EXPERIMENTAL STUDY FOR THE

PRODUCTION OF HIGH STRENGTH

CONCRETE IN PAKISTAN

Session: 2013-2017

PROJECT ADVISOR
DR. ASAD ULLAH QAZI
PROFESSOR

SUBMITTED BY

ABDUL BASIT ALI 2013-CIV-24

YASIR IQBAL 2013-CIV-33
MUHAMMAD NOMAN MEHBOOB 2013-CIV-23
MUHAMMAD TAHA 2013-CIV-18

DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY
LAHORE, PAKISTAN
 EXPERIMENTAL STUDY FOR THE PRODUCTION OF
HIGH STRENGTH CONCRETE IN PAKISTAN

Session: 2013-2017

GROUP MEMBERS

ABDUL BASIT ALI 2013-CIV-24

YASIR IQBAL 2013-CIV-33
MUHAMMAD NOMAN MEHBOOB 2013-CIV-23
MUHAMMAD TAHA 2013-CIV-18

INTERNAL EXAMINER External Examiner

DR. ASAD ULLAH QAZI

Final year project report submitted in partial fulfilment of the requirements for the Degree of
B.Sc. Civil Engineering

DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY LAHORE,
PAKISTAN
 DEDICATED TO
BELOVED PARENTS AND FACULTY
MEMBERS
 ACKNOWLEDGEMENTS

All praises and gratefulness to The Almighty Allah who bestowed upon us the illumination and
courage to fulfil our commitments towards our research thesis.

Though only names of group members appears on the cover of this dissertation, a great many
people have contributed to its production. We owe our gratitude to all those people who have
made this dissertation possible and because of whom our graduate experience has been one that
we will cherish forever.

Our deepest gratitude is to our advisor, Sir Dr. Asad Ullah Qazi, Professor Department of
Civil Engineering, U.E.T Lahore. We have been amazingly fortunate to have an advisor who
gave us the freedom to explore on our own, and at the same time the guidance to recover when
our steps faltered. He taught us how to question thoughts and express ideas. His patience and
support helped us overcome many crisis situations and finish this dissertation.

We also express our gratitude to Dr. Abdul Sattar Shakir, Dean Faculty of Civil Engineering,
Dr. Zahid Ahmed Siddiqui, Chairman Civil Engineering Department, Dr. Usman Akmal, Dr.
Imtiaz Rasheed and Dr. Rashid, Civil Engineering Department, for their advices, productive
criticism, and comments were of utmost significance and rampant honour to us. Their valuable
suggestions, painstaking attention and friendly counselling provided us a backing in achieving
our objectives which otherwise seemed to be extremely intricate.

We also attribute our acknowledgments to Habib Construction Services Pvt. Limited for
providing the necessary information, manuals and the materials for the purpose of casting and
Testing. We owe our sincere thanks to Sir Engineer Abid Mahmood, Deputy Project Manager
at Habib Construction Services Pvt. Limited. For their guidance.

We are greatly thankful to Mr. Muhammad Munir and other laboratory staff for their assistance
in the laboratory testing.

Most importantly, none of this would have been possible without the love and patience of our
families. Our families to whom this dissertation is dedicated to, have been a constant source of
love, concern, support and strength all these years.

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 ABSTRACT

Concrete is a durable and versatile construction material. It is not only strong, economical and
takes the shape of the form in which it is placed, but it is also aesthetically satisfying. However
experience has shown that concrete is vulnerable to deterioration, unless precautionary
measures are taken during the design and production. For this we need to understand the
influence of components on the behaviour of concrete and to produce a concrete mix within
closely controlled tolerances. Concrete is the largest man-made material used globally for
various purposes. In India the annual consumption is exceeding 100 million cubic meters. The
time is arrived at which, concrete must be developed for high strength which is an important
factor in the design of a mix. What is needed most is a systematic, reproducible procedure for
attaining high strength concrete with readily available materials using conventional ready-mix
batching procedures. If an engineer is to take advantage of this material, he must be given
reason to be confident that high strength concrete can be produced and used safely,
economically, and efficiently. This research program constitutes the much needed first step
towards the development of the necessary information for using high strength concrete in
Pakistan.

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Table of Contents
ACKNOWLEDGEMENTS ..................................................................................................... i
ABSTRACT ..............................................................................................................................ii
1. INTRODUCTION............................................................................................................ 2
1.1 A Need for This Research ................................................................................................ 2
1.2 Objectives ........................................................................................................................ 3
1.3 Definition of High Strength Concrete .............................................................................. 3
1.4 Applications of High Strength Concrete .......................................................................... 4
1.4.1 High Rise Buildings .................................................................................................. 5
1.4.2 Highway Bridges ...................................................................................................... 6
1.5 Disadvantages of High Strength Concrete ....................................................................... 6
1.6 Methods of Producing High Strength Concrete ............................................................... 7
1.7 Scope for This Program ................................................................................................... 7
2. RESEARCH BACKGROUND AND LITERATURE REVIEW .............................. 10
2.1 Research Background: ................................................................................................... 10
2.2 Local Approaches: ......................................................................................................... 11
2.3 Strength Classification for Pakistan: .............................................................................. 12
2.4 Mechanical properties of HSC ....................................................................................... 13
2.4.1 Compressive strength .............................................................................................. 13
2.4.2 Tensile Strength ...................................................................................................... 13
2.4.3 Durability ................................................................................................................ 13
2.4.4 Ductility .................................................................................................................. 14
2.4.5 Modulus of Elasticity .............................................................................................. 14
2.5 Characterization Studies of HSC............................................................................... 14
2.5.1 Shrinkage ........................................................................................................... 14
2.5.2 Permeability ....................................................................................................... 15
2.5.3 Diffusion ............................................................................................................ 15
2.5.4 Chemical attack .................................................................................................. 15
2.5.5 Carbonation ........................................................................................................ 15
2.5.6 Abrasion Resistance ........................................................................................... 15
2.5.7 Air Entrainment ................................................................................................. 16
2.5.8 Placing, Consolidation and Curing .................................................................... 16
2.6 Materials: ................................................................................................................... 18

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 2.6.1 Cement ............................................................................................................... 19
2.6.2 Coarse Aggregate ............................................................................................... 21
2.6.3 Fine Aggregate ................................................................................................... 22
2.6.4 Mineral and Chemical Admixtures .................................................................... 23
3. MATERIALS AND TEST PROCEDURES ................................................................ 27
3.1 Introduction .................................................................................................................... 27
3.2 Material Properties ......................................................................................................... 27
3.2.1 Cement .................................................................................................................... 28
3.2.2 Coarse Aggregate. ................................................................................................... 29
3.2.3 Fine Aggregate. ....................................................................................................... 29
3.2.4 Chemical Admixtures. ............................................................................................ 30
3.2.5 Silica fume .............................................................................................................. 30
3.2.6 Moisture content of aggregates ............................................................................... 31
3.2.7 Sand to aggregate ratio............................................................................................ 31
3.2.8 Water ....................................................................................................................... 32
3.3 Proportioning Mixing and Testing ............................................................................ 32
3.3.1 Introduction. ............................................................................................................ 32
3.3.2 Proportioning .......................................................................................................... 33
3.3.3 Mixing Procedures .................................................................................................. 33
3.3.4 Tests on Fresh Concrete. ......................................................................................... 34
3.3.5 Testing..................................................................................................................... 34
3.4 Conclusion ..................................................................................................................... 35
4. Test Results and Discussion on Test Results ................................................................... 37
4.1 Introduction .................................................................................................................... 37
4.2 Cement Content ............................................................................................................. 37
4.3 Water/Cement Ratio....................................................................................................... 37
4.4 Cement Type .................................................................................................................. 37
4.5 Super plasticizer Dose and Brand .................................................................................. 38
4.6 Coarse Aggregate Size ................................................................................................... 38
4.7 Coarse Aggregate Gradation .......................................................................................... 38
4.8 Coarse Aggregate ........................................................................................................... 38
4.9 Sand Fineness................................................................................................................. 39
4.10 High Strength Concrete and Test Age ......................................................................... 39

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 4.11 Compaction, Curing and Capping................................................................................ 39
4.12 Mold Types and Sizes .................................................................................................. 39
4.13 Super plasticizers and Workability .............................................................................. 39
4.14 Experimental Works .................................................................................................... 40
Tentative Work 1 ............................................................................................................. 40
Tentative Work 2 ............................................................................................................. 42
Tentative Work 3 ............................................................................................................. 44
Tentative Work 4 ............................................................................................................. 46
Tentative Work 5 ............................................................................................................. 48
Tentative Work 6 ............................................................................................................. 50
Tentative Work 7 ............................................................................................................. 52
Tentative Work 8 ............................................................................................................. 54
Tentative Work 9 ............................................................................................................. 56
Tentative Work 10 ........................................................................................................... 58
4.15 Failure Patterns ............................................................................................................ 60
5. Conclusions and Recommendations ................................................................................. 62
6. References ........................................................................................................................... 65

v|Page
LIST OF TABLES AND FIGURES

TABLE 2.1: DIFFUSION CO-EFFICIENT OF DIFFERENT TYPE OF CEMENT ..................................... 15

TABLE 3.1: MATERIALS USED IN HIGH STRENGTH CONCRETE.................................................... 28
TABLE 3.2 PHYSICAL PROPERTIES OF 53 GRADE CEMENT ........................................................ 28
TABLE 3.3: SUMMARIZES THE PROPERTIES OF COARSE AGGREGATES. ...................................... 29
TABLE 3.4 SUMMARIZES THE PROPERTIES OF THE FINE AGGREGATES USED IN THIS STUDY. ...... 29
TABLE 3.5: SUMMARY OF ADMIXTURES USED IN THE BATCHING PROCESS. ............................... 30
TABLE 3.6: THE VARIATION IN THE MOISTURE CONTENT IN EACH BATCHING. ........................... 31
FIGURE 3.1: CONCRETE BATCHING LABORATORY WITH THE CONCRETE MIXER USED ............... 32
FIGURE 3.2: THE 400-TONS COMPRESSIVE TESTING MACHINE USED IN THIS STUDY. ................. 35
TABLE 4.1: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 1 ................................. 40
TABLE 4.2: TEST RESULTS FOR TENTATIVE WORK 1 ................................................................ 41
TABLE 4.3: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 2 ............................... 42
TABLE 4.4: TEST RESULTS FOR TENTATIVE WORK 2 ................................................................ 43
TABLE 4.5: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 3 ............................... 44
TABLE 4.6: TEST RESULTS FOR TENTATIVE WORK 3 ................................................................ 45
TABLE 4.7: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 4 ............................... 46
TABLE 4.8: TEST RESULTS FOR TENTATIVE WORK 4 ................................................................ 47
TABLE 4.9: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 5 ............................... 48
TABLE 4.10: TEST RESULTS FOR TENTATIVE WORK 5 .............................................................. 49
TABLE 4.11: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 6 ............................. 50
TABLE 4.12: TEST RESULTS FOR TENTATIVE WORK 6 .............................................................. 51
TABLE 4.13: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 7 ............................. 52
TABLE 4.14: TEST RESULTS FOR TENTATIVE WORK 7 .............................................................. 53
TABLE 4.15: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 8 ............................. 54
TABLE 4.16: TEST RESULTS FOR TENTATIVE WORK 8 .............................................................. 55
TABLE 4.17: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 9 ............................. 56
TABLE 4.18: TEST RESULTS FOR TENTATIVE WORK 9 .............................................................. 57
TABLE 4.19: CONCRETE MIX DESIGN CRITERION FOR TENTATIVE WORK 10 ........................... 58
TABLE 4.20: TEST RESULTS FOR TENTATIVE WORK 10 ............................................................ 59

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CHAPTER 1 INTRODUCTION

CHAPTER 1

INTRODUCTION

1|Page
CHAPTER 1 INTRODUCTION

1. INTRODUCTION

Engineers are currently faced with increasing demands for improved efficiency and reduced
concrete construction costs from developers and governmental agencies. As a result, engineers
are beginning to design larger structures using higher strength concrete at higher
stress levels.
There are distinct advantages in the use of concrete with compressive strengths in the range
from 9,000 to 12,000 psi (60 MPa to 85 MPa) in both reinforced and pre-stressed concrete
construction. For a given cross-section, pre-stressed concrete bridge girders can carry greater
service loads across longer spans if made using high strength concrete. In high-rise buildings,
where the main disadvantages of using concrete compared to steel are higher dead loads and
large column cross-sections, using high strength concrete makes possible significant reductions
in total structural dead weight and in column dimensions. Thus, concrete becomes technically
and economically feasible as a structural alternative to steel in tall buildings when high strength
concrete is used.
In addition, cost comparisons have shown that the savings obtained through the use of smaller
and lighter high strength concrete members are significantly greater than the added cost of the
higher quality concrete. Also, observed improvements in durability, shrinkage, and creep
characteristics of high strength concrete will decrease serviceability and maintenance
problems.
Numerous high strength concrete structures now standing in the developed countries and
elsewhere were constructed using concrete with a compressive strength of between 8,000 psi
and 11,000 psi (55 MPa and 75 MPa). Remarkably, the use of high strength concrete has
preceded full information on its engineering properties, which are significantly different in
some respects from those of ordinary strength materials. Current understanding of the
behaviour of concrete under load and the empirical equations now used to predict such basic
properties as modulus of elasticity and tensile strength are based mainly on tests of concrete
having a compressive strength of about 5,000 psi or less (35 MPa or less). Extrapolation to
higher strength levels is unjustified and may be dangerous. There is an urgent need for studies
focussing on the development of constitutive relationships applicable to design of structural
members made using high strength concrete. For example, little is known about predicting the
material's behaviour in high shear zones or its confined strength in overstressed compression
members.
Concrete compressive strengths of over 15,000 psi (100 MPa) have been achieved in the
laboratory for many years. It has been demonstrated that the production of high strength
concrete having a compressive strength of 9,000 to 12,000 psi, using conventional materials
and production methods, is technically and economically feasible. However, very little
information has been developed concerning the identification of the most relevant parameters
in the selection of materials and their proportions for producing high strength concrete. This is

2|Page
CHAPTER 1 INTRODUCTION

not surprising, given the variability in physical properties and availability of concrete-making
materials in different regions of the PAK Mix design guidelines for high strength concrete need
to be developed for each region of the country. Also, current quality control standards, as they
relate to materials used in concrete, especially cement, are not narrow enough to ensure
consistent production of good quality high strength concrete.
What is needed most is a systematic, reproducible procedure for attaining high strength
concrete with readily available materials using conventional ready-mix batching procedures. If
an engineer is to take advantage of this material, he must be given reason to be confident that
high strength concrete can be produced and used safely, economically, and efficiently. This
research program constitutes the much needed first step towards the development of the
necessary information for using high strength concrete in highway structures in the State of
Pakistan.

