREF-IMG (coaxial cylinder)

IBB (impeller/mixing action)

Two-point (impeller/mixing action)

Two point and IBB based rheometers operate in a similar manner by rotating an impeller

or vane in fresh concrete contained within a container. However, the IBB is fully

automated and uses a data input system, which automatically generates the rheological

parameters, yield stress and plastic viscosity (Feraris, et al., 20011). In addition, the IBB

rheometer requires 21 litres of concrete (Fig 2.20 – 2.21) and is suitable in testing concrete

with slumps ranging from 20 mm to 300 mm and does not require calibration and,

therefore, the results are not expressed in fundamental units.


34

Fig 2. 20: IBB Rheometer (after Feraris et al.

20011).

Fig 2. 21: H impellers for IBB rheometers for

concrete (after Feraris et al. 20011).

The opposite applies to the Two-point apparatus, in that, it is not fully automated and

requires two stage calibration: (i) torque calibration and (ii) calibrating the two constants.

Furthermore, the two-point apparatus possessing a helical vane arrangement, which is

suitable for slumps higher than 100 mm (See Fig 2.22 – 2.23). In both cases (Two-

point/IBB), the rotational speed of the vane or impeller is increased and then decreased

while the resulting pressure is measured at appropriate speed settings or intervals (Feraris,

et al., 2001; Tattersall and Banfill, 1983; Tattersall, 2003).

Fig 2. 22: Two-point workability rheometer (after

Feraris et al. 20011).

Fig 2. 23: Impeller arrangement and dimensions

(after Feraris et al. 20011).


35

CEMAGREF-IMG and BML are coaxial rheometers. The CEMAGREF-IMF rheometer

(Fig 2.24 – 2.25) is a large coaxial rheometer, which requires approximately 500 litres of

concrete. Due to its large concrete requirement, it not considered practical. The BML

rheometer (Fig 2.26 – 2.27) requires approximately 17 litres of concrete with slumps

greater than 120 mm (Roussel. N, 2011). In both cases, a cylinder is rotated at increasing

and decreasing speeds and hence the resulting torque is measured.

Fig 2. 24: CEMAGREF-IMG Rheometer (after


Fig 2. 25: Inside view of CEMAGREF-IMG

Rheometer with grid and blades (after Feraris et

al. 20011).

Fig 2. 26: BML Rheometer-version 3 (after


Fig 2. 27: BML Rheometer-version 4 (after


According to Feraris et al. (2001) evaluating and modelling the flow of concrete in the

IBB and Two-point rheometer is no easy task. In addition, the flow of concrete can be

mathematically modelled for coaxial rheometers (such as BML, CEMAGREF-IMG) and

for the parallel plate rheometer (BTRHEOM), while for the BML, CEMAGREF-IMG and

BTRHEOM rheometers it is possible to express their rheological properties in

fundamental units of plastic viscosity and yield stress by suitable calibration.


36

The BTRHEOM is a parallel plate rheometer (Fig 2.28 – 2.29) which consists of two

parallel disks, one of which is fixed at the bottom while the other is free to shear the

material and hence its rotational speed and resistance to shear are measured (Feraris, et al.,

2001; Roussel, 2011). According to Roussel (2011), the rotational speed range is between

0.1 rev/s to 1.0 rev/s while its maximum measurable torque is around 14 N/m.

Furthermore, its principal requirements are seven litres of concrete, which must possess a

slump greater than 100 mm.

Fig 2. 28: BTRHEOM Rheometer (after Feraris et

al. 20011).

Fig 2. 29: BTRHEOM Rheometer showing

arrangement of blades at top and bottom (after


During the period 2000 – 2001, a study was carried out in France (Feraris, et al., 2001),

which involved comparing five different rheometers to assess the appropriate method in

evaluating concrete workability in terms of yield stress and plastic viscosity. It is

important to recognise that no self-compacting mixtures were used in this study.

Nevertheless, their study is a good indication of whether any differences exist in the

rheological properties between different rheometers. Consequently, the authors concluded

that the degree of correlation of both yield stress and plastic viscosity between any two

rheometers possessed considerable differences. Furthermore, they stated that these

differences were most likely due to calibration, wall slippage and volumetric confinement.

Fig 2.30 – 2.31 adapted from Feraris et al. (2001) illustrates these differences in both yield

stress and plastic viscosity measurement between five different rheometers.


37

Fig 2. 30: Comparison of yield value (after


Fig 2. 31: Comparison of plastic viscosity (after


2.7. Mixer and mix procedure

In SCC, the mixer is a key element in producing a well-mixed concrete. SCC can be

produced with any concrete mixer, such as paddle mixers (free-fall mixers), truck mixers

and force-action mixers. However, force action mixers are preferred if available. The

mixing time is doubled when using a paddle mixer to mix SCC when compared with

traditional concrete (De Schutter, et al., 2008). The reason for this is due to the higher

addition of fine material, which may stick to certain parts of the mixer. According to De

Schutter et al. (2008), adding some of the water with some of the superplasticiser and all

of the coarse aggregates before adding the finer materials may reduce the adhesion of the

fine material to the mixer.

EFNARC (2005) suggests adding two thirds of the water and superplasticiser followed by

the aggregates and cementitious materials. However, previous studies have suggested that

delaying the addition of superplasticiser could significantly reduce the shear stresses

between the cementitious particles, which will improve concrete workability when

compared with stage one addition. Therefore, adding more superplasticiser towards the

second stage could be a very useful means of achieving the required deformation capacity

(650-800 mm) without having to alter the constituents and dosage of superplasticiser in

the mix.

Wallevik and Wallevik (2011) stated that when using a free-fall mixer the dosage of

superplasticiser has to double to maintain the SCC properties (yield value and plastic

viscosity) when compared with using a force action mixer. The reason for this may be due


38

to the high shearing of materials in the force action mixer. Furthermore, the VMA should

be added after the superplasticiser and just before adjusting the water content for

consistency.

Grünewald (2004) and Grünewald and Walraven (2001) suggest the following mixing

procedure for steel fibre reinforced self-compacting concrete:

Fig 2. 32: Mixing procedure for SFSCC in a force action mixer (after Grunewald and Walraven 2001).

It is important to recognise that the above mixing method is used in combination with a

force action mixer. Therefore, adopting this mixing method for a free-fall mixer may

cause the paste to adhere to the drum and it does not allow for the adjustment of water

content and superplasticiser dosage for consistency.

Testing-SCC reported that a change in mixing temperature from 14ᵒC to 22ᵒC reduced the

slump flow value by approximately 50-100 mm. In addition, they stated that the

temperature should be maintained at 20ᵒC ± 2ᵒC.

CHAPTER 3 – EMPIRICAL AND RHEOLOGICAL TESTS

39


3.1. Rheological and workability tests

During 1983, it was found that the use of superplasticisers to produce very high workable

concrete led to workability assessment problems because none of the existing British

Standard tests could be used. These tests include the Vebe test, the Compacting Factor test

and the Slump test. For example, the slump test could not be used because concretes

possessing a high degree of workability all give collapsed slumps (See Fig 3.1).

Fig 3. 1: Four types of slump (after Koehler and Fowler 2003).

The solution to this assessment problem was to introduce a new testing procedure, known

as the flow-table test (See Fig 3.2). The apparatus usually consists of an upper wooden

square board with 700 mm sides, which is connected to a baseboard by hinges. In

principle, the cone is filled in two layers while each layer is tamped ten times with a

wooden rod. Once full, and after the resting and cleaning period, the top board is lifted to

the stopping position and allowed to drop, and after 15 consecutive drops the mean of the

largest diameter and the diameter perpendicular to it are recorded. According to Tattersall

(1991), the flow-table test was reasonably good for assessing segregation by visual

inspection, which would suggest that the flow-table method could be used to assess the

consistency of concrete. However, the flow-table test was severely criticised by Dimond

and Bloomer well before its inclusion in British Standards.


40

Fig 3. 2: Slump flow table test (after Koehler and Fowler 2003).

Due to these criticisms, a modified slump test was developed for evaluating high workable

TVC, known as the slump flow test. As SCC possesses a high deformation capacity, the

slump flow test is now one of the primary methods for evaluating SCC workability.

Many tests have been developed in an attempt to characterise the fresh properties of SCC.

The European federation for SCC, EFNARC, sets out specifications and guidelines for

evaluating the fresh properties of SCC. Table 3.1 adapted from EFNARC (2002)

illustrates the various test methods for SCC.

Table 3. 1: Various SCC testing methods (after EFNARC 2002).

Method Property

1 Slump-flow by Abram’s cone Filling ability

2 T500 slump flow Filling ability

3 J-ring Passing ability

4 V-funnel Filling ability

5 V-funnel at T 5 minutes Segregation resistance

6 L-box Passing ability

7 U-box Passing ability

8 Fill-box Passing ability

9 GTM screen stability test Segregation resistance

10 Orimet Filling ability

In order for SCC to fulfil its workability requirements, that is its passing and filling

abilities, EFNARC (2002) provides minimum and maximum acceptable criteria for each


41

test method (See Table 3.2). In addition, there is no reliable test for segregation; therefore,

it is important to pay close` attention to the risk of segregation.

Table 3. 2: Minimum and maximum criteria for various testing methods (after EFNARC 2002).

Method Unit Typical range of values

Minimum Maximum

1 Slump-flow by Abram’s cone mm 650 800

2 T500 slump flow sec 2 5

3 J-ring mm 0 10

4 V-funnel sec 6 12

5 V-funnel at T 5 minutes sec 0 3

6 L-box (h2/h1) 0.8 1

7 U-box (h2-h1) mm 0 30

8 Fill-box % 90 100

9 GTM screen stability test % 0 15

10 Orimet sec 0 5

3.2. Passing ability tests

SCC is required to achieve self-compactability and possesses a relatively high resistance

against segregation, while also being able to flow in and around heavily congested

reinforcing areas. Amongst the various empirical test methods listed in Table 3.1, the J-

ring and L-box are the most common methods for assessing the passing ability of SCC.

3.2.1. J-ring

The J-ring test simulates concrete flow through reinforcement by the use of numerous

vertical blocking mechanisms. More specifically, the apparatus is composed of a ring with

12 or 16 vertical steel bars; the latter simulates a more congested reinforcement system

(See Fig 3.3).


42

Fig 3. 3: Dimensions of J-ring and measurement positions.

IS EN 12350-12:2010 sets out the basic procedure, in which the conical mould is lifted at a

steady rate in an upward direction, which allows the concrete to flow through the bars, and

across the base plate. Consequently, the J-ring measures three parameters: flow spread

(SFj), flow time (t500j) and blocking step (Bj). The flow spread and flow time simulates

SCC deformability within confined reinforcement and defines the rate of deformation (De

Schutter, 2005; Testing-SCC, 2005). Once the concrete has ceased flowing and/or reached

a spread diameter of 500 mm, the largest spread diameter, dmax, and the one perpendicular

to it, dperp, are measured and the t500j time is recorded; that is, the time taken for the

concrete to reach a 500 mm spread diameter. The flow spread, SFj, is expressed as the

average of dmax and dperp. In an attempt to quantify the blocking mechanism, the average

relative flow heights outside the J-ring minus the flow height at a central position inside

the J-ring are measured and quantified, called the blocking step value (De Schutter, 2005;

Testing-SCC, 2005; IS EN 12350-12:2010).


43

Drawbacks and limitations (De Schutter, et al., 2008):

(i) The base plate must be placed on stable level ground to record the appropriate

deformation. An oval shape spread rather than a circular spread indicates

uneven ground. It is important to measure the largest spread diameter and the

spread diameter perpendicular to it.

(ii) Appropriate results depend on the surface moisture of the base plate therefore

the base plate should be wet, but not too wet.

3.2.2. L-box test

In a similar manner to the J-ring, the L-box simulates concrete flow through reinforcement,

which evaluates the passing ability of SCC. The L-box is composed of a chimney section

and a channel section with different arrangements of vertical bars. The concrete flows from

the chimney section, through the vertical bars and into the horizontal channel section (See

Fig 3.4).

Fig 3. 4: L-box test on a stable SCC and L-box dimensions (after Nguyen et al. 2006).


44

Expression of results

The mean depths of concrete within both the chimney section H1, and channel section H2

are measured and expressed as a ratio, known as the passing ratio PL:

PL = 𝐻2

𝐻1 . (3. 1)

If the concrete flows freely through the vertical bars, then the passing ratio is equal to 1.0.

Likewise, if the ratio is equal to 0.8, then the concrete is too stiff and hence is deemed

unacceptable (De Schutter, 2005). ERNARC (2002) recommends acceptable passing ratios

ranging from 0.8 – 1.0. Nguyen et al. (2006) stated that yield stress is the most important

parameter in deciding on whether the concrete will flow and fill all the spaces within the

formwork.


(i) If a concrete has an extremely high passing and filling ability, the passing ratio

maybe greater than 1.0, which can result in the concrete pilling up and

splashing out of horizontal channel. This pilling up and spilling effect will

significantly affect the test results.

3.2.3. U-test

In a similar manner to the L-box test, the U-test is used to evaluate the passing ability of

SCC. The U-test consists of a channel that is divided by a middle wall and hence splits the

channel into two compartments. An opening at the bottom of the apparatus is fitted with a

sliding door and the sliding door consists of an arrangement of vertical bars with centre to

centre spacing of 50 mm (See Fig 3.5).

Fig 3. 5: Schematic of U-box test.


45

The passing ability of the U-box is determined by comparing the heights of the concrete in

both compartment and is expressed as a ratio.

3.3. Filling ability tests

The fundamental principle for filling ability tests is to assess the flowability or the

deformation of concrete under its own weight, while visually inspecting the concrete for

signs of static and dynamic segregation.

EFNARC (2002) recommends various testing methods: slump flow, V-funnel, and Orimet;

amongst these methods, the slump flow, and V-funnel are most commonly used.

3.3.1. Slump Flow Test

The slump flow test is the most widely used test for evaluating the flowability of SCC (Fig

3.6 – 3.7). It is a modified version of the slump test. The flow test allows the concrete to

flow out in all directions. Therefore, the test evaluates two parameters: horizontal flow

spread and flow time. The flow spread evaluates unconfined deformability and the flow

time evaluates the rate of deformation within a confined flow distance (De Schutter, 2005).

Fig 3. 6: Slump flow test (after Loukili 2013).

Fig 3. 7: Testing in progress (after Testing-SCC

2005).

IS EN 12350-8, 2010 sets out the basic procedure for evaluating the deformation capacity

of SCC. Broadly speaking, the slump cone is lifted at a steady rate, typically 1 to 3

seconds, in an upward direction. Once the concrete has achieved its maximum

deformation, the largest spread distance dmax, and the one perpendicular to it dperp are

measured. Additionally, if the difference between dmax and dperp does not exceed 50 mm, a

mean value is calculated, known as the slump flow value. The t500 time is used to evaluate


46

the deformation of SCC within a defined spread distance. Intuitively, the lower the t500

value, the greater the deformation rate of SCC, providing no dynamic segregation has

occurred. EFNARC (2002) recommends acceptable t500 values in the range of 2 to 5

seconds.

The slump flow test can be performed by inverting the slump cone (See Figure 2.38).

When the slump test is performed with the cone upright, the cone has a tendency to rise up

while the cone is being filled. When using the inverted cone only one operator is required

to carry out the test. According to Ramsburg (2003) there is no difference in both the

slump flow spread values and T500 values when using the inverted cone instead of the

upright cone.

In evaluating the workability of steel fibre reinforced concrete (SFRC), the inverted slump

cone test is the preferred choice when compared to using the conventional upright slump

cone method (See Fig 3.8). Generally speaking, the inverted slump flow time is

recommended rather than the traditional slump value when evaluating the workability of

SFRC (Kasimmohamed, 2014).

Fig 3. 8: Schematic of upright and inverted cone (after Ramsburg 2003).

The occurrence of a segregation border is an indication of dynamic segregation. If the

coarse aggregates have separated or segregated from the paste/mortar then a pile of coarse

aggregates would be concentrated in the middle of the slump spread. (West, 2003; De

Schutter, et al., 2008).


(i) The J-ring has various drawbacks and limitations, and these same drawbacks

and limitations apply to the slump flow test.


47

3.3.2. V-funnel test

In principle, the V-funnel is used to assess the viscosity and filling ability of SCC, where

the V-funnel flow time (tv) is used to measure these characteristics. The V-funnel is

composed of rectangular container, which tapers from the top down to a vertical

rectangular channel (See Fig 3.9 – 3.10).

Fig 3. 9: V-funnel test (IS EN 12350-9 2010).

Fig 3. 10: V-funnel testing in progress (after

Hossain et al. 2012).

As outlined in IS EN 12350-9 (2010), the procedure involves filling the apparatus with

concrete, while ensuring no compaction has taken place. After, approximately 10 ± 2

seconds, a bottom gate is opened thus allowing the concrete to flow. The flow time tv, that

is, the time taken for the cementitious composite to fully discharge is recorded. The

European Federation for SCC conformity (EFNARC, 2002) sets out well-defined

acceptable criteria on which typical tv values range from 6 – 12 seconds.


(i) The V-funnel gate cannot be adjusted for mixes comprised of small coarse

aggregates and mortars.

(ii) Transporting the apparatus is difficult due to its mass and size.

(iii) Operating the apparatus with a single operator can lead to inaccuracies in

recording the tv times.

3.3.3. Orimet test

The Orimet test is used for evaluating the filling ability of very high workable concrete.

The apparatus consists of an orifice rheometer, which measures the fluidity of concrete by


48

means of the Orimet flow time to, which is the time required for the concrete to pass

through the orifice (See Fig 3.11). The apparatus can be fitted with different orifices of

different diameters, which allows one to assess the filling ability of mortars and grouts.

Fig 3. 11: Orimet testing in progress (Testing-SCC 2005).

3.4. Segregation tests

In SCC, various tests are available to assess the stability of SCC and hence its resistance

against segregation, which are visual inspection, sieve stability, settlement column and

penetration.

