effect of binder composition on durability and mechanical properties of high performance self...

7/29/2019 Effect of Binder Composition on Durability and Mechanical Properties of High Performance Self Compacting Concr

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EFFECT OF BINDER COMPOSITION ON DURABILITY AND MECHANICAL

PROPERTIES OF HIGH PERFORMANCE SELF-COMPACTING CONCRETE

by

Mehmet Emre Batopu

B.S., Civil Engineering, Boazii University, 1997

M.S., Civil Engineering, Boazii University, 2000

Submitted to the Institute for Graduate Studies in

Science and Engineering in partial fulfillment of

the requirements for the degree of

Doctor of Philosophy

Graduate Program in Civil Engineering

Boazii University

2006


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EFFECT OF BINDER COMPOSITION ON DURABILITY AND MECHANICAL

PROPERTIES OF HIGH PERFORMANCE SELF-COMPACTING CONCRETE

APPROVED BY:

Prof. Turan zturan

(Thesis Supervisor)

Prof. Cengiz Karako

Prof. Hulusi zkul

Prof. Mehmet Ali Tademir

Assoc. Prof. Cem Yaln

DATE OF APPROVAL:


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To my dearest Wife and Daughters,

Erva, Merve and Mina Begm BATOPU


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ACKNOWLEDGEMENTS

I would like to start by expressing my deep gratitude to Prof. Dr. Turan zturan, my

thesis advisor, for his guidance, help and support throughout the course of my graduate

studies, both masters and PhD. He always managed to save some of his valuable time for me

in his busy schedule.

I am also grateful to E. Gneyisi and M. Gesolu, assistants of the Boazii

University Construction Materials Laboratory, for their help and support. I also would like

to thank help-to-technician I. Gltekin and other lab staff for their assistance during the

experiments.

I would also like to thank Yapkim Yap Kimya Sanayi A.. for providing chemical

admixtures (Glenium 51), ISFALT A.. for providing materials and technical support and

NUH imento Sanayi A.. for providing cement.

Finally, I would like to thank my family who has never deprived me from their

support and encouragement during my academic life. Without their support I probablywouldnt be able to complete this work.


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ABSTRACT

EFFECT OF BINDER COMPOSITION ON DURABILITY

AND MECHANICAL PROPERTIES OF HIGH PERFORMANCE

SELF-COMPACTING CONCRETE

This study was carried out in order to investigate the effect of binder composition on

fresh and mechanical properties of self-compacting concrete (SCC). Total of eight different

concrete mixtures have been produced. All mixes had a total binder powder content of 550

kg/m3. One of these was a control mix with only cement and no powder replacement. The

other seven had varied percentages (5, 10, 27, and 36 per cent) of fly ash (FA), silica fume

(SF) and limestone powder (LP) replacing Portland cement in the mix. In the fresh state,

mixes were tested according to the self-compactability criteria tests; such as flow table, U-

tube, V-funnel, L-box and visual segregation rating. The mechanical tests consisted of

compressive strength, splitting tensile strength, lollipop pullout. Another set of results was

obtained from pullout, compression, ultrasound, and rebound hammer tests applied on

specimens sawn from different sections of full size columns (10x20x200 cm). The cut

surfaces of these columns also allowed the investigation of variations in concrete

microstructure with changing depth along the column length. The concrete-steel interface

was also examined using video-microscope techniques. The durability properties were

assessed using water absorption, sorptivity, rapid chloride permeability, deicing salt

scaling, carbonation, sulfate resistance and drying shrinkage tests performed on different

number of specimens for each mix. In the fresh state, all the mixes exhibited satisfactory

self-compactability and resistance to segregation which was also credited for the

homogeneity of the full size columns properties. The results showed that the combined use

of SF and FA replacement of cement improved the mechanical and durability properties of

the SCC, where as the LP especially in large percentages reduces these properties. The

only exception is the drying shrinkage, which is reduced by LP and increased by SF

replacement of cement.


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ZET

BALAYICI ERNN YKSEK PERFORMANSLI

KENDLNDEN YERLEEN BETONUN DAYANIM VE

DAYANIKLILIK ZELLKLER ZERNDEK ETKLER

Bu alma balayc ieriinin yksek performansl kendiliinden yerleen betonun

(KYB) dayanm ve dayankllk zellikleri zerindeki etkilerini aratrmak amac ile

gerekletirilmitir. Toplam olarak sekiz farkl beton karm retilmitir. Karmlarn

tamamnda balayc miktar 550 kg/m3 olarak belirlenmitir. Bunlardan biri, hibir

mineral katk eklenmeyen ve sadece imento ihtiva eden kontrol karmdr. Dier yedi

karmda farkl oranlarda (yzde 5, 10, 27, 36) uucu kl (UK), silis duman (SD) ve ta

tozu (TT) imento yerine kullanlmtr. Taze betonda kendiliinden yerleebilme

ltlerine uygunluk testleri olan, yaylma, U-tp, V-huni, L-kutu ve grsel ayrma

testleri gerekletirilmitir. Mekanik zellikler basn dayanm, yarmada ekme dayanm

ve aderans testleri ile incelenmitir. Bir dier sonu kmesi ise byk boyutta dklen

kolonlardan (10x20x200 cm) farkl derinliklerde kesilip kartlan numunelerden elde

edilmitir. Bu numunelere de basn, ekme dayanm, ultrasonik ses hz ve yzey sertlii

testleri uygulanmtr. Farkl derinliklerde elde edilen kesit grntleri stnde detayl

grnt analizleri yaplm ve kolon boyunca mikro-yapdaki deiimler aratrlmtr.

Kolonlara yerletirilen yatay donatlarda beton-donat ara yz video-mikroskop ile

incelenmitir. Dayankllk zellikleri ise su emme, klcal geirimlilik, hzl klorr

geirgenlii, buz zc tuzlara kar diren, karbonatlama, slfat dayanm ve kuruma

rtresi testleri ile belirlenmitir. Karmlarn tm kendiliinden yerleme zelliini

salamakta ve ayrma gstermemektedir, kolon elemanlarnn yapsndaki homojenlik de

buna balanabilir. Sonulara gre KYBde imentonun yerine katk olarak SD ve UKnn

birlikte kullanm, ta tozuna gre daha iyi mekanik ve dayankllk zelliklerinin

olumasn salamaktadr. Bunun tek istisnas TT kullanm ile azalan ve SD ile artan

kuruma rtresi deerleridir.


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TABLE OF CONTENTS

DEDICATION.iii

ACKNOWLEDGEMENTiv

ABSTRACT. v

ZET vi

LIST OF FIGURES .??

LIST OF TABLES ..??

LIST OF SYMBOLS / ABREVIATIONS...??

1. INTRODUCTION. .. 12. LITERATURE REVIEW. 4

2.1. Brief History of Self-Compacting Concrete42.2. Theory of Self-Compactibility.. 52.3. Types of Self-Compacting Concrete.. 7

2.3.1. Powder Type SCC 72.3.2. Viscosity Type SCC. 8

2.4. Previous Research on Self-Compacting Concrete..102.4.1.

Mix Design10

2.4.2. Binder Composition..132.4.3. Fresh Concrete Properties.16

2.4.3.1. Flow Table Test.162.4.3.2. U-Tube Test...192.4.3.3. V-Funnel Test212.4.3.4. L-Box.212.4.3.5. Rheological Studies...222.4.3.6. Segregation25

2.4.4. Mechanical Properties...262.4.4.1. Compressive Strength....262.4.4.2. Splitting Tensile Strength..292.4.4.3. Bond Strength31

2.4.5. Durability Properties.322.4.5.1. Rapid Chloride Permeability.32

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2.4.5.2. Sulphate Resistance...342.4.5.3. Freeze-Thaw Resistance362.4.5.4. Deicing Salt-Scaling Resistance382.4.5.5. Carbonation...392.4.5.6. Capillary Absorption.402.4.5.7. Drying Shrinkage..41

3. EXPERIMENTAL PROGRAM AND METHODOLOGY...443.1. Materials.44

3.1.1. Cement..443.1.2. Fly Ash ... 453.1.3. Silica Fume.. 453.1.4. Limestone Powder .. 453.1.5. Aggregate. 473.1.6. Superplasticizer.... 48

3.2. Concrete Mixture... 493.3. Production of Test Specimens... 503.4. Test Procedures. 51

3.4.1. Fresh Concrete Properties 513.4.1.1. Slump Flow Test.. 513.4.1.2. U-Tunnel Test.. 523.4.1.3. V- Funnel Test. 523.4.1.4. L-Box Test 523.4.1.5. Segregation... 52