The overall objectives of this research are as follows:

1. To identify the most relevant properties of cement, aggregate, and admixtures for
producing high strength concrete.
2. To evaluate the suitability of commercially available cements, aggregates, and
admixtures in Pakistan for the production of high strength concrete.
3. To establish, in a form useful for practicing engineers in Pakistan, guidelines for the
selection of materials and their proportions for producing high strength concrete.
4. To study the effect of different curing conditions, temperature and relative humidity,
typical of those existing in Pakistan upon the compressive strength of high strength
concrete.
5. To study the effect of mixing temperature and different mixing times typical of those
in construction in Pakistan on the properties of fresh high strength concrete.
6. To study the applicability of current methods of measuring concrete strength such as
standard concrete cylinder and flexural strength tests in predicting the strength of high
strength concrete.

High strength concrete refers to concrete which has a uniaxial compressive strength greater
than that which is ordinarily obtained in a region. This definition has been widely accepted by
practicing engineers because the maximum strength concrete which is currently being produced
varies considerably from region to region in the Islamic State of Pakistan.
Further complications in defining high strength concrete arise from specimen types used for
compression testing and age at testing. For example, a 6-in. dia. x 12-in. cylinder, as is used in
the U.S., and a 6-in. x 6-in. cube, as is used in Europe, molded from the same batch of concrete
will yield two completely different compressive strengths. Whether specimens are tested at 28,
56, or 90 days, any of which may be more appropriate than the others for a particular job, can
make a tremendous difference in the measured compressive strength.

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CHAPTER 1 INTRODUCTION

Researchers and practicing engineers have not yet agreed on what compressive strength
constitutes high strength for plain concrete. High strength, Normal weight concrete has been
defined by some as concrete having a compressive strength of at least 6,000 psi (40 MPa) at 28
days. Shah defined high strength for lightweight concrete as having a compressive strength of
over 4,000 psi, whereas Albinger set the lower limit for lightweight concrete at 5,000 psi.
Others used 8,000 psi as the minimum compressive strength for normal weight high strength
concrete. Engineers in the Chicago area who have for some time been using 10,000 psi concrete
in high-rise buildings have been developing the technology needed to consistently produce
concrete having strengths in excess of 12,000 psi. Perenchio suggested that the
upper limit to high strength concrete will not be reached until the strength of the cement paste
is fully utilized at about 25,000 psi.
According to Saucier, the eventual ceiling on concrete strength is virtually unlimited. He
reported, however, that very high compressive strengths will only be achieved by changing
production methods. Currently, he stated, 5,000 to 10,000 psi concrete can be produced nearly
anywhere in the U.S. by using conventional production techniques, by properly selecting
materials and by maintaining good quality control. It is possible to produce concrete with a
compressive strength of up to 15,000 psi by utilizing more expensive materials and improved
production techniques. For concrete compressive strengths over 15,000 psi, “exotic”
procedures and materials may have to be employed.
The main objective of this research program was to establish criteria for selection of materials
and their proportions to achieve uniform, economical, high-quality concrete with a compressive
strength between 9,000 and 12,000 psi at 56 days using 6-in. dia. x 12-1n. Cylinders cast in
steel molds. Only ordinary concrete-making materials and conventional production techniques
currently used by pre-stressing plants in Pakistan were used in this project.

There are definite advantages, both technical and economical, in using high strength concrete
in structures today. Carpenter listed the advantages of using high strength concrete in highway
bridge applications as:
1. Greater compressive strength per unit cost, per unit weight, and per unit volume.
2. Increased modulus of elasticity which aids when deflection and stability control the
design.
3. Increased tensile strength, which is a controlling parameter in the design of pre-stressed
concrete members under service loads.
Nilson and Anderson concluded that losses in pre-stressing forces will be reduced because of
improved long-term deflection properties of high strength concrete. The National Crushed
Stone Association reported that high strength concrete has greater durability and resistance to
abrasion and wear than normal strength concrete. Cracking and damage of precast concrete
products during delivery and handling can be reduced by using high strength concrete. Due to
a higher fines content, high strength concrete can give a more satisfactory appearance on
formed and finished surfaces than normal strength concrete.

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CHAPTER 1 INTRODUCTION

It has been estimated that for certain minimum heights and spans of structures, high strength
concrete gnerally permits more economical construction due to reduced structural member
cross-section dimensions. This results in a reduction in the volume of concrete
required and smaller dead loads.
1.4.1 High Rise Buildings
Most applications of high strength concrete to date have been in high-rise buildings. High
strength concrete has already been used in columns, shear walls, and foundations of high-rise
buildings in cities such as Houston, Dallas, Chicago, New York, and abroad. Tall structures
whose construction using normal strength concrete would not have been feasible have been
successfully completed using high strength concrete. Column and beam dimensions can be
reduced resulting in decreased dead weight of the structure, and an increase in the amount of
rentable floor space in the lower stories. Reduced dead weight can substantially lessen the
design requirements for the building's foundation.
It has been shown that in a 50-story structure requiring 4 ft. dia. columns using 4,000 psi
concrete, redesign using 8,000 psi concrete would result in a reduction of 33 percent in column
diameters. Typically, high strength concrete is used only in columns in the lower stories. It has
been suggested that 30 stories is the minimum height for a building for which high strength
concrete is beneficial.
Nilson stated that despite differences in shrinkage and creep behaviour of higher strength
concrete used in columns and normal strength concrete used in adjoining slabs, no problems
have been encountered in actual structures. Based on material and labour costs and the price of
rental space in high-rise buildings in the Chicago area, it was determined that using high
strength concrete to obtain the smallest member sections having only 1 percent reinforcement
resulted in the most economical construction alternative.
The Chicago Task Force reported that 1,500 psi concrete was first used in Chicago in 1965 in
the Lake Point Tower. In 1912, concrete having a compressive strength of 9,000 psi was used
in the first 20 stories of the 50-story Mid-continental Plaza Building. In 1916, two
experimental 11,000 psi concrete columns were instrumented and constructed as part of the
River Plaza Project. The tallest concrete structure to date is the 19-story Water Tower Place in
Chicago, the first 28 stories of which are supported by 48-in. dia., 9,000 psi tied columns with
8 percent longitudinal reinforcement.
At least two high-rise buildings in New York City have utilized 8,000 psi concrete in the lower
story columns. 101 Park Avenue Tower (46 stories) and The Palace Hotel (51 stories). In
Toronto's Royal Bank Plaza Project, 8,000 psi concrete was also used.
In Houston, 35 percent of the concrete in the Texas Commerce Tower had a compressive
strength of 6,000 psi or greater. Columns, shear walls, and spandrels in the first eight floors
were cast using a 7-in. slump, pumped concrete mix which had a 7,500 psi compressive
strength.
In the 72-story InterFirst Plaza in Dallas, the design strength of the concrete was 10,000 psi. The
structure's 16 exterior columns, which vary in size from 6 ft x 6 ft to 8 ft x 8 ft, are set on 30 ft centers
and are designed to carry the gravity load and base shear.

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CHAPTER 1 INTRODUCTION

1.4.2 Highway Bridges

Pre-stressed, precast concrete bridge girders in Texas normally do not exceed 135 ft to 150 ft in length.
Steel members are currently used for spans greater than 135 ft to 150 ft. High strength concrete would
permit using greater spans for a given number of girders, or fewer girders for ordinary spans, than when
using normal strength concrete. Carpenter showed that a typical bridge design for a 150 ft span would
require using nine girders if 6,000 psi concrete were used while only four girders would be needed if
10,000 psi concrete were used. As a result, the slab thickness had to be increased from 5.5 in. to 6.5 in.
in order to support the traffic load on the wider girder spacing. However, the overall dead load of the
bridge was reduced. This comparison was based on allowable tensile stresses in the concrete of 3 √fc’
an allowable compressive stress of 0.4 √fc’ and a live load deflection criteria of L/800, where fc’ refers
to concrete compressive strength (psi) and L refers to the girder span. The limiting factor controlling
the design in this case was spacing of the pre-stressing tendons within the girders. The use of fewer
tendons of a larger diameter and of new girder sections and shapes may have to be considered for
efficient use of high strength concrete in bridge girders.
Japanese I-shaped, box, and rectangular section bridge girders have been constructed using
8,500 psi concrete. These highway and railroad bridges have clear spans of between 100 and
280 ft. The 1-girders spanned over 150 ft.
A reduction in number and size of bridge columns and piers can result from a reduction in dead
load and use of longer spans due to the use of a higher concrete compressive strength. This will
allow for significant savings in cost, labour, and construction time.
Other applications of high strength concrete include both heavily loaded transfer girders and
offshore structures.
No special or "exotic" techniques were employed in constructing any of the high strength
concrete structures mentioned in this section. All utilized high-quality materials and good
quality control programs.

Most of the disadvantages of using high strength concrete listed by engineers result from a
lack of research and available information on the behaviour of high strength concrete under
actual field conditions. Some of the drawbacks reported in the past have been alleviated by
recent developments and improvements in admixtures.
Possible drawbacks in using high strength concrete are listed below:
1. Increased quality control is needed.
2. High quality materials are less available and often cost more.
3. Allowable stresses in codes may discourage the use of high strength concrete.
4. Minimum thickness or cover may govern the design, preventing realization of full
benefit of higher strength.
5. Total available pre-stress force may be insufficient to fully develop the strength.
6. Adequate curing can be difficult due to self-desiccation of low water/cement ratio
mixes. Even with no water loss by evaporation there is inadequate water for full
hydration.

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CHAPTER 1 INTRODUCTION

7. Curing can also be difficult because of the rapidly increasing im-permeability of

high strength concrete, which prevents applied curing water from compensating for
any initial moisture loss.
A further disadvantage may be that, in structural members where excessive deflections control
the design, full utilization of the material's load-carrying capacity when using high strength
concrete would not be possible. For instance, the higher flexural strength of a high strength
concrete flat slab or plate is of little consequence since deflection often controls design.

Several exotic methods for producing high strength concrete have been studied, such as
 Modification with polymers.
 Fiber reinforcement.
 Slurry mixing (preb1ending water and cement at high speed for efficient hydration).
 Compaction by pressure.
 Compaction by pressure combined with vibration.
 Autoclave curing.
 Mix proportioning using active or artificial aggregates.
One study advocated re-vibration 2.5 hours after initial vibration as a means for achieving
higher strengths. Structural design which accounts for additional concrete strength resulting
from tri-axial compression or concrete confinement is also possible.
However, cost-effective production of high strength concrete in construction today is achieved
by carefully selecting, controlling, and combining cement, fly ash, admixtures, aggregates, and
water. Freedman stated that in order to achieve higher strength concretes the concrete producer
must optimize the cement characteristics, aggregate quality, paste proportioning, aggregate-
paste interaction, mixing, consolidation, and curing procedures. The use of fly ash and very
low water-cement ratios has been widely recommended for producing high strength concrete.
The National Crushed Stone Association further stated that cooperation and coordination
among the engineer, architect, materials suppliers, ready-mix producers, contractor, and the
testing and inspection agency are required for a successful high strength concrete project.

This report is divided into six chapters. An introduction and a brief literature review of the
production of high strength concrete are presented in Chapters I and II. The experimental work
is described in Chapter III. Test results are presented and discussed/ analyzed in Chapter IV.
Conclusions and recommendations for producing high strength concrete are presented in
Chapter V. The selected references are listed in Chapter VI.
Approximately 150 concrete specimens, representing over 10 different batches of concrete
were made and tested as part of this study. While mixing procedures and slump were kept
constant, the variables studied include materials, proportions, and specimen types, mixing
temperature, test age, capping material and curing conditions.
A detailed listing of mix proportion and strength test data for all mixes made is included in
Chapter IV.

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CHAPTER 1 INTRODUCTION

In this study, the research approach was to investigate basic interactions among concrete
components in mix proportions which are suitable for producing high strength concrete, i.e.,
low water-cement ratio and high cement content. For this reason, it was important first to know
the effects of using different cements and aggregates in high concrete mixes which contained
no admixtures, and second, to develop fundamental knowledge regarding other available
materials such as silica fume and super plasticizers. Only commercially available materials and
conventional production techniques used by the Islamic State of Pakistan, Department of
Highways and Public Transportation were utilized in this program. Valuable guidelines have
been established to be followed by practicing engineers in the development of trial mixes for
producing high strength concrete. Without question, a trial mix design procedure must be used
for proportioning high strength concrete in the field.