3.4.1. Visual Inspection

Visual inspection involves inspecting the concrete for any signs of segregation, for

example, when inspecting the final spread of concrete in the slump flow test; an indication

of segregation resistance would involve a uniform spread of constituents right up to the

boundary. Indeed, this would not hold true if segregation had occurred. Furthermore, both

dynamic and static segregation can be assessed; however, it depends upon the experience

of the operator (Testing-SCC, 2005; Liu, 2009).

3.4.2. Sieve Stability test

The resistance of SCC to segregate can be evaluated by the sieve stability test. In IS EN

12350-11 (2010) the procedure involves pouring a concrete sample from a height, typically

500 ± 50 mm, onto a 5 mm sieve. In general, the test involves evaluating the degree of

separation between the paste/mortar and coarse aggregates (See Fig 3.12 – 3.13).


49

Fig 3. 12: Sieve stability test (IS EN 12350-11,

2010).

Fig 3. 13: Testing in progress (Testing-SCC,

2005).

In principle, the container is filled with concrete and allowed to rest for approximately 15 ±

0.5 min. The concrete mixture is then poured onto the sieve, whereby the retained mass of

concrete, mps, is subtracted from the initial sieve mass, mp, and divided by the initial mass

of concrete, mc, and expressed as a percentage, known as the segregation index, SI (EN

12350-11, 2010; De Schutter, 2008).

A segregation index value of less than 5 per cent indicates an over cohesive mix, while a

value ranging from 15 – 30 per cent indicates inadequate segregation resistance (Testing-

SCC, 2005). Consequently, Testing-SCC (2005) stated an acceptable value within the 5 –

15 per cent range.

Testing-SCC (2005) stated that the sieve stability test is capable of assessing both static

and dynamic segregation. However, De Schutter (2008) suggests only static segregation is

measured. In addition, good correlations were shown to exist in relation to onsite SCC

placement (Testing-SCC, 2005).

3.4.3. Penetration Test

The penetration test detects the resistance of concrete to segregate. The penetration test

detects a change in coarse aggregate content at the upper region of the concrete sample

(Fig 3.14 – 3.15), thus it evaluates the occurrence of static segregation (De Schutter, 2008).


50

Fig 3. 14: Penetration for segregation analysis

(after Bui et al. 2002).

Fig 3. 15: Penetration test in progress (Testing-

SCC 2005).

The penetration test involves placing a penetration device, which has a weight of 54 grams

on top of the concrete. After 2 min, the device is lowered and allowed to penetrate the

concrete. After 45 s, the recorded penetration value, known as the penetration depth, pd, is

used to evaluate the concrete’s resistance to segregation.

3.4.4. Review of empirical tests for SCC

During the period, 2001 – 2005, 12 countries participated in an inter-laboratory evaluation

on the performance of test methods used in measuring the properties of fresh SCC.

Testing-SCC (2005) stated that one single test is not sufficient to evaluate the key

characteristics of SCC; consequently, two or three test methods are required. In addition,

visual inspection was noted as useful for identifying the occurrence of segregation

resistance.

The European research project “Measurement of properties of fresh SCC” recommended

the following four tests for European standardisation: Slump flow, L-box, J-ring and sieve

stability. Concerning the filling ability of SCC, the combined slump-flow and T500 tests

were deemed the best, due to a number of factors, such as, good correlations with the

rheological parameters, good reproducibility, R, and repeatability, r, values and their

simplistic and universal usage (De Schutter, 2005).

Concerning the passing ability of SCC, the L-box and J-ring tests were given equal merit

(De Schutter, 2005). In addition, the author reported reasonably good R and r values. In

relation to the ability of SCC to resist segregation, the sieve stability was deemed the best,


51

mainly due to its close resemblance with onsite conditions and better statistical values, R

and r.

According to Testing-SCC (2005) some correlations were shown to exist between the

slump flow and the L-box as a highly workable concrete easily achieved a minimum L-box

ratio of 0.8. Different formwork materials and the use of surface release agents did not

exhibit significant variations in testing results. Rheologically speaking, good correlations

were shown to exist between plastic viscosity and the L-box t500j times with a correlation

coefficient (R2) of 0.78, when using the three bar arrangement (See Fig 3.16) (Testing-

SCC, 2005). In addition, the upright slump flow spread value showed a good correlation

with the rheological parameter of yield stress, with a correlation coefficient of 0.79.

However, the t500 tests showed a poor correlation (0.3) with plastic viscosity (See Fig

3.16). De Schutter (2008) and West (2003) stated that the t500 time is related to plastic

viscosity. However, the t500 time does not quantify this rheological parameter (De Schutter,

2008).

Fig 3. 16: Correlation between rheological parameters and empirical test methods (SF: slump flow; H2/H1:

L-box blocking; T50-L: T50 from the L-box; T50: T50 from the slump flow; FT: Orimet; t0: V-funnel)

Good correlations were shown to exist between the L-box and J-ring acceptable values, in

which the L-box minimum ratio of 0.8 corresponded to a maximum blocking step value of

10 mm (See Fig 3.17). More specifically, either the L-box or J-ring were deemed

acceptable in simulating concrete deformation within a confined reinforcement zone.

When using the J-ring severe segregation can be assessed by visual inspection;

consequently, the J-ring has the potential to assess all the physical workability

characteristics of SCC, but not its rheology (Testing-SCC, 2005).


52

Fig 3. 17: Simultaneously performed L-box and J-ring blocking tests (after Testing-SCC 2005).

3.4.5. Two point workability test

In order to characterise the flow properties of concrete, the two-point workability test

measures two data points. In principle, the concrete within the two point apparatus

(typically a rotational rheometer) is sheared between two cementitious surfaces (failure

plane), one of which is rotating by the use of an external device (impeller), where the

rotation speed or angular velocity, and torque are measured (Ferraris and Martys, 2012).

The Two-point workability apparatus was developed to evaluate the workability of

medium to high workability concretes. The concrete sample is placed in a cylindrical

container of 254 mm diameter and 305 mm high (See Fig 3.18). During testing, the

impeller must shear the concrete without giving rise to segregation and/or bleeding. For

this reason, an axial impeller with four angled blades positioned in a helical arrangement

around a central drive was deemed the most successful because the anticlockwise rotation

of the impeller combined with its helical vane arrangement raises the concrete while also

allowing concrete to fall back through the gaps (the MH system). These characteristics

minimise the effects of segregation and bleeding. In addition, an offset H impeller can be

used, which rotates in the concrete in a planetary motion (the LM system). However, the

MH system should be used for high workable concretes in excess of 100 mm slumps

(Banfill et al, 2001).

The required torque-speed relationship is obtained by the use of a half horsepower (hp)

single-phase electric motor, which rotates a drive shaft by the use of a hydraulic

transmission (Carter Gear F10). A right angle reduction gear allows the drive shaft to


53

rotate around the vertical axis while also providing a torque range of 0 – 16 Nm and a

variable speed range of -3.15 to 3.15 rev/s. The reason for selecting the Carter Gear F10

arrangement is because the torque produced is proportional to the pressure of the oil in the

hydraulic transmission.

Fig 3. 18: Interrupted helix Impeller rotating in concrete (after Banfill et al. 2001).

The final arrangement of the Two-point apparatus is shown in Fig 3.19. The cylindrical

bowl containing the concrete is supported by means of an adjustable arm. This allows the

concrete sample to be raised and supported during testing and lowered following the

testing regime. A speed control knob is provided, which allows the speed setting to be

adjusted, to record the relationship between speed (rev/s) and pressure (lb/in2), the resulting

pressure is recorded by reading the pressure tachometer.

Fig 3. 19: Tattersall Two-point apparatus.


54

Prior to using the Two-point workability apparatus, the gearbox and the hydraulic units

must be filled with appropriate oils, ensuring no trapped air remains in the hydraulic unit.

Removing the trapped air is done by bleeding the unit.

When initialising the apparatus, the apparatus must run for about 30 minutes to allow the

oils to reach their operating temperature, especially for the hydraulic unit, as the hydraulic

oil is used to determine the resulting pressures of the impeller as it rotates through the

shearing plane. During the warmup period, the recommended speed is approximately 0.7

rev/s. However, Wallevik and Gjorv recommended higher speeds of 3 rev/s during the

warmup period because at a warmup speed of 0.7 rev/s the idling pressure can change even

after an 80 minute warmup period.

Following the warmup period in the MH mode, the procedure is as follows.

(i) The bowl is raised, such that there is a clearance of 60 mm between the bottom

of the bowl and the bottom of the impeller shaft.

(ii) Fill the bowl with concrete to approximately 75 mm from the top of the bowl,

while the impeller is rotating at 0.7 rev/s.

(iii) Increase the speed to 1.3 rev/s and allow the pressure to stabilise.

(iv) Read the speed by tachometer.

(v) Read the resulting average pressure, while ignoring large oscillations due to

aggregate size and aggregate trapping.

(vi) Repeat (iv) and (v) at speeds of 1.2, 1.0, 0.9, 0.7, 0.5, and 0.3 rev/s.

(vii) Remove the bowl and record the idling pressure at each of the speeds used in

the testing.

Expression of results

The pressures obtained by shearing the concrete at various speeds are subtracted from the

idle pressures, known as the net pressures. These net pressures are then converted to torque

and are plotted on a graph against their corresponding speeds. This allows one to calculate

the intercept and slope. It has been shown that the relationship between torque and speed

for TVC conforms to a Bingham model and therefore a linear relationship of torque to

speed describes the flow curve. However, in some cases, the relationship between torque

and speed can conform to a Hershel-Bulkley model and therefore the flow curve is

nonlinear. The equations for a linear and concave relationship are, respectively, as follows:

T = g + hN (3. 2)


55

and

T = g + ANb (3. 3)

where, the torque T (N/m) is a measurement of the impeller’s resistance to rotate in the

concrete. N (rev/s) is the impeller speed, g is the intercept with the torque axis, which is

related to yield stress and h is the reciprocal slope of the line which is related to viscosity

(Tattersall, 2003; Tattersall and Banfill, 1983; Cullen and West, 2001; Banfill, et al.,

2001). The parameters A and b depend on both the geometry of the apparatus and the

concrete, which are related to viscosity.

During the period, 2000 – 2001, a study was carried out in France (Banfill, et al., 2001),

which involved the comparison of five different rheometers to assess the appropriate

method of evaluating concrete workability in terms of yield stress and plastic viscosity.

Consequently, the authors concluded that a high risk of concrete slippage is associated with

the two-point test, mainly due to the lack of blades on the boundary surfaces.

3.4.6. Summary

There exists various empirical tests for evaluating the workability of SCC. In addition, the

slump flow, L-box and J-ring tests are highly recommended due to their reasonably good

correlations with the rheological parameters of yield stress and plastic viscosity, good

reproducibility, R, and repeatability, r, values and their simplistic and universal usage.

Rheological speaking, good correlation exist between yield stress and the upright slump

flow value, but a poor correlation exists between plastic viscosity and the upright slump

flow t500 time. However, the inverted slump flow test is the preferred choice in evaluating

the workability of SFRC.

CHAPTER 4 – PARAMETRIC STUDY ON CONSTITUENT MATERIALS AND TESTS

56


4.1. Introduction

In order to obtain accurate results, it is important to mix and test concrete under identical

conditions throughout the course of this study. This includes using the same equipment, the

same testing procedures and the same materials. To determine the appropriate

characteristic properties of SCC, i.e., adequate passing ability, filling ability and

segregation resistance, various tests are used.

In this chapter, the constituent materials used in this study are described and discussed.

Aggregates, cement, superplasticiser and VMA were obtained from the same source and

hence all materials used in this study were the same. The fly ash and ground granulated

blast furnace slag were obtained from, respectively, Moneypoint Power station and

Ecocem. In addition, trial tests were performed on SCC and TVC in order to, respectively,

determine the correct proportions of constituent materials and assess any variability due to

experimental error. The performed tests used in this chapter and throughout this study were

the Two-point workability, J-ring, L-box and slump flow.

4.2. Coarse and fine aggregates

In this study, the aggregates used were obtained from Belgard plant of Roadstone. During

initial trials, a finer sand was used (Sand A). Rheologically speaking, sand A performed

well, mainly due to its fineness and hence its increased contribution to the overall paste

content and reduced interparticle frictional forces. However, further testing could not be

completed as sand A was in short supply. Therefore, a much coarser and highly available

sand was used (Sand B). The physical appearance of Sand A and B are illustrated in Fig

4.1 – 4.2).

Fig 4. 1: Sand A.

Fig 4. 2: Sand B.


57

Figure 4.3 illustrates the particle size distribution for both sand A and sand B and the

overall distribution of coarse and fine aggregates (sand B and coarse aggregates). In this

study, the particle size distribution corresponding to sand B and coarse aggregate were

used in all the mixtures undergoing both rheological and workability testing.

4.2.1. Particle size distribution of aggregates

Fig 4. 3: Particle size distribution of aggregates.

4.3. Powders

CEM II/A-L (Portland cement with 6-12 percent limestone replacement), PFA and GGBS

were used in this study. In addition, limestone powder was used as a filler, and this was

also obtained from Roadstone. The physical appearance of all the powders are illustrated in

Fig 4.4 – 4.7.

Fig 4. 4: CEM II/A-L.

Fig 4. 5: Limestone filler.

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100

PER

CEN

TAG

E P

ASS

ING

%

PARTICLE SIZE MM

Sand A

Sand B & Coarse aggregates

Sand B


58

Fig 4. 6: PFA.

Fig 4. 7: GGBS.

4.3.1. Particle size distribution of powders

Laser Scattering Particle Size Analyser, the Malvern Mastersizer 2000 was used to

determine the particle size distribution of each of the powders. Fig 4.8 illustrates the

particle size distributions of all the powders used in this study. The particle size

distribution of the fly-ash (PFA) is the finest of all powders used and it is expected that

incorporating PFA for the partial replacement of CEM II will improve particle packing and

hence improve workability and consistency (segregation resistance). In addition, the GGBS

is not quite as fine as CEM II (A-L), but finer than the limestone filler.

Fig 4. 8: Particle size distribution of powders.

0

10

20

30

40

50

60

70

80

90

100

0.0001 0.001 0.01 0.1 1

PER

CEN

TAG

E P

ASS

ING

%

PARTICLE SIZE MM

GGBS

CEM II/A-L

Fly-ash

LS


59

4.4. Water

Ordinary mains water was used in all mixes throughout this study. It is well known that

water temperature will cause an increase or decrease in workability. However, in this

study, the effects of varying water temperatures were neglected and assumed constant.

4.5. Chemical admixtures

All admixtures used throughout this study were obtained from the Belgard plant of

Roadstone. Glenium 27, a polycarboxylate-based superplasticiser was used to produce

SCC. The normal recommended dosage rate of Glenium 27 is approximately 0.8 - 2.0

percentage weight of cementitious material. As for the viscosity modifying agent, a

RheoMATRIX 100 was used throughout; Appendix G gives the specifications for all the

admixtures. The normal recommended dosage of viscosity modifying agent is

approximately 0.8 – 1.5 percentage weight of cementitious material.

4.6. Fibres

The steel fibres used in this study were acquired from the UK. Figure 4.9 illustrates the

fibres used throughout this study. Furthermore, their length, diameter and aspect ratio are,

respectively, 35 mm, 0.55 mm and 65, also known as Dramix R-65/35 type fibres (refer to

Appendix G for the technical data sheet).

Fig 4. 9: Steel fibres (Dramix R-65/35).


60

4.7. Rheological study of trial mixes

In this section, trial mixes determine the variability associated with operating the two-point

apparatus. In addition, the torque-speed relationship of TVC and SCC were measured with

the two-point apparatus and experimental values of torque versus speed and hence torque

intercept and slope were obtained by applying both the Bingham and Hershel-Bulkley

models.

Table 4. 1: Quantities of constituent materials per cubic meter of concrete.

Mixture type

Cement (CEM II)

Filler (LS) Fine

aggregate Coarse

aggregate Water SP VMA Total

(kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3)

NVC-1 367 - 571 1057 209 - - 2204

NVC-2 367 - 571 1057 147 - - 2142

NVC-3 367 - 571 1057 209 - - 2204

SCC-4 450 50 960 735 220 8.65 5.85 2433

NVC-1b 367 - 571 1057 222 - - 2217

Table 4. 2: Quantities of constituent materials undergoing rheological analysis.

Mixture type

Cement (CEM II)

Filler (LS)

Fine aggregate

Coarse aggregate

Water SP VMA Total

(Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg)

NVC-1 5.14 - 7.99 14.80 2.926 - - 30.856

NVC-2 5.14 - 7.99 14.80 2.058 - - 29.988

NVC-3 5.14 - 7.99 14.80 2.926 - - 30.856

SCC-4 6.30 0.7 13.44 10.29 3.08 0.121 0.082 34.062

NVC-1b 5.14 - 7.99 14.80 3.108 - - 31.038

Table 4.1 and Table 4.2 represents, respectively, the constituent materials per cubic meter

of concrete and the constituent materials undergoing analysis, which corresponds to a

volume of 0.0180 m3. The only difference between Trial 1 (NVC-1) and Trial 2 (NVC-2)

is a difference in water content and hence water-cement ratio. Trial 3 (NVC-3) is similar to

Trial 1 except for an additional idle time of 80 minutes after the addition of mixing water.

The SCC mix (SCC-4) was analysed 60 minutes after the addition of mixing water. In

addition, trial mix NVC-1b underwent two-point workability testing at times

corresponding to 15, 43, 65, 87, 107 and 126 minutes after the addition of water.


61

During testing, the resulting pressures were recorded at speeds varying from 0.3 to 1.3

rev/s and these pressures were calibrated and, consequently, converted to torque by the

following equation proposed by Tattersall and Banfill (1983):

T = 0.0286P (4. 1)

where T is the resulting torque expressed in N/m and P is the recorded pressure expressed

in lb/in2. However, it was later noted that this calibration factor incorporates a planetary

gear ratio (MK III) and since the two-point workability apparatus (MK II) does not have a

planetary gear ratio, then the conversion factor is as follows:

T = 0.0643P (4. 2)

The initial calibration factor was used, i.e., T = 0.0286P in the following section. However,

further rheological analysis will be carried out by the appropriate calibration factor, i.e., T

= 0.0643P.