3.4.2. Hardened Concrete Properties. 533.4.2.1. Compressive Strength..533.4.2.2. Splitting Tensile Strength 533.4.2.3.

Pull-out Strength. 54

3.4.2.4. Test on Full Size Structural Elements.. 563.4.2.5. Ultrasonic Pulse Velocity Test. 61

3.4.3. Permeability Tests 613.4.3.1. Water Absorption. 613.4.3.2. Capillary Absorption 613.4.3.3. Chloride Ion Permeability 63

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3.4.3.4. Carbonation 663.4.4. Durability Tests. 66

3.4.4.1. Deicing Salt Scaling Resistance. 663.4.4.2. Sulphate Resistance 68

3.4.5. Drying Shrinkage 694. TEST RESULTS AND EVALUATION 70

4.1. Fresh Concrete Properties 704.2. Hardened Concrete Properties.. 73

4.2.1. Mechanical Properties. 734.2.1.1. Compressive Strength.. 734.2.1.2. Splitting Tensile Strength. 754.2.1.3. Pull-out Strength.. 764.2.1.4. Ultrasonic Pulse Velocity Test. 774.2.1.5. Test on Full Size Structural Elements.. 77

4.2.2. Permeability Tests 1094.2.2.1. Water Absorption.. 1094.2.2.2. Sorptivity 1094.2.2.3. Chloride Ion Permeability.. 1104.2.2.4. Carbonation 110

4.2.3. Durability Tests. 1114.2.3.1. Deicing Salt Scaling Resistance. 1114.2.3.2. Sulphate Resistance 112

4.2.4. Drying Shrinkage... 1134.3. Cost Analysis of SCC. 1144.4. Analytical Correlations between Concrete Properties 120

4.4.1. Relationship between Water Absorption and Sorptivity (S).. 1214.4.2.

Relationship between Total Charge Passed (Q) andSorptivity (S).

4.4.3. Relationship between Total Charge Passed (Q) andWater Absorption

4.4.4. Relationship between Total Charge Passed (Q) and InitialCurrent (IC).

4.4.5. Relationship between Total Charge Passed (Q) and

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Compressive Strength (fc)..

4.4.6. Relationships between Splitting Tensile Strength,Compressive Strength and Pull-out Strength.

4.4.7. Relationships between Compressive Strength, Pull-outStrength and UPV of Column and Lab Specimens...112

4.4.8. Relationship between Compressive Strength and UPV.4.4.9. Relationship between In-situ Mechanical Properties and

Distance from the Top of the Columns..112

4.5. Overall Evaluation of the SCC Mixes..5. CONCLUSIONS .2136. RECOMMENDATIONS FOR FUTURE WORK ..217APPENDIX A: PHOTOGRAPHS.

REFERENCES ..225

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LIST OF FIGURES

Figure 2.1. Excess paste theory .

Figure 2.2. Relation between spherical factor of powders and paste fluidity

Figure 2.3. Schematic representation of slump flow..

Figure 2.4. Flow spread test mould and data representation

Figure 2.5. Schematic representation of U-type test apparatus

Figure 2.6. Schematic representation of the V-Funnel apparatus

Figure 2.7. Schematic representation of the L-Flow apparatus.

Figure 2.8. Relationship between torque and speed in Newtonian and Bingham

Model.

Figure 2.9. Two-point workability apparatus

Figure 2.10. Pullout specimen .

Figure 3.1. Aggregate grading curve and zones..

Figure 3.2. Pull-out Test Set-up

Figure 3.3. Schematic representation of the column specimen

Figure 3.4. Experimental setup for sorptivity test

Figure 3.5. RCPT experimental setup.

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Figure 3.6. The deicing salt scaling specimen with galvanize dike.

Figure 4.1. Compressive strength test results at 7 days..

Figure 4.2. Compressive strength test results at 28 days..

Figure 4.3. Compressive strength test results at 90 days ..

Figure 4.4. Compressive strength developments at 7, 28, 90, and 900 days..

Figure 4.5. Splitting tensile strength test results at 7 days..

Figure 4.6. Splitting tensile strength test results at 28 days.

Figure 4.7. Splitting tensile strength test results at 90 days

Figure 4.8. Splitting tensile strength developments at 7, 28, and 90 days

Figure 4.9. Pull-out strength test results at 7 days

Figure 4.10. Pull-out strength test results at 28 days..

Figure 4.11. Pull-out strength test results at 90 days

Figure 4.12. Pull-out strength developments at 7, 28, and 90 days

Figure 4.13. Ultrasonic pulse velocity results at 28 and 90 days

Figure 4.14. Results of pullout strength of lab specimens compared with column

specimens

Figure 4.15. Results of compressive strength of lab specimens compared with

column specimens

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Figure 4.16. Results of Schmitt rebound hammer values changing with depth of

column..

Figure 4.17. Results of ultrasonic pulse velocity test changing with depth of

column.....

Figure 4.18. Linear expansion versus time for concretes exposed to sulphate attack.

Figure 4.19. Drying shrinkage test results.

Figure 4.20. Relationship between sorptivity and water absorption at 28 - 90 days

Figure 4.21. Relationship between total charge passed and sorptivity at 28- 90 days.

Figure 4.22. Relationship between water absorption and total charge passed at 28

and 90 days.

Figure 4.23. Relationship between initial current and total charge passed at 28 and

90 days

Figure 4.24. Relationship between initial current and total charge passed for all data.

Figure 4.25. Relationship between comp. strength and total charge passed at 28 and

90 days

Figure 4.26. Relationship between compressive and splitting tensile strength at 7, 28

and 90 days..

Figure 4.27. Relationship between splitting tensile and pull-out strength at 7, 28

and 90 days..

Figure 4.28. Relationship between compressive strength and pull-out strength at 7,

28 and 90 days..

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Figure 4.29. Relationship between compressive strength of column and lab

specimens...

Figure 4.30. Relationship between pull-out strength of column and lab specimens..

Figure 4.31. Relationship between UPV of column and lab specimens.

Figure 4.32. Relationship between compressive strength and UPV at 28 and 90 days..

Figure 4.33. Relationship between compressive strength and distance from the top

of the column..

Figure 4.34. Relationship between pull-out strength and distance from the top

of the column.

Figure 4.35. Relationship between UPV and distance from the top of the column...

Figure 4.36. Relationship between Schmitt hammer rebound value and distance

from the top of the column.

Figure 4.37. Relationship between cost of materials and compressive strength

of SCC

Figure A.1. Slump flow test in a time sequence

Figure A.2. Column specimen formwork (a), demolded column specimen before

sawing operation(b)

Figure A.3. Deicing salt scaling resistance specimens after increasing numbers of

F&T cycles.

Figure A.4. Deicing salt scaling specimens after 50th cycle, with severely

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Figure A.5. Test set-up for Rapid Chloride Permeability.

Figure A.6. Carbonation test; spraying of phenolphthalein (a), close-up photo of

M6 where slight carbonation was observed (b)

Figure A.7. Video-microscope images of concrete-steel interface without any

visible defects ..

Figure A.8. Video-microscope images of concrete-steel interface without any

visible defects.

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LIST OF TABLES

Table 2.1. Mixture proportion guidelines for SCC1

Table 3.1. Physical, chemical and strength properties of cement and powder

materials..

Table 3.2. Sieve analysis and physical properties of the aggregates

Table 3.3. Analysis report of the superplasticizer (Glenium 51)..

Table 3.4. Mix proportioning of concretes

Table 3.5. Classification of the column sections...

Table 3.6. The criterion for the ultrasonic pulse velocity..

Table 3.7. Interpretation of results obtained using RCPT T 277-89..

Table 3.8. The rating scale for ASTM C 672

Table 4.1. Properties of fresh concrete

Table 4.2. General acceptance criteria for SCC and EN 206-1:2000 classes.

Table 4.3. Compressive strength results at 7, 28 and 90 days

Table 4.4. Splitting tensile strength results at 7, 28 and 90 days

Table 4.5. Pull-out strength results at 7, 28 and 90 days

Table 4.6. Ultrasonic pulse velocity test results.

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Table 4.7. Test results of column sections at 28 days..

Table 4.8. Correlation between the properties of column and lab specimens

Table 4.9. Different stages of image analysis in calculating the area ratio for

column M1


column M2.


column M3 .


column M4


column M5.


column M6..