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CHAPTER 2 RESEARCH BACKGROUND AND LITERATURE REVIEW

CHAPTER 2

RESEARCH BACKGROUND
&
LITERATURE REVIEW

9|Page
CHAPTER 2 RESEARCH BACKGROUND AND LITERATURE REVIEW

2. RESEARCH BACKGROUND AND LITERATURE REVIEW

Use of high/ultra strength concrete (HSC) is still a dream in Pakistan. No doubt some laboratory
experimentation has recently been conducted to achieve similar strength but its use in actual
construction is not yet started. In Lahore all under-construction buildings are planned on the
basis of normal to moderately HSCs. Increased land cost compelled engineers to plan high rise
frame structures about 20 stories or more. Use of HSC may result in major reduction in member
cross-sections, hence saving a lot of precious space otherwise occupied by columns and other
structural members.
The production of HSC that consistently meets requirements for workability and strength
development places more stringent requirements on material selection than for lower-strength
concretes. Quality materials are needed and specifications require enforcement. HSC has been
produced using a wide range of quality materials based on the results of trial mixtures (ACI
363R-97).
The strength of concrete is its foremost characteristic. The compressive strength of concrete
depends on the water to cement ratio, degree of compaction, ratio of cement to aggregate, bond
between mortar and aggregate, and grading, shape, strength and size of the aggregate
(Roccoand Elices, 2009; Elices and Rocco, 2008). Concrete can be visualized as a multi-phase
composite material made up of three phases; namely the mortar, mortar/aggregate interface,
and the coarse aggregate phase. The coarse aggregate in normal concrete are mainly from rock
fragments characterized by high strength. Therefore, the aggregate interface is not a limiting
factor governing the strength requirement (Beshr, Almusallam, and Maslehuddin 2003). The
onset of failure is manifested by crack growth in the concrete. The key concept for making
HSC is to prevent failures as far as possible (Subash Paudel, 2008). A very small region
between matrix and coarse aggregate is known as transition zone. Properties of both matrix and
transition zone can be improved by adjusting the cement content, water to binder ratio, adding
micro/pore fillers, using pozzolanas, providing sufficient rheology and reduction of void space
(E Limsuwan, P Haleerattanawattana, 2007) or even changing the mixing sequence.

While designing for HSC, the hardened cement paste and the transition zone are no more
strength-limiting, but it is the mineralogy and strength of coarse aggregates that control the
ultimate strength of concrete (Aitin PC, Mehta PK, 1990). With most natural aggregates, it is
possible to make concretes up to 120 MPa compressive strength by improving the strength of
the cement paste, which can be controlled through the choice of water-content ratio and type
and dosage of admixtures (Mehta and Aitcin, 1990). However, with the recent advancement in
concrete technology and the availability of various types of mineral and chemical admixtures,
and special superplasticizer, concrete with a compressive strength of up to 100 MPa can now
be produced commercially with an acceptable level of variability using ordinary aggregates
(FIP/CEB, 1990). These developments have led to increased applications of HSC all around
the globe.

Production of HSC may or may not require special materials, but it definitely requires materials
of highest quality and their optimum proportions (Carrasquillo, 1985). The production of HSC
that consistently meets requirements for workability and strength development places more
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stringent requirements on material selection than that for lower strength concrete (ACI 363R,
1992). However, many trial batches are often required to generate the data that enables the
researchers and professionals to identify optimum mix proportions for HSC. Practical examples
of mix proportions of HSC used in structures already built can also be the useful information
in achieving HSC. The various techniques of producing HSC, as summarized by Nagataki and
Sakai (1994), are presented in Fig. 1.

ACI 318 allows mix designs to be proportioned based on field experience or by laboratory trial
batches. When the concrete producer chooses to select high-strength concrete mix proportions
based upon laboratory trial batches, confirming tests results from concretes placed in the field
should also be established.

Study of a local research related to investigate the effect of size of aggregate on the
compressive strength of HSC in UET Taxila (2006), have used different sizes of Margallah
coarse aggregates. Different trial mix ratios have used in this study. Mix ratio (1:0.75:1.5) with
aggregate sizes 10mm & 5mm has given optimum strength up to 170 MPa in 28 days.

Another contradictory local research attempt was made to assess the suitability of Margalla
aggregates to produce ultrahigh strength concrete in UET Lahore (2010). This effort was
failed rendering Margalla crush as suitable for high and ultrahigh strength concrete.

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The researcher has suggested that Margalla crush is not suitable for UHSC, rather it is not even
be recommended for HSC. The study has concluded that though above 9000 psi (62 MPa)
concrete strength has been achieved in the laboratory using Margalla crush, but due to presence
of uncertainty, these aggregates should be used for construction where required cylinder
strength does not exceeds 6000 Psi (42 MPa).

Another local study of Physio-mechanical and aggregate properties of limestones from

Pakistan (2014) has concluded their analysis and laboratory tests indicate that values of all the
physical parameters of the limestones of Margallah Hills Samana Suk Formation, Kawagarh
Formation, Lockhart Limestone and Shakhai Formation are within limits of the ASTM
standards values thus can be utilized as an aggregate source for road, cement concrete and other
engineering purposes.

A laboratory experimentation based on ranking of Marghalla crush aggregtes (2015) by

UET Taxila has stated in their research work that in Pakistan, aggregates manufactured in
Margalla crush quarry is considered to be the best aggregates for the pavement construction.
The source and consensus properties vary throughout the quarry.

The study of all above native researches connected to strange phenomenon of strength
development of concrete using commonly available Margallah Crush, has attracted the
attention to further investigate the suitability of aggregates for development of mix design for
HSC. This research will highly be focused to investigate the behavior of locally available
coarse aggregates on mix design development for HSC from different quarries of Pakistan,
especially from Margallah Hills.

It is observed that no specifying limits are available for each class concrete. HSC ranges from
as low as 5000 psi (35 MPa), (Vietnam, 2009) and as high as 14,500 psi (100 MPa) (Subash
Paudel, 2008). These classifications are accepted by different researchers according to their
own regional requirements. For Pakistan following classification is suggested, based on certain
logic described below.
According to S.K. Al-Oraimi et al. (2006) in normal strength concrete (compressive strength
less than 6000 psi (42 MPa)) ―the properties of coarse aggregate seldom become strength
limiting. According to Odd E Gjorv et al. (1990), up to compressive strength of about 12,800
psi (90 MPa) the fracture of the concrete is controlled largely by failure of bond between the
aggregate particles and the cement paste. For compressive strength above this level, however,
it appears that concrete fracture is controlled largely by the strength of rock aggregate. Hence
following division deems suitable for strength based concrete classification for Pakistan.
Concrete below 6000 psi (42 MPa) may be considered as normal strength concrete where
fracture is controlled by cement paste, 6000- 12,800 psi (42-90MPa) can be termed as HSC
where fracture is largely controlled by the transition zone and above 12,800 psi (90 MPa) it is
classified as UHSC where fracture is largely controlled by the strength of aggregate.
Concrete strength varying from 45 MPa to 60 MPa has been used in bridges at Pakistan, Lahore
and other metro cities. Rathoa Haryam Bridge at Azad Kashmir was built using concrete of
41 MPa (6000 psi) in prestressed girders and slabs. In Metro Orange Line Project, concrete

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strength of 45 MPa (6500 psi) for the Pretensioned U-tub girders and 70 MPs in sleepers, is
being used in Lahore.

2.4.1 Compressive strength

It is the most important property in design of concrete structure. It is one which is most
frequently measured. This is affected by cement, sand, water and their proportions. However
some admixtures are also be used for this purpose. Effect of each is explained briefly below,
Cement that yields the highest compressive strength at expected ages (91 days) is preferable.
For HSC, a cement should produce minimum 7-days mortar strength of approximately 30MPa.
Aggregates in High Strength Concrete, careful attention must be given to aggregate shape,
surface, texture, mineralogy and cleanness. For each source of aggregate and concrete strength
level, there is an optimum-size aggregate that will yield more compressive strength per unit of
cement. To find that optimum size, trial batches are used. To obtain high compressive strength,
it is necessary to use low water to cementations materials ratio and high Portland cement
content. The water requirement of concrete increases as fine aggregates content is increased
for any given size of coarse aggregate. Low water increases strength but reduces workability.
So use of super plasticizers is encouraged.
2.4.2 Tensile Strength
In conventional design for concrete bridges, the tensile strength of concrete is assumed to be
zero in reinforced concrete design. It is often taken as 6(fc) 1/2 in pre-stressed concrete-girder
different tests are being used to know the tensile strength of concrete. Some of them are stated
below.
 Standard tensile strength methods to assess the cracking strength of conventional
concrete.
 Standard test method for Flexural strength of concrete (Using Simple beam with three
Points).
 Standard test method for splitting tensile strength of concrete specimen.

Beside the stated tests, variety of tension tests methods has been developed. In direct tension
test, the HSC specimen is loaded in uniaxial tension and thus the tensile response can be
directly captured by measuring load on specimen. Graybeal has proposed that tensile strength
is improved by method of curing specially steam curing.
2.4.3 Durability
The durability of concrete is defined as its ability to resist weathering action, chemical action,
chemical attack or any other process of deterioration. One of the main reason for deterioration
of concrete is, concentration is being given on compressive strength. The deterioration of
reinforced concrete structures usually involves transport of aggressive materials from
surrounding environment followed by physical & and chemical action.
Yatin H Patel et al. used alccofine and Fly-ash to solve issue. They used ordinary Portland
cement-53 grade (Ambuja cement ), Fine sand as per IS:383-1987 having bulk density 1860
kg/ m3 , coarse aggregates of IS:383-1987 having size of 20 mm and 10 mm. Alcoffine 1203
based on slag high glass test content, super-plasticizer , Glenium sky 784.Tests performed
showed that 7,14,28 and 56 days strength as 44.06 , 50.56, 54.89 , and 72.97 Mpa respectively.

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Results shows that concrete incorporating alcoffine and fly ash have higher compressive
strength. Alcoffine enhanced durability and reduced chloride diffusion.
B B Patil et al. used matakaolin to improve strength and durability. He stated that, HPC mixes
incorporating different percentages of high reactivity of matakaolin by weight of cement along
with suitable plasticizer improves workability, compressive strength and durability. Generally,
high reactivity matakaolin is proved to be reactive Pozzolan. The strength improved is probably
due to combination of filler, effected and accelerated cement hydration.
2.4.4 Ductility
HSC is usually more brittle when compared with NSC, especially when high strength is main
focus of performance. Based on above discussion, it is known that ductility can be improved
by applying a confining pressure on HSC. Besides confinement, the ductility of HSC can be
improved by altering its composition through addition of fibers in design mix. Concrete with
fiber inside is fiber reinforced concrete. The conventional FRC made by adding fibers in NSC
only exhibits an increase in ductility compared with plain matrix. Because of improvement in
ductility, high performance FRC is referred as ultra-ductile.
2.4.5 Modulus of Elasticity
It is ratio of stress to strain. Graybeal measured the modulus of elasticity and in compression
in accordance with ASTM C 469 at 1 to 56 days. He had used 6 cylinders, for this he used
different approaches and found values. By using steam curing, the measured values were 50
GPA, cylinder cured under standard laboratory condition had modulus of elasticity values of
47.7 GPA, at 28 days .These values were also noted down in direct tension test. The average
values were also noted down in direct tension test. The average values for steam tested were
51.9 GPA and 47.6 GPA for untreated.

2.5.1 Shrinkage
There are two types of shrinkage.

 Drying shrinkage
 Endogenous shrinkage

Drying shrinkage is caused by loss of moisture from high Strength concrete. Endogenous
shrinkage is caused by decrease in volume as the cementations materials hydrate. The drying
shrinkage measurement is being started just after concrete has hardened .Endogenous shrinkage
is measured immediately after HSC is placed.
Train Onet stated that using fiber admixtures and replacing parts of heavy aggregates with that
of light one, problem of endogenous shrinkage is being solved .Hennry G. Russel in his
experimental work found initial shrinkage of HPC using separates tests. He used steam curing
and further shrinkage was eliminated. Measurement of shrinkage by Burkart and Muller
starting 1-2 days after casting, showed no difference between sealed and unsealed cylinders.
Suzuko et.al. Used expensive additive and shrinkage reducing admixtures to reduce shrinkage.

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2.5.2 Permeability
David Lau et.al. stated that total porosity of cement paste matrix influence the strength of
concrete , the pore structure and its connectivity has impact on permeability .High permeability
usually means low durability and inner part of concrete is more readily to be attacked by
surrounding chemicals. Mineral admixtures such as quartz powder, fly ash, rice husk ash,
metakaolin, silica fumes are commonly used in long term performance of HSC through reduced
permeability resulting in improved durability.
2.5.3 Diffusion
Aggressive ions, such as chloride, in contact with surface concrete will diffuse through concrete
until state of equilibrium in ion concentration is achieved. If concentration of ion on surface is
high, diffusion may result in corrosion – inducing concentrations at level of reinforcement. The
lower water cementing materials ratio, the lower will be diffusion concentration for any set of
materials. Supplementary cementing materials, particularly silica fume, further reduce the
diffusion coefficient. Typical values for diffusion of HPC are as follow.
Table 2.1: Diffusion Co-efficient of different type of cement

Type of concrete Diffusion Coefficient

Portland cement fly ash silica fume mix 1000*10-15 m2/sec

Portland cement Fly-ash mix 1600*10-15 m2/sec

2.5.4 Chemical attack

For resistance to chemical attack on most structure HSC offers a much improved performance.
Resistance to various sulphates is achieved primarily by use of a dense, strong concrete of low
permeability and low water - to - cement materials ratio; these are all HSC characteristics.
2.5.5 Carbonation
HSC has very good resistance to carbonation due to its lower permeability. Bicktly et al.
determined in CN tower in Toronto had carbonated after 17 years up to depth of 6mm.The
concrete mixture in CN tower had water-cement ratio of 0.42. For lower water cementing
materials ratios common to HSC, significantly longer times to corrosion would result,
assuming a crack free structure. In practical terms, untracked HSC cover concrete is immune
to carbonation to depth that would cause corrosion.
2.5.6 Abrasion Resistance
This is directly related to strength of concrete. This makes high strength concrete ideal for
abrasive environments. The abrasion resistance of HSC incorporating silica fume is especially
high. This make silica fume concrete particularly useful for spillways and stilling basins, and
concrete pavements or concrete pavements overlays subjected to heavy abrasive traffic.