Figure 4.10 and 4.11 illustrates the torque-speed relationship for similar concretes, i.e.

comprised of identical constituent materials concerning quality and quantity. The only

difference between these two concretes undergoing two-point workability testing is the

time at which they were tested. Trial-1 was tested initially after mixing (15 min), while

Trial-3 was tested 80 minutes after the addition of mixing water.

Detailed analysis plots of different correlation coefficients (R2) for the different

relationships between torque and speed, and hence yield stress and plastic viscosity, are

presented in Fig 4.10 – 4.13.

In considering all the possible functional relationships for the mixes (Fig 4.10 – 4.13), it is

observed that the polynomial function seems to produce the best-fit correlation between

torque and speed. However, there is a considerable amount of variability associated with

recording the resisting pressures on the two-point workability apparatus. In evaluating the

resisting pressures or torques, large oscillations were encountered – mainly due to the

coarse aggregates colliding with the impeller. For example, it can be stated that the

standard deviation and hence the standard error associated with recording the resisting

pressures (lb/in2) decreases with decreasing speeds (rev/s) (See Fig 4.11 and 4.13).


62

Fig 4. 10: Relationship between torque and speed

with respect to different functional equations for

Trial-1, 15 min after the addition of water.

Fig 4. 11: Relationship between torque and speed

with respect to different functional equations for

Trial-3, 80 min after the addition of water.

Based on the analysis presented in Fig 4.10 and 4.11, and by using either the Bingham or

Hershel Bulkley models it can be seen that the rheology of concrete is time-dependent. For

example, Fig 4.11 shows an increase in torque intercept and a decrease in slope when

compared with Fig 4.10, and the intercept and slope are related to, respectively, yield stress

and plastic viscosity. Then it may be observed that an increase in idle time, after the

addition of water, caused an increase in yield stress and a decrease in plastic viscosity.

Intuitively, the degree of change concerning the intercept when comparing Trial-1 to Trial-

3 suggests that the two-point apparatus is operating as it should. However, according to

Tattersall (1991) the plastic viscosity should increase with an increase in time after the

addition of mixing water.

Fig 4. 12: Relationship between torque and

speed with respect to different functional

equations.

Fig 4. 13: Relationship between torque and

speed with respect to different functional

relationships for Trial-2, 15 min after the

addition of water.

Producing concrete consisting of different water contents and hence different water-cement

ratios has a profound effect on the torsional resistance at different speeds. According to

R² = 0.971

y = 0.8511x + 1.5972R² = 0.9243

R² = 0.9518

R² = 0.86470.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

T/N chart for Trial 1-NVC, w/c 0.57

NVC

Poly. (NVC )

Linear (NVC )

Expon. (NVC )

Power (NVC )

y = 0.4834x + 4.7267R² = 0.9581

R² = 0.9909

R² = 0.9624

R² = 0.8784

4.6

4.7

4.8

4.9

5.0

5.1

5.2

5.3

5.4

5.5

5.6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

T/N chart for Trial 3-NVC, 0.57 w/c, 80 min after mixingNVC

Linear (NVC)

Poly. (NVC)

Expon. (NVC)

Power (NVC)

y = 0.8582x + 0.6523R² = 0.9166

R² = 0.9475

R² = 0.9382

R² = 0.8880.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

T/N chart for Trial 4-SCC, 60 min after mixing

SCC

Linear (SCC )

Power (SCC )

Poly. (SCC )

Expon. (SCC )

y = 0.2474x + 4.4234R² = 0.9491

R² = 0.9932

R² = 0.952

R² = 0.8584

4.4

4.5

4.6

4.7

4.8

4.9

5.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

T/N chart for Trial 2-NVC, w/c 0.4

NVC

Linear (NVC )

Poly. (NVC )

Expon. (NVC )

Power (NVC )


63

Tattersall (2001), adding more water causes a reduction in both yield and plastic viscosity.

Fig 4.10 (Trial-1) shows a decrease in torque intercept and an increase in slope when

compared to Fig 4.13 (Trial-2). This comparison suggests that increasing the water-cement

ratio causes a reduction in pressure and hence torque, while it also causes an increase in

slope. Based on this analysis, increasing the water-cement ratio reduced the dynamic yield

stress and increases the plastic viscosity. Intuitively, this analysis suggests that the two-

point apparatus is not functioning as normal, as the slope should decrease with an increase

in water content. However, the standard deviation associated with the encountered

variability in recording the resulting pressures is considered large (See Fig 4.11 and 4.13).

During two-point testing, it was clearly seen that a high degree of slippage occurred within

the interface between the concrete sample and the bowl. In addition, a high degree of

slippage was noted at high speeds relative to low speeds. Therefore, the slippage associated

with high speeds and hence high rates of shear causes a decrease in slope and, therefore an

increase in plastic viscosity. It is very likely that this slippage will also influence the

intercept on the torque axis and, consequently, the yield value. In addition, a high degree of

slippage was noted at a speed corresponding to 1.3 rev/s, which diminished to zero

slippage at a speed corresponding to approximately 0.5 rev/s.

The standard deviations associated with the encountered variability in recorded pressures

while testing mixture Trial-4, the SCC mix (See Fig 4.12) is considered low when

compared to the traditional concretes (See Fig 4.11 and 4.13), because a self-compacting

mixture has a lower coarse aggregate content and a higher paste content. Intuitively, these

differences in constituent materials (coarse aggregates and paste) result in reduced

oscillations due to a reduction in coarse aggregates and an increase in viscosity. In

addition, the torque-speed relationship for the SCC mixture (Trial-4 SCC) behaved like a

pseudoplastic material, i.e., exhibited shear thinning behaviour. However, immediately

after testing a high degree of segregation was noted as a considerable proportion of the

coarse aggregates had settled to the bottom of the bowl.

Based on the above analysis, it was necessary to develop a nonlinear model to represent the

torque-speed relationship of concrete. Therefore, the Hershel-Bulkley model was used to

represent the relationship between torque and speed.

Fig 4.14 illustrates the relationship between torque and speed for four concrete samples

undergoing two-point workability analysis. The A and b parameters shown in Fig 4.14

represents the fitted Hershel-Bulkley parameters for each concrete mixture.


64

Fig 4. 14: Hershel-Bulkley relationship between torque and speed for NVC-1 to NVC-3 and SCC-4.

As mentioned within the literature, the relationship of shear stress to shear strain rate for a

shear thickening material is concave towards the shear stress axis. This nonlinear

relationship suggests that the apparent viscosity decreases with increasing shear strain rates

until a certain shear rate is reached, shearing beyond this shear rate causes an increase in

apparent viscosity. Fig 4.15 illustrates apparent viscosity as a function of shear rate for the

concretes undergoing analysis. In order to illustrate the influence of shear thickening

and/or shear thinning on the apparent viscosity, it is was necessary to predict the

relationship of shear stress to shear strain rate by the use of the calculated Hershel-Bulkley

rheological parameters K and n. Predicting this relationship seems to be the best approach

as increasing the speed beyond 1.3 rev/s and, therefore increasing the shear strain rate in

the two-point apparatus will cause particle migration and segregation. From Fig. 4.15 it can

be clearly seen that the apparent viscosity increases with increasing shear rates for NVC-1,

which suggests shear thickening behaviour.

Fig 4. 15: Apparent viscosity as a function of shear strain rate.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

TWT Apparatus and Concrete Parameters (A & b), Hershel

BulkleyNVC-1, w/c

0.57

NVC-2, w/c 0.4

NVC-3, w/c

0.57, 80 min

after mixing

SCC-4, 60 min

after mixing

A = 0.27597 & b = 2.5837

A = 0.12397 & b =2.62

A = 0.43014 & b = 2.78585

A = 1.144 & b = 0.752

0

50

100

150

200

250

300

350

0 5 10 15 20 25 30 35 40 45 50 55

Ap

par

ent

vis

cosi

ty

Shear rate

NVC-1, w/c 0.57

NVC-2, w/c 0.4

NVC-3, w/c 0.57, 80 min after mixing

SCC-4, 60 min after mixing


65

Previous research has indicated that shear thickening is most probably caused by cluster

formation. The phenomenon of cluster formation occurs when under increasing rates of

shear strain, the fine particles join and form clusters, which leads to an increase in apparent

viscosity, and hence shear thickening. This suggests that increasing the volume fraction of

fine material. i.e., sands and powders, consequently, increases the intensity of shear

thickening.

Based on the above analysis, and due to excessively large variations in recording the

resulting pressures, it was deemed necessary to perform further rheological tests on a

traditional concrete sample in an attempt to more accurately determine the resulting

pressures due to large oscillations. Accurately recording the resulting pressure is highly

user dependent. However, the error in recording the resulting pressures can be significantly

reduced by ignoring the oscillations and homing in on the resulting pressure by using the

pressure control valve. The following torque-speed relationships (See Fig 4.16 – 4.21)

were determined for NVC-Trial 1b for idle times corresponding to 15, 43, 65, 87, 107 and

126 minutes after the addition of mixing water. In addition, detailed analysis plots of

different correlation coefficients (R2) for the different relationships between torque and

speed are presented and the encountered variation, standard deviation, due to recording the

pressure, is presented in the form of error bars. Also Fig 4.16 – 4.21 shows the torque

intercepts for different torque-speed functional relationships and the equations

corresponding to the straight-line relationship of the Bingham model are also shown. It is

important to recognise that a certain amount of error is associated with the obtained g and h

parameters. For example, Tattersall (2001) states that if the number of experimental points

of torque versus speed is seven, and the correlation coefficient is 0.98; and the rheological

parameter h is 1.49, then the experimental error for g and h is ± 0.2. Intuitively, if the

correlation coefficient is less than 0.98 and/or the parameter h is greater than 1.49, then the

experimental error for g and h is greater than ± 0.2.

The mix design for NVC-Trial 1b is presented in Table 4.1 and 4.2 with a water-cement

ratio corresponding to 0.61.


66

Fig 4. 16: Relationship of torque and speed for

different functional equations.

.











In considering all the possible functional relationships for TVC (See Fig 4.16 – 4.21), it is

observed that the polynomial function seems to produce the best-fit correlation between

torque and speed with correlation coefficients (R2) ranging from 0.89 – 0.96. Furthermore,

these correlation coefficients suggest an error in the fundamental values of g and h of

y = 1.3372x + 1.3805R² = 0.885

R² = 0.9576

R² = 0.9079

R² = 0.79340.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

NVC-Trial 1b, 15 min after mixing

NVC-1b

Linear (NVC-1b)

Poly. (NVC-1b)

Expon. (NVC-1b)

Power (NVC-1b)

y = 0.7669x + 1.8061R² = 0.9363

R² = 0.9554R² = 0.9534

R² = 0.8966

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


NVC-2b

Linear (NVC-2b)

Poly. (NVC-2b)

Expon. (NVC-2b)

Power (NVC-2b)

y = 0.6844x + 2.1616R² = 0.9615

R² = 0.9846

R² = 0.8828

R² = 0.9702

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


NVC-3b

Linear (NVC-3b)

Poly. (NVC-3b)

Power (NVC-3b)

Expon. (NVC-3b)

y = 0.7714x + 2.3171R² = 0.8992

R² = 0.9711

R² = 0.8036

R² = 0.922

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


NVC-4b

Linear (NVC-4b)

Poly. (NVC-4b)

Power (NVC-4b)

Expon. (NVC-4b)

y = 0.633x + 2.83R² = 0.89

R² = 0.9725

R² = 0.7849

R² = 0.90560.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


NVC-5b

Linear (NVC-5b)

Poly. (NVC-5b)

Power (NVC-5b)

Expon. (NVC-5b)

y = 0.5309x + 2.9897R² = 0.7826

R² = 0.8975

R² = 0.6454

R² = 0.7883

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


NVC-6b

Linear (NVC-6b)

Poly. (NVC-6b)

Power (NVC-6b)

Expon. (NVC-6b)


67

between ± 0.14 and ± 0.13. In addition, the standard deviations are considered low as can

be seen from figures 4.16 – 4.21, which are presented in Fig 4.16 – 4.21 in the form of

error bars.

Based on the above analysis (See Fig 4.16 – 4.21), the intercept and slope of the straight-

line relationship. i.e., the Bingham model for the illustrated graphs suggests that the idle

time has a profound effect on the resulting torque. For example, an increasing in idle time

after the addition of water, consequently, increases the torque intercept. Intuitively, this

suggests that an increasing idle time causes an increase in yield stress, which is to be

expected. Also in Fig 4.16 – 4.21, it may be observed that the slope remains somewhat

constant except for Trial-1b, 15 min (See Fig 4.16). The occurrence of a constant slope

could be due to the high water-cement ratio (0.61). Furthermore, one can state that the

two-point apparatus is functioning as it should. In addition, the difference in slope

between NVC-Trial 1b, 15 min and its subsequent test is considered large (1.337 –

0.7669), the reason for this will be discussed shortly.

The Hershel-Bulkley model was fitted to the experimental curves of torque versus angular

velocity. This model fits the curves quite well and the rheological parameters A and b

were determined as illustrated in Fig. 4.22.

Fig 4. 22: Fitted Hershel-Bulkley relationships of torque to speed for Trial-1b, 15 – 127 min after the

addition of water.

As illustrated in Fig 4.22, the slope of the torque-speed relationship for NVC-Trial 1b, 15

min, which corresponds to an idle time of 15 minutes after the addition of mixing water is

significantly larger than the preceding test (NVC-Trial 1b, 43 min). The reason for this

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)

TWT apparatus and concrete parameters (A & b), Hershel Bulkley model







A = 0.5, b = 1.6

A = 0.4, b = 1.7

A = 0.3, b = 3.3

A = 0.28, b = 3.1

A = 0.23, b = 3.4


68

may have been due to a mistake on the author’s behalf as the concrete sample within the

two-point workability bowl corresponding to NVC-Trial 1b, 15 min had a clearance of

approximately 40 mm and not the recommended 75 mm. Consequently, the 75 mm

clearance level was marked for further tests.

4.8. Proposed mix design, mixes and testing procedure

Based on the results within the previous section, it was necessary to design a self-

compacting concrete with a high degree of segregation resistance. As previously

mentioned, a high degree of segregation was encountered in SCC-4. This following

section is aimed at designing a self-compacting concrete that conforms to the criteria set

out in EFNARC. In addition, the mixing sequence and the adopted workability tests will

be discussed.

An SCC mix from an external source was acquired, and is presented below in Table 4.3.

Table 4. 3: SCC mix design received in confidence.

Mixture type

Cement (CEM II/A-L)

GGBS Filler (LS)

Fine aggregate

Coarse aggregate

Water SP VMA Total

(kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3) (kg/m3)

SCC 270 180 50 960 735 195 4.25 3.74 2398

In order to determine the appropriate mix design quantities for a SFRSCC mixture

containing zero GGBS and, consequently, a 100% CEM II/A-L content, it was necessary

to perform a vector analysis. Fig. 4.23 illustrates the influence of GGBS for the partial

replacement of cement on the rheological parameters of yield stress and plastic viscosity.

In order to design a SCC mixture without GGBS, and with the same yield and plastic

viscosity as a concrete with GGBS, it is necessary to increase the dosage of both the

superplasticiser and viscosity modifying admixtures (See Fig 4.23). Furthermore, the

particle size of the GGBS will influence the dosage rate of the superplasticiser and

stabilising admixtures. Nevertheless, the inclusion of GGBS for the partial replacement of

cement will reduce the yield value and increase the plastic viscosity.


69

Fig 4. 23: Vector analysis of the influence of GGBS on yield stress and plastic viscosity.

4.8.1. Mixing sequence and mixer

The above mixing sequence was used throughout the trial SCC mixtures, and all the tests

throughout this study. Adding 40% of the water to the coarse aggregates minimised the

dust produced during mixing the fine aggregates and powders. In addition, it is important

to recognise that the fine particles, in particular, the powders and the percentage of fine

aggregates which passes the 125 µm sieve must be sufficiently saturated before adding the

superplasticiser. From the above mixing sequence, it can be seen that the total mixing time

after the addition of water and cementitious materials corresponds to 230 seconds, with an

additional 10-minute relation time.

As mentioned within the literature, a force-action mixer is the preferred mixer for

producing SCC mainly because of its increased rate of shearing. However, the free-fall

mixer was used throughout this study. Furthermore, the dosage of superplasticiser has to

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8

Yiel

d s

tres

s

Plastic viscosity

GGBSSP

VMA

REF

Coarse

Aggregates

Fine

Aggregate +

Powders

Superplasti-

ciser

Viscosity

Modifying

Agent

40% Water 50% Water 10% Water

10 s 60 s 20 s

10 minutes rest

120 sec mix Test

20 s


70

increased when using the free-fall mixer compared with the force-action mixer, mainly

because of the reduced shearing effect of the free-fall mixer

Fig 4. 24: Free-fall mixer.

Fig 4. 25: Force-action mixer.

Prior to commencing mixing, the inside of the free-fall mixing drum was washed out with

water. This cleaned out any particles, and more importantly wetted the mixing drum. This

procedure was carried out throughout this study. In addition, during the final mixing stage

the tilt of free-fall mixer was slightly reduced to promote the shearing effect.

4.8.2. Testing methods

In order to evaluate the rheological and workability properties of SCC, various tests were

used. In this section, the selected test methods are briefly discussed and illustrated.

Fig 4. 26: TWT apparatus (MK II).

Fig 4. 27: TWT bowl.

Pressure

gauge

Speed

control

Rack and

pinion

Pressure

control valve

Speed

display

75 mm clearance


71

Fig 4. 28: L-box test.

Fig 4. 29: L-box rebar arrangement.

Fig 4. 30: Slump flow test.

Fig 4. 31: J-ring test.

Fig 4.26 – 4.31 illustrates the various tests methods for testing both the rheological and

empirical parameters of steel fibre reinforced self-compacting concrete (SFRSCC). As

mentioned within the literature, the inverted slump cone method was the preferred choice,

and all the tests throughout the course of this study were performed in this manner (See

Fig 4.30 – 4.31).