Table 4.15. Area ratios of concrete column cross-sections found by image

analysis and used in segregation coefficient calculations157

Table 4.16. Segregation coefficients of the concrete mixtures casted in columns

Table 4.17. Stages of image analysis at the steel-concrete interface for column M1...155

Table 4.18. Stages of image analysis at the steel-concrete interface for column M2..

Table 4.19. Stages of image analysis at the steel-concrete interface for column M3..

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Table 4.20. Stages of image analysis at the steel-concrete interface for column M4...



Table 4.23. Water absorption test results at 28 and 90 days..

Table 4.24. Sorptivity test results of the concrete mixtures at the age of 28

and 90 days..

Table 4.25. Rapid chloride permeability test results at 28 and 90 days.

Table 4.26 Visual rating results of the deicing salt scaling tests on concrete

specimens

Table 4.27. Depth of carbonation of concretes exposed to outdoor environment...

Table 4.28. Compressive strength of concretes stored in water and in

sulfate solution.

Table 4.29. Cost analysis of SCC mixes used in this study

Table 4.30. Initial current readings of RCPT tests..

Table 4.31. Results of the regression analyses for the correlation between themechanical properties and distance from the top of the columns.

Table 4.32. Relative values of mechanical properties of SCC mixes..

Table 4.33. Relative values of durability properties of SCC mixes

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Table 4.34. Relative values of overall properties of SCC mixes including cost of

materials140


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LIST OF SYMBOLS / ABREVIATIONS

C Yield value (mobility)

C Plastic viscosity

D Percentage damage during sulphate exposure

d b Bar diameter

ESS Explained sum of squares

fc n Compressive strength at age n

fpn Pull-out strength at age n

ft n Splitting tensile strength at age n

Gi Concentration of coarse aggregate

Mean of coarse aggregate concentration

i Cumulative water absorption per unit area of inflow surface

ls Embedment length (bonded length)

N Angular speed

P Ultimate applied load

Q Total charge passed during RCPT

R Coefficient of correlationR2 Coefficient of determination

Rm Viscosity

rn, Dn Flow diameter

RSS Residual sum of squares

S Sorptivity

T Torque

t Elapsed time during sorptivity test

TSS Total sum of squaresVagg Volume of total aggregate

Vb Volume of binder

Vc Volume of coarse aggregate

VC Actual value of the cost of the mix

VCmin Lowest value of the cost among the mixes

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VCr Relative value of the cost of the mix

VD Actual value of a durability / permeability property of the mix

VDmin Lowest value of a durability /permeability property among the mixes

VDr Relative value of a durability / permeability property of the mix

Vf Volume of fine aggregate

VM Actual value of a mechanical property of the mix

VMmax Highest value of a mechanical property among the mixes

VMr Relative value of a mechanical property of the mix

Vp Volume of paste

Vs Volume of total solids

Vw Volume of water

m Flowability

Concrete strength without sulphate exposure

R Concrete strength after sulphate exposure

Bond strength

AEA Air entrainment admixture

FA Fly ash

F&T Freezing and thawing

IC Initial current reading during RCPT

ITZ Interfacial transition zone

LP Limestone powder

OPC Ordinary Portland cement

RCPT Rapid chloride permeability test

PBFS Powdered blast furnace slag

PLS Powdered limestone

SC Segregation coefficient

SCC Self-compacting concrete

SF Silica fume

UPV Ultrasonic pulse velocity

WA Water absorption

VMA Viscosity modifying admixture


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1. INTRODUCTION

The concept of self-compacting concrete (SCC) was first introduced in Japan in 1988

as part of an effort to achieve durable concrete structures. In order to achieve the design

properties of the concrete mixtures, it was realized that the greatest obstacle at site was

poor compaction. The solution to these problems came along with other advantages by the

use of SCC, which can be compacted into every corner of a formwork, purely by means of

its own weight and without the need for vibrating compaction (Okamura and Ouchi, 1999).

Although the SCCs greatest claim is given above, the experimental studies on SCC are

mainly focused on lab specimens rather than larger scale representations of the real-sizeconstructional elements.

It has been shown that having a powder content (materials finer than 0.1 mm) of 500

to 600 kg/m3 is critical for attaining self-compactability in concrete (Topu and Khurana,

2000). Since the excessive use of cement, as a fine material in concrete is uneconomical

(along with other drawbacks), mix-proportions with replacement powders such as silica

fume, fly ash, limestone powder is investigated. Here the aim was to distinguish between

the effects of different mineral powders (used separately or combined with varying

contents, properties and finenesses) in SCC with reasonable explanations.

The fundamental objective of this work was to provide information on the hardened

properties of self-compacting concrete produced using different powders as cement

replacements. To this end, the engineering properties of SCC in sampled specimens were

to be compared with those of in full size structures. So this study aimed to combine and

compare results of the tests conducted on the laboratory scale and the larger scalespecimens to investigate the extent of the observed self-compactability on the lab floor.

The concrete was produced in a laboratory pan-mixer, and the following mechanical

properties of sampled specimens were tested: compressive and flexural strength, shrinkage,

bond strength with reinforcement. In addition, in order to assess durability, longer-term

comparative tests were made on freeze-thaw resistance, water absorption, sulphate


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resistance, deicing salt scaling, drying shrinkage, rapid chloride permeability and

carbonation. Testing of fresh concrete was a part of the work, also necessary for mix

design verification and acceptance purposes. To supplement this, special tests were made

on settlement and segregation. The full-size elements were tested in two ways. Firstly a

number of in-situ tests were carried out in order to determine mechanical properties at

changing heights of vertical elements, and secondly, the cut surfaces of the elements were

examined through image analysis to determine coarse aggregate segregation at changing

heights of the vertical elements.

Thus the scope of this study might be summarized as;

Comparison of basic mechanical properties of hardened SCC with varying binder

composition.

Comparison of some aspects of the durability of hardened SCC with varying binder

composition.

Evaluation of the effects of different mineral powders (used separately of

combined).

Verification of properties of hardened SCC in full-size columns using in situ test

methods.

Evaluation of the relation between mechanical and durability properties of SCC. Evaluation of the problems associated with mineral admixtures, such as thermal

cracking or incompatibility with superplastizers.

Comparison of the economical aspects of using different mineral admixtures for

specific concrete properties.

Since self-compacting concrete is a relatively new topic there are some areas of

research where the existing data is limited making this study significant.

(1) Further study is necessary for the comprehensive evaluation of durability in SCC

(combined with mechanical properties), since most of the recent work is on fresh concrete

properties and mix design. For instance, there is contradiction among researchers about the

effect of mineral admixtures on carbonation and shrinkage of concrete.


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(2) There is also limited data on the frost durability and scaling resistance of SCC which is

susceptible to such damage with a high potential of being used in congested reinforced

sections of beams and girders of bridges.

(3) More data is also required to correlate the results of simple (relatively new) empirical

tests used in determining fresh properties of SCC.

(4) Last but not the least, in evaluating the effects of mineral admixtures, cost analysis

should be done since economical considerations is one of the main drawbacks of the wider

use of SCC in the construction industry.

Commenting on the future of SCC, Okamura et al. (Okamura, 1999) concluded that

the rational mix-design method and appropriated testing method at site have almost been

established for SCC and these eliminate some of the obstacles for making SCC widely

used. The next task is to distribute the manufacturing, qualification and construction

techniques for SCC. In addition, new structural design and construction systems making

full use of SCC should be introduced, such as the sandwich structures in the immersed

tunnel in Kobe, Japan.

As mentioned above the main obstacle against the wide use of SCC is surely its price. The

superplastizers used are expensive to produce and some of the inorganic fillers such as

silica fume are also expensive due to high demand. But it should not be forgotten that high

w/c (0.6) present concrete is not durable, and consequently often requires repairs and

causes inappropriate level of service. Therefore, the initial cost should not be evaluated

alone, but together with life-cycle cost. It is also worth noting that SCC containing up to

50% fly ash replacement can attain 28-day target strengths of 35 MPa. It is also shown by

cost analysis that such a SCC mix has no significant extra cost compared to ordinary

concrete and would be flowable with a slump flow of 500 mm and more resistant to

segregation and thermal cracking, but might exhibit higher bleeding water and long setting

time (Bouzoubaa, et al. 2002). When self-compacting concrete becomes so widely usedthat it will be seen as the standard concrete rather than an expensive special concrete,

it would be much more convenient for engineers to design durable and reliable concrete

structures worldwide.