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Hollana et.al. In 1986 described how severe abrasion-erosion had occurred in stilling basin of
a dam; repairs using fibre-reinforced concrete had not proven to be durable. The new HSC used
to repair the structure the second time contained following constituent
Cement……………386 kg/m3
Silica fumes………70 kg/m3
Admixtures and had water to cement materials ratio of 0.28 and 90-day compressive strength
exceeding 130 MPa. Berra et.al. Studied the addition of fiber to silica fumes mortars to
optimize abrasion resistance. The best results were obtained with a mix using slag cement, steel
fibers, and silica fume. Mortar strengths ranged from 75 MPa to 100 MPa. In addition to less
drying shrinkage, high freeze-thaw resistance and good bond to substrate were obtained.
2.5.7 Air Entrainment
Air entraining agents are not required, nor have they been recommended for high strength
concrete in buildings, since the primary applications of high strength concrete, such as interior
columns, and shear walls, will normally not require air-entrained concrete. One investigation
recommended that if high strength concrete is to be used under saturated freezing conditions,
air entrained concrete should be considered despite the loss of strength due to air entrainment.
High strength concrete is much more durable than lower strength concrete; but an air-entrained
concrete with only half the strength of high strength concrete is more durable than the 37 high
strength concrete containing no entrained air. Ryan stated that effective levels of air content
cause an increase in void space which quickly reduces the strength and limits the use of the
water/cement ratio as a factor for field control of the mix. It has been shown, however, that
adding an air entrained additive to a mix with 2 percent air to get a 5 percent air content reduced
the 90-day strength of a 9,400 psi mix by only 2 to 5 percent. In that study, the air entrained
mix had a water/cement ratio of 0.03 less than the control mix. This shows that the resulting
reduction in the water/cement ratio cannot fully compensate for strength loss due to increased
air content. It has been reported that as compressive strengths increase and water/ cement ratios
decrease, air void parameters improve and entrained air percentages can be set at the lower
limits of the acceptable range.
2.5.8 Placing, Consolidation and Curing
Delays in delivery and placing of concrete must be eliminated sometimes it may be necessary
to reduce batch size if placing procedure is less than anticipated. Increase in workability should
only be achieved by addition of super plasticizer. Consolidation is very important in achieving
potential strength of HSC. Concrete must be vibrated as quickly as possible after placing. High
performance vibrator should be used to allow sufficient clearance between vibrating head and
reinforcing steel. Over vibration of workable normal strength concrete often result in
segregation, loss of entrained air or both. On the other hand, high strength concrete without
super-plasticizer, will be relatively stiff and contain little air. Most high strength concrete
particularly very high strength concrete is placed in slump value 200 mm.
Curing of high strength concrete is even more important that curing normal strength concrete.
Providing adequate moisture and favour-able temperature conditions is recommended for
prolonged period, particularly when 56-91 day concrete strengths are specified.

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Additional curing consolidation apply with HSC, where low water-cement ratio are used in
flat work and particularly where silica fume is used in the mixture , there will be little if any
bleeding before and after finishing.
Several variables which have direct impact on the results of concrete compressive strength tests
are unrelated to the concrete itself. These other influencing factors are partially responsible for
the differences between the strengths of laboratory specimens and field specimens. Variations
in results from tests performed on the same material can be caused by differences in specimen
shape and size, mold, materials, methods of consolidation, curing procedures, capping
materials and specimen test procedures. The age of the specimens when tested is extremely
important for high strength concrete. If loading of a high strength concrete bridge girder will
not occur until the concrete is at least go days old, then the required compressive strength test
age could be increased beyond 28 days to take advantage concrete strength in the design of
structure. It is very reasonable to specify strengths in a high-rise building construction since
lower floors may not be fully loaded for a year or more, depending on construction loads. The
later age strength criterion may be an additional expense and leave the concrete strength issue
in doubt for an uncomfortable length of time in situations of questionable concrete strength.
Testing at go days of age will typically provide for at least 10 percent greater usable strength
compared to 28-day test results. The type of cylinder mold used to cast the compression
specimens has a strong effect on compressive strength test results. Rigid steel molds aid in
achieving higher and more uniform compressive strength test results due to the more uniform
and effective compaction of the concrete and the exactness of standard specimen shape and
dimensions which cannot be matched by plastic or cardboard molds. A steel mold reportedly
results in a higher compressive strength test result than does a plastic mold. Using cardboard
molds results in compressive strength test results between 2 and 15 percent lower than those of
steel-molded concrete. 40 Cylindrical specimen size has an effect on concrete strength as well.
It was suggested that as specimen size increases, the probability of the presence of a critical
flaw in a critical location and orientation likewise increases. Using larger test specimen results
in lower average compressive strengths and lower coefficients of variation. Cylinder specimens
6 in. dia. x 12 in. result in an average compressive strength which is 90 percent of that obtained
when using 4 in. dia. x 8 in. Cylinder specimens. However, one study reported that concrete
made with in. coarse aggregate gave the highest strength when using 6 in. dia. x 12 in.
specimens, compared to other mold sizes, while concrete made with 3/8 in. stone showed a
higher strength when tested using 3 in. dia. x 6 in. cylinder. Curing temperature and humidity
affect compressive strength test results in high strength concrete, especially when curing
variations occur at early ages. Water curing can add 1,000 psi to the 28-day compressive
strength compared to sealed curing. When cured at temperatures above 100oF, variations in
water temperatures do not change the concrete strength. Compared with curing at 73oF, curing
at 100oF results in higher concrete strengths. Continuous moist curing for cent greater flexural
strength in high strength concrete, compared to specimens moist cured for 7 days followed by
curing at 50 to 65 percent relative humidity until testing. Moist curing for 14 days results in
about a 5 percent reduction in compressive strength of concrete compared to continuous moist
curing. 41 Capping thickness and capping compounds have been shown to be important, too.
Capping becomes more critical as the strength of the concrete increases.

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Capping of cylinders must be done with extreme precision using only high strength capping
compounds. All caps on high strength concrete cylinders must be allowed to develop adequate
strength prior to testing. Caps with a non-uniform thickness will not under load resulting in
induced tensile stresses at the specimen ends. Contamination of the capping compound by oil
and other impurities must be avoided also. ACI Committee 363 recommended using a 3/8-in.
thick high strength cap, having a compressive strength in the range from 48 MPa to 55 MPa,
or else forming or grinding of all specimen ends. Caps should be allowed to cool for 2 hours,
according to Freedman. In addition, testing machines and loading procedures have been shown
to cause significant variations in strength. High strength concrete is more sensitive to loading
rates than low or moderate strength concretes. When no other information is available,
researchers agree that recommended ASTM procedures should be followed when testing high
strength concrete.

Strength development will depend on both cement characteristics and cement content.
Commercially available ASTM C150 Type I Ordinary Portland Cement will be used for this
purpose. HSC typically contains such high contents of fine cementitious materials that the
grading of the Fine aggregate used is relatively unimportant. However, it is sometimes helpful
to increase the fineness modulus as the lower Fineness modulus of fine aggregate can give the
concrete a sticky consistency (i.e. making concrete difficult to compact) and less workable
fresh concrete with a greater water demand. Therefore, sand with a Fineness modulus of about
3.0 is usually preferred for HSC (ACI 363R, 1992). The optimum gradation of fine aggregate
for HSC is determined more by its effect on water requirement than on physical packing. In
this study fineness modulus of fine aggregates will be calculated for many samples in that one
sample will be selected the fine aggregate having the fineness modulus value was 3.0. Many
studies have shown that for optimum compressive strength with high cement content and low
water-cement ratios the maximum size of coarse aggregate should be kept to a minimum, at ½
in. (12.7 mm) or 3/8 in. (9.5 mm). Maximum sixes of ¾ in. (19.0 mm) and 1 in. (25.4) mm also
have been used successfully (ACI 363R, 1992). There is a good correlation between the
compressive strength of aggregates and some of the engineering properties of concrete (Chang
and Su, 1996). The quality of coarse aggregate has a significant effect on the compressive
strength of HSC. Since the calcareous limestone is known to be weaker than the dolomitic and
quartz tic limestone aggregates, so in this research work, effects of quality of coarse aggregates
will also be accounted along with the optimum size. Aggregate, conforming to ASTM C33,
will be obtained locally from Pakistan. Absorption and specific gravity tests will be performed
for fine and coarse aggregates according to ASTM C127 and ASTM C128 specifications.
The requirements for water quality for high-strength concrete are no more stringent than those
for conventional concrete. Usually, water for concrete is specified to be of potable quality.
Water needed for the mix was adjusted based on the absorption of aggregate. Ordinary tap
water will be used for all the mixes to prepare fresh concrete.
Admixtures are widely used in the production of high-strength concretes. Use of chemical
admixtures in high-strength concrete may serve the purpose of increasing strength at the slump
or increasing slump. Variations in mineral admixtures (i.e. Fly Ash, Silica Fumes, etc.),
although within the tolerances of these specifications, may cause appreciable variations in
properties of high-strength concrete. Selection of type, brand, and dosage rate of all admixtures
should be based on performance with the other materials being considered or selected for use

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on this research. Reliable performance on previous work should be considered during the
admixtures selection process. Therefore, admixtures will be evaluated using laboratory trial
batches to establish the optimum desirable qualities for this research.
High range water reducer (HRWR) as chemical admixtures, Fly Ash and Silica Fumes will be
used as natural pozolons in compliance to ASTM-C 494, ASTM-C 618 and ASTM-C 1240-
2000, respectively for this research study.

2.6.1 Cement
Proper selection of the cement is one of the most important steps in the production of high
strength concrete. For a given set of materials, the optimum cement content beyond which no
additional increase in strength is achieved from increasing the cement content must be
determined. A1binger and Moreno stated that for any particular combination of materials, an
optimum cement content exists above which strength declines and the mix becomes too sticky
to handle. Additional cement above the optimum cement content will not compensate for the
loss in strength due to the increase in mixing water demand needed in order to make the mix
manageable in the field. Variations in the chemical composition and physical properties of the
cement affect the concrete compressive strength more than variations in any other single
material. It has been recommended that careful studies be made of variations within one brand
and between brands for any area of the country which has plans to produce high strength
concrete. These studies should include evaluations of mortar cube strengths in conjunction with
concrete trial mixtures. Other studies have concurred, and cautioned that the final selection of
cement must not be based solely on mortar cube results. As a result of studies made in Chicago
it was recommended that the cement used should provide a minimum 1-day mortar cube
strength of at least 30 Mpa. Cement fineness of 4,000 cm 2/g (Blaine) was suggested as a
maximum. Another report recommended limiting cement fineness to a maximum of 3,500
cm 2/g to 4,000 cm2/g (Blaine) for producing high strength concrete. Perenchio found that a
much higher early strength was achieved for a cement with a fineness of 10,000 cm2/g (Blaine),
but determined that there was no difference in 90-day strengths between mortars made with the
10,000 cm2/g cement (Blaine) and one made with a 4,000 cm2/g (Blaine) cement.
Strength development of concrete will depend on both cement characteristic and cement
content. The choice of Portland cement for HSC is extremely important (Hester, Weston,
1977, Chicago Committee Report 1977 and Freedman, Sydney, 1970). Unless high initial
strength is the objective, such as in pre-stressed concrete, there is no need to use a Type-III
cement. When the temperature rise is expected to be a problem, a Type-II low heat-of-hydration
cement can be used, provided it meets the strength-producing requirements (ACI 363R, 1992).

2.6.1.1 Water and the Water/Cement Ratio

A U.S. Air Force investigation concluded that the single most important variable in achieving
high strength concrete is the water/cement ratio. Others reported that the highest concrete
strengths were achieved with the lowest water/cement ratios, although considerable effort was
required to compact the concrete in some cases. For example, Perenchio acknowledged that the
very dry concretes he studied which produced the highest strengths would probably be
unacceptable for use in the field in cast-in-place structures.

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Most sources agree that high strength concrete cannot be obtained with a water/cement ratio in
excess of 0.40. It has been reported that a water/cement ratio in the field of about 0.27 is
adequate for hydration of cement. However, others have stated that complete hydration cannot
occur with a water/cement ratio of less than 0.38 to 0.40. Concretes having a compressive
strength of 62 MPa to 69 MPa or more have been produced with water/cement ratios of less
than 0.35 in most cases.. In a study, a 90-day compressive strength of 76 MPa was achieved
with a concrete mix which had a water/cement ratio of ~30 and a slump of 1/2 in. The difficulty
with requiring low water/cement ratios for the production of high strength concrete is
overwhelmingly said to be control of water content in the field. Ryan urged close monitoring
of moisture content of aggregates and careful control of slump in the field. It was strongly
recommended that concrete be delivered or the job with the proper slump so that additional
water was not required. When enough water was added to raise the slump by 1 in., Cook
reported that at least 2 MPa in compressive strength was immediately lost; another study
determined that strength was decreased by 500 MPa for the same addition of water at the job
site. Quality of the water used in concrete is thought to be of no major concern if drinking water
is used. Although water temperature affects workability, it alone will not affect strength
significantly. Freedman concluded that unless ice is necessary for hot weather concreting, the
small, if any, increase in strength resulting from the use of ice does not outweigh the problems
encountered.
The single most important variable in achieving HSC is the water-cement ratio (Peterman and
Carrasquillo, 1986).