500 mm

circle

700 mm

circle

Inverted

slump cone

700 mm

circle

Inverted

slump cone 500 mm

circle

Horizontal

channel

Vertical

channel

Sliding gate

30 mm spacing


72

4.8.3. Trial SCC mixes

In order to design SFRSCC, it was necessary to conduct trial SCC mixes. Intuitively,

incorporating steel fibres in SCC causes a reduction in both filling and passing abilities.

Therefore, a relatively high passing and filling ability was required in order to assess the

feasible use of steel fibres (SF) in SCC with regards to the maximum acceptable criteria

for filling and passing abilities as set out by EFNARC.

Table 4. 4: Initial SCC mix design.

Mixture type

Cement (CEM II/A-L)

Filler (LS)

Fine aggregate

Coarse aggregate

Water SP VMA Total


SCC-4 450 50 960 735 215.5 8.65 6.85 2429

Table 4.4 summarises the initial constituents undergoing rheological and workability

analysis. The dosage of SP and VMA are, respectively, at 1.92 and 1.5 percentage weight

of cementitious material, and are within the maximum dosages of 2.5% and 1.5% of

cementitious material for SP and VMA, respectively. During testing, however, it was

found that the mix design was incapable of meeting the minimum acceptable criteria

because the sand did not possess a sufficient amount of fine material. Furthermore, the

dosage of VMA used was at a near maximum dosage of 1.4 percentage weight of

cementitious material. Therefore, it was necessary to increase the paste content in order to

provide a sufficient amount of fine material. Also, the coarse aggregate content was

reduced, because the sand was slightly coarse. This was done by increasing the cement

content to 580 kg per cubic meter, decreasing the coarse aggregate content to 630 kg per

cubic meter and increasing the fine aggregate content to 1020 kg per cubic meter. Table

4.5 presents the new mix design.

Table 4. 5: New mix design.

Mixture type

Cement (CEM II/A-L)

Filler (LS)

Fine aggregate

Coarse aggregate

Water SP VMA Total


SCC-4B 580 20 1020 630 215.5 8.65 6.85 2429

Table 4.6 represents the initial trial mix (SCC-4B) and subsequent trial mixes (SCC-4B to

SCC-4E) with respect to the dosage of admixtures, water-cement ratio and the obtained


73

empirical values. Achieving the required blocking step value of between 5 mm and 10 mm

presented some minor issues. Therefore, it was decided to increase both the dosage of

VMA and SP in order to, respectively, provide an increase in stability and deformation

capacity. The dosage of SP and VMA are, respectively, at 2.2 and 1.34 percentage weight

of cementitious material, both within the maximum recommended.

Table 4. 6: Evolution of mix design with an increase in both SP and VMA.

J-ring

Mixture type

VMA SP w/c Slump flow L-box ratio

Spread Blocking

step t500

(Kg/m3) (Kg/m3) Spread (mm)

t500 (sec)

(mm) (mm) (sec)

SCC-4B 6.85 8.65 0.371 650 2.8 0.65 590 17 3.6 SCC-4C 6.85 9.85 0.371 690 2.6 0.74 620 14 3.2 SCC-4D 6.85 10.5 0.371 730 2.4 0.75 680 12 3.2 SCC-4E 7.8 12.5 0.371 700 2.1 0.94 700 7.25 3.1

Trial mix SCC-4E performed well concerning its filling and passing abilities for all the

tests, while also possessing an adequate resistance against segregation (See Table 4.6 and

Fig 4.32 – 4.33).

From these observations, as shown in Fig 4.32 and 4.33, SCC-4E is considered highly

stable.

Fig 4. 32: SCC-4E flow spread.

Fig 4. 33: L-box test for SCC-4E.


74

4.8.4. Summary

This chapter has presented information on the constituent materials used in this study. In

addition, the physical appearance and particle size distributions of both the powders and

aggregates are presented.

Trial mixes were used to determine the variability associated with TWT. Also, various

functional torque-speed relationships are presented with their associated correlation

coefficients (R2). It may be observed that the polynomial function seems to best describe

the torque-speed relationship.

The proposed mix design is presented along with the selected rheological and empirical

tests, i.e., TWT, slump flow, L-box and J-ring. During the mix design for SFRSCC it was

necessary to increase the paste and the fine aggregate content and decrease the coarse

aggregate content. This was done because the sand used in this study was somewhat

coarse. Therefore, the paste content was increased to 580 kg/m3; the fine aggregate was

increases to 1020 kg/m3 and the coarse aggregate was reduced to 630 kg/m3. In doing so,

and by increasing the dosage of SP and VMA content, a sufficient mix design was

acquired.

During TWT, it was noted that a high degree of slippage occurred in the interface between

the concrete and TWT bowl, especially at high speeds, such as 1.3 rev/s.

When using the TWT apparatus to determine the torque-speed relationship of SCC, the

encountered pressure variations are considered low when compared to traditional concrete,

because SCC has a lower coarse aggregate content and a higher past content.

Consequently, these constituent requirements minimise the colliding effect of the coarse

aggregates on the impeller.

CHAPTER 5 – RHEOLOGICAL STUDY ON SFRSCC WITH PFA AND GGBS

75

CHAPTER 5 - RHEOLOGICAL STUDY ON SFRSCC WITH PFA AND GGBS.

5.1. Introduction

In this chapter, the influence of GGBS and PFA on both the rheological and the

workability parameters of SFRSCC are determined. The rheological parameters were

determined by using the Tattersall two-point workability apparatus, while the workability

parameters were assessed by various workability tests, as mentioned in the previous

chapter.

The rheological parameters g and h were determined by plotting the obtained torque-speed

relationships for twenty-one mixes undergoing rheological testing. It is important to

recognise that the parameters g and h are, respectively, used to determine the yield value

and plastic viscosity of SCC. Therefore, this study is aimed at determining these

parameters. The workability aspects were evaluated by empirical tests, i.e., slump flow, L-

box and the J-ring tests. It is well known that the slump flow spread value for SCC is

inversely related to the yield value and the t500 time is related to the plastic viscosity.

During idle times, the rheology and workability of SCC changes, because SCC is highly

thixotropic, and even more so with the addition of steel fibres. Also, an increase in time

after the addition of water, ultimately, influences concrete rheology and concrete

workability. Therefore, the various mixes throughout this study are evaluated concerning

the evolution of time after the addition of mixing water as well as establishing any

possible relationships between the individual empirical test results and the rheological

parameters for SFRSCC with and without 50% GGBS and 30% PFA cement

replacements.

5.2. Testing sequence

The sequence of tests involved testing the various mixes at different idle times. Initially,

and following the mixing process, the rheological aspects were evaluated by the Tattersall

two-point workability apparatus. Immediately after two-point testing, the concrete

mixtures were tested by using the slump flow, L-box and J-ring tests. In order to evaluate

the effects of time on both the fundamental and empirical parameters; this sequence was

carried out three time. Table 5.1 summarises the twelve tests performed on each individual

sample. After each test, the concrete sample was remixed with the remaining concrete in

the free-fall mixer for approximately 15 - 20 seconds. This was done to try to eliminate the


76

effects of segregation caused by the MK II apparatus and to promote an even distribution

of steel fibres throughout all the tests.

Table 5. 1: SCC-Testing regime.

Test No Test type Test No Test type Test No Test type 1 TWT-Testing 5 TWT-Testing 9 TWT-Testing 2 Slump-flow 6 Slump-flow 10 Slump-flow 3 L-box 7 L-box 11 L-box 4 J-ring 8 J-ring 12 J-ring

5.3. Experimental program on SFRSCC with GGBS and PFA

The experimental program on SFRSCC with GGBS and PFA consisted of three self-

compacting reference mixtures with different cementitious compositions, i.e., 100% CEM

II/A-L, 30% PFA CEM II/A-L replacement and 50% GGBS CEM II/A-L replacement.

Various equivalent volumetric proportions of steel fibres were incorporated into each

reference mix, i.e., 5 to 30 kg per cubic meter (See Table 5.2). The constituent materials

were quantified in similar proportions throughout the course of this experimental program.

The constituent materials used in this study were discussed in the previous chapter. Table

5.2 summarises the mix design for SCC-1 to SCC-21. Appendix A presents the mix design

for SCC-1 to SCC-21.

Table 5. 2: Experimental mix design for SCC-1 to SCC-21.

Mixture type

Cement (CEM

II) PFA GGBS

Filler (LS)

Sand 10

mm Water SP VMA SF Total

(Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg) (Kg)

SCC-1 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0 46.49

SCC-2 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.094 51.49

SCC-3 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.188 56.49

SCC-4 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.282 61.49

SCC-5 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.376 66.49

SCC-6 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.470 71.49

SCC-7 10.85 - - 0.374 19.07 11.78 4.03 0.234 0.146 0.564 76.49

SCC-8 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0 46.49

SCC-9 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.094 51.49

SCC-10 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.188 56.49

SCC-11 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.282 61.49

SCC-12 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.376 66.49

SCC-13 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.470 71.49

SCC-14 7.60 3.255 - 0.374 19.07 11.78 4.03 0.234 0.146 0.564 76.49

SCC-15 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0 46.49

SCC-16 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.094 51.49

SCC-17 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.188 56.49

SCC-18 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.282 61.49

SCC-19 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.376 66.49

SCC-20 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.470 71.49

SCC-21 5.43 - 5.425 0.374 19.07 11.78 4.03 0.234 0.146 0.564 76.49


77

5.3.1. Rheological analysis of SFRSCC with PFA and GGBS

In this following section, the rheological parameters obtained from two-point testing are

analysed and discussed. The results obtained from both the rheological and workability

analysis for the SCC-1 to SCC-21 can be found in Appendix B. In considering all the

possible time evolution functional relationships for SCC-1 to SCC-21, it may be observed

that the polynomial function seems to produce the best-fit correlation between torque and

speed. An example of a set of fits is given in Fig 5.1; Appendix C gives the full results of

the fits. In addition, Fig 5.1 illustrates the time evolution relationship of torque versus

speed for SCC-1. For example, the time evolution torque-speed relationship for SCC-1, 45

min corresponds to two-point testing time of 45 minutes after the addition of water (See

Fig 5.1).

Fig 5.1 illustrates the fitted Hershel-Bulkley models for the time evolution of SCC-1, i.e.,

the fitted models for SCC-1 corresponding to two-point testing times of 15, 45 and 75

minutes after the addition of water. The model fits the curves quite well and the

rheological parameters A and b were determined as summarised in Table 5.3; Appendix

C.4 gives the full results of the obtained rheological parameters.

Fig 5. 1: Time evolution relationship of torque versus speed for SCC-1.

The correlation coefficients (R2) are shown in Fig 5.1 for the different testing times after

the addition of mixing water. For example, a correlation coefficient (R2) of 0.998 was

obtained for SCC-1, 15 min after the addition of mixing water. The slope values presented

in Fig 5.1 were calculated by a linear approximation of the Hershel-Bulkley model, and

R² = 0.998R² = 0.9958R² = 0.9645

y = 2.5027x + 0.8y = 2.6893x + 0.93y = 2.9442x + 1.12

0

1

2

3

4

5

6

7

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)

SCC-1, 15 minSCC-1, 45 minSCC-1, 75 minHershel-Bulkley, 15 minHershel-Bulkley, 45 minHershel-Bulkley, 75 minPoly. (SCC-1, 15 min)Poly. (SCC-1, 45 min)Poly. (SCC-1, 75 min)Linear (Hershel-Bulkley, 15 min)Linear (Hershel-Bulkley, 45 min)Linear (Hershel-Bulkley, 75 min)


78

are represented by the black dashed lines. Also, the equations of these linear dashed

torque-speed relationships are shown alongside their individual Hershel-Bulkley linear

approximations. Therefore, the slopes and intercepts and hence the h and g parameters can

be seen. In addition, the coloured asterix symbols (SCC-1, 15, 45 and 75) represents the

obtained torques during two-point testing.

Fig 5. 2: Comparison of the torque-speed

relationship for the fitted Hershel-Bulkley model

for SCC-1 to SCC-7, 15 min after the addition of

water.

Fig 5. 3: Comparison of the torque-speed

relationship for the fitted Hershel-Bulkley model

for SCC-8 to SCC-13, 15 min after the addition

of water.

Fig 5. 4: Comparison of the torque-speed relationship for the fitted Hershel-Bulkley model for SCC-14 to

SCC-21, 15 min after the addition of water.

Fig 5.2 – 5.4 illustrates the fitted Hershel-Bulkley relationships of torque to speed for

SCC-1 to SCC-21, 15 min after the addition of water. In most cases, the rheological

parameters g and h are increasing with an increase in steel fibre content. Also, this can be

seen in Table 5.3. The Hershel–Bulkley parameters (A and b) presented in Table 5.3 were

determined by plotting ln (T – T0) versus ln N. The constant A is determined by the

intercept on the y-axis (ln T –T0 axis) and b is the slope of the straight-line relationship. In

0

1

2

3

4

5

6

7

8

9

10

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)

SCC-1, 15 minSCC-2, 15 minSCC-3, 15 minSCC-4, 15 minSCC-5, 15 minSCC-6, 15 minSCC-7, 15 min

SFRSCC

0 kg/m3 SF5 kg/m3 SF

10 kg/m3 SF15 kg/m3 SF20 kg/m3 SF25 kg/m3 SF30 kg/m3 SF

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3To

rqu

e (N

/m)

Speed (rev/s)


SFRSCC with PFA


10 kg/m3 SF15 kg/m3 SF20 kg/m3 SF25 kg/m3 SF30 kg/m3 SF

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Torq

ue

(N/m

)

Speed (rev/s)


SFRSCC with GGBS


10 kg/m3 SF15 kg/m3 SF20 kg/m3 SF25 kg/m3 SF

30 kg/m3 SF


79

addition, the yield parameters (g) obtained for the SFRSCC with PFA are lower when

compared with the other two self-compacting mixtures. This suggests that the use of PFA

(30% PFA used in this study) for the partial replacement of cement reduces the yield value

when compared with SFRSCC with and without 50% GGBS. Also, the results suggest that

the rheological parameter h increases when using PFA for 30% replacement of cement.

Table 5. 3: Summarised rheological parameters for SCC-1 to SCC-21, 15 min after addition of water.

As summarised in Table 5.3, and in most cases, the rheological parameter b increases with

an increasing in fibre content for all the self-compacting mixtures (i.e. SFRSCC with and

without GGBS and PFA cement placements), 15 min after the addition of water. This

suggests that an increase in fibre content causes an increase in shear thickening behaviour

and/or an increase in thixotropy. However, it was noted, during two-point testing that an

increase in segregation was encountered with an increase in fibre content. Therefore, it is

likely that the fibres combined with the geometry of the vane are disturbing the mix and,

consequently, giving rise to segregation. However, for the SFRSCC mixture with 30%

PFA cement replacement, the rheological parameter b remains somewhat constant up to an

equivalent fibre content of 20 kg per cubic meter. Increasing the equivalent steel fibre

content beyond 20 kg per cubic meter causes an increase in shear thickening behaviour,

SCC min g h A b

1 15 0.80 2.503 2.466 1.40

2 15 0.89 2.690 2.670 1.20

3 15 1.06 3.049 2.996 1.45

4 15 1.37 3.866 3.757 1.60

5 15 1.43 3.065 2.922 1.60

6 15 1.71 4.527 4.471 1.35

7 15 1.75 4.848 4.720 1.56

8 15 0.55 3.550 3.550 1.00

9 15 0.74 3.954 3.950 1.04

10 15 0.78 3.984 4.000 0.90

11 15 0.89 4.147 4.150 0.96

12 15 1.10 4.066 4.038 1.22

13 15 1.10 4.688 4.650 1.25

14 15 1.32 3.859 3.800 1.40

15 15 0.74 5.222 5.200 1.15

16 15 0.94 5.808 5.800 1.06

17 15 1.14 5.753 5.700 1.20

18 15 1.32 6.265 6.200 1.30

19 15 1.21 6.446 6.430 1.08

20 15 1.32 6.093 6.000 1.40

21 15 1.15 5.302 4.935 1.65

SFR

SC

CS

FRS

CC

wit

h P

FAS

FRS

CC

wit

h G

GB

S


80

i.e., increasing nonlinear behaviour. Therefore, this suggests that the use of PFA reduces

the yield parameter g, which influences the degree of shear thickening with an increase in

steel fibre content. For example, the obtained parameter indicative of yield (g) for the

SFRSCC mixture with 30% PFA cement replacement is somewhat lower than other

concrete mixtures (See Table 5.3).

Fig 5. 5: Effect of PFA and GGBS replacement

on the fundamental parameter, g.

Fig 5. 6: Effect of PFA and GGBS replacement

on the fundamental parameter, h.

From Fig 5.5 – 5.6, it can be seen that the use of 50% GGBS increases both the parameters

g and h when compared to 30% PFA replacement of cement. In addition, when comparing

the SFRSCC mixture with the mixtures containing 30% PFA and 50% GGBS cement

replacements, it can be seen that the use of these replacements causes an overall reduction

in yield value (g) and an increase in plastic viscosity (h).

During the two-point operation, it was later found that the idle pressure changes with time.

For example, the rheological parameters associated with SCC-1 were determined at times

corresponding to 15, 45 and 75 minutes after the addition of water. During this testing

regime, the idle pressures were recorded immediately after each test. However, when

testing SCC-2 to SCC-7 the idle pressures were not recorded after each test - instead they

were recorded after the initial test. i.e., the test corresponding to 15 minutes after the

addition of mixing water. In all cases, it was found that the idle pressure reduces with

time, especially at speeds ranging from 0.5 to 1.3 rev/s. Therefore, the obtained torque-

speed relationships associated with the rheological tests for SCC-2 to SCC-7 beyond 15

min after the addition of water are most likely incorrect due to changing idle pressures.