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2. LITERATURE REVIEW

2.1. Brief History of Self-Compacting Concrete

The concept of self-compacting concrete (SCC) was first introduced in Japan in

1988 as part of an effort to achieve durable concrete structures. In order to achieve the

design properties of the concrete mixtures, it was realized that the greatest obstacle at

site was poor compaction. The need for sufficient compaction increased the demand for

skilled workmanship (recently declining in Japan) and time required for concrete

placement. The solution to these problems came along with other advantages by the useof SCC, which can be compacted into every corner of a formwork, purely by means of

its own weight and without the need for vibrating compaction (Okamura and Ouchi,

1999).

In 1988, Okamura completed the first prototype of SCC using materials already on

the market. The prototype performed satisfactorily with regard to drying and hardening

shrinkage, heat of hydration, denseness after hardening, and other properties. This concrete

was defined as follows at the three stages of concrete:

(1)fresh: self-compacting

(2)early age: avoidance of initial defects

(3)hardened: protection against external factors (Okamura and Ouchi, 1999)

After the development of the prototype, SCC caught the attention of research

institutes of large construction companies in Japan and soon found many practical

applications. The most important reasons for this quick popularity were (Bouzoubaa and

Lachemi 2002);

(1) reducing construction time and labor cost (important since 50% of total

construction cost is related to manpower (Byfors, 1999);

(2) assuring of proper compaction; especially in confined zones where vibrating

compaction is difficult and therefore eliminating the need for compaction,

forming better finished surfaces, reducing leveling work (il, 2000);


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(3) eliminating noise due to vibration; effective especially at pre-cast concrete

industry and urban construction sites, for better working environment.

During the anchorage construction of Akashi-Kaikyo Bridge (1.991 meter, longest

suspension bridge in the world with 500.000 m3 of concrete poured at the piers) in 1998,

SCC proved to eliminate segregation although it fell as much as 3 meters and contained

large size coarse aggregates (40 mm). Another positive effect was observed in the 20%

reduction in the construction period. There are many other recent projects where the

workmanship (up to 80% reduction), and construction time has been reduced similarity

with the use of SCC (Nagataki, 2000).

Self-compacting concrete is shown also to be proper repair material which has good

filling capacity, and that the absence of segregation enhances the characteristics with the

old concrete, even in an inverted position (a common practice in repairing bridge girders

damaged by frost). Microstructure studies also indicated that SCC performed as well as

conventional dry-mix shotcrete, making it a very interesting new repair material (Lacombe

et al., 1999).

SCC has a great potential for new application methods in construction since it allows

the use of new techniques, which were not feasible before with conventional concrete.

2.2. Theory of Self-compactability

According to Okamura self-compactability might be achieved by separating the

concrete into two constitutes, coarse aggregates and mortar and then adjusting the

rheology of the mortar to achieve self-compactability by incorporating a variety of

mineral additives, plasticizers, and thickeners. Contrarily, A.W. Saak argues thatoptimizing the particle size distribution of the binder (for example, cement, silica fume,

fly ash, etc. ) and of fine and coarse aggregates based on packing considerations provide

a better understanding of the physical properties required to achieve SCC (Saak et al.,

2001).


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It has been argued that high packing density cant be used as criteria for producing

highly flowable concrete, but according to recent experimental work, particle-packing

density should be used in conjunction with interparticle separation (IPS) in order to explain

the physical behavior of the paste (Saak et al., 2001). In concrete, the volume of the binder

and particle size distribution of the aggragetes governs the IPS. For a given particle size

distribution, the volume of the binder should be sufficient to fill the interstitial voids

between the aggregates to produce a desired IPS. These arguments can also be explained

by the Excess Paste Theory proposed by Kennedy (Kennedy, 1940), which states that to

attain workability, it is necessary to have not only enough cement paste to cover the

surface area of the aggregates, so as to minimize the friction between them, but also more

of it to give better flowability. The application of this theory is illustrated in Figure 2.1

(Noguchi et al., 2001).

Figure 2.1 Excess paste theory

Aggregate Excess paste

Add pasteVoid

ThicknessofExcess paste

( Compacted )( Dispersion )


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2.3. Types of Self Compacting Concrete

The method for achieving self-compactability involves not only high

deformability of paste or mortar, but also resistance to segregation between coarse

aggregate and mortar when the concrete flows through the confined zone of reinforcing

bars. Yield stress of a paste is easily decreased with the addition of a superplastizer, but

yield stress must be above a critical minimum to insure that segregation of aggregates

does not occur when the mix is at rest (Saak et al., 2001). Since segregation prevention

is critical in producing SSC, generally three methods were proposed to obtain adequate

segregation resistance (Nagataki, 2000), (Topu and Khurana, 2000).

(1)limiting coarse aggregate content and reducing the water to powder ratio byincreasing the powder content using cement and/or mineral admixtures such as

limestone powder, fly ash, or granulated blast furnace slag powder (Powder

Type SCC),

(2)adding viscosity agent with superplastizer (Viscosity Type SCC),

(3)doing both of the above (Combination Type SCC).

2.3.1. Powder Type SCC

To make the concrete deform well, it is beneficial to reduce the friction between

the solid particles, which includes coarse aggregate, fine aggregate and all types of

powder. To reduce the aggregate-aggregate friction, it is necessary to reduce the

possibility of aggregate inter-particle contact. One way to achieve this is to increase the

aggregate inter-particle distance by reducing the aggregate content or, in other word,

increasing the paste content. The friction among powder materials is not possible to

reduce by increasing the inter-particle distance through increasing the water content of

the paste. The paste phase itself needs to have excellent deformability and that require

dispersion of fine particles which in turn require surface active agents like

superplasticizers. The use of too high a water content leads to segregation and

undesirable performance of the hardened concrete e.g. strength and durability. The

shape of the powder particles has an effect on the demand of water and

superplasticizers. The use of spherical pozzolans such as FA is considered effective for


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this purpose. A reduction of the friction between aggregate and powder particles tends

to reduce the resistance to segregation. It may then be effective not to increase the

deformability of the paste and concrete as a whole, but rather to increase the viscosity of

the paste (Skarendahl, 1999).

In mixing SCC increasing the paste volume by increasing powder content

consequently leads to lower content of coarse aggregates. The theory behind can be best

explained by changes in internal stress of the mix. The frequency of collisions and

contact between aggregate particles can increase as the relative distance between the

particles decreases and the internal stress can increase when concrete is deformed,

particularly near obstacles. It has been revealed that the energy required for flowing isconsumed by the increased internal stress, resulting in blockage of aggregate particles.

Limiting the coarse aggregate content, whose energy consumption is particularly

intense, to a level lower than normal proportions is effective in avoiding this kind of

blockage (Okamura and Ouchi, 1999). Limiting coarse aggregate also serves to avoid

segregation on superplastizer addition and a simple approach consists of increasing the

sand content replacing 4 to 5 % coarse aggregate (Bouzoubaa and Lachemi, 2002). But

this reduction of coarse aggregate leads to a use of high volume of cement, which in

turn causes cost, temperature increase. Previous investigations showed that fly ash

improves rheological properties and reduces thermal cracking due to excessive heat of

hydration. Most of the studies contained concrete mixes with different percentages of

fly ash replacing cement not exceeding 30% replacement (Bouzoubaa and Lachemi,

2002).

2.3.2. Viscosity Type SCC

Highly viscous paste is also required to avoid the blockage of coarse aggregate

when concrete flows through obstacles. When concrete is deformed, paste with a high

viscosity also prevents localized increases in the internal stress due to the approaching

coarse aggregate particles. High deformability can be achieved only by the employment


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9

of a superplasticizer, keeping the water-powder ratio to be very low value (Okamura

and Ouchi, 1999).

The action of superplastizers in SCC takes place as these large molecules surround

the surface of hydrating cement particles. Since the cement particles are normally

positively charged, the dipolar water molecules are attracted on their surface and for a

sheath of water with the help of SP. This sheath prevents the cement particles from

flocculating, and its dispersive action also allows more surface of cement to be in

contact with water. While increasing the water/cement ratio to enhance flowability leads

to a decrease in viscosity, SP increase can make the paste more flowable with little

reduction in viscosity, and avoids segregation. But it is also worth mentioning that thereis a limit for the increase in flowability with increasing SP dosage (Venugopal et al.,

2000).

Viscosity-modifying admixtures (viscosity agent) are used as an alternative

approach to producing SCC with high powder content (Bilberg, 2000), but they also

increase the materials cost. So the best alternative is using mineral additives like fly ash,

blast furnace slag, or limestone powder to enhance stability.