The relationship between water-cement ratio and compressive strength, which has been
identified in low strength concretes, has been found to be valid for higher strength concretes
also. Higher cement contents and lower water contents have produced higher strengths.
Proportioning larger amounts of cement into the concrete mixture, however, has also increased
the water demand of the mixture. Increases in cement beyond a certain point have not always
increased compressive strengths. (ACI 363R, 1992).

HSC produced by conventional mixing technologies are usually prepared with water-cement
ratios in the range of 0.22 to 0.40, and their 28 days compressive strength is about 60 to 130
MPa when normal density aggregates are used (FIP/CEB, 1990).

The requirements for water quality for HSC are no more stringent than those for conventional
concrete. Usually, water for concrete is specified to be of potable quality (ACI 363R, 1992).

Water-cementitious ratios by weight for high-strength concretes typically have ranged from
0.27 to 0.50. (ACI 363R, 1992).
The use of high-range water reducers has provided lower water-cementitious ratios and higher
slumps. (Hester, Weston, T., and Leming, M.)

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2.6.2 Coarse Aggregate

Wittman stated that the strengths of aggregates are decisive for determining the ultimate load-
bearing capacity of concrete. In ordinary concrete most aggregates have sufficient strength,
but, for high strength concrete, aggregates have to be tested carefully. For concretes with
strengths of less than 35 Mpa, the aggregate strength is generally greater than the mortar
strength. However, for higher strength concrete, the differences in strength and stiffness
between the aggregate and the mortar are important parameters. Ideal coarse aggregate
properties seem mostly to relate to aggregate-mortar bond characteristics and mixing water
requirements. According to Freedman, for a constant cement content and maximum aggregate
size, differences in the mixing water requirements for a given slump tend to control the
strength. Aggregate shape, surface texture, and deleterious coatings are partly responsible for
these variations in mixing water requirements. Use of a strong coarse aggregate with moderate
absorption has been recommended. Clean cubical, 100 percent crushed stone with a minimum
of flat or elongated particles is desirable as well. Freedman advised using an aggregate with an
absorption in the range from 1.5 percent to 2.5 percent. He discouraged the use of lightweight
aggregate in high strength-concrete The Chicago Task Force stated that mineralogy of the
aggregate is also highly important. Researchers and engineers have agreed that a smaller
maximum size coarse aggregate is desirable for high strength concrete. The optimum size for
coarse aggregate in concrete depends on the relative strengths of the mortar, the mortar-
aggregate bond, and the aggregate particles. For each concrete strength level there is an
optimum size for the coarse aggregate that will yield the greatest compressive strength per
pound of cement. Use of a 3/4-in. stone has been recommended for producing 52 Mpa concrete,
but, for concrete strengths above 62 Mpa , 3/8-in. or 1/2-in. maximum size coarse aggregate is
recommended. Since using 1/2-in. coarse aggregate produces a more workable, less sticky
concrete mix than using a 3/8-in. stone, 1/2in. maximum size coarse aggregate is generally
recommended for high strength concrete. Reducing the aggregate size to 112 in. 24 in rich
mixes has resulted in increases in concrete strength of 10 to 20 percent, even though the
water/cement ratio is also increased for a constant cement factor and slump. The smaller
aggregate size increases the total surface area, thus reducing disruptive stress concentrations
and reducing the average mortar-aggregate bond stress. However, Bloem and Gaynor stated
that similar aggregates with the same maximum size, but which are from separate sources, may
vary more in concrete strength-development characteristics than different sized aggregates
from the same source. For a compressive strength of 28 MPa, the most efficient coarse
aggregate size is 1 -1 /2 in., but using 3/8-in aggregate is more efficient in producing 48 MPa
concrete. In general, it is agreed that smaller size aggregates and higher cement contents
produce the highest strengths in concrete mixes with and without admixtures. Another aspect
of coarse aggregate selection which has received considerable attention is the difference in
surface texture and particle shape between gravel and rounded aggregate, and crushed stone.
Among the different crushed aggregates that have been studied, Traprock, quartzite,
Limestone, graywacke, granite, and crushed gravel-traprock tends to produce the highest
strength concretes. Limestone, however, is more readily available in USA and in other areas,
and 27 produces concrete strengths nearly as high as those achieved using traprock. Crushed
limestone provides a high aggregate-mortar tensile bond strength in concrete, has a uniform
mineralogical composition, and its mineralogical compatibility with the cement matrix may aid
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in producing high strength concrete. However, smooth, rounded coarse aggregates require
much less mixing water to obtain a workable concrete. This raises the question of which is
more important for concrete strength: the lower water/cement ratio possible when using gravel,
or stronger aggregate-mortar bond resulting from the use of crushed limestone. It has been
concluded that strength gains from using crushed aggregates overshadow the benefits of
increased workability with lower water requirements from using rounded coarse aggregate.
Carrasquillo et ale noted that cracking behaviour was similar for gravel and limestone concretes
at various strength levels, but that limestone can result in greater ultimate strength, static
modulus of elasticity, and ultimate strain. Others have also reported a higher strength and static
modulus of elasticity for concretes containing crushed limestone. Gradation of the coarse
aggregate within ASTM limits makes very little difference in strength of high strength
concrete. Optimum strength and workability of high strength concrete are attained with a ratio
of Coarse to fine aggregate above that usually recommended for normal strength concretes.
This means using a higher coarse aggregate factor. 28 The Chicago Task Force recommended
using higher coarse aggregate factors than those recommended by ACI Committee 211. Due
to the already high fines content of high strength concrete mixes, use of ordinary amounts of
coarse aggregate results in a sticky mix.
S.K. AlOraimi et al (2006) say the mineralogy and the strength of the coarse aggregate is
responsible to control the ultimate strength of concrete.
A formula was derived by Chang and Su NK. (1996) from the theory of granular mechanics
to estimate the compressive strength of coarse aggregate to be used in HSC. This study showed
that there is a good correlation between the compressive strength of aggregates and some of
the engineering properties of concrete.
Aitcin et al. (1987) investigated the effect of three different coarse aggregates in super
plasticized concrete mixtures with identical materials and properties (w/c=0.24). They found
that for a calcareous-limestone aggregate (85% calcite), a dolomitic-limestone aggregate (80%
dolomite), and a quartzitic-gravel aggregate containing schist, the 91 day compressive strengths
were 93, 103 and 83 MPa, respectively. Moreover, they concluded that the aggregate–cement
paste bond was stronger in the limestone aggregate concrete than in the gravel concrete due to
the interfacial reaction effect.

2.6.3 Fine Aggregate

Some studies have stated that the fine aggregate gradation is not highly critical for the
production of high strength concrete. However, it has also been reported that properties of the
fine aggregate, especially sand particle shape and texture, have as great an effect on the mixing
water requirement of concrete as the properties of coarse aggregate. The fines content in high
strength concrete is generally so high due to increased cement contents that using a smaller
sand content or a coarser sand is beneficial. Finish-ability is provided by the high cement
content, so that additional fines may only produce stickier, less workable fresh concrete with a
greater water demand. Parrott used 10 percent fine aggregate content by weight of total
aggregate in producing 11,000 psi concrete. Use of a coarse sand with a fineness modulus in
the range between 2.70 and 3.20 has been recommended.
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One report stated that natural sand is preferable to manufactured, or crushed, sand. The higher
mixing water requirement for crushed sand results in lower concrete strengths in spite of the
improvement in aggregate bonding characteristics of manufactured sands. Blending sands for
improved capabilities to produce higher strength concrete has also been suggested. If one fine
aggregate 29 is detrimental to high strength concrete production, combining it with another
different fine aggregate may permit use of the poorer sand in high strength concrete. Blending
may aid a ready-mix plant which primarily depends on a source of less desirable fine aggregate
for its concrete production.
Fine aggregates with a rounded particle shape and smooth texture have been found to require
less mixing water in concrete and for this reason are preferable in high-strength concrete (Wills,
Milton H., Jr., 1967, and Gaynor, R.D., and Meininger, R.C. 1983)
One report stated that a sand with a fineness modulus (FM) below 2.5 gave the concrete a sticky
consistency, making it difficult to compact. Sand with an FM of about 3.0 gave the best
workability and compressive strength. (Blick, Ronald L., 1973).

2.6.4 Mineral and Chemical Admixtures

The use of mineral and chemical admixtures in producing high strength concrete results in
significant increases in concrete strength while reducing the cement requirement and the
water/cement ratio. However, the compatabl1ity between these admixtures and the cement used
must be checked prior to their use in high strength concrete. The fact that a cement, silica fume,
and a chemical admixture individually meet ASTM requirements does not ensure that they are
compatible in combination for use in producing high strength concrete. Some concern has been
expressed by cement producers that the increasing use of silica fume as a partial replacement
for cement in concrete may detract from the demand for cement in this country. On the contrary,
the use of silica fume will likely make possible new and unforeseen uses of concrete, resulting
in an overall expansion of the market for concrete and cement. This has been the case in the
past with the arrival of admixtures such as water reducers.

2.6.4.1 Mineral Admixtures

Malaikah (2003) investigated the properties of HSC with w/c ratios ranging between 0.20 and
0.35 as well as with an increase of Silica Fumes according to the following percentages: 0, 10
and 15%, respectively. The results showed that the highest strength resulted from the addition
of 10% Silica Fumes with 0.20 w/c ratio, which resulted in a strength exceeding 100 MPa.

Mazloom et al. (2003) studied experimentally the short and long term mechanical properties
of high-strength concrete containing different levels of Silica Fumes. As the proportion of
Silica Fumes increased, the workability of concrete decreased. However, short-term
mechanical properties such as the 28-day compressive strength and secant modulus improved.

It has been possible to produce concrete mixes in laboratory conditions using such Mineral Ad-
mixtures that produced a compressive strength which exceeded 180 MPa. The in-place strength
in some tall buildings has attained a compressive strength of approximately 125 MPa (Haque
and Kayali, 1998).
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The ability of fly ash to aid in achieving high ultimate strengths has made it a very useful
ingredient in the production of high-strength concrete (Kosmatka et al. 2002).

2.6.4.2 Chemical Admixtures –

Annadurai and Ravichandran (2014), conducted experiments for mix design of HSC with
admixtures, varying super plasticizer with a range 0.6 to 0.9% with an increment of 0.1% and
concluded that addition of silica fume increases compressive strength and decreases the slump.
High-range water reduction provides high-strength performance, particularly at early (24-hour)
ages. Matching the admixture to the cement, both in type and dosage rate, is important. The
slump loss characteristics of a high-range water reducer (HRWR) will determine whether it
should be added at the plant, at the site, or a combination of each. (ACI 363R, 1992).

Use of a HRWR in high-strength concrete may serve the purpose of increasing strength at the
slump or increasing slump. (ACI 363R, 1992).

2.6.4.3 High Range Water Reducers (Superplasticizers).

Three types of superplasticizers are currently available
1. A sulfonated melamine formaldehyde condensate which, when added to concrete,
forms a lubricating film on the cement particle surfaces
2. A sulfonated naphthalene formaldehyde condensate, which causes a reduction in the
surface tension of the water
3. A modified lingo-sulfate which electrically charges the particles of cement so that they
repel each other.
The net effect of using any type of super plasticizer is enhanced dispersion of cement particles.
The initial cement hydration rate is increased since overall water-cement contact is increased.
However, the later hydration rate is slower than usual because the reaction product which forms
at first around the cement particles tends to be thicker and more impermeable than in non-
super-plasticized mixes. The film of admixture on hydrating cement 35 particles also tends to
restrict further water movement into the cement particles. Some of the admixture apparently
even associates with the water on a molecular level, completely preventing a small fraction of
the water from ever hydrating the cement. Super plasticizers increase concrete strength by
reducing the mixing water requirement for a constant slump, and by dispersing cement
particles, with or without a change in mixing water content, permitting more efficient
hydration. The addition of super plasticizers to a mix can save cement and increase the slump
without changing the consistency of the fresh concrete. High-slump flowing concrete with high
compressive strengths have been produced and used which thoroughly fill in the volume
surrounding tightly spaced reinforcement, harden quickly to facilitate rapid slip forming, and
as a result save 20 to 30 percent in labour cost .An additional advantage of using super
plasticizers results from their use in hot-weather concreting. Slump loss can be successfully
readjusted by re-dosage with super plasticizers instead of with water. A second dosage
generally restores the slump and results in greater 28-day strengths. Third and subsequent re-
doses may not improve strength, but it is important to experiment with higher dosages than
those recommended by the admixture manufacturers.
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CHAPTER 2 RESEARCH BACKGROUND AND LITERATURE REVIEW

Dosage rates as high as 50 percent above manufacturers' recommended amounts have resulted
in zero percent increases in compressive strength without detrimental effects.
The main consideration when using super plasticizers in concrete are the high fines
requirements for cohesiveness of the mix and rapid slump loss. Neither is harmful for the
production of high strength concrete. High strength concrete mixes generally have more than
sufficient fines due to high cement contents. The use of retarders, together with high doses and
re-doses of super plasticizers at the plant or at the job site can improve strength while restoring
slump to its initial amount. Even a super-plasticized mix that appears stiff and difficult to
consolidate is very responsive to applied vibration. Long-term studies of super-plasticized
concrete have been conducted in Japan. Test results from l1-year studies showed better strength
improvement of super-plasticized concretes than of concretes made using a conventional water-
reducing admixture or with no admixture at all. Five-year tests showed significantly less
corrosion of reinforcement in super-plasticized concrete than in control specimens.
2.6.4.4 Silica Fume
Silica fume is one of the effective pozzolonic material used in the development of high strength
concrete (HSC). Silica fume, also known as micro silica (MS) or condensed silica fume is a
by-product of the production of silicon metal or ferrosilicon alloys. Although silica fume is
relatively old additive, however the amount as supplementary materials in concrete mixture is
not fully understood. To get a dense granular mixture of HPC, optimal amount of silica fume
should be 25% by the weight of cement (Jianxin Ma). Kennouche S. founded that best
workability result for HSC can be achieved by using 15% of silica fume of the cement content.
For this particular research the amount of silica fume used was between 30 to 45% of the
cement content. The silica fume was obtained from local BASF chemicals Lahore.
2.6.4.5 Super Plasticizer
HSC has to fulfil contradictory requirements of high flowing ability when it is being cast and
high viscosity when it is at rest, in order to prevent segregation and bleeding. These
requirements make the use of mineral and chemical admixtures essential for self-compacting
concrete. High flowing ability is achieved using super plasticizers. Super plasticizer on the
other hand results in delayed strength and setting time of the concrete. Most of the strength is
achieved at later stages. The super plasticizer used for the study purposes was obtained from
different resources and best one i.e. from Imporient chemicals was selected for mix design.
Typical super plasticizers used were Gelenium-51 and SP-303.