Intuitively, this means that both the torque intercept and the slope are, respectively,

overestimated and underestimated. Therefore, the tests carried out beyond 15 min after the

addition of water cannot be used to determine the correlation between the empirical values

and the rheological parameters. Nevertheless, the idle pressures corresponding to 15

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 5 10 15 20 25 30

Rh

eolo

gica

l par

amet

er, g

Steel fibre content (kg/m3)

SFRSCC

SFRSCC with PFA

SFRSCC with GGBS

0

1

2

3

4

5

6

7

0 5 10 15 20 25 30

Rh

eolo

gica

l par

amet

er, h


SFRSCC

SFRSCC with PFA

SFRSCC with GGBS


81

minutes after mixing were recorded and, therefore can be used to determine, if indeed, a

correlation exists.

Based on the above analysis, the torque intercept and slope and, therefore the yield value

and plastic viscosity increases with an increase in fibre content. However, the cube

strength of SCC-5, which has a lower viscosity when compared to SCC-4, was slightly

less than the encountered cube strengths of SCC-1 to SCC-7 (See appendix D). The reason

for this is most likely due to an error in batching.

Fig 5. 7: Correlation between g and h for SCC-1

to SCC-7, 15 min after addition of water.

Fig 5. 8: Correlation between g and h for SCC-8

to SCC-13, 15 min after addition of water.

Fig 5. 9: Correlation between g and h for SCC-8 to SCC-13, 15 min after addition of water.

Fig 5.7 – 5.9 illustrates the obtained correlation coefficients for SCC-1 to SCC-21, 15 min

after the addition of water. As shown in Fig 5.7, a second order polynomial function

seems to yield the best-fit correlation between the rheological parameters g and h, with a

best-fit correlation, R2, of 0.85. It is the author’s opinion that the obtained rheological

parameters (g and h) associated with SCC-7 are most likely underestimated, because

SCC-5SCC-1

SCC-2

SCC-3

SCC-4

SCC-6

SCC-7

h = 1.9389g2 - 2.7644xg+ 3.6014R² = 0.8552

0

1

2

3

4

5

6

7

8

0 0.4 0.8 1.2 1.6 2 2.4

Rh

eolo

gica

l par

amet

er, h

Rheological parameter, g

SCC-8

SCC-9SCC-10

SCC-11

SCC-12

SCC-13

SCC-14

h = 2.9232e0.3863g

R² = 0.8413

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

4.8

0.4 0.6 0.8 1 1.2 1.4

Rh

eolo

gica

l par

amet

er, h


SCC-15

SCC-16

SCC-17

SCC-18

SCC-19

SCC-20

SCC-21

y = 4.3618e0.2723x

R² = 0.708

4

4.5

5

5.5

6

6.5

7

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

Rh

eolo

gica

l par

amet

er, h



82

during testing a significant degree of segregation was encountered. Nevertheless, the

results for SCC-7 were included in this analysis. From Fig 5.8 – 5.9, an exponential

function seems to yield the best fit correlation between g and h for SCC-8 to SCC-13, and

SCC-15 to SCC-20 with best fit correlations of, respectively, 0.84 and 0.71. Also, the

torque-speed relationships and hence the obtained parameters g and h for SCC-14 and

SCC-21 were not included in this analysis, as the obtained torque-speed relationship for

these data points possessed a significant degree of nonlinearity, which is an indication of

segregation. Furthermore, during rheological testing a high degree of segregation was

encountered (i.e., there was a significant amount of coarse aggregates and steel fibres

stuck to the bottom of the mixing bowl) in SCC-14 and SCC-21, 15 min after the addition

of water. Furthermore, the flow index parameter b for SCC-14 and SCC-21 is considered

large, especially for SCC-21. For clarity, the data is not shown (but can be seen in

Appendix C4.1). It may be observed (Fig 5.7 – 5.9) that an increase in fibre content causes

an increase in g and h and, therefore an increase in, respectively, yield stress and plastic

viscosity. In addition, it may be observed (Fig 5.7 – 5.9) that the rheological parameter h

increases at a slightly larger rate than the rheological parameter g, with an increasing steel

fibre content.

5.3.2. Empirical tests

This section is aimed at illustrating the results obtained using the empirical test methods,

i.e., Slump flow, L-box and J-ring. Fig 5.10 – 5.12 illustrates the quantitative empirical

relationships for the obtained slump flow, and J-ring flow values versus the various SCC

mixtures, i.e., SCC-1 to SCC-21. For example, SCC-3, which possesses the equivalent of

10 kg of steel fibres per cubic meter, has a slump flow and J-ring flow of, respectively,

670 and 660 mm. Also from Fig 5.10 – 5.12, it can be seen that both the slump spread and

the J-ring spread measured values decrease with an increase in fibre content. However, in

some cases the slump and J-ring measured values increase. In considering the slight

increases in slump flow values with an increase in fibre content, this could be due to

experimental variability in recording the true spread value and/or an uneven distribution of

steel fibres prior to testing, i.e., in the mixer. In addition, the results presented in this

section were determined at approximately 15 to 40 minutes after mixing.


83

Fig 5. 10: Comparison of measured Slump spread

and J-ring spread values versus SCC-1 to SCC-7.


and J-ring spread values versus SCC-8 to SCC-

14.


and J-ring spread values versus SCC-15 to SCC-

21.

Fig 5. 13: Comparison of measured t500 times for

both the Slump flow and J-ring versus SCC-1 to

SCC-7.



SCC-14.



SCC-21.

0

100

200

300

400

500

600

700

800

630

640

650

660

670

680

690

700

710

1 2 3 4 5 6 7

J-ri

ng

spre

ad v

alu

e (m

m)

Slu

mp

flo

w s

pre

ad v

alu

e (m

m)

SCC mix number

Slump flow (SCC-1 to SCC-7)

J-ring slump flow (SCC-1 to SCC-7)

560

580

600

620

640

660

680

640

660

680

700

720

740

8 9 10 11 12 13 14

J-ri

ng

spre

ad v

alu

e (m

m)

Slu

mp

flo

w s

pre

ad v

alu

e (m

m)

SCC mix number

Slump flow (SCC-8 to SCC-14)

J-ring slump flow (SCC-8 to SCC-14)

620

640

660

680

700

720

660

680

700

720

740

760

15 16 17 18 19 20 21

J-ri

ng

slu

mp

flo

w (

mm

)

Slu

mp

flo

w s

pre

ad v

alu

e (m

m)

SCC mix number

SF, t500 time (SCC-15 to SCC-21)

JR, t500 time (SCC-15 to SCC-21)

0

1

2

3

4

5

6

7

8

9

0

0.5

1

1.5

2

2.5

3

3.5

4

1 2 3 4 5 6 7

J-ri

ng,

t50

0 ti

me

(sec

)

Slu

mp

flo

w, t

500

tim

e (s

ec)

SCC mix number



0

1

2

3

4

5

6

7

0

0.5

1

1.5

2

2.5

3

3.5

4

8 9 10 11 12 13 14

J-ri

ng,

t50

0 ti

me

(sec

)

Slu

mp

flo

w, t

500

tim

e (s

ec)

Concrete mix number


JR, t500 (SCC-8 to SCC-14)

0

1

2

3

4

5

6

7

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

15 16 17 18 19 20 21

J-ri

ng

slu

mp

flo

w, t

500

(sec

)

Slu

mp

flo

w, t

500

tim

e (s

ec)

SCC mix number




84

In some cases, the J-ring slump value increases with an increase in fibre content, this

could also be due to various errors in testing, both in performing the tests and measuring

the empirical values. Also, an uneven fibre distribution (i.e. in the mixer) would cause an

error in evaluating the true empirical value.

As shown in Fig 5.13 – 5.15, the slump flow t500 times and the J-ring t500 times are plotted

against their corresponding mix number. i.e., SCC-1 to SCC-21. Also in Figure 5.13 –

5.15, it can be seen that the t500 times for both the slump flow and J-ring increases with an

increase in fibre content, in most cases. It is important to recognise that a single operator

carried out these empirical tests and, therefore it is reasonable to assume that the measured

values contain errors. For example, the rate of speed at which the slump-cone is lifted will

influence the measured values of both the slump-flow spread and the t500 time. In addition,

the probability of error in recording the t500 time is considered high as a single operator has

to lift the cone and record the t500 time simultaneously.

Fig 5.16 – 5.18 illustrates the relationship between the measured empirical values of both

the L-box blocking ratio and the J-ring step of blocking versus their corresponding SCC

mix number (SCC-1 to SCC-21). Also from Fig 5.16 – 5.18, both the measured L-box and

J-ring blocking values indicate an increase in blocking with an increase in fibre content.

Fig 5. 16: Comparison of both the L-box and J-

ring blocking values for SCC-1 to SCC-7.

Fig 5. 17: Comparison of both the L-box and J-

ring blocking values for SCC-8 to SCC-14.

0

5

10

15

20

25

30

35

40

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7

J-ri

ng,

ste

p o

f b

lock

ing

(mm

)

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

SCC mix number

L-box (SCC-1 to SCC-7)J-ring (SCC-1 to SCC-7)

0

2

4

6

8

10

12

14

16

18

0

0.2

0.4

0.6

0.8

1

1.2

8 9 10 11 12 13 14

J-ri

ng,

ste

p o

f b

lock

ing

(mm

)

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

SCC mix number

L-box (SCC-8 to SCC-14)

J-ring (SCC-8 to SCC-14)


85

Fig 5. 18: Comparison of both the L-box and J-ring blocking values for SCC-15 to SCC-21.

Immediately apparent is the significant difference in the minimum acceptable passing

criteria for both the obtained L-box and J-ring results (See Fig 5.16 – 5.18). Of particular

significance is the difference between the obtained results for SCC-15 to SCC-21 and

SCC-1 to SCC-14. This is because the initial mix (SCC-1) possessed a relatively high

plastic viscosity, and the addition of GGBS for partial replacement of cement increased

the plastic viscosity, which consequently reduced the passing ability of SCC-15 to SCC-

21.

Fig 5. 19: Correlation between the L-box and J-ring blocking values for SCC-1 to SCC-21, 15 min after the

addition of water.

Fig 5.19 illustrates the correlation between the L-box blocking ratio (H2/H1) and the J-ring

step of blocking (mm). It may be observed that there exists a good linear relationship

between these empirical parameters, with an obtained correlation coefficient of 0.899.

0

5

10

15

20

25

30

35

0

0.2

0.4

0.6

0.8

1

1.2

15 16 17 18 19 20 21

J-ri

ng,

ste

p o

f b

lock

ing

(mm

)

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

SCC mix number

L-box (SCC-15 to SCC-21)

J-ring (SCC-15 to SCC-21)

SCC-1

SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7

SCC-8

SCC-9

SCC-10

SCC-11

SCC-12

SCC-13

SCC-14

SCC-15 SCC-16

SCC-17

SCC-18

SCC-19SCC-20

SCC-21

LB = -0.027JR + 1.098R² = 0.899

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35 40

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

J-ring, step of blocking (mm)

CV = -1.04


86

Also, the obtained coefficient of variation (CV) is -1.04 which suggests that J-ring step of

blocking is inversely related to the L-box blocking ratio. The following empirical

relationship may be obtained by the least square regression:

LB = 1.098 – 0.027(JR) (5. 1)

It is important to recognise that these tests were not performed simultaneously. Performing

the tests simultaneously eliminates the influence of various chemical reactions, idle times

and over mixing, which affects concrete workability and, consequently errors are included

in the empirical values. Nevertheless, the J-ring test was carried out following the L-box

test with an approximate in-between testing time of 5 to 10 minutes.

5.3.3. Correlation of empirical tests with rheological parameters

When testing SCC on-site it is not practical to determine the rheological characteristics of

SFRSCC by means of rheological testing. Therefore, various empirical tests have been

developed in an attempt to approximate these parameters for the successful placement of

SCC concerning both SCC filling and passing abilities. In this section, the results obtained

using the empirical test methods (i.e. Slump-flow, L-box and J-ring) were compared with

the rheological parameters, i.e., g and h. Therefore, this section is aimed at establishing

any possible correlations between the individual empirical test results and the obtained

rheological parameters for SCC-1 to SCC-21. In addition, the obtained parameters g and h

for SCC-14 and SCC-21 were not included in this analysis, i.e., the occurrence of

segregation.

Fig 5. 20: Correlation between empirical slump flow and the rheological parameter, g, 15 min after addition

of water.

SCC-1

SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7

SCC-8

SCC-10

SCC-9

SCC-11

SCC-12

SCC-13

SCC-15

SCC-16

SCC-17SCC-18

SCC-20

SCC-19

SCC-14

SCC-21

SF = -43g + 730.9R² = 0.796

640

650

660

670

680

690

700

710

720

730

0.00 0.50 1.00 1.50 2.00 2.50

Slu

mp

-flo

w s

pre

ad v

alu

e (m

m)


SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21

CV = -4.57


87

The variation in slump flow with g for SCC-1 to SCC-21, 15 min after the addition of

water is presented in Fig 5.20; Appendix E gives the individual correlations for SCC-1 to

SCC-21. It may be observed that there exists a linear relationship between the slump flow

value and the rheological parameter g with a correlation coefficient of 0.796. Also, in Fig

5.20 it can be seen that the obtained coefficient of variation (CV) is -4.57 which suggests

that the parameter g is inversely related to the slump flow for SCC-1 to SCC-21, 15 min

after the addition of water. As the parameter g increases, the slump value decreases. The

following empirical relation may be obtained by the least square regression, as illustrated

in Fig 5.20:

SF = 730.9 – 43(g) (5. 2)

Fig 5. 21: Correlation between empirical slump flow, t500 time and the rheological parameter, h, 15 min after

addition of water.

Fig 5.21 illustrates the variation of slump flow, t500 time with h for SCC-1 to SCC-21, 15

min after the addition of water; Appendix E gives the individual correlations for SCC-1 to

SCC-21. It may be observed that there exists a linear relationship between the rheological

parameters h and the slump flow t500 times with an obtained correlation coefficient of

0.835. Furthermore, as the rheological parameter h increases, the slump flow t500 time

increases and therefore the obtained coefficient of variation (CV) is +0.717, which suggest

that the slump flow t500 times are positively related to the parameter h. The following

SCC-1 SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7SCC-8

SCC-9

SCC-10

SCC-12

SCC-11

SCC-13

SCC-15

SCC-16

SCC-17

SCC-18

SCC-19

SCC-20

SCC-14

SCC-21

h = 1.628t500 - 0.68R² = 0.835

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6

Rh

eolo

gica

l par

ame

ter,

h

Slump-flow, t500 time (sec)

SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21

CV = 0.717


88

empirical relationship may be obtained by the least square exponential regression, as

illustrated in Fig 5.21:

h = 1.628(t500) -0.68 (5. 3)

It is important to recognise that certain nonlinear (i.e. exponential, polynomial and

logarithmic) regression models give slightly better fits. However, as observed, a linear

regression model was used. In addition, the existence of other correlations were examined,

the results of which can be seen in Appendix E.

5.3.4. Influence of time on the parameters

In this following section, the influence of time on the both the empirical and rheological

parameters after the addition of water are illustrated and discussed. Therefore, this section

is aimed at the following:

(i) Evaluating the influence of time on both the calculated rheological parameters

g and h, and the measured empirical parameters for SCC-1 to SCC-21.

(ii) Establishing any possible time evolution relationships between the individual

empirical test results and the obtained rheological parameters (g and h) for

SCC-1 to SCC-21.

Fig 5. 22: Time evolution of the rheological

parameter, g, for SCC-1 to SCC-7.



0

0.5

1

1.5

2

2.5

3

3.5

15 25 35 45 55 65 75 85 95

Rh

eolo

gica

l par

amet

er, g

Time after addition of water (min)

SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-7

0

0.5

1

1.5

2

2.5

15 25 35 45 55 65 75 85

Rh

eolo

gica

l par

amet

er, g


SCC-8 SCC-9SCC-10 SCC-11SCC-12 SCC-13SCC-14


89



Fig 5. 25: Time evolution of slump flow for SCC-

1 to SCC-7.

Fig 5.22 – 5.24 illustrates the time evolution relationships of the obtained g parameters for

SCC-1 to SCC-21. Immediately apparent in most cases is an increase in the yield value g

with an increase in time after the addition of water, which suggests that SCC-1 to SCC-21

is losing its fluidity over time. In addition, the overall increase in the rheological

parameter g for SCC-8 to SCC-21 is less severe when compared to SCC-1 to SCC-7,

which suggests that the workability of SFRSCC is retained for longer periods when

incorporating 30% PFA and 50% GGBS cement replacements. However, the change in

idle pressures were not recorded during the two-point workability testing of SCC-2 to

SCC-7.


8 to SCC-14.


15 to SCC-21.

The time evolution of the slump flow spread values for SCC-1 to SCC-21 are shown in

Fig 5.25 – 5.27. It may be observed that an increase in slump value occurs beyond the 15

0

0.5

1

1.5

2

15 25 35 45 55 65 75 85

Rh

eolo

gica

l par

amet

er, g

Time after mixing (min)

SCC-15 SCC-16

SCC-17 SCC-18

SCC-19 SCC-20

SCC-21

500

550

600

650

700

750

15 25 35 45 55 65 75 85 95

Slu

mp

sp

read

val

ue

(mm

)


SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-7

500

550

600

650

700

750

800

15 25 35 45 55 65 75 85

Slu

mp

sp

read

val

ue

(mm

)


SCC-8 SCC-9 SCC-10

SCC-11 SCC-12 SCC-13

SCC-14

500

550

600

650

700

750

800

15 25 35 45 55 65 75 85

Slu

mp

sp

read

val

ue

(mm

)


SCC-15 SCC-16

SCC-17 SCC-18

SCC-19 SCC-20

SCC-21


90

min testing time. This could be due to a number of things, such as: (i) testing and

recording errors (ii) insufficient mixing duration (approximately 3 minutes) and (iii) over

mixing, due to the number of tests (twelve) performed on the same sample.


parameter, h, for SCC-1 to SCC-7.


parameter, h, for SCC-8 to SCC-14


parameter, h, for SCC-15 to SCC-21.

Fig 5. 31: Time evolution of slump flow, t500 time

for SCC-1 to SCC-7.

