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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
deteriorated surfaces
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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
Table 4.10. Different stages of image analysis in calculating the area ratio for
column M2.
Table 4.11. Different stages of image analysis in calculating the area ratio for
column M3 .
Table 4.12. Different stages of image analysis in calculating the area ratio for
column M4
Table 4.13. Different stages of image analysis in calculating the area ratio for
column M5.
Table 4.14. Different stages of image analysis in calculating the area ratio for
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 4.21. Stages of image analysis at the steel-concrete interface for column M5...
Table 4.22. Stages of image analysis at the steel-concrete interface for column M6...
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
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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
G
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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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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,
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