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CHAPTER 3

MATERIALS
&
TEST PROCEDURES

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CHAPTER 3 MATERIALS AND TEST PROCEDURES

3. MATERIALS AND TEST PROCEDURES

In order to achieve the required aims and objectives, as a first step, the fundamental study
parameters and materials are selected and described as under. Preparation of concrete mixes, testing
of materials, casting of specimens and testing of specimens are complying with applicable current
ASTM Standards. In order to achieve the required objectives, following study parameters were
selected.

 Characterization of high strength concrete (HSC) mainly in compression.

 Effect of replacement of coarse aggregate with the fine aggregate materials on the
compressive strength.
 Effect of variation of concrete gradients on the strength, workability and economy of
the concrete.
High strength concrete is being used increasingly in the field, not only because its production
has become economically feasible but also because designers and contractors are slowly
beginning to have confidence in its use. Whether or not high strength concrete, especially in
the strength range above 10,000 psi (68 MPa), will ever command a significant share of the
structural concrete market depends on the ease and consistency with which it can be produced
and placed. Although high strength concrete must have a low water/cement ratio, it can be
produced using readily available materials and having appropriate workability for ease of
placement and proper finishing, even under extreme temperature conditions.

Throughout this investigation, an attempt has been made to include only commercially
available materials currently used by precast pressurising plants approved by the National
development authorities (LDA, NHA etc.). Mix design of high strength concrete is influenced
by properties of cement, sand aggregates & water-cement ratio have compressive strength
above 40 MPa. To achieve high strength, it is necessary to use lowest possible water-cement
ratio, which invariably affects the workability of the mix and necessitates the use of special
vibration techniques for proper compaction. In the present state of art, a concrete with a desired
28 day compressive strength of up to 100 MPa can be made with suitably proportioning the
ingredients using normal vibration techniques for compacting the concrete mix. Workability,
as measured by the slump test, was the controlling factor for all mixes. All concrete mixes had
slumps of at least 3 to 9 .5 inches. Production, curing and testing of concrete specimens in this
study were conducted according to applicable procedures described in the American Society
for Testing and Materials' 1980 Annual Book of ASTM Standards, Part 14 Concrete and
Mineral Aggregates. In this chapter, a description of the materials, mix proportioning and
mixing procedures used in this study are presented.

The materials used in this study include two cements, two coarse aggregates, and single fine
aggregates, two Admixtures (SP-303, Fospack), silica fume and local tap water. First of all, I
would like to list the number of gradients used in the high strength concrete mix design. These
gradients are shown in the Table 3.1.

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Table 3.1: Materials used in high strength concrete

S.NO Materials Primary contribution

1 Cement brand (Fauji, D.G) Binder
2 Coarse aggregate Economy purpose
3 Fine aggregate Economy purpose
4 Silica fume Water reducing agent
5 Admixtures Strength increasing agent
6 Water Causes the hardening (hydration)

3.2.1 Cement
Two cement types, ASTM types I, were included in this study. Fauji and D.G were the types
of cement that were used in the laboratory. Same grade of 53 was used for both types of cement.
Our lab and Habib construction company provided us the cement bags. More ratio, less
workability. Since less cement mean less water, so the paste is stiff. Process of hydration and
resulting the rate of strength gain is affected by fineness of cement. Finer cement offers more
surface area for hydration thus rapid strength gain occurs during first seven days. Soundness is
define as the ability of a hardened cement paste to retain its volume after setting without
delayed expansion. Many factors affects setting time of cement such as fineness of cement,
chemical content, admixtures etc. Setting time of cement test is done by Vicat Apparatus.
Usually two setting times are define i.e. Initial setting time and Final setting time. For
construction purposes, the initial set must not be too soon and the final set must not be too late.
53 grade ordinary Portland cement shall confirm to following
a) Initial setting time shall not be less than 30 minutes
b) Final setting time shall not be greater than 600 minutes.

The physical properties of 53 grade cement is shown in the Table 3.2

Table 3.2 Physical properties of 53 grade cement

S.NO Property Value

1 Normal consistency 29%
2 Initial setting time(min) 120 min (not less than 30 min)
3 Final setting time(min) 270 min (not greater than 600 min)
4 Specific gravity 3.15
5 Fineness of cement 1mm ( Le Chateliers Method)

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3.2.2 Coarse Aggregate.

Remember that while discussing mix-design of High strength concrete the term "cement" is
use to describe all the cementitious materials in the concrete and not just the Portland cement.
In general, smaller size aggregates have been shown to produce higher strength concretes, for
a fixed w/c ratio. However, the use of the largest possible coarse aggregate may be an important
consideration in terms of optimizing modulus of elasticity, creep, and drying shrinkage of the
concrete. ACI 318 recommends that the maximum aggregate size not exceed one-fifth of the
narrowest dimension between the sides of the forms, one-third of the depth of slabs, nor three-
quarters of the minimum clear spacing between individual reinforcing bars or pressurising
tendons. Particularly for a high-strength concrete, a coarse aggregate should be chosen that is
sufficiently hard, clean, and free of surface coatings.
All the coarse aggregates were crushed dolomitic minerals from several aggregate producers
in Sargodha and Sakhi Sarwar. The maximum size of both type of aggregates used were 3/4 in.
and 1/2 in., respectively. We used the sakhi sarwar crush to observe the effect on compressive
strength. The slight variation in the results due to variation in the use of the type of coarse
aggregate.

Table 3.3: Summarizes the properties of coarse aggregates.

Aggregate type Bulk specific gravity Absorption (%) Dry rodded unit weight
Sargodha 2.70 2.2 1580 kg/m3
Sakhi Sarwar 2.67 2 1600 kg/m3

3.2.3 Fine Aggregate.

If a fineness modulus less than 2.5 is used, the resultant mixture may be "sticky", resulting in
poor workability and a higher water demand. In general, because of the increased cement
(fines) content of a high-strength mixture, the volume of sand is kept to the minimum necessary
to achieve workability and compatibility. In our case, Lawrence pur sand was our available
material. In spite of the low fineness modulus, it gave better results. The fine aggregate used in
the laboratory was Lawrence pur sand. Initially, the sand was taken from the laboratory. After
some batching processes, Lawrence pur sand was taken from the stock of Habib construction.
The fineness modulus evaluation of Lawrence pur sand gave the result of 2.4.

Table 3.4 summarizes the properties of the fine aggregates used in this study.
S.NO. Properties Numeric values
1. Fineness Modulus 2.4
2. Bulk Specific Gravity (SSD) 2.7
3. Absorption 2.2 %
4. Dry rodded unit weight 1580 kg/m3

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3.2.4 Chemical Admixtures.

Two brands of high-range water reducers, or super plasticizers, Fospack and Imporient
chemicals. In calculating the water/cement ratio of mixes containing superplasticizer, the
quantity of admixture added was included as part of the water. Chemical admixtures can be
used to increase workability. Use of air entraining agent produces air bubbles which acts as a
sort of ball bearing between particles and increases mobility, workability and decreases
bleeding, segregation. The use of fine pozzolanic materials also have better lubricating effect
and more workability.
In every batching, various amount of admixtures had been used. The amount of admixtures
shown in the Table. 3.5

Table 3.5: Summary of admixtures used in the batching process.

MIX NO. Respective to cementitious Amount of admixtures

material (ml/kg)
Mix 1 (Fospack) 21 84
Mix 2(SP-303) 15 60
Mix 3 (SP-303) 22 88
Mix 4 (SP-303) 18 383.4
Mix 5 (SP-303) 20 380
Mix 6 (SP-303) 16 379.1
Mix 7 (SP-303) 25 475
Mix 8 (SP-303 ) 19 361
Mix 9 (SP-303) 20 380

3.2.5 Silica fume

Silica Fume (Very effective in lowering the water –cement ratio required for Workable
concrete)
Is a waste by-product of the production of silicon and silicon alloys Silica fume is available in
different forms of which the most commonly used in a densified form. In developed countries
it is already available readily blended with cement.
The most commonly used in a densified form. In developed countries it is already available
readily blended with Silica fume is one of the effective pozzolonic material used in the
development of high performance concrete (HSC). Silica fume, also known as micro silica
(MS) or condensed silica fume is a by-product of the production of silicon metal or ferrosilicon
alloys. Although silica fume is relatively old additive, however the amount as supplementary
materials in concrete mixture is not fully understood. To get a dense granular mixture of HPC,
optimal amount of silica fume should be 25% by the weight of cement (Jianxin Ma).
Kennouche S. founded that best workability result for HSC can be achieved by using 15% of
silica fume of the cement content. For this particular research the amount of silica fume used
was between 30 to 45% of the cement content. The silica fume was obtained from local BASF
chemicals Lahore.

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3.2.6 Moisture content of aggregates

The moisture content and aggregate absorption values are used in adjusting the amounts (mass)
of aggregates and water to be included in batch proportions. The measured moisture content is
used to adjust the mass of aggregate to achieve the necessary mass of saturated surface dry
(SSD) aggregates. Absorbed water doesn't become part of the mixing water, so the mass of
water is adjusted based on the difference between the moisture contents and absorptions of the
coarse and fine aggregates, weighted by their dry masses in the mixture. In our case, we vary
the moisture content in each batching to adjust the strength of concrete corresponding to the
moisture content. We change the moisture content in each batching ranging from 0.21 to 0.32.
The variation in the moisture content in each batching is shown in the Table 3.6
Table 3.6: The variation in the moisture content in each batching.
WORK NUMBER MOISTURE CONTENT

TENTATIVE WORK 1 0.275

TENTATIVE WORK 2 0.25

TENTATIVE WORK 3 0.25

TENTATIVE WORK 4 0.25

TENTATIVE WORK 5 0.26

TENTATIVE WORK 6 0.22

TENTATIVE WORK 7 0.32

TENTATIVE WORK 8 0.21

TENTATIVE WORK 9 0.23

TENTATIVE WORK10 0.23

3.2.7 Sand to aggregate ratio

If the amount of sand is more the workability will reduce because sand has more surface area
and more contact area causing more resistance. The ingredients of concrete can be
proportioned by weight or volume. The goal is to provide the desired strength and
workability at minimum expense. A low water-cement ratio is used to achieve a stronger
concrete. It would seem therefore that by keeping the cement content high one could use
enough for god workability and still have a low w/c ratio. The problem is that cement is the
most costly of the basic ingredients. In our case, this ratio ranges from 0.5 to 0.62.

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3.2.8 Water
To obtain high strength, it is necessary to use low water to cementitious materials ratio and
high Portland cement content. The water requirement of concrete increases as fine aggregates
content is increased for any given size of coarse aggregate. Low water increases strength but
reduces workability. So use of super plasticizers is encouraged.

3.3.1 Introduction.
All mix designs were based on a saturated surface dry condition of the aggregates. The main
variables considered in mix proportioning were: the water/cement ratio required to produce
concrete of a given slump, cement factor, and coarse aggregate/fine aggregate weight ratio.
Most mixes containing super plasticizers had slumps in the range from 3 to 9.5 in. Two cement
brands, 550-1000 (kg/m3) were considered. Coarse aggregate/fine aggregate ratios of 1.62-2.0
by weight were also considered. No air entraining admixtures were included in this study.

For most concrete batches, the following specimens were cast: 6in. dia. x 12 in. cylinders and
6in. x 6in cubes. Three 6 in. dia. x 12 in. cylinders from each batch were tested for compressive
strength at 56 days. In each batching, four cylinders and four cubes tested after 7 days, 28 days,
56 days and 90 days. To achieve the desired result, we vary the proportion of cement sand and
crush value. We also somehow reduce the size of crush to increase the strength. We wash the
sand to remove the dust particles. The concrete mixing room including the concrete mixer used
in this study are shown in Figure 3.1.

Figure 3.1: Concrete batching laboratory with the concrete mixer used in this study.