Fig 5.28 – 5.30 shows the time evolution of obtained rheological parameter h and Fig 5.31

– 5.33 illustrates the time evolution of the measured slump flow t500 times; Appendix E

gives the time evolution relationship of the both J-ring t500 times and spread values. In

most cases, the parameters h and the slump flow t500 times are increasing with an increase

in time after the addition of water. This suggests a decrease in workability due to an

increase in time after the addition of water.

2

2.5

3

3.5

4

4.5

5

5.5

6

15 25 35 45 55 65 75 85 95

Rh

eolo

gica

l par

amet

er, h


SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-7

2

2.5

3

3.5

4

4.5

5

15 25 35 45 55 65 75 85

Rh

eolo

gica

l par

amet

er, h



4

4.5

5

5.5

6

6.5

7

15 25 35 45 55 65 75 85

Rh

eolo

gica

l par

amet

er, h


SCC-15 SCC-16

SCC-17 SCC-18

SCC-19 SCC-20

SCC-21

0

2

4

6

8

10

12

15 35 55 75 95

Slu

mp

flo

w, t

500

tim

e (s

ec)

Time after the addition of water (min)

SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-7


91





It is important to recognise that the occurrence of thixotropy is notable factor, especially

when conducting two-point workability tests on a concrete mixture beyond a sufficient

amount of time after the addition of water. Therefore, performing a two-point analysis on

such a concrete will most likely result in an inaccurate representation of the torque-speed

relationship and, therefore, an inaccurate relationship of shear stress to shear strain rate,

because an increase in energy (torque) at various speeds breaks the concrete structure

which, ultimately underestimates the rheological parameters g and h.

Fig 5. 34: Time evolution correlation between slump flow spread and the rheological parameter g for SCC-1

to SCC-20, 15 – 95 min after the addition of water.

1

1.5

2

2.5

3

3.5

4

15 25 35 45 55 65 75 85

Slu

mp

flo

w, t

500

tim

e (s

ec)


SCC-8 SCC-9 SCC-10


SCC-141

2

3

4

5

6

7

15 25 35 45 55 65 75 85

Slu

mp

flo

w, t

500

tim

e (s

ec)


SCC-15 SCC-16SCC-17 SCC-18SCC-19 SCC-20

y = -42.88x + 730.27R² = 0.7592

y = -47.472x + 761.58R² = 0.3808

y = -40.799x + 745.48R² = 0.1531

y = -35.468x + 734.67R² = 0.2152

500

550

600

650

700

750

800

0 0.5 1 1.5 2 2.5 3 3.5 4

Slu

mp

flo

w s

pre

ad (m

m)


SCC-1 to SCC-20, 15 min

SCC-1 to SCC-20, 30 - 65 min

SCC-1 to SCC-20, 60 - 95 min CV = -9.98


92

Fig 5. 35: Time evolution correlation between slump flow t500 time and the rheological parameter h for SCC-

1 to SCC-20, 15 – 95 min after the addition of water.

Fig 5.34 – 5.35 illustrates two plots, one of which illustrates the rheological parameter (g)

versus the slump flow value for SCC-1 to SCC-20 at different testing times from the

addition of mixing water (Fig 5.34). For example, the relationship between the measured

slump flows and the calculated rheological parameters of g for all the tests (i.e. SCC-1 to

SCC-20) corresponding to a testing time of 15 minutes after the addition of water are

illustrated in Fig 5.34 by the blue data points. The other (Fig 5.35) illustrates the

rheological parameters (h) versus the slump flow t500 times for SCC-1 to SCC-20 at

different testing times. Also, the obtained results for SCC-14 and SCC-21 were not

included in this analysis, because a high degree of segregation was encountered. In both

figures, linear regression was used and the correlation coefficients were determined. In Fig

5.34 – 5.35, the black dashed line represents a linear regression of all results obtained from

SCC-1 to SCC-20, 15 to 95 min after the addition of water. As shown in Fig 5.34 – 5.35, it

may be observed that the obtained g – slump flow correlation and coefficient of variance

for all the results is 0.22 and -9.98, respectively and 0.30 and 1.0 for the h – slump flow,

t500 time, respectively. In addition, these parameters correspond to testing times ranging

between 15 to 95 minutes after the addition of mixing water; Appendix E.6 gives the

individual correlations. In both cases, the obtained correlation coefficients are considered

low. However, the obtained COV parameters (-9.98 and 1.0) indicate that their relations

are going in the right direction, that is, inversely and positively related. This reason for

these poor correlations could be the result of a number of factors, such as: (i) the degree of

y = 0.5662x + 0.5478R² = 0.8498

y = 0.6264x + 0.6168R² = 0.4313

y = 0.5209x + 1.9468R² = 0.1477

y = 0.6142x + 0.8365R² = 0.3028

0

2

4

6

8

10

12

0 2 4 6 8 10

Slu

mp

flo

w, t

500

tim

e (s

ec)

Rheological parameter, h


SCC-1 to SCC-20, 30 - 65 min

SCC-1 to SCC-20, 60 - 95 min CV = 1.0


93

thixotropy and/or concrete hydration (setting) (ii) errors in performing the tests and

recording the data and (iii) an insufficient initial mixing time and/or over mixing the

concrete due to the high volume of tests performed on the same sample. What is

interesting is that the data points become more spread out with an increase in time after the

addition of mixing water, which can be observed from the obtained correlation

coefficients (R2) for each data set (See Fig 5.34 – 5.35).

Fig 5. 36: Time evolution correlation between L-box blocking ratio and J-ring step of blocking for SCC-1 to

SCC-21, 15 – 95 min after the addition of water.

In Fig 5.36, the combined obtained L-box blocking results are plotted versus the J-ring

step of blocking results. Linear regression was used and the correlation coefficient

determined; the obtained L-box – J-ring correlation is 0.83 and the obtained coefficient of

variation is -2.132 which suggests that the J-ring step of blocking is inversely related to

the L-box blocking ratio. Also in Fig 5.36, an outlier is illustrated (SCC-7, 95 min). The

main reason for this is because during the L-box testing of SCC-7, 95, the concrete failed

the test, and more importantly, its final resting point was at a considerable distance from

the end of the horizontal channel. For example, the degree of failure in the L-box ranges

from the sliding gate to the end of the horizontal channel, but not in contact with it. In

order to represent the appropriate correlation between the J-ring step of blocking and the

L-box blocking step, the concrete undergoing testing in the L-box must be at a distance of

a few millimetres from the end of the horizontal channel. Therefore, this value was not

included in this analysis. In addition, the data points associated with SCC-14 and SCC-21

were included in this analysis – mainly because the concrete was remixed before each L-

box and J-ring test.

y = -0.0291x + 1.091R² = 0.8297

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60 70

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



SCC-1 to SCC-21, 30 - 65 min

SCC-1 to SCC-21, 60 - 95 min

SCC-7, 95 min

CV = -2.132


94

5.3.5. Summary

This chapter has presented the selected testing sequence for evaluating the rheological and

empirical parameters of SFRSCC with PFA and GGBS CEM II/A-L cement replacements.

In considering the time evolution functional torque-speed relationship for SCC-1 to SCC-

21, the polynomial function seems to yield the best fit. In addition, the Hershel-Bulkley

model was adapted. Furthermore, the fitted Hershel-Bulkley parameters are presented for

SCC-1 to SCC-21.

A good correlation was shown to exist between the parameter g and h with an increase in

steel fibre contents. However, there is a considerable amount of error associated with the

Tattersall-two point apparatus. In addition, the rheological h increases at a slightly greater

rate than the rheological parameter g with an increase in steel fibre content.

The use of 30% PFA and 50% GGBS replacement of cement in SFRSCC caused an

overall reduction in the obtained rheological parameter g, while incorporating PFA and

GGBS increased the rheological h. In addition, the use of 50% GGBS cement replacement

(CEM II/A-L) reduced the passing ability of SFRSCC when compared to the use of 100%

CEM II/A-L – mainly because the initial mix (SCC-1) possessed a relatively high plastic

viscosity.

During TWT, it was found that the idle pressures decreases with time, especially within

speeds ranging from 0.3 to 1.3 rev/s.

Both the slump flow and J-ring spread values decreased with an increase in steel fibre

content, while the slump flow and J-ring t500 times increased with an increase in fibre

content. However, this was not the case in some cases. The reason for this could be due to

experimental variability in performing the tests and measuring the empirical values. Also,

an uneven fibre distribution (i.e. in the mixer) would most likely cause experimental

variability.

A good correlation was shown to exist between the L-box blocking ratio (H2/H1) and the

J-ring step of blocking (0.90) for SCC-1 to SCC-21, 15 min after the addition of water.

The workability of SFRSCC is retained for longer periods after the addition of water when

incorporating 30% PFA and 50% GGBS CEM II/A-L cement replacements.

In some cases, the obtained empirical values corresponding to 15 min after the addition of

water showed an increase in slump flows and a decrease in slump flow t500 times when


95

compared to the empirical tests carried out at 15 min after the addition of water. In

addition, poor correlations were shown to exist between the slump flow versus the

rheological parameter g (0.22) and the slump flow t500 time versus the rheological

parameter h (0.30) for SCC-1 to SCC-21, 15 to 95 min after the addition of water, which

suggests a third parameter is causing an increase in variation between the three testing

regimes and that parameter is time.


J-ring step of blocking (0.83) for SCC-1 to SCC-21, 15 to 95 min after the addition of

water. In addition, the obtained CV was -1.043 which suggests that the J-ring step of

blocking is inversely related to the L-box blocking ratio.

The obtained rheological parameters g and h showed reasonably good correlations (R2)

with, respectively, the inverted slump flow (0.796) and the inverted slump t500 time

(0.835) for SCC-1 to SCC-21, 15 min after the addition of water and cementitious

materials. The parameter g is inversely related to inverted slump flow with a coefficient of

variation (CV) of -4.57. Therefore, the parameter g decreases as inverted slump flow

increases. In addition, the parameter h is positively related to slump flow t500 time with a

coefficient of variation of +0.717. Therefore, the parameter h increases as inverted slump

flow t500 time increases. Intuitively, both these reasonably good correlations (R2) and

coefficients of variations (CV) suggest that the inverted slump flow test could be used

onsite instead of rheology to determine, once suitable calibration has been carried out, the

fundamental parameters of yield stress and plastic viscosity. In addition, the inverted

slump flow test could be used to determine the actual steel fibre content, when using the

relationships of g to slump flow, h to slump flow t500 time and the variation of g and h

with an increase in steel fibre content as proxy.

CHAPTER 6 – CONCLUSION AND RECOMMENDATIONS

96

6. CONCLUSION AND RECOMMENDATIONS

At commencement, this dissertation had four main and connected objectives. The author

aimed firstly to carry out a comprehensive literature review relating to:

Constituent materials used in SCC production.

Mechanism for achieving self-compactability.

Rheology and concrete rheometers.

Influence of constituent materials on SCC rheology and workability.

Mix procedure.

Empirical and rheological tests.

The second goal had two primary objectives: (i) to determine the performance of the two-

point workability apparatus and (ii) to determine an appropriate mix design for SFRSCC.

The third goal was to determine the fundamental and empirical characteristics of SFRSCC

with PFA and GGBS.

Finally, and based on the results of the previous three objectives, this dissertation sought

to determine the existence of any correlations between the fundamental and empirical

parameters.

6.1. Objective Number One: Conclusion

Carrying out the literature review proved useful for a number of reasons. The author

gained a vast knowledge of the production of self-compacting concrete. It also give an

insight into the importance of evaluating the fundamental rheological parameters of self-

compacting concrete, i.e., yield stress and plastic viscosity.

6.2. Objective Number Two: Conclusion

To satisfy objective two, two-point workability testing was carried out on both traditional

and self-compacting concrete mixtures. In addition, empirical and rheological tests were

performed on various self-compacting mixtures comprised of different proportions of

constituent materials. This was done to determine an appropriate mix design for SFRSCC

with regards to the minimum and maximum acceptable empirical criteria for SCC, as set

out by EFNARC.


97

The analysis of the two-point workability data for both the TVC and SCC are contained in

Chapter Four. In considering all the possible functional relationships for these mixes, it

may be observed that the polynomial function seems to produce the best-fit correlation

between torque and speed.

During TWT, it was noted that a high degree of slippage occurred within the interface

between the concrete and TWT bowl, especially at high speeds, such as 1.3 rev/s.

Therefore, steel ribs should be welded to the inside of the TWT bowl.

6.3. Objective Number Three: Conclusion

The result of the rheological and empirical characteristics are contained in Chapter Five.

In considering all the time evolution functional relationship of torque to speed, the

polynomial function seems to yield the best fit. Therefore, the Hershel-Bulkley model was

selected to represent these relationships. However, it is the opinion of the author that the

Hershel-Bulkley model is overestimating the obtained rheological parameter g.

Nevertheless, the Hershel-Bulkley model was used as the Bingham model resulted in a

negative g value on one occasion.

During TWT, an increase in segregation was encountered with an increase in steel fibre

content, especially at an equivalent fibre content of 30 kg per cubic meter. This suggests

that the fibres combined with the geometry of the impeller are disturbing the mix and,

therefore shows shear thickening behaviour.

The use of 30% PFA and 50% GGBS cement replacements in SFRSCC improved the

workability by causing an overall reduction in the obtained rheological parameter g.

However, both the use of PFA and GGBS increased the rheological parameter h and,

consequently made the mix more cohesive. The use of 50% GGBS reduced the passing

ability when compared to 100% CEM II/A-L. The reason for this was that the initial mix

(SCC-1) possesses a relatively high plastic viscosity. The workability of SFRSCC is

retained for longer periods after the addition of water when incorporating 30% PFA and

50% GGBS CEM II/A-L cement replacements.

It is important to recognise that the idle pressure changes with time. During TWT, it was

found that the idle pressures decreases with time, especially within speeds ranging from

0.3 to 1.3 rev/s.


98

6.4. Objective Number Four: Conclusion:

The rheological parameter g showed a reasonably good correlation with the rheological

parameter h with an increase in steel fibre content for SCC-1 to SCC-21, 15 min after the

addition of water. In addition, the rheological h increases at a slightly greater rate than the

rheological parameter g with an increase in steel fibre content.


J-ring step of blocking (0.90) for SCC-1 to SCC-21, 15 min after the addition of water. In

addition, the obtained CV (-1.043) suggests that the J-ring step of blocking is inversely

related to the L-box blocking ratio. Also, a good correlation was shown to exist between

the L-box blocking ratio (H2/H1) and the J-ring step of blocking (0.83) for SCC-1 to SCC-

21, 15 to 95 min after the addition of water. Therefore, the J-ring should be used to

evaluate the passing ability of SFRSCC, as the L-box is large and makes testing difficult.

Poor correlations were shown to exist between the slump flow versus the rheological

parameter g (0.22) and the slump flow t500 time versus the rheological parameter h (0.30)

for SCC-1 to SCC-21, 15 to 95 min after the addition of water. The reason for this and the

encountered increases and decreases in the obtained empirical values could be due to the

following:

Experimental variability, both performing the tests and recording the empirical

values;

insufficient mixing time and/or over mixing the concrete due to the high volume of

tests performed on a single sample and

the degree of thixotropy and/or the cement hydration rate.

However, good correlations were showed to exist between the relative parameter g and

slump flow and the relative parameter h and slump flow t500 time, 15 min after the addition

of both mixing water and cementitious materials. Therefore, quick and easy empirical tests

(such as the inverted slump flow test) could be used onsite instead of rheology to

determine, once suitable calibration has been carried out, the fundamental parameters of

yield stress and plastic viscosity. In addition, the inverted slump flow test could be used to

determine the actual steel fibre content, when using the relationships of g to slump flow, h

to slump flow t500 time and the variation of g and h with an increase in steel fibre content

as proxy.


99

It is recommended that the J-ring test be used to evaluate the passing ability of SFRSCC.

This will make passing ability testing of SFRSCC a lot easier, since the L-box test is very

large, heavy and makes testing difficult.

6.5. Recommendations

Further rheological and empirical research on SCC with both different types of

steel fibres and constituent materials. In doing so, once reasonably good

correlations are achieved, one could use quick and easy empirical tests (such as the

inverted slump flow test) on-site instead of rheology to determine, once suitable

calibration has been carried out, the fundamental parameters of yield stress and

plastic viscosity. In addition, once suitable correlations have been determined, the

inverted slump flow test could be used to determine the actual steel fibre content.

Weld steel ribs to the inside on the TWT bowl. In doing so, the degree of slippage

can be minimised.

Fabricate a coaxial vane arrangement for the two-point apparatus. In doing so, one

can evaluate the fundamental parameters of yield stress and plastic viscosity by the

use of the Reiner-Rivlin equation.

Expressing the rheological parameters of g and h into the fundamental units of,

respectively, yield stress and plastic viscosity by using Newtonian and non-

Newtonian materials of known flow properties.

The use of concrete simulation software (such as OpenFoam) to simulate the

empirical tests, i.e., slump flow, J-ring and L-box. In doing so, one could

determine, once reasonably good correlations exists between the simulated

empirical tests and the experimental empirical tests, a correlation between

rheology and empiricism.

Research on the influence of supplementary cementitious materials (such as PFA

and GGBS) on the steel fibre cement matrix.

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100

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http://www.icar.utexas.edu/publications/105/105_1.pdf

APPENDIX A – MIX DESIGN

109


A.1 – Mix design for SCC-1 to SCC-7




110

A.1 – Mix Design for SCC-1 to SCC-7.

SCC-1

Material Density (kg/m3)

Kg

VMA 7.8 0.146 SP 12.5 0.234 20 mm aggregate 0.0 0.000 10 mm aggregate 630 11.781 Fines/Sand 1020 19.074 Cement (CEM II) 580 10.846 Limestone filler 20 0.374 Water 215.5 4.030 Steel fibres 0.0 0.000 Total 2485.8 46.484

Fig A. 1: SCC-1 mix design.