A study by M. Collepardi et al. aimed to optimize the type and the dosage of

superplasticizer in Class F flyash concrete, so that compressive strengths as high as those

of superplastizer silica fume concretes could be obtained (Collepardi, 2001). In this study

the superplastizer dosage and the pozzolan addition ranged from 2 to 4% and from 12 to

20% respectively by weight of cement. The cement factor varied from 255 to 400 kg/m3.

The results of this work indicated that only in the presence of ASTM Type III Portland

cement, superplastizer flyash concrete can be as strong as the corresponding silica fume

concrete, particularly at relatively high cement factors ( 300 kg/m3). In their discussion

the results are evaluated as follows. The ASTM Type III cement has high C3S content and

higher fineness, the hydration of this cement produces more Ca(OH)2 , to be used in the

pozzolanic reactions of both flyash and silica fume. But the higher amount of Ca(OH) 2

should favor fly ash more than silica fume, since fly ash is potentially less reactive for the


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lower fineness and lower content of amorphous silica. A less pronounced similiar

advantage for fly ash is the increased cement content.

Another study by zkul et al. points out that at least 500 kg/m3 of fine material (>

100 m), including the cement, is necessary to produce a self-compacting concrete (zkul

et al., 2000). The concrete mixes used in this study contained fly ash and silica fume, and it

is observed that 50 kg/m3 of fly ash addition to 450 kg/m3 of cement is not sufficient for

self-compactability. The best results are observed for 100 and 150 kg/m3 of fly ash

addition, but a value of 200 kg/m3 fly ash caused rapid flow loss as observed with an

excessive increase in cement content.

2.4. Previous Research on Self-compacting Concrete

2.4.1. Mix Design

Self-compactability can be largely affected by the characteristics of materials and the

mix-proportion. A simple mix-proportioning system for mixing SCC has found general

acceptance (Okamura and Ouchi, 1999). The coarse and fine aggregate contents are fixed

so that the self-compactability can be achieved easily by adjusting the water-powder ratioand the superplasticizer dosage only. The catch-points are listed as;

(1)Coarse aggregate content in concrete is fixed at 50% of the solid volume

(2)Powder content (materials finer than 0.1 mm): 500-600 kg/m3

(3) Fine aggregate (sand 0.1 to 5mm) content is fixed at 40% of the mortar

volume.

(4)Water-powder ratio in volume is assumed as 0.9 to 1.2, depending on the

properties of the powder.

(5)Maximum size of aggregate: up to 20 mm(6)Superplastizer (polycarboxylate ethers), AEA, VMA dosage and the final

water-powder ratio are determined so as to ensure self-compactability (using

following tests in (7)-(9)).

(7)Slump flow: 60 to 70 cm

(8)V-funnel: 8 to 12 sec

(9)U-box: h> 30 cm


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There are other guidelines for SCC using the recommended volume ratios of each

constitute and there is little variation in the suggested guidelines given by different

authors as given in Table 2.1 (Saak et al., 2001).

Table 2.1 Mixture proportion guidelines for SCC.

Researchers Vc / Vagg Vf/ Vagg Vb / Vs (Vb + Vf) / Vagg

Okamura 0.64 0.36 0.22 0.64

Yurgui et al 0.54 0.46 0.24 0.78Ambrose et al 0.44 0.56 0.18 0.78

where Vc: volume of coarse aggregate; Vf: volume of fine aggregate.; Vagg : volume of

total aggregate.; Vb : volume of binder (solids); and Vs = v. of total solids (aggregates +

binder).

The mortar or the paste of SCC needs to be deformable as well as being viscous.

This can be achieved by proper dosage of superplastizer, which ensure a low water-

powder ratio for the high deformability. Okamura et al. suggested that, the best way to

determine the proper water-powder ratio and superplastizer dosage is to make trial

mixes (Okamura and Ouchi, 1999). So when the mix proportion is decided, self-

compactability has to be tested by U-type test, slump-flow and funnel tests. The

relations between the properties of the mortar in SCC and the mix proportion have been

investigated and then formulated by Okamura and Ouchi. These formulae can be used

for establishing a rational method for adjusting the water-powder ratio andsuperplasticizer dosage for achieving appropriate deformability and viscosity. In these

formula Ouchi et al. defines indexes for flowability and viscosity as m and Rm ,

respectively (Ouchi et al., 1996).

m = (r1r2 r02) /r0

2 (2.1)


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where r1,r2 are the measured flow diameter and r0 is the flow cones diameter.

Rm = 10/t (2.2)

where t is the measured time (in seconds) for mortar to flow through the V-funnel.

These indexes are practical to use since they are obtained by simple tests. Larger m

value indicates higher flowability and larger Rm indicates higher viscosity. Ozawa et al.

investigated these indexes and concluded that mortar with a m of 5 and an Rm of 1 is the

most appropriate mixture for achieving SCC (Ozawa et al., 1996). Another suggestion for

m and Rm values comes from Edamatsu et al., saying 3 m 7 and 1 Rm 2 is

sufficient for SCC (Edamatsu et al., 1999).

Since a rational-mix design method which determines the necessary superplastizer

amount, Sp / P, and water-powder ratio, Vw / Vp, the (since these values are specific for

each different material) best way to attain self-compactability is making assumptions and

that checking m and Rm values. Ouchi et al. also emphasizes the fact the chemical action

of the superplastizer might be influenced by combination with the powder, which has to be

assessed with use of trial mixes (Ouchi et al., 1996).

In mixing conventional concrete, water-cement ratio is fixed to ensure

predetermined design strength. With SCC, however the water-powder ratio has to be

selected taking self-compactability into account because self-compactability is very

sensitive to this ratio. Despite this fact, usually the water-powder ratio is still low

enough to satisfy the strength for ordinary structures unless the most of powder

materials in use is not reactive (which is not the case for silica fume, fly ash). Mixingprocedure of SCC is also different for conventional concrete and a typical SCC mixing

procedure is presented below (Khayat et al., 2000).

(1)All concrete mixtures are prepared in 60 L batches in rotating drum mixer

(2)First, sand and coarse aggregate are mixed (homogenized) for 30 sec.

(3)Then 75% mixing water and superplastizer is added and mixed for 30 sec.


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(4)Cement and mineral additives are added and mixing is resumed for 1 min.

(5)The remaining water is added and mixed for 3 min.

After 2 min at rest the concrete is mixed for a final additional 2 min.

2.4.2. Binder Composition

The pozzolanic additives such as fly ash, slag, silica fume, zeolite silica, etc. are

often used to produce SCC in order to improve its strength, workability and durability

and to reduce the cost as well (Jianxiong et al., 1999).

The roles of these pozzolanic additives are as follows;

(1)increasing the hydration products due to additional pozzolanic reactions;

reducing porosity can improve durability and resistance to chemical attack with

increases strength.

(2)reducing heat of hydration and reaction rate; reducing micro cracks and

transition zones

(3)increases filling effect of micro aggregate, adjusting grading of the components

to achieve optimum compact, adjusting cohesiveness(4)improving workability due to increased fines content and shape effect (Fang

et al., 1999).

(5)reducing use of cement, achieving economic and environmental benefits

(Jianxiong et al., 1999).

The most common knowledge about increasing the powder content in the concrete

paste is that it generates an exponential increase in yield value and plastic viscosity.

When a new generation superplastizer is added to this paste the yield value is

significantly reduced with little reduction in plastic viscosity and this is the principle of

forming SCC. A drawback of high powder content in SCC is the potential formation of

thermal cracks, especially in mass concreting. For this reason, such concrete is mostly

used with granulated blast furnace slag powder, fly ash and limestone powder. When

water to powder ratio of the concrete is low, the resulting w/c ratio leads to high


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compressive strength values of over 40 MPa. When limestone powder is used as the

mineral admixture, its content might be adjusted to attain normal strength concrete

(Nagataki, 2000).

The rheological studies by Nischer clearly shows that flowability of the paste

increases as the Blaine fineness of the different additions of fly ash, lime stone powder

increases, and the same increase also evident in replacement of cement with 50% blast

furnace slag powder (Nischer, 2000). According to Saak et al., SCC paste with 30%

silica fume (replacing cement) exhibits an increase in yield stress and equilibrium

viscosity as the SP dosage increases (Saak et al., 2000). They further noted that at zero

yield stress, replacement of cement by 30 % silica fume leads to a 36% reduction inequilibrium viscosity compared to the all-cement mix, and attributed this to the increase

in the solid packing density and spherical morphology of the silica fume particles.