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3.3.2 Proportioning
The trial mixture approach is best for selecting proportions for high-strength concrete. To
obtain high strength, it is necessary to use a low water to cementing materials ratio and a high
Portland cement content. The unit strength obtained for each unit of cement used in a cubic
meter (yard) of concrete can be plotted as strength efficiency to assist with mix designs. The
water requirement of concrete increases as the fine aggregate content is increased for any given
size of coarse aggregate. Because of the high cementing materials content of these concretes,
the fine aggregate content can be kept low. However, even with well-graded aggregates, a low
water-cementing materials ratio may result in concrete that is not sufficiently workable for the
job. If a super plasticizer is not already being used, this may be the time to consider one. A
slump of around 200 mm (8 in.) will provide adequate workability for most applications. ACI
Committee 211 (1998).
No mix design method directly gives the exact proportions that will most economically achieve
end results. These methods only serve as a base to start and achieve the end results in the fewest
possible trials.
Different mix design methods help us to arrive at the trial mix that will give us required
strength, workability, cohesion etc. These mix design methods have same common threads in
arriving at proportions but their method of calculation is different. Basic steps in mix design
are as follows:
 Find the target high strength.
 Determine the curve of cement based on its strength.
 Determine water/cement ratio.
 Determine cement content.
 Determine fine and coarse aggregate proportions

3.3.3 Mixing Procedures

The mixing procedure for all concrete mixes containing no super plasticizer was to first mix
50 percent of the water with the aggregates followed by the addition of the cement, and then
the remainder of the water was added as required to reach the desired slump. In some case, we
have to add the extra super plasticizer to achieve the desired slump. We have to increase the
water cement ratio. According to water cement ratio, we have to add the extra water. Batches
containing super plasticizer were mixed similarly to the mixes without admixture, except that
the maximum allowable water/cement ratio was set at 0.32. Slump was then adjusted by adding
super plasticizer instead of water. A minimum super plasticizer dose of 15 cement was added
with the initial mixing water to every batch. A limit of 25 ml/kg of super plasticizer (7% for
silica fume) per kg of cement was added. A water/cement ratio of 0.18 and an admixture dose
of 20ml/kg of cementitious material cement were insufficient to produce the desired slump in
some 9-batch mixes, so a water/cement ratio higher than 0.32 was used for those mixes. Slump
was checked at 15 minute intervals. After mixing for 30 minutes, slump was adjusted, if
necessary, by adding either water or super plasticizer and four cylinders and four cubes were
cast. If the slump was right, then we just cast the cylinders and cubes. After mixing for 60
minutes the slump was again adjusted. All other mixes required approximately 15-20 minutes
mixing time before casting.

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3.3.4 Tests on Fresh Concrete.

The mixer used was a 6 cu.ft maximum capacity Essex drum mixer with a mixing speed of 30
rev/min.
Concrete was made and moulded according to ASTM C192-76, Standard Method of Making
and Curing Concrete Test Specimens in the Laboratory, and Tex-418-A, Compressive
Strength of Moulded Concrete Cylinders, except for the following exceptions from some of
the specified procedures:
1. A primary goal of this research was to show whether or not high strength concrete
could be produced with materials presently used by precast prestressing plants.
Therefore, coarse and fine aggregates were stored as received, in bins and bags, at a
constant moisture content rather than in separate size fractions or under water.
2. The mixer was moistened thoroughly, but was not buttered before each mix. It is
believed that, since this procedure was used constantly throughout this project, it had
no effect on relative strength of these mixes.
3. Except for "hot weather" mixes, every batch was steadily mixed for about 10 to 20
minutes, with stops as necessary to check and adjust the slump until the desired slump
was reached.
4. The vibrating table was used to compact 6 in. dia. x 12 in cylinders and 6 in. dia. x 6
in cylinders. This simplified the casting process with vibrating table.

Slump tests were conducted according to ASTM C143-78, Standard Test Method for Slump of
Portland Cement Concrete, and Tex-415-A, Slump of Portland Cement Concrete. The fresh
unit weight of every mix was measured according to ASTM C138-77, Standard Test Method
for Unit Weight, Yield, and Air Content (Gravimetric) of Concrete, using a 0.10 cu.ft container.
Yield was calculated on the basis of batch weights and specific gravities. As applicable, the
Standard Method of Sampling Fresh Concrete, ASTM C172-71, was followed. The
temperature of each mix was also recorded.
Specimens were cured in a moisture room meeting ASTM C511-BO, Standard Specifications
for Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic
Cements and Concrete.
3.3.5 Testing.
With the exceptions mentioned below, the following specifications were followed for
compressive: ASTM C39-72, Standard Test Method for Compressive Strength of Cylindrical
Concrete Specimens; Tex-41B-A, Compressive Strength of Moulded Concrete Cylinders.
Exceptions to these specifications are as follows:
1. Nominal specimen dimensions were used in stress calculations and were deemed
adequate for the purposes of this project.
2. The suspended spherically seated block was slightly larger than recommended
specifications for the 4 in. dia. x B in. cylinders. Compressive tests were performed
using a SATEC 400 kip compression testing machine, shown in Fig. 3.2. Half of
compressive strength test specimens were capped using plaster of Paris, a high strength
capping compound. As an initial estimation, we did the first two tests after three days.
Rest of the tests were done after 7, 28, 56 and 90 days respectively. These cylinders
were submerged in curing tank and were tested at required day.
34 | P a g e
CHAPTER 3 MATERIALS AND TEST PROCEDURES

Figure 3.2: The 400-tons compressive testing machine used in this study.

Out of the various methods of mix design, some of them are not very widely used these days
because of some difficulties or drawbacks in the procedures for arriving at the satisfactory
proportions. The ACI committee 211 methods, the DOE method and Indian standard
recommended methods are commonly used. The ISI method can be applied both medium
strength and high strength concrete. The ACI committee method has the advantage of
simplicity
In that it applies equally well, and with more or less identical procedure to round or angular
coarse aggregate, to regular or light-weight aggregates and to air-entrained or non-air-entrained
concretes. Preparation of trial mix and test the compressive strength at 7 days will give the
actual idea about the mix proportion.

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CHAPTER 4 RESULTS AND DISSCUSSION

CHAPTER 4

RESULTS
&
DISCUSSION

36 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

4. Test Results and Discussion on Test Results

Experimental test results are presented in this chapter. In Chapter V, the results are discussed
and analysed in relation to the production of high strength concrete.
Chapter IV is divided into sections dealing with the effects of particular component materials
or their relative proportions on concrete compressive strength. The effects of compression
cylinder mould type and size on the measured compressive strength of high strength concrete
are presented. In addition, observations on the workability of fresh concrete mixes containing
high dosages of super plasticizers, high coarse aggregate contents are reported.
In this study, the research approach was to investigate basic interactions among concrete
components in mix proportions which are suitable for producing high strength concrete. The
effects of aggregate type and gradation, and cement type and brand on concrete compressive
strength were initially studied in concrete mixes containing no admixtures. Later, super
plasticizers was added to the mix proportions. The results presented apply to the specific
materials used in this study. Changing the materials can be expected to affect the results
somewhat.
The term "w/c" refers to the ratio by weight of water to Portland cement; the ratio of coarse
aggregate to fine aggregate by weight is referred to as "CA/FA".
All compressive strengths reported are average values of at least three 6 in. dia. x 12 in.
cylinders cast using steel molds unless otherwise noted.

Nearly all mixes studied contained either 20 to 25 kg of cement per cubic yard of concrete.
With very few exceptions, this cement amount containing no chemical or mineral admixtures
resulted in greater compressive strengths, regardless of mix proportions. Compressive strengths
of approximately 6500 psi (45 MPa) were obtained at 7 days.

The w/c ratio was the most influential parameter affecting the compressive strength of high
strength concrete mixes in this study. It is clear that the lower the water/cement ratio, the higher
the compressive strength, regardless of test age, materials used, and mix proportions. However,
if the compressive strength of the concrete is plotted versus the water/binder ratio (w/b) where
binder refers to the total weight of cement, a much better correlation is observed. It is clear that
a low w/c ratio is of primary importance for producing high strength concrete regardless of
specimen age, and materials and mix proportions used.

Early in the research program, numerous comparisons were made among different brands of
cement, and we used two cement types, in concrete mixes made using 3/4-in. crushed
limestone, sand, almost 20 kg of cement/batching and no admixtures. For these mixes,
compressive strengths were less than 40 MPa. There was a definite effect on concrete
compressive strength of the brand of cement used independent of aggregate proportions and

37 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

water-cement ratio. The effect of cement type on concrete compressive strength was more
significant in high strength concrete mixes than in concrete having a compressive strength less
than 40 MPa.
In concrete mixes made Using 3/4-in. and 1-in. maximum size coarse aggregate which resulted
in compressive strengths of less than 6,000 psi (42 Mpa), the use of DG cement comparatively,
did not result in higher concrete strength than that obtained when using Fauji cement regardless
of testing age and aggregate proportions, regardless of cement content, aggregate proportions,
testing age, and sand fineness. Concrete compressive strengths achieved in mixes containing
no admixture using Fauji cement were greater than 6,000 psi, less mixing water was required
for a given workability in high strength concrete mixes containing Fauji cement than in mixes
made with DG cement.
On the other hand, concrete mixes having a CA/FA ratio of 2.0 were rocky in texture compared
to mixes having a lower CA/FA ratio, so a higher superplasticizer dose was required to reach
a slump of 4 in. at a given w/c ratio. In general, a CA/FA ratio of 1.5 in 8.5-sack mixes resulted
in slightly lower compressive strengths but produced the most workable mix requiring the
lowest admixture dose. Further addition of superplasticizer above that needed to produce a 4-
in. slump at a w/c ratio of 0.30 was not investigated. Using as much superplasticizer as a mix
can hold without workability or segregation problems could result in both higher strengths and
higher slumps.

It was generally observed that for two identical high strength concrete mixes having the same
w/c ratio, the one with a higher super plasticizer dosage produced concrete with higher
compressive strength. We used Sp-303 and FOS-Pak.

After the cement and both chemical and mineral admixtures, the coarse aggregate maximum
size had the greatest influence on the compressive strength of high strength concrete. Three
maximum sizes of crushed limestone coarse aggregate, 1/2-in., 3/4-in., and 1-in., were included
in this study.

One concrete mix containing the same dosage of super plasticizer was made using each of the
three coarse aggregate gradation. The only variable besides coarse aggregate gradation in these
mixes was the mixing water requirement for producing a 6-in.slump.
At 56 days, the compressive strength increases as the w/c ratio of the concrete mix decreases.
The mix made with the coarsest coarse aggregate gradation required the least amount of mix
water resulting in the highest compressive strength. Concretes made with the fine gradation of
coarse aggregate resulted in the highest mixing water demand and therefore the lowest
compressive strength at 56 days.

Two types of coarse aggregate were used: Sargodha crush and Sakhi Sarwer. In addition,
limestone coarse aggregates taken from two different sources were considered.

38 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

The purpose was to study how texture, shape, and mineralogy affect the compressive strength
of high strength concrete.

Three sands with fineness moduli ranging from 2.10 to 3.0 were used to compare the effects of
sand fineness on concrete strength for high strength concrete containing no admixtures. Sands
from the same source having fineness moduli ranging from 2.45 to 2.85 were used to compare
mixes containing super plasticizers. In general, researchers have recommended the use of
coarse sands for the production of high strength concrete. In addition, it is agreed that because
of the high fines content of high strength concrete due to high cementitious content, the need
for fine aggregate for finish ability of fresh concrete is reduced.

Four different high strength concrete mixes were tested for compressive strength at curing ages
of 3, 7, 28 and 56 days. The mix proportions for these concretes are listed in Tables next in the
chapter.
The l-day strength of both mixes containing super plasticizer with silica fume was of the order
of 6,000 psi. For mixes containing no super plasticizers, the l-day compressive strength was
approximately 4,200 psi.

The effects of different compaction, curing, and capping procedures on 28-day compressive
strength of high strength concrete are compared. The highest 28-day compressive strength was
achieved by moist curing for 90 days. Cylinders compacted by rodding resulted in higher
compressive strengths than cylinders compacted by 2 min. of external vibration. Using high
strength capping compound material results in higher concrete compressive strength test results
than using conventional sulfur compounds. These results show that the compressive strength
of high strength concrete is not adversely affected by a hot and dry environment after 7 days
of ideal curing.

The effects on compressive strength of high strength concrete of using cylindrical concrete
specimen molds made of steel. The effects of specimen size on compressive strength were
studied as well. Based on the test results using 6-in. dia. x 12-in. cylinder specimens and 6-in
x 6-in cubes concrete made in steel molds always had higher compressive strength.

When super plasticized mixes were first introduced into this program, it was intended for all
batches to contain a final water-cement ratio of 0.30 or less and it was desired to have 6 inch
slump.

39 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 1
The first experimental work was done on October 17, 2016 after the complete literature
review and criterion used for this casting is tabulated below in Table 4.1

Tentative Work 1 Dated: October 17, 2016.

Mix Design Ratio 1: 1.44 : 2.52
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of Cubes Prepared 2

Table 4.1: Concrete mix design criterion for Tentative Work 1

Mix Design Ratio ( 1 : 1.44 : 2.52 )

Cement 4 Kg
Silica Fume Percentage Replacement 5% of Cement
Quantity 200g
Water Cement Ratio 0.275
Quantity of Water Including Water of Absorption 1270 ml
Admixture (FosPack) 21 ml/kg of Cementations Material 84 ml
Coarse Aggregate ½ Inch Down 7 Kg
¾ Inch Down 3 Kg
Fine Aggregate Fineness Modulus = 2.4 5.76 Kg

40 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Test Results
The samples were not subjected to any sort of curing. Moreover the end product obtained was
having good workability. The results obtained are produced below in the Table 4.2 and has
been illustrated in the graph.
Table 4.2: Test Results for Tentative Work 1

Density 2350 kg/m3

Slump 237.5 Mm 9.5 Inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 29 MPa 4205 Psi
28-days 40 MPa 5800 Psi
56-days 42 MPa 6090 Psi
90-days 49 MPa 7105 Psi

50 49

45 42
COMPRESSIVE STRENGTH (MPA)

40
40
35
29
30 3-days
25 7-days
20 56-days
15
90-days
10
5
0
3-days 7-days
56-days
90-days

Observations
 Curing Condition : No curing

 3 day strength: 29 MPa

 7 Day Strength: 40 MPa

 Percentage Increase in Strength (3-7 days) of about 37.93 was observed.