SCC-2


Kg

VMA 7.8 0.146 SP 12.5 0.234 20 mm aggregate 0 0.000 10 mm aggregate 630 11.781 Fines/Sand 1020 19.074 Cement (CEM II) 580 10.846 Limestone filler 20 0.374 Water 215.5 4.030 Steel fibres 5 0.094 Total 2490.8 46.578


SCC-3


Kg



SCC-4


Kg



SCC-5


Kg



SCC-6


Kg



SCC-7


Kg




111

A.2 – Mix design for SCC-8 to SCC-14.

SCC-8


Kg

VMA 7.8 0.146 SP 12.5 0.234 20 mm aggregate 0 0.000 10 mm aggregate 630 11.781 Fines/Sand 1020 19.074 Cement 406 7.592 Limestone filler 20 0.374 PFA 174 3.254 Water 215.5 4.030 Steel fibres 0.00 0.000 Total 2485.8 46.484


SCC-9


Kg

VMA 7.8 0.146 SP 12.5 0.234 20 mm aggregate 0 0.000 10 mm aggregate 630 11.781 Fines/Sand 1020 19.074 Cement 406 7.592 Limestone filler 20 0.374 PFA 174 3.254 Water 215.5 4.030 Steel fibres 5 0.094 Total 2490.8 46.578


SCC-10


Kg



SCC-11


Kg



SCC-12


Kg



SCC-13


Kg



SCC-14


Kg




112

A.3 – Mix design for SCC-15 to SCC-21.

SCC-15


Kg

VMA 7.8 0.146 SP 12.5 0.234 20 mm aggregate 0 0.000 10 mm aggregate 630 11.781 Fines/Sand 1020 19.074 Cement 290 5.423 Limestone filler 20 0.374 GGBS 290 5.423 Water 215.5 4.030 Steel fibres 0 0.000 Total 2485.8 46.484


SCC-16


Kg



SCC-17


Kg



SCC-18


Kg



SCC-19


Kg



SCC-20


Kg



SCC-21


Kg



APPENDIX B –RHEOLOGICAL DATA

113

APPENDIX B – RHEOLOGICAL DATA

B.1 - Rheological data

APPENDIX C –TIME EVOLUTION RELATIONSHIPS

114

APPENDIX C – TIME EVOLUTION RELATIONSHIPS

C.1 – Time evolution relationship of torque versus speed for SCC-1 to SCC-7.



C.4 – Rheological parameters for SCC-1 to SCC21.


115

C.1 – Time evolution relationship of torque versus speed for

SCC-1 to SCC-7.

Fig C. 1: Time evolution of torque-speed relationship for SCC-1.

Fig C. 2: Time evolution of torque-speed relationship for SCC-2






R² = 0.998R² = 0.9958R² = 0.9645

y = 2.5027x + 0.8

y = 2.6893x + 0.93y = 2.9442x + 1.12

0

1

2

3

4

5

6

7

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9991R² = 0.9876R² = 0.9812

y = 2.6902x + 0.83y = 2.5798x + 1.19y = 3.1957x + 1.187

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9852R² = 0.9891R² = 0.9743

y = 3.0487x + 1.06y = 3.0508x + 1.53y = 3.8064x + 1.41

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9947R² = 0.9807R² = 0.9961

y = 3.8664x + 1.37

y = 3.6115x + 1.79y = 4.5593x + 1.63

0

1

2

3

4

5

6

7

8

9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9902R² = 0.9859R² = 0.9873

y = 3.0651x + 1.43y = 3.8243x + 1.27y = 3.9783x + 1.47

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9942R² = 0.9692R² = 0.9771

y = 4.5273x + 1.71y = 3.3287x + 2.49y = 3.9843x + 2.22

0

1

2

3

4

5

6

7

8

9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.991R² = 0.9875

R² = 0.9855y = 4.8476x + 1.75y = 4.9288x + 2.39y = 5.4509x + 2.99

0123456789

10111213141516

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)

SCC-7, 15 minSCC-7, 65 minSCC-7, 95 minHershel-Bulkley, 15 minHershel-Bulkley, 65 minHershel-Bulkley, 95 minPoly. (SCC-7, 15 min)Poly. (SCC-7, 65 min)Poly. (SCC-7, 95 min)Linear (Hershel-Bulkley, 15 min)Linear (Hershel-Bulkley, 65 min)


116


Fig C. 8: Time evolution relationship of torque versus speed for SCC-8.







R² = 0.9794R² = 0.9735R² = 0.9848

y = 3.55x + 0.5514y = 3.128x + 1.0851

y = 3.3438x + 1.279

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9927R² = 0.9891R² = 0.9947

y = 3.9536x + 0.7387y = 4.2908x + 1.005y = 4.4355x + 1.182

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9965R² = 0.98R² = 0.9743

y = 3.9839x + 0.78y = 4.1176x + 1.085

y = 4.3448x + 1.628

0

1

2

3

4

5

6

7

8

9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9879R² = 0.9866R² = 0.9793

y = 4.147x + 0.8875y = 4.3348x + 1.056

y = 4.6111x + 1.376

0

1

2

3

4

5

6

7

8

9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9887R² = 0.9923R² = 0.9689

y = 4.0659x + 1.098y = 4.0646x + 1.306y = 2.9621x + 2.043

0

1

2

3

4

5

6

7

8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9899R² = 0.9613R² = 0.9874

y = 4.6879x + 1.0987y = 4.1353x + 1.778

y = 4.7845x + 1.772

0

1

2

3

4

5

6

7

8

9

10

11

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9961R² = 0.9891R² = 0.9504

y = 3.8593x + 1.3229y = 3.8743x + 1.706

y = 4.0053x + 2.099

0

1

2

3

4

5

6

7

8

9

10

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)



117



Fig C. 16: Time evolution relationship of torque versus speed for SCC-16





Fig C. 21: Time evolution relationship of torque to speed for SCC-21.

R² = 0.9935R² = 0.9998R² = 0.9994

y = 5.2219x + 0.7372y = 5.9379x + 0.815y = 5.9278x + 1.04

0

1

2

3

4

5

6

7

8

9

10

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9942R² = 0.998

R² = 0.9893y = 5.8084x + 0.942

y = 6.1695x + 1.003

y = 5.748x + 1.48

0

1

2

3

4

5

6

7

8

9

10

11

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9901R² = 0.9927R² = 0.9859

y = 5.7532x + 1.1338y = 6.4274x + 1.22y = 6.2513x + 1.626

0

1

2

3

4

5

6

7

8

9

10

11

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9985R² = 0.9945

R² = 0.9938y = 6.2648x + 1.317y = 6.533x + 1.489

y = 6.75x + 1.616

0

1

2

3

4

5

6

7

8

9

10

11

12

13

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9991R² = 0.9951R² = 0.9938

y = 6.4461x + 1.206y = 6.5802x + 1.45y = 6.7141x + 1.616

0

1

2

3

4

5

6

7

8

9

10

11

12

13

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9985R² = 0.9946R² = 0.9941

y = 6.0932x + 1.319y = 6.437x + 1.556y = 6.6822x + 1.684

0

1

2

3

4

5

6

7

8

9

10

11

12

13

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)


R² = 0.9951R² = 0.9956R² = 0.9897

y = 5.3022x + 1.538y = 5.5873x + 1.668

y = 5.7271x + 1.611

0

2

4

6

8

10

12

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

Torq

ue

(N/m

)

Speed (rev/s)



118

C.4 - Hershel-Bulkley Rheological parameters for SCC-1 to SCC-21.

Table C. 1: Rheological parameters for SCC-1 to SCC-7.


min g h A b

SCC-1 15 0.80 2.503 2.466 1.4045 0.93 2.689 2.650 1.4075 1.12 2.944 2.900 1.38

SCC-2 15 0.89 2.690 2.670 1.2040 1.19 2.579 2.550 1.3275 1.19 3.196 3.180 1.17

SCC-3 15 1.06 3.049 2.996 1.4530 1.53 3.051 2.950 1.6760 1.41 3.806 3.770 1.27

SCC-4 15 1.37 3.866 3.757 1.6030 1.79 3.612 3.356 2.1385 1.63 4.559 4.450 1.55

SCC-5 15 1.43 3.065 2.922 1.6045 1.27 3.824 3.821 1.0075 1.47 3.978 3.980 1.00

SCC-6 15 1.71 4.527 4.471 1.3545 2.49 3.328 3.176 1.8675 2.22 3.984 3.965 1.18

SCC-7 15 1.75 4.848 4.720 1.5665 2.39 4.929 4.690 1.8695 2.99 5.451 5.259 1.72

min g h A b

SCC-8 15 0.55 3.550 3.550 1.0060 1.08 3.128 3.100 1.2780 1.28 3.344 3.320 1.23

SCC-9 15 0.74 3.954 3.950 1.0445 1.01 4.290 4.280 1.1065 1.18 4.435 4.400 1.25

SCC-10 15 0.78 3.984 4.000 0.9045 1.09 4.118 4.100 1.1585 1.63 4.345 4.300 1.30

SCC-11 15 0.89 4.147 4.150 0.9645 1.01 4.335 4.300 1.2575 1.38 4.611 4.550 1.36

SCC-12 15 1.10 4.066 4.038 1.2250 1.31 4.065 4.000 1.4185 2.04 2.962 2.792 1.99

SCC-13 15 1.10 4.688 4.650 1.2550 1.78 4.135 3.890 2.0085 1.77 4.785 4.560 1.86

SCC-14 15 1.32 3.859 3.800 1.4045 1.71 3.874 3.780 1.5575 2.10 4.005 3.775 1.99


119


min g h A b SCC-15 15 0.74 5.222 5.200 1.15 30 0.82 5.938 5.900 1.17 60 1.00 5.928 5.900 1.77 SCC-16 15 0.94 5.808 5.800 1.06 40 1.00 6.169 6.100 1.32 65 1.50 5.748 5.550 1.70 SCC-17 15 1.14 5.753 5.700 1.20 50 1.22 6.427 6.380 1.25 85 1.63 6.251 6.100 1.35 SCC-18 15 1.32 6.265 6.200 1.30 35 1.49 6.533 6.450 1.35 65 1.62 6.750 6.650 1.39 SCC-19 15 1.21 6.446 6.430 1.08 40 1.45 6.580 6.500 1.34 75 1.62 6.714 6.600 1.43 SCC-20 15 1.32 6.093 6.000 1.40 35 1.56 6.437 6.340 1.37 60 1.68 6.682 6.580 1.40 SCC-21 15 1.15 5.302 4.935 1.65 40 1.67 5.587 5.230 2.05 80 1.61 5.727 5.500 1.77

APPENDIX D –COMPRESSIVE STRENGTHS

120

APPENDIX D – COMPRESSIVE STRENGTHS

D.1 - Cube Strengths

Table D. 1: Obtained seven day cube strengths for SCC-1 to SCC-21.

Fig D. 1: Comparison of the 7-day strength developments for SCC-1 to SCC-21

Cube Strengths 7 day strength (N/mm) STDEV

SCC-1 67.9 1.284152

SCC-2 66.5

SCC-3 67.1

SCC-4 68.1

SCC-5 64.7

SCC-6 65.8

SCC-7 68

SCC-8 35.8 1.082765

SCC-9 36.7

SCC-10 35.4

SCC-11 34.7

SCC-12 36.8

SCC-13 33.9

SCC-14 36.4

SCC-15 52.6 1.502221

SCC-16 54.5

SCC-17 54.5

SCC-18 54.5

SCC-19 52.1

SCC-20 56.3

SCC-21 55.6

SFR

SCC

SF

RSC

C w

ith

PFA

SFR

SCC

wit

h G

GB

S

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

7-D

ay s

tren

gth

(N

/mm

)


SFRSCC

SFRSCC with 30% PFA

SFRSCC with 50% GGBS

STD: 1.3

STD: 1.08

STD: 1.5

APPENDIX E – CORRELATION BETWEEN EMPIRICAL AND RHEOLOGICAL PARAMETERS

121


E.1 Correlation between empirical and rheological parameters for SCC-1 to SCC-7



E.4 Correlation between empirical and rheological parameters

E.5 Time evolution of empirical tests

E.6 Time evolution correlation between empirical and rheological parameters


122

E.1 - Correlations between empirical and rheological parameters for SCC-1 to

SCC-7.

Fig E. 1: Correlation between workability

parameters and g for SCC-1 to SCC-7, 15 min

after addition of water.


parameters and h for SCC-1 to SCC-7, 15 min


Fig E. 3: Correlation of workability parameters

and g for SCC-1 to SCC-7, 15 min after addition

of water.

Fig E. 4: Correlation of workability parameters

and h for SCC-1 to SCC-7, 15 min after addition

of water.

Fig E. 5: Correlation between L-box blocking ratio and J-ring step of blocking, 15 min after addition of

water.

SCC-1

SCC-2

SCC-3

SCC-4SCC-5

SCC-6

SCC-7

y = -36.713x + 724.76R² = 0.7585

640

650

660

670

680

690

700

710

0.7 0.9 1.1 1.3 1.5 1.7 1.9

Spre

ad (

mm

)

g

SCC-1SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7

y = 1.4099x - 0.3086R² = 0.6118

0

1

2

3

4

5

6

7

1.5 2.5 3.5 4.5

h

Slump flow, t500 (sec)

SCC-1SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7

y = 0.5151x - 0.1041R² = 0.4867

0

0.5

1

1.5

2

2.5

1.5 2.5 3.5 4.5

g


SCC-1

SCC-2

SCC-3

SCC-5

SCC-4

SCC-6

SCC-7

y = -15.564x + 732.03R² = 0.8124

640

650

660

670

680

690

700

710

0.7 1.7 2.7 3.7 4.7 5.7

Spre

ad (

mm

)

h

SCC-1SCC-2

SCC-3

SCC-4

SCC-5

SCC-6

SCC-7

y = -0.0386x + 1.2043R² = 0.9835

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



123

E.2 - Correlations between empirical and rheological parameters for SCC-8 to

SCC-14.













Fig E. 10: Correlation between L-box blocking ratio and J-ring step of blocking, 15 min after addition of

water.

SCC-8

SCC-9

SCC-10

SCC-11

SCC-12SCC-13

SCC-14

y = -0.0144x + 10.864R² = 0.8916

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

650 675 700 725 750

g

Slump flow spread (mm)


SCC-14, 15 min

SCC-9

SCC-8

SCC-10

SCC-11

SCC-12

SCC-13

SCC-14

y = 0.7282x + 2.0724R² = 0.745

2

2.5

3

3.5

4

4.5

5

5.5

1 2 3 4 5

h



SCC-14, 15 min

SCC-8

SCC-9

SCC-10 SCC-11

SCC-12

SCC-13

SCC-14y = 0.2452x + 0.1471

R² = 0.214

0

0.2

0.4

0.6

0.8

1

1.2

1.4

2 2.5 3 3.5 4

g

Slump flow t500 time (sec)

SCC-8 to SCC-13, 15 minSCC-14, 15 min

SCC-8

SCC-9

SCC-10

SCC-11

SCC-12

SCC-13

SCC-14

y = -0.0252x + 21.616R² = 0.9263

3

3.2

3.4

3.6

3.8

4

4.2

4.4

4.6

4.8

5

640 660 680 700 720 740

h



SCC-14, 15 min

SCC-8SCC-9

SCC-10

SCC-11

SCC-12

SCC-13

SCC-14

y = -0.0296x + 1.1099R² = 0.9508

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)


SCC-8 to SCC-14, 15 minLinear (SCC-8 to SCC-14,…


124

E.3 - Correlation between empirical and rheological parameters for SCC-15 to

SCC21.













SCC-15

SCC-16SCC-17

SCC-18

SCC-19

SCC-20

SCC-21

y = -0.0174x + 12.885R² = 0.7815

0

0.4

0.8

1.2

1.6

2

650 670 690 710 730 750

g



SCC-21, 15 min

SCC-15

SCC-16

SCC-17

SCC-18

SCC-19

SCC-20

SCC-21

y = 1.2739x + 0.8938R² = 0.802

4

4.5

5

5.5

6

6.5

7

3 3.5 4 4.5

h

Slump flow, t500 time (sec)


SCC-21, 15 min

SCC-15 SCC-16

SCC-17

SCC-18

SCC-19SCC-20SCC21

y = 0.6661x - 1.5153R² = 0.7762

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2.5 3 3.5 4 4.5

g

Slump flow, t500 time (sec)


SCC-21, 15 min

SCC-15

SCC-16

SCC-17

SCC-18SCC-19

SCC-20

SCC-21

y = -0.0241x + 22.231R² = 0.4239

3

3.5

4

4.5

5

5.5

6

6.5

7

660 680 700 720 740 760

h



SCC-21, 15 min


125

E.4 - Correlation between empirical and rheological parameters

Fig E. 15: Correlation between L-box blocking ratio and J-ring step of blocking for SCC-15 to SCC-21, 15

min after the addition of water.

Fig E. 16: Correlation between J-ring spread value and the rheological parameter, g for SCC-1 to SCC-21,

15 min after the addition of water.

Fig E. 17: Correlation between the rheological parameter, h and the J-ring, t500 time for SCC-1 to SCC-21,

15 min after the addition of water.

SCC-15

SCC-16

SCC-17

SCC-18SCC-19

SCC-20SCC-21

y = -0.0252x + 1.0995R² = 0.908

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



y = -60.798x + 715.38R² = 0.3176

500

550

600

650

700

750

0 0.5 1 1.5 2 2.5

J-ri

ng

spre

ad v

alu

e (m

m)


SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-14 to SCC-20

SCC-14 and SCC-21

y = 0.5385x + 1.9082R² = 0.3378

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12

Rh

eolo

gica

l par

amet

er, h

J-ring slump-flow, t500 time (sec)

SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21


126

Fig E. 18: Correlation between the L-box blocking ratio and the slump flow value for SCC-1 to SCC-21, 15

min after the addition of water.

Fig E. 19: Correlation between the L-box blocking ratio and the rheological parameter, g for SCC-1 to SCC-

21, 15 min after the addition of water.