Khayat et al. produced SCC containing 3% silica fume and 20% fly ash

replacement, with water-to-binder ratios and binder contents ranging from 0.37 to 0.50

and 360 to 600 kg/m3, respectievly (Khayat et al., 2000). Topu et al. produced SCC

with 350 kg/m

3

cement with 200 kg/m

3

fly ash (%36) from ayrhan power plant, withwater-to-binder ratio of 0.35 and 1.2% superplastizer (Glenium 27) (Topu et al., 2000)

and compared homogeneity according to compressive strength of lab and site samples

of SCC and ordinary concrete. Their slump flow, V-funnel, and U-box values were 49-

63 cm, 10 sec, 32 cm respectively and all were found to be within the appropriate range

for SCC [4]. According to Khurana et al., a silica fume content of 50 kg/m3 makes a

total fines content of 450 to 500 kg/m3 sufficient for producing SCC. They also reported

that for other types of fines (fly ash, limestone or quartz filler) the total fines content

should be between 500 to 600 kg/m3

(Khurana et al., 2000). Comparing the use of thesepowders, they noted that fly ash is very advantageous for ready mix concrete since it is

readily available at a low price and also limestone filler is preferred among precast

industry since it has an even lower price and it produces a lighter color concrete more

appreciated by the customers.


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In order to distinguish between the effects of different mineral powders in SCC,

Nagataki (Nagataki, 2000) defined the term spherical factor (packing bulk density /

specific gravity) and concluded that powders having higher spherical factors improve

the fluidity of the paste better. In measurement of fluidity of cement paste, the

replacement ratio of inorganic powders was 40% and the water to powder ratio is 90%

by volume. The results revealed that silica fume performs better than fly ash due to

higher spherical factor as seen in Figure 2.2. Nagataki also investigated the effect of

particle size distribution on fluidity and made studies with different particle sizes of

limestone powder. The use of combination of fine and coarse powder resulted in higher

packing density and larger amount of free water and highest fluidity is also observed at

that mix (Nagataki, 2000).

OPC

PBFSPFA

PLS

PCS

PSS

0,0

1,0

2,0

3,0

4,0

5,0

6,0

0,50 0,55 0,60 0,65 0,70

Spherical factor of powders

Fl

uidity

(1/Pa.s

)

Figure 2.2 Relation between spherical factor of powders and paste fluidity (Nagataki,

2000)

Other experiments carried out by Ozawa focused on the influence of mineral

admixtures, like fly ash and blast furnace slag, on the flowing ability and segregation

resistance of self-compacting concrete. He found out that the flowing ability of the

concrete improved remarkably when Portland cement was partially replaced with fly ash

and blast furnace slag. After trying different proportions of admixtures, he concluded that


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10-20% of fly ash and 25-45% of slag cement, by mass, showed the best flowing ability

and strength characteristics (Ozawa and Okamura, 1996)

Meanwhile Subrahamanian et al. were working on new mix designs in India aimed to

investigate and improve the Okamura-Ozawa studies (Subrahmanian et al., 2002). They

were trying to determine different coarse and fine aggregate contents from those developed

by Okamura. The coarse aggregate content was varied, along with water-powder (cement,

fly ash and slag) ratio, being 50%, 48% and 46% of the solid volume. The U-tube trials

were repeated for different water-powder ratios ranging from 0.3 to 0.7 in steps of 0.10. On

the basis of these trials, it was discovered that self-compactability could be achieved when

the coarse aggregate content was restricted to 46 percent instead of 50 percent tried by

Okamura. In the next series of experiments, the coarse aggregate content was fixed at 46

percent and the sand content in the mortar portion was varied from 36 percent to 44 percent

on a solid volume basis in steps of 2 percent. Again, the water-powder ratio was varied

from 0.3 to 0.7 and based on the U-tube trials a sand content of 42 percent was selected. In

order to show the necessity of using a viscosity-modifying agent along with a

superplasticizer, to reduce the segregation and bleeding, the mixture proportion developed

by the two researchers was used to cast a few trial specimens. In these trials, viscosity-

modifying agent was not used. The cast specimens were heavily reinforced slabs having

2400x600x80 mm and no vibration or any other method of compaction was used.

However, careful qualitative observations revealed that the proportions needed to be

delicately adjusted within narrow limits to eliminate bleeding as well as settlement of

coarse aggregate. It was difficult to obtain a mixture that was at the same time fluid but did

not bleed. This led to the conclusion that slight changes in water content or granulometry

of aggregate may result either in a mixture with inadequate flowing ability, or alternatively

one with a tendency for coarse aggregate to segregate. Therefore, it became necessary to

incorporate a viscosity-modifying agent in the concrete mixture.

The fresh concrete experimental results for replacing part of the binder with ultrafine

materials indicate a vast variation. So it can be concluded that the selection of a fine

material for improved concrete workability is not a simple phenomena and it cannot be

predicted from the physical or chemical characteristic of the admixture, and can only be

determined by trial mix designs.


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2.4.3. Fresh Concrete Properties

2.4.3.1. Flow Table Test. The slump flow test is one of the most popular methods in

evaluating the consistency of concrete, both in lab and on site due to its ease of operation

and the portability, where the slump is greater than 24 cm (Noor and Umoto, 1999). The

slump flow test (Figure 2.3) specified by the Japan Society of Civil Engineers (JSCE)

judges the capability of concrete to deform under its own weight against the friction of the

surface with no other external restraint present. Although slump flow test has been

designed for testing deformability it must be sometimes misleading since even concrete

with the same slump flow can have different behavior when passing through such obstacles

as reinforcing bars, depending on their mix proportion. This is why there are some other

tests (U, V,L type tests) devised to make this differentiation.

Khayat et al. used the slump flow for their measurements and took readings of the

diameter (D1,D2) of spread along two perpendicular lines as shown in Figure 2.3. Their

slump values ranged from 260 to 280 mm and their mean slump flow values (D1+D2 / 2)

ranged between 500 and 610 mm, which are comparable to the minimum accepted value of

520 mm for SCC (Beupre et al., 1999). According to Nagataki, a slump flow ranging from

500 to 700 mm is considered as the slump required for a concrete to be self-compacted

(Nagataki, 2000).

Figure 2.3 Schematic representation of slump flow

slump

D2

D1

slump flow = (D1+D2)/2

slump cone


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Venugopal et al. devised another method for flow spread test and used a mould as

shown in Figure 2.4a (Venugopal et al., 2000). The bottom diameter of the mould is 100

mm, so they defined a term for relative flow area, R, as follows;

( )1

100100

1002

2

22

=

=

DDR (2.3)

Their values for R typically ranged from 0.2 to 15, and they also found that, for a

paste made with particular powder the relative flow area, R, and the water content by

volume (Vw/Vp) are linearly related as shown in Figure 2.4.b. The characteristics of the

powder with water+SP are defined by two parameters, intercept and slope of the line. The

intercept is retained water ratio, which can be thought of as comparing water absorbed on

the powder surface together with that required to fill the voids in the powder system and to

provide sufficient dispersal of the particles. The slope angle is the deformation coefficient,

which is a measure of the sensitivity of the fluidity of the paste to increasing water content

(Venugopal et al., 2000).

Figure 2.4 Flow spread test mould and data representation (Venugopal et al., 2000)


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According to Fang et al. the slump of SCC increases with increased fly ash

content in the range of 20-40% when water binder ratio was constant (Fang et al., 1999).

This might be explained by the shape effect due to the spherical, smooth surface of the

fly ash particles, which act as lubricating balls in the mixture. They also observed a loss in

fluidity above 30% grounded fine fly ash replacement, related to increased absorption

effect between FA and cement particles after grinding.

Fang et al. also investigated the effect of silica fume and concluded that although

strength of concrete was increased to some extent, fluidity of the paste decreased. Some of

the slumps did not meet the requirements for SCC, and more SP dosage and higher water

binder ratios were required. The reasons for these were given as;(1)SF particles are fine and lightweight: they are easily absorbed on larger

particles at low water binder ratios and form flocculation

(2)Agitation time is insufficient

(3)Silica fume is not compatible with all superplastizers.

Considering these and high price of silica fume, they concluded that it is best to

use fly ash and blast furnace slag powder rather than SF (Fang et al., 1999).