41 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 2
In this concrete mix design we kept w/c ratio moderate i.e. 0.25 and silica fume used 5% of
cement replacement .We used Sargodha crush and lawrancepur sand. Super Plasticizer (Sp-
303) was added to obtain workability. Complete Concrete Mix design Criterion and the results
obtained are produced below in Table 4.3.

Tentative Work 2 Dated: October 20, 2016.

Mix Design Ratio 1: 1.44 : 2.52
Cement Brand DG, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of Cubes Prepared 2

Table 4.3: Concrete Mix Design Criterion for Tentative Work 2

Mix Design Ratio ( 1 : 1.44 : 2.52 )

Cement 4 Kg
Silica Fume Percentage Replacement 5% of Cement
Quantity 200g
Water Cement Ratio 0.25
Quantity of Water Including Water of Absorption 1169 ml
Admixture (Sp-303) 15 ml/kg of Cementations Material 60 ml
Coarse Aggregate ½ Inch Down 7 Kg
¾ Inch Down 3 Kg
Fine Aggregate Fineness Modulus = 2.4 5.76 Kg

42 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
The samples were properly cured. A slight increase in the Compressive Strength of Concrete
was observed due to curing. Moreover the end product obtained was having good workability.
The results obtained are tabulated below in Table 4.4.
Table 4.4: Test Results for Tentative Work 2

Density 2428 kg/m3

Slump 225 mm 9 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 50 MPa 7250 psi
28-days 55 MPa 7975 psi
56-days 60 MPa 8700 psi
90-days 70 MPa 10150 psi

70
COMPRESSIVE STRENGTH OF CONCRETE(MPA)

70
60
60 55
50
50

40 7-days
28-days
30
56-days
20 90-days

10

0
7-days
28-days
56-days
90-days

Observations
 7th day strength: 50 Mpa

 90th day Strength: 70 Mpa

 The Late gain of Strength was observed. This was due to the addition of pozolone.

43 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 3
Problem were faced in the previous two batches regarding voids in crushed samples, so we
used concrete mixer machine. So it was decided to use rapid concrete mixer. Moreover the
percentage of cement was increased by about 5% and W/C ratio remain same 0.25. We
increased Super plasticizer amount up to 22ml/kg the results obtained are stated below in Table
4.5.
Tentative Work 3 Dated: October 21, 2016.
Mix Design Ratio 1: 1.44 : 2.52
Cement Brand DG, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of Cubes Prepared 2

Table 4.5: Concrete Mix Design Criterion for Tentative Work 3

Mix Design Ratio ( 1 : 1.44 : 2.52 )

Cement 4 Kg
Silica Fume Percentage Replacement 5% of Cement
Quantity 200g
Water Cement Ratio 0.25
Quantity of Water Including Water of Absorption 1175.27 ml
Admixture (Sp-303) 22 ml/kg of Cementations Material 88 ml
Coarse Aggregate ½ Inch Down 10 Kg
¾ Inch Down 5.76 Kg
Fine Aggregate Fineness Modulus = 2.4 5.76 Kg

44 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
In this batch the aggregate used was properly washed and dried. There was slight increase in
the Strength observed in Table 4.6.
Table 4.6: Test Results for Tentative Work 3

Density 2428 kg/m3

Slump 225 Mm 9 Inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 39.8 MPa 5771 psi
28-days 50.12 MPa 7267.4 psi
56-days 60 MPa 8700 psi
90-days 72 MPa 10440 psi

80
COMPRESSIVE STRENGTH OF CONCRETE(MPA)

72
70
60
60
50.12
50
39.8 7-days
40 28-days
30 56-days

20 90-days

10

0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Normal

 7th day strength : 40 MPa

 90th Day Strength: 51 MPa

 Percentage Increase in Strength (3-90days) of about 44.44 was observed.

45 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 4
The number of the prepared specimen were increased. Unlike the previous batches, in which
dry mixing was carried out by lesser layers this time concrete mixer was used frequently for
more layers compaction to decrease air voids .We kept same w/c ratio but increase silica
fume up to 7%. The complete data has been produced below in Table 4.7.

Tentative Work 4 Dated: November 3, 2016.

Mix Design Ratio 1: 1.14 : 1.85
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 6

Table 4.7: Concrete Mix Design Criterion for Tentative Work 4

Mix Design Ratio ( 1 : 1.14 : 1.85 )

Cement 21.3 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1431g
Water Cement Ratio 0.25
Quantity of Water Including Water of Absorption 5377.6 ml
Admixture (Sp-303) 18 ml/kg of Cementations Material 383.4 ml
Coarse Aggregate ½ Inch Down 20 Kg
¾ Inch Down 20 Kg
Fine Aggregate Fineness Modulus = 2.4 5.76 Kg

46 | P a g e
CHAPTER 4 RESULTS AND DISSCUSSION

Test Results
This was the golden mix of all of the batches which indicated the highest strength results. The
one of the reasons was that the good control over quality and compaction was maintained, and
the increased dosage of cement and pozolone was used. Moreover proper curing of the sample
was done in the curing Tank for the life span of the 90 days. The results produced here are the
average results of more than one samples. The test results are tabulated in Table 4.8.

Table 4.8: Test Results for Tentative Work 4

Density 2428 kg/m3
Slump 125 Mm 5 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 64 MPa 9280 psi
28-days 75 MPa 10875 psi
56-days 92 MPa 13340 psi
90-days 102 MPa 14790 psi
COMPRESSIVE STRENGTH OF CONCRETE(MPA)

120

102
100
92

80 75
64
7-days
60
28-days
56-days
40
90-days
20

0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Properly cured in the Curing Tank.

 7th day strength : 64 MPa

 90th Day Strength: 102 MPa

 Percentage Increase in Strength (3-90days) of about 60 percent was observed.

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 5
In this batch the equal fractions of the aggregate size were used. The concrete mix criterion
has been produced in Table 4.9.
Tentative Work 5 Dated: November 3, 2016.
Mix Design Ratio 1: 1 : 2
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.9: Concrete Mix Design Criterion for Tentative Work 5

Mix Design Ratio ( 1 : 1 : 2 )

Cement 19 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1330g
Water Cement Ratio 0.26
Quantity of Water Including Water of Absorption 5548 ml
Admixture (Sp-303) 20 ml/kg of Cementations Material 380 ml
Coarse Aggregate ½ Inch Down 19 Kg
¾ Inch Down 19 Kg
Fine Aggregate Fineness Modulus = 2.4 19 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
In this batch the dosage of the super plasticizer was increased to obtain more slump. There
was reduction in the compressive strength due to increased Super plasticizer quantity. The
results are in Table 4.10
Table 4.10: Test Results for Tentative Work 5

Density 2589 kg/m3

Slump 150 Mm 6 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 52.867 MPa 7665.715 Psi
28-days 57 MPa 8265 Psi
56-days 87.43 MPa 12677.35 Psi
90-days 90.1 MPa 13064.5 Psi

100
COMPRESSIVE STRENGTH OF CONCRETE

90 87.43 90.1

80
70
52.867 57
60 7-days
50 28-days
40
56-days
30
90-days
20
10
0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Normal Curing in the curing tank.

 7th day strength:53 MPa

 28th Day Strength:57 MPa

 56th Day strength: 87.5 MPa

 Percentage Increase in Strength (7-90days) of about 65 percent was observed.

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 6
In this batch the water cement ratio was further reduced to 0.22 from 0.3. It has been
produced in Table 4.11.
Tentative Work 6 Dated: November 11, 2016.
Mix Design Ratio 1: 0.75 : 1.5
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha Crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrance Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.11: Concrete Mix Design Criterion for Tentative Work 6

Mix Design Ratio ( 1 : 0.75 : 1.5 )

Cement 23.69 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1658g
Water Cement Ratio 0.22
Quantity of Water Including Water of Absorption 5828 ml
Admixture (Sp-303) 16 ml/kg of Cementations Material 379.1 ml
Coarse Aggregate ½ Inch Down 18 Kg
¾ Inch Down 18 Kg
Fine Aggregate Fineness Modulus = 2.4 18 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
There was slight increase in the compressive strength of the concrete due to the reduction of
w/c ratio. Table 4.12 indicates the results.
Table 4.12: Test Results for Tentative Work 6

Density 2517 kg/m3

Slump 225 mm 9 Inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 37.1 MPa 5379.5 Psi
28-days 51.5 MPa 7467.5 Psi
56-days 84.15 MPa 12201.75 Psi
90-days 92 MPa 13340 Psi

100
COMPRESSIVE STRENGTH OF CONCRETE(MPA)

92
90 84.15
80
70
60 51.5 7-days
50 28-days
37.1
40 56-days
30
90-days
20
10
0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Normal

 7th day strength: 37 MPa

 28th Day Strength: 52 MPa

 90th Day strength: 92 MPa

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 7
Mixing was started with w/c = 0.18, but it could not work even the w/c ratio went on increasing
to 0.3. Finally at w/c = 0.32 with high dosage of SP-303 of 25 ml/kg, a workable mix was
achieved with slump of 6 inches. Strange behavior of mix was observed, by just changing the
source of Coarse Aggregates. Sakhi Sarwer Crush has some weak particles along with rounded
shaped particles as well. Sakhi Sarwer Crush was found to be very dusty and used as unwashed.
Pores in samples were seen on testing. Table 4.13 indicates the concrete mix design.

Tentative Work 7 Dated: November 17, 2017.

Mix Design Ratio 1: 1 : 2
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sakhi sarwer
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.13: Concrete Mix Design Criterion for Tentative Work 7

Mix Design Ratio ( 1 : 1 : 2 )

Cement 19 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1330g
Water Cement Ratio 0.32
Quantity of Water Including Water of Absorption 6688 ml
Admixture (Sp-303) 25 ml/kg of Cementations Material 475 ml
Coarse Aggregate ½ Inch Down 19 Kg
¾ Inch Down 19 Kg
Fine Aggregate Fineness Modulus = 2.4 19 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
Compressive strength results were not much realistic. There were fluctuations in the strength
results. The compressive strength decreased at the age of 56 days and it was again observed
that compressive strength increased at the age of 90 days. The possible reasons may be the
improper placing of the sample in the jaws of the UTM (Universal Testing Machine). Table
4.14 indicates the test results.
Table 4.14: Test Results for Tentative Work 7

Density 2500 kg/m3

Slump 150 Mm 6 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 39.1 MPa 5669.5 psi
28-days 48.1 MPa 6974.5 psi
56-days 40 MPa 5800 psi
90-days 50 MPa 7250 psi

50 48.1 50

45
39.1
COMPRESSIVE STRENGTH OF

40
40
CONCRETE(MPA)

35
30 7-days
25 28-days
20
56-days
15
90-days
10
5
0
7-days
28-days
56-days
90-days

Observations
 7th day strength: 39 MPa

 28th Day Strength:48 MPa

 56th Day strength : 40 MPa

 Physical properties of Sahki Sarwer Crush also need to be examined properly.

 Compaction of the concrete in the steel mould needs improvement.

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 8
In this batch washed Sakhi Sarwar Crush was used. Due to washing the slump characteristics
of the concrete was improved and the w/c ratio was also reduced. Further the compressive
strength of the Crush was enhanced dramatically. Table 4.15 indicates the concrete mix deign.
Tentative Work 8 Dated: November 24, 2016.
Mix Design Ratio 1: 1 : 2
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sakhi sarwer
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrence Pur Sand
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.15: Concrete Mix Design Criterion for Tentative Work 8

Mix Design Ratio ( 1 : 1 : 2 )

Cement 19 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1330g
Water Cement Ratio 0.21
Quantity of Water Including Water of Absorption 4598 ml
Admixture (Sp-303) 19 ml/kg of Cementations Material 361 ml
Coarse Aggregate ½ Inch Down 19 Kg
¾ Inch Down 19 Kg
Fine Aggregate Fineness Modulus = 2.4 19 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
By merely washing the Crush, W/C suddenly drops to 0.21 at an optimum dose of 19 ml/kg,
with slump of 9 inches. Samples were compacted in the moulds in 4-5 layers to minimize
porosity. Test Results are produced in the Table 4.16.
Table 4.16: Test Results for Tentative Work 8

Density 2500 kg/m3

Slump 225 Mm 9 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 51.5 MPa 7467.5 psi
28-days 60.5 MPa 8772.5 psi
56-days 83.1 MPa 12049.5 psi
90-days 100 MPa 14500 psi

100 100
COMPRESSIVE STRENGTH OF CONCRETE

90
83.1
80
70
60.5
60 51.5 7-days
50 28-days
40
56-days
30
90-days
20
10
0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Heated

 7th day strength: 51 MPa

 28th Day Strength: MPa

 56th Day Strength: 83 MPa

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 9
In this batch special size equal or smaller than 3/8” is introduced in this mix. Aggregates (Fine
&Coarse) were washed and used in SSD state no additional water is added. No sharp increase
is seen in 7 - days. Concrete mix Design criterion is tabulated in Table 4.17.

Tentative Work 9 Dated: December 20, 2016.

Mix Design Ratio 1: 1 : 2
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrencepur
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.17: Concrete Mix Design Criterion for