Fig E. 20: Correlation between the L-box blocking ratio and the rheological parameter, h for SCC-1 to SCC-

21, 15 min after the addition of water.

y = 0.0076x - 4.4107R² = 0.506

0

0.2

0.4

0.6

0.8

1

1.2

1.4

640 660 680 700 720 740 760

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

Slump-flow spread value (mm)

SCC-1 to SCC-7

SCC-7 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21

y = -0.1021x2 - 0.1446x + 1.0963R² = 0.5547

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)


SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21

y = -0.0651x + 1.0938R² = 0.2087

0

0.2

0.4

0.6

0.8

1

1.2

0.00 2.00 4.00 6.00 8.00 10.00

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)

h

SCC-1 to SCC-7

SCC-8 to SCC-13

SCC-15 to SCC-20

SCC-14 and SCC-21


127

E.5 - Time evolution of empirical tests

Fig E. 21: Time evolution of J-ring flow value for

SCC-1 to SCC-7.

Fig E. 22: Time evolution of J-ring, t500 time for

SCC-1 to SCC-7.


SCC-8 to SCC-14.


SCC-8 to SCC-14.


SCC-15 to SCC-21


SCC-15 to SCC-21.

400

450

500

550

600

650

700

750

15 25 35 45 55 65 75 85 95

J-ri

ng

spre

ad v

alu

e (m

m)


SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-70

2

4

6

8

10

12

14

15 35 55 75 95

J-ri

ng

slu

mp

flo

w, t

500

(sec

)


SCC-1 SCC-2 SCC-3

SCC-4 SCC-5 SCC-6

SCC-7

450

500

550

600

650

700

750

15 25 35 45 55 65 75 85

J-ri

ng

spre

ad v

alu

e (m

m)


SCC-8 SCC-9 SCC-10


SCC-14

0

1

2

3

4

5

6

7

8

15 25 35 45 55 65 75 85

J-ri

ng

slu

mp

flo

w, t

500

(sec

)


SCC-8 SCC-9 SCC-10


SCC-14

0

2

4

6

8

10

12

14

15 25 35 45 55 65 75 85

J-ri

ng

slu

mp

flo

w, t

500

(sec

)


SCC-15 SCC-16

SCC-17 SCC-18

SCC-19 SCC-20400

450

500

550

600

650

700

750

15 25 35 45 55 65 75 85

J-ri

ng

spre

ad v

alu

e (m

m)




128

E.6 - Time evolution correlation between empirical and rheological parameters

Fig E. 27: Time evolution correlations between Slump flow and the rheological parameter, g, for SCC-1 to

SCC-7.

Fig E. 28: Time evolution correlations between Slump flow, t500 time and the rheological parameter, h, for

SCC-1 to SCC-7.

Fig E. 29: Time evolution correlation between L-box ratio and J-ring step of blocking for SCC-1 to SCC-7.

y = -35.4x + 721.69R² = 0.703

y = -39.988x + 736.92R² = 0.2987

y = -34.458x + 697.06R² = 0.2658

y = -39.792x + 723.38R² = 0.332

500

550

600

650

700

750

0 1 2 3 4

Slu

mp

flo

w s

pre

ad v

alu

e (m

m)

g


SCC-1 to SCC-7, 30 - 65 min

SCC-1 to SCC-7, 60 - 95 min

y = 0.4991x + 0.9139R² = 0.6876

y = 1.4426x - 1.6688R² = 0.5079

y = 2.5281x - 4.886R² = 0.7348

y = 1.6647x - 2.3488R² = 0.5069

0

2

4

6

8

10

12

2 3 4 5 6

Slu

mp

sp

read

, t5

00

tim

e (s

ec)

h


SCC-1 to SCC-7, 30 - 65min

y = -0.0327x + 1.0911R² = 0.8948

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



SCC-1 to SCC-7, 30 - 65minSCC-1 to SCC-7, 60 - 95min


129


SCC-14.

Fig E. 31: Time evolution correlations between slump flow t500 time and the rheological parameter, h for

SCC-8 to SCC-14.

Fig E. 32: Time evolution correlation between L-box ratio and J-ring step of blocking for SCC-8 to SCC-14.

y = -67.924x + 754.28R² = 0.9183

y = -69.341x + 792.22R² = 0.3395

y = -12.993x + 713.98R² = 0.0311

y = 5.0466x + 698.9R² = 0.0157

500

550

600

650

700

750

800

0 0.5 1 1.5 2 2.5

Slu

mp

flo

w s

pre

ad v

alu

e (m

m)

g


SCC-8 to SCC-14, 45 - 60 min

SCC-8 to SCC-14, 60 - 85 min

y = 0.8735x - 0.7338R² = 0.2871

y = -0.3436x + 4.096R² = 0.054

y = 0.1238x + 2.617R² = 0.0509

y = 0.0838x + 2.5121R² = 0.0078

0

0.5

1

1.5

2

2.5

3

3.5

4

2 2.5 3 3.5 4 4.5 5

Slu

mp

sp

read

, t5

00

tim

e (s

ec)

h


SCC-8 to SCC-14, 45 - 60 min

SCC-8 to SCC-14, 60 - 85 min

y = -0.0337x + 1.1301R² = 0.9345

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



Scc-8 to SCC-14, 45 - 60 min

SCC-8 to SCC-14, 60 - 85 min


130


SCC-21.

Fig E. 34: Time evolution correlations between Slump flow, t500 time and the rheological parameter, h, for

SCC-15 to SCC-20.

Fig E. 35: Time evolution correlation between L-box ratio and J-ring step of blocking for SCC-15 to SCC-

21.

y = -40.804x + 723.59R² = 0.6421 y = -38.113x + 751.18

R² = 0.2391

y = -66.238x + 808.37R² = 0.1877

y = -8.5556x + 707.72R² = 0.0083

600

620

640

660

680

700

720

740

760

780

0.6 0.8 1 1.2 1.4 1.6 1.8

Slu

mp

flo

w s

pre

ad (m

m)


SCC-15 to SCC-20, 15 min SCC-15 to SCC-20, 30 - 50 minSCC-15 to SCC-20, 60 - 80 min SCC-21, 15 minSCC-21, 40 min SCC-21, 80 min

y = 0.6333x + 0.1835R² = 0.8288

y = 1.183x - 2.9442R² = 0.1634

y = 1.2715x - 3.3153R² = 0.3718

y = 1.1617x - 2.7926R² = 0.4173

0

1

2

3

4

5

6

7

4 4.5 5 5.5 6 6.5 7 7.5

Slu

mp

flo

w, t

50

0 t

ime

(sec

)

Rheological parameter, h


SCC-15 to SCC-20, 30 - 50 min

SCC-15 to SCC-20, 60 - 85 min

SCC-21, 15 - 85 min

y = -0.0268x + 1.1263R² = 0.8412

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50

L-b

ox

blo

ckin

g ra

tio

(H

2/H

1)



SCC-15 to SCC-21, 30 - 50min

APPENDIX F– TWO-POINT THEORY AND CALIBRATION

131

APPENDIX F – TWO-POINT THEORY AND CALIBRATION

F.1 Theory of the Two-point method

F.2 Calculation of results and calibration


132

F.1 - Theory of the Two-point method

According to Tattersall and Banfill (1983), there are numerous parameters that the affect

power consumption (P) during mixing, such as the diameter of the impeller D, the speed

of the impeller N, the density of the fluid undergoing mixing ρ, the viscosity of the fluid η

and gravitational acceleration gr and is expressed in the following form:

P = f(D, N, ρ, η, gr) (F. 1)

The relationship between these various parameters can be expressed in terms of

dimensionless groups:

Np = P

𝑁3𝐷5𝜌 . (F. 2)

Re = 𝐷2𝑁𝜌

η . (F. 3)

Fr = 𝑁2𝐷

𝑔𝑟 . (F. 4)

Where Np is the power number, Re is the Reynolds number and Fr is the Froude number.

Determining these dimensionless groups allows equation (F. 1) to be written as

Np = B Rex Fry . (F. 5)

Where B is a constant and x and y are unknown. The term B is known as the apparatus

constant and its value depends on the geometry of the apparatus. The terms x and y

depend on the flowing nature of the concrete. According to Tattersall and Banfill (1983),

the term y is zero for baffled mixers and in laminar flow the Froude number is equal to

one. Therefore, equation (F. 5) becomes:

Np = B Rex . (F. 6)

In order to determine the values of B and x, a range of experimental values are plotted,

i.e., log Np vs log Re. The term x is the slope of this straight-line relationship.

Fig F. 1: Relationship between power number and Reynolds number for a mixer (after Tattersall 1983).

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8

Log Np

Log Re

A

B

C

D

Laminar

Transitional

Turbulent


133

Fig F.1 illustrates the various flow regimes, in that the region between A and B is

consistent with laminar flow, B-C is the transition region and C-D is the turbulent region.

Providing that the flow in the Two-point workability apparatus is consistent with laminar

flow, the slope of this linear laminar region is equal to -1. In this case, the region A-B is

important during mixing conditions as resistance to flow within the laminar region is only

caused by viscous forces and not on inertial forces as is the case for transitional and

turbulent regimes. Therefore, equation (F. 6) can be written as:

Np = B Re-1 . (F. 7)

If T is the torque and P = 2πTN, then equation (F. 2) can be written as:

Np = T

𝑁2𝐷5𝜌 .

Equation (7) can also be written as:

In Np =In B + x In Re . (F. 8)

Where plotting In Np vs In Re determines the constants B and x. The constant B is

determined by the intercept on the y axis (In Np axis) and x is the slope of the straight line

relationship.

As previously mentioned the shear stress for a Bingham material is equal to the viscosity

multiplied by the shear rate (τ = ηγ).

Extensive experiments performed by Tattersall and Banfill (1983) found that for a

Newtonian fluid in the Two-point apparatus, the torque is proportional to viscosity and the

rotational velocity of the impeller in the form:

T = GηN . (F. 9)

Where G is the apparatus constant. If G = BD3, then substituting equation (F. 9) in

equation (F. 8), it can be shown that the slope (x) of the log/log plot is equal to -1 in the

form:

Log Bn

N𝐷2𝜌 = Log B + x Log Re . (F. 10

This negative slope of 1 suggests that the apparatus is operating under laminar conditions.

In addition, plotting In Np against In Re as in equation (F. 8) should produce a straight line

relationship with a slope (x) of -1.


134

According to Tattersall and Banfill (1983), the average shear rate in the Two-point

apparatus is proportional to the speed of the impeller, expressed in the following form:

γ = KN . (F. 11)

Actuality, the rate of shear varies from point to point on the flow curve. However, it is not

feasible to perform a full shear rate analysis, so equation (F. 11) is assumed and adopted.

where γ is the shear rate, K is the constant of proportionality or the mean shear rate and N

is the speed (rev/s).

As previously mentioned, and for a Non-Newtonian material, the apparent viscosity is

equivalent to the viscosity of a Newtonian material at similar shear rates. Therefore, the

apparent viscosity for a Bingham material can be determined by the following:

ηapp = τo

γ η . (F. 12)

Substituting equations (F. 11) and (F. 12) in equation (F. 3) allows one to deduce the Re

number with respect to the apparent viscosity in the form:

Re = D2Nρ

(τo

KN)+η

. (F. 13)

Substituting equation (F. 13) into equation (F. 7) yields the following:

T

𝑁2𝐷5𝜌 = B(

D2Nρ

(τo

KN)+η

)-1

T

𝑁2𝐷5𝜌 = B (

(τo

KN)

D2Nρ) + B (

η

D2Nρ)

T = BD3 (τo

K) + BD3 (ηN)

T = BD3

K τo + BD3 ηN. (F. 14)

Comparing equation (14) with

T = g + hN (F. 15)

yields

g = BD3

K τo, (F. 16)

h = BD3 η. (F. 17)


135

For a pseudoplastic or dilatant material, the following shear stress-shear rate relationship

can be assumed, which obeys the power law:

τ = rϔs . (F. 18)

Re = D3𝑁𝜌

r(KN)(s−1) . (F. 19)

Substituting equations (F. 11), (F. 18) and (F. 19) in equation (F. 7) yields the following:

T

𝑁2𝐷5𝜌 = B (

D3𝑁𝜌

r(KN)(s−1))-1

T

𝑁𝐷3 = B rKs-1

T = BD3 rKs-1 Ns . (F. 20)

In both the Two-point apparatus and rheometer, equation (F. 20) suggests that a power law

fluid should adhere to a power law relationship and the power index (s) should be of the

same value in both the Two-point apparatus and the viscometer undergoing similar

shearing rates. However, the power law relationship between torque and speed for the

two-point apparatus is assumed as equation (F. 18), but in the following form:

T = pNq . (F. 21)

Therefore

ηapp = T/N

G =

pNq−1

G . (F. 22)

Where G is known as the apparatus constant and is obtained by plotting a straight line

relationship between T/N and η for a series of Newtonian materials or a series of different

viscosities for the same Newtonian material, i.e., different temperatures. The terms p and q

are, respectively, constants which describe the consistency of the concrete and the type of

flow curve.

Comparing the value of ηapp from equations (F. 18) and (F. 22), the rate of shear is in the

following form:

ϔ = (p

rG)1/(s-1) N(q-1)/(s-1) (F. 23)

If the indices for the power law fluid, q and s, are equal in value, the relationship between

ϔ and N does not depend on N and hence the proportionality constant K is given by


136

K = (p

rG)1/(s-1) (F. 24)

If the indices are not equal, it should be written as

K = (p

rG)1/(s-1) N(q-1)/(s-1) (F. 25)

In addition, and as G = BD3, equations (F. 16) and (F. 17) can be expressed as

τo = K

G g (F. 26)

and

η = 1

G h . (F. 27)

F.2 - Calculation of results and Calibration

Calibrating the two-point apparatus involves two-stage calibration. Firstly, the torque must

be calibrated with the pressure, known as the torque/pressure calibration constant. To

determine the torque/pressure calibration constant a lever arm is attached to the impeller

shaft by means of a clamp. A spring balance is then attached to both the free end of the

lever arm and the frame of the apparatus. This allows the resulting breaking force (kg) to

be measured at various pressures (lb/in2). A graph is then plotted of pressure against

breaking force and the slope of this straight-line relationship is used to obtain the

calibration constant C:

C = 9.81 * lever arm (m) * (1/slope) (F. 28)

Where 9.81 m/s2 converts Kilograms (Kg) to Newton’s (N) and the lever arm (m) converts

Newton’s (N) to Newton meter (Nm) and therefore the torque T is obtained by the

following equation:

T = C * P (F. 29)

Where P is the pressures obtained during testing.

By calibrating the rheometer with oils of known rheological properties, one can relate the

measured rheological values g and h with the fundamental parameters τ0 and µ (Tattersall

and Banfill, 1983; Cullen and West, 2005). Fig F.2 adapted from Banfill (2001) illustrates

the relationship between the measured units of both torque and rotational speed with the

fundamental units of shear stress and shear rate.


137

Fig F. 2: Relationship between the measured units and rheological parameters (after Banfill 2001).

Obtaining the calibration constants is very straightforward and this following section will

set out to do just that. As previously mentioned, Tattersall and Banfill (1983) suggested

the following equations for calibrating the two-point workability test with known

rheological parameters for Newtonian fluids:

τ0 = K

Gg (F. 30)

µ = 1

Gh (F. 31)

As previously mentioned, when shearing the material in the two-point workability

apparatus, the rate of shear varies but it is assumed that there is a mean effective shear rate

which is proportional to the speed of the vane given by

γ = KN (F. 32)

The apparatus constant G is obtained by plotting and comparing a straight line relationship

between T/N and η for a series of Newtonian materials or a series of different viscosities

for the same Newtonian material, i.e., a Newtonian fluid of different temperatures in both

the two-point apparatus and the rheometer. The viscosity of the Newtonian fluids at

various temperatures in the two-point test are determined by interpolating the viscosities

obtained from the rheometer and hence the apparatus constant is obtained from the

following equation:

G = T/N

η (F. 33)

In addition, the viscosity of the selected Newtonian fluid should fall within the range of

typical viscosities of SCC.


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The constant K is proportional to the yield stress and is known as the mean shear rate,

which is obtained by comparing the power-law relationship between torque and angular

velocity in the two-point apparatus and that obtained from a rheometer. It is important to

recognise that evaluating the calibration constant K requires the use of a power law fluid

of a known viscosity, and the selected viscosity should represent the concrete undergoing

rheological testing. For example, calibrating the two-point apparatus for testing TVC

would involve selecting a power law fluid of a viscosity ranging from 20 – 40 pa.s as these

viscosities are closely matched to the typical viscosities of TVC. On the other hand, SCC

possesses viscosities greater than 40 pa.s and, therefore the viscosity of the power law

fluid should be selected to reflect a viscosity greater than 40 pa.s.

According to Tattersall and Banfill (1983), a power-law relationship should exist between

the two-point test and that of a rheometer, which are, respectively, in the following form

T =pNq (F. 34)

τ = rϔs (F. 35)

Where p, q, r and s are constants, determined from the following equations:

In T = In p + q In N (F. 36)

In τ = In r + s In ϔ (F. 37)

In equation (F. 36) the constants q and p are determined by plotting the relationship

between ln Torque (ln T) and ln Speed (ln N) obtained by the Two-point apparatus where

q is slope of the straight line relationship and p is intercept on the ln Torque axis. The

same applies to the constants r and s in equation (F. 37), where r and s are determined by

plotting the relationship between ln shear stress (In τ) and ln shear rate (ln γ) obtained in

the rheometer where r and s are, respectively, the intercept and slope.

In general, the constant K is calculated from the following equation, providing both the

range of shear rates are the same in both the two-point test and the rheometer and if the

indices for the power law fluid q and s are the same (Banfill et al, 2001):

K = (p

rG)1/(s-1) (F. 38)

If the indices q and s are not equal then the constant K should be calculated by the

following equation:

K = (p

rG)1/(s-1) N(q-1)/(s-1) (F. 39)

APPENDIX G – TECHNICAL DATA SHEETS

139

APPENDIX G – TECHNICAL DATA SHEETS

G.1 – Steel fibres

G.2 – Admixtures

Roy Belton: M.Sc. Dissertation - The Rheological and Empirical Characteristics of Steel Fibre...

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