According to Jianxiong et al. increased fly ash addition (above 45% cement) reduces

the flowability of SCC due to increased water requirement due to increased specific

surface. They also reported that the combined addition of fly ash and superfine slag reveals

an improved flowability comparing the slump flow (Jianxiong et al., 1999). Gram et al.

recorded that, slump flow for SCC increases with filler content (Gram et al., 2000). Studies

by Hokkaido verified that fly ash is superior to other powders (blast furnace slag and

limestone powder) in its effect to enhance flowability and control heat of hydration(Hokkaido, 1998).

2.4.3.2. U- Tube Test. A highly flowable concrete is not necessarily self-compacting,

because SCC should not only flow under its own weight, but should also fill the entire

form and achieve uniform consolidation without segregation. This characteristic of SCC is


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called the filing capacity and several test methods are designed to measure filling capacity,

U test being the most common of all.

Among the many testing methods proposed for evaluating self-compactability,

Okamura and Ouchi (Okamura and Ouchi, 1999) claims that, U-type test proposed by

the Taisei group seems, at this stage to be the most appropriate (Figure 2.5.). In this test,

the degree of compactability can be indicated by the height that the concrete reaches

after flowing through an obstacle. Concrete with the filling height of over 300 mm can

be judged as self-compacting.

The results by Khayat et al. (Khayat et al., 2002), indicate that a SCC made with highbinder content of 550 kg/m3, low sand/paste (S/Pt) volume 0.60 to 0.66, and low coarse

aggregate volume of 300 to 330 l/m3 is more suitable to ensure high filling capacity of

densely reinforced sections than a concrete of similar slump flow (650 mm) with moderate

binder content of 425 kg/m3, 0.70 to 0.85 S/Pt volume, and 275 to 405 l/m3 of coarse

aggregate.

Figure 2.5 Schematic representation of U-type test apparatus.

400 mm

Filling height

Sliding gate

Concrete

fill

Reinforcing bars4 @50 mm = 200 mm

Opening of gate

571 mm

140 mm

280 mm


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2.4.3.3. V- Funnel Test. Funnel test has been proposed for testing viscosity (Figure 2.6)

Slump flow and V-funnel flow time might be determined at different times (e.g. 6 and 60

min after first contact of cement with water).

The flow time is determined using a simple procedure; the funnel is completely

filled with fresh concrete, and the flow time is measured as the time between the opening

of the orifice and the complete emptying of the funnel. According to Bouzoubaa, a funnel

flow time of less than 6 sec was recommended for SCC (Bouzoubaa and Lachemi, 2002).

Figure 2.6 Schematic representation of the V-Funnel apparatus

2.4.3.4. L Box. Khayat et al. used the L-box for determining flowability and recorded L-

flow spread, L-flow slope and flow duration as fresh concrete properties. (Figure 2.7.)

They found that in general the mixes with higher w/cm exhibited greater flow spread and

flatter surface slopes, and concluded that such mixes might be expected to exhibit greater

deformability and filling capacity despite their similar slump flow values (Beupre et al.,

1999).

1

2

500 mm

450 mm

150 mm

75 mm

75 mm

slide gate

concrete fill


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Figure 2.7 Schematic representation of the L-Flow apparatus (Beupre et al., 1999)

2.4.3.5. Rheological Studies Although the repeatability, reliability and simplicity of the

above empirical tests are advantageous, there are many claims that a better understanding

of concrete behavior can be gained from rheological assessments. On the other hand, it has

been shown that self-compactability of concrete evaluated by U-box test can be related to

rheological parameters, such as yield stress and plastic viscosity of the mortar. Ferraris et

al. (Ferraris et al., 2000) investigated the workability of SCC with different rheometers, U-

type and V-tunnel tests and concluded that the plastic viscosity and yield stress values do

not correlate with V-funnel or U-flow test. They also claimed that slump flow is not

enough to determine whether a flowable concrete is SCC. A similar criticism to

conventional workability test methods comes from Villareal et al., arguing that a

rheological Bingham model should be used to evaluate workability of SCC (Tattersall,

1991).

When a torque is applied to an impeller immersed in a Newtonian liquid it is

observed that the there is a linear relationship between the angular speed (N) of the

impeller and torque (T). This relation is expressed as;

T= C.N (2.4)


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where C is the slope of the linear plot of N versus T and is proportional to fluidity and

viscosity of the liquid. It is obvious that this graph goes through the origin implying that

the liquid gets into motion without any initial stress to be imposed, but in the case of

concrete some minimum stress or force is necessary to get it moving at all. Which means

that it posses a yield value, and consequently the flow curve cannot pass through the

origin. So concrete does not behave like a Newtonian liquid, although the relationship

between torque and speeds is a simple straight line see Figure 2.8, at it has an intercept on

the torque axis. The equation of the line may be written;

T= C + C. N (2.5)

where T is the torque at angular speed N, C is a measure of yield value (mobility) and C

is a measure of plastic viscosity. This relation is defined by the Bingham model and

therefore concrete is called a Bingham material.

Torque, T

Speed,N

B

Slope= C''

Bingham

A

Newtonian

C'

Figure 2.8 Relationship between torque and speed in Newtonian and Bingham Model

Tattersall and Banfill classified the test methods for rheology of fresh concrete, andformed two groups of testing; empirical and rigorously defined (Tattersall, 1991). They

defined the disadvantages of empirical testing as the incomparability of the results obtained

by different methods, presence of a single-point test representing only a single operating

condition. The approach of Tattersall and Banfill has been to use the Bingham model for

fluid flow to represent the rheological behavior of fresh concrete. This is a relatively

simple linear mathematical model that relates shear rate and stress applied to fresh concrete


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with constants; the yield stress and plastic viscosity. Tattersall tried to simplify the

measurements of concrete rheology using the two-point workability test. This would be

done by obtaining a flow curve from measurements of the torque required to rotate a

suitable impeller immersed in concrete at several different speeds using the setup shown in

Figure 2.9. The application of this model to fresh concrete is an approximation, but it

appears to work reasonably well at relatively low shear rates. And in addition to the two-

point testing method there are some recently developed and more complex rheometers,

such as BML, BTRHEOM, CEMAGREF-IMG, and IBB Rheometer. (Tattersall, 1991). .

Figure 2.9 Two-point workability apparatus (Tattersall, 1991)


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2.4.3.6. Segregation. Segregation is defined by Neville, as the separation of the constituent

of a heterogeneous mixture so that their distribution is no longer uniform (Neville, 1986).

Concrete is naturally susceptible to segregation due to the different particle sizes and

specific gravities of its constituents. This natural tendency can be controlled by suitable

grading, care in handling, or using admixtures to attain flowability and appropriate

viscosity as in SCC.

There are two basic types of segregation. In the first coarser aggregate separates

out as they travel further down a slope or settle more than finer particles. In the second

form of segregation, which is mostly observed in wet mixes, grout is separated from the

mix.

There are different ways to determine the segregation in fresh concrete. The

segregation of the aggregates might be monitored during slump flow test. The concrete

having proper self-compactability should not exhibit any segregation even at the periphery

of slumped material (Beupre et al., 1999). Another common method in testing segregation

in hardened concrete is to cut the specimens in two and to observe the cross-section for any

apparent segregation of coarse aggregate (Saak et al., 2001).

Using a modified sum of squares approach (Khayat, 1998), mean of coarse aggregate

concentration and the segregation coefficient were calculated using the following

expressions Eq. 2.6.

whereG , Gi , N, and SC correspond to the mean of coarse aggregate concentration, the

concentration of coarse aggregate (percentage of surface area of concrete section), the

number of cross-sections (6 in this case) and the segregation coefficient (percent)

respectively. It has been reported that typical values of segregation coefficients of a stable,

self-compacting concrete can be lower than 7 per cent (RILEM Report on SCC, 2000).

=

=

n

i

i

N

GG

1 N

GG

SC

n

i

i=

=1

2)((2.6)


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zkul et al., investigated segregation using cores taken from different locations of a

1500x200x1000 mm specimen along with visual segregation monitoring during flow tests

(zkul et al., 2000). In the study by Khayat et al. segregation was determined by gently

pouring a fresh concrete sample from a 2 L container over a 5 mm mesh to observe the

quantity of mortar passing through the screen after 5 min (Khayat et al., 2000). The

segregation index, SI, is taken as the ratio of the mortar passing through the screen to that

contained in the 2 L concrete sample. A stable concrete should exhibit an SI value lower

than 5%. Bouzoubaa investigated segregation index of SCC using the same method

(Bouzoubaa and Lachemi, 2002) and reported that segregation index of SCC with similar

water-to-cementitious materials ratio (0.45) decreases with an increase of the percentage of

the fly ash used.

Considering the powder type SCC that contains 40% greater volume of powder

compared to ordinary concrete and experiments have shown that, this increase in powder

content enhances stability and segregation resistance of the mix (Sonebi et al., 2000).

2.4.4. Mechanical Properties

2.4.4.1. Compressive Strength. When testing the compressive strength of SCC, generally,

150x200 cylinders are tested according to ASTM C 39 or BS 1881: Part 116 B. There are

also elastic modulus and core compressive strength evaluations to determine the

homogeneity in larger SCC samples.

Working with SCC, Beupre et al., reported that higher strengths (64 MPa) at 28 days

(ASTM C 39) were obtained in non-air entrained concrete made with low w/cm (0.35) and

silica fume (%3 replacement) (Beupre et al. 1999). According to test core studies by

Khayat (Khayat et al. 2001), Zhu (Zhu et al., 2001) and also zkul (zkul et al., 2000)

there are no significant difference in the uniformity of in situ properties between the SCC

mixes and the corresponding well compacted conventional mixes. However, compressive

strength and modulus of elasticity were greater for SCC samples than those obtained from

the medium fluidity conventional concrete.


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In a different approach, Paultre et al. reported that SCC, despite its high deformability,

could develop lower in-place (in a reinforced column) compressive strength (10% lower)

than strength determined on control cylinders of same concrete (Khayat et al., 2001).

It has been reported that SCC containing up to 50% fly ash (Class F) replacement can

attain 28-day target strengths of 35 MPa (Bouzoubaa and Lachemi, 2002). It is also shown

by cost analysis that SCC made with 50% of fly ash and with a water-to-cementitious

materials ratio of 0.45 can reach a 28-day compressive strength of 35 MPa with no

significant extra cost compared to ordinary concrete. Such a SCC would be flowable with a

slump flow of 500 mm and flow time of 3 sec, more resistant to segregation and thermal

cracking, but might exhibit higher bleeding water and long setting time. It should be notedthat, this cost comparison is in contradiction with some research reporting average cost of

SCC as 25 to 50 % more than conventional concrete (Khayat et al., 2002).

According to compressive strength studies by Topu et al on SCC, the cementitious

factor for fly ash is approximately 0.25 (4 kg of fly ash is equivalent to 1 kg of cement) and

that for silica fume is about 2.5 (Topu and Khurana, 2000). Generally, studies with fly ash

replacement have shown that it is possible to produce high volume fly ash concrete (50-60% cement by weight) with compressive strength values similar or even higher than

conventional concrete with the use of proper high range water reducers and air entrainment

admixtures

Fang et al. concluded that 20, 30 and 40 % fly ash replacement of cement reduces the

early strength of SCC, but the 28 day compressive strength values reaches (40% FA) or

even exceeds (2030% FA) the values for corresponding concretes without fly ash (Fang et

al., 1999). Jianxiaong et al. found that SCC can be produced with superfine sand (0.63-1.2

FM) and 30-60% slag and fly ash, having 28 days compressive strengths of 50-86 MPa

(Jianxiaong, 1999). And Takada et al. (Takada et al., 1998) also found that silica fume

addition increased the strength of SCC with an increased demand for SP. On the other

hand, fly ash increases workability without additional dosage of SP, but its contribution to

strength is limited although increasing with time (Jacobs and Hunkeler, 1999).


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Perssons study (Persson, 2001), reveals that elastic modulus, creep, and shrinkage of

SCC did not differ significantly from the same properties in normal concrete. Other

researchers (Gram et al., 2000), (Sonebi and Bartos, 2000) support the finding for modulus

of elasticity adding that compressive strength of SCC is better than ordinary concrete both

at 1 and 28 days. They related this strength increase to the homogeneity of the SCC with

much less voids due to water separation and smaller cement grains forming better packed

smaller crystals, rather than big ones. At a given strength the modulus of elasticity of SCC

is found to be lower than that of a common concrete due to the smaller maximum grain

size and the higher amount of cement paste in SCC (Jacobs and Hunkeler, 1999).

Ray and Chattopadhyay carried out studies on the effects of 4, 8, 12, 16% of silica

fume by weight of cement on compressive strength. Concretes with a content of 8% silica

fume showed the highest compressive strength values after 28 days (45 MPa), followed by

concretes having 4, 12, and 16%. Addition of silica fume at all percentages improved the

flexural strength, with a significant rise for a 4% SF to 8.5 MPa (Ray and Chattopadhyay

1999).

The influence of silica fume on workability and compressive strength of concretes

were the major research objectives for Duval and Kadri. Concretes that have been

investigated had low water-cement ratios (0.25 to 0.40). The type I Portland cement was

replaced by 10-30% by mass silica fume and superplasticizer was added. It was found that

silica fume increased best the compressive strength (25%) and the workability of concretes

when its content was between 4 and 8 %. Duval and Kadri also found out that if silica

fume exceeds 15% of the cementitious material, both compressive and tensile strengths are

reduced (Duval and Kadri 1998).

Yan et al., studied the hydration process of cement-fly ash pastes with

superplasticizer. At low water-binder ratio, the presence of fly ash improved the fluidity of

fresh paste. Nagataki et al. measured the strength of fly ash high-performance concrete

containing variable amounts of silica fume. Flowability increased with fly ash content

whereas strength increased with silica fume content. Pore size distribution was determined

to show the positive effect of adding silica fume to fly ash (Hawkins et al., 1998).


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An extensive survey of the literature conducted by the Portland Cement Association

concluded that "in general, the use of up to 5 % limestone does not affect the performance

of Portland cement." Even higher contents of ground limestone could potentially be

utilized in lower water-to-cement ratio (< 0.45) systems, where a substantial fraction of the

cement clinker particles remains unhydrated, effectively acting as a rather expensive filler

material (Bentz, 2005) .

Compressive strength decreases as limestone is added because the amount of cement

in the mixture decreases as the limestone powder increases (Selih et al., 2003). It has been

also observed by other researchers that limestone powder reduces compressive strength

(Lert, et al. 2000). Limestone accelerates the hydration of C3S to form a calcium silicate

hydrate that incorporates CO2 in its structure. When mixed with limestone, the hydration

of C3A led to the formation of calcium monocarboaluminate. Study of the mixture C3S-

C3A-limestone-anhydrous calcium sulfate showed that initially ettringite and a calcium

silicate aluminate hydrate gel incorporating CO2 were formed. Later, calcium

monocarboaluminate was formed (Hawkins et al., 1998). All of these reactions seem to

contribute to the final strength of concrete to a very limited extent.

Sprung and Siebel found that the use of inert material as a very fine filler can lead to

an increase in strength due to improved packing of the particles (i.e., filling of voids

between the cement grains). This effect is seen at early ages, but unlike the case with fly

ash or other pozzolanic materials, does not produce additional increases in strength with

continued curing. When limestone is included in large quantities (15% to 25%) it acts as a

diluent so that strengths are lower than for comparable Portland cement concretes (Sprung

and Siebel, 1991).

2.4.4.2. Splitting Tensile Strength. For high performance silica fume concretes it was

found that the fracture resistance (toughness and energy) decreased and the brittleness

increased with the age of the concrete. This was attributed to the increase in the strength of

the cement paste and the interface leading to fewer bond cracking and more aggregate

rupture. Hence it appears as the tendency of a higher splitting tensile strength of SCC.

Likely as not, the reason for this fact is given by the better microstructure, especially the


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smaller total porosity and the more even pore size distribution within the interfacial

transition zone of SCC. Further a denser cement matrix is present due to the higher content

of ultra-fines.

SCC can be obtained in such a way, by adding chemical and mineral admixtures, so

that its splitting tensile and compressive strengths are higher than those of normal vibrated

concrete. An average increase in compressive strength of 60% has been obtained for SCC,

whereas 30% was the increase in splitting tensile strength. Also, due to the use of chemical

and mineral admixtures, SCC has shown smaller interface micro-cracks than normal

concrete, fact which led to a better bonding between aggregate and cement paste and to an

increase in splitting tensile and compressive strengths. A measure of the better bonding

was the greater percentage of the fractured aggregate in SCC (20-25%) compared to the

10% for normal concrete.

Pfeifer (Pfeifer,

effect of binder composition on durability and mechanical properties of high performance self...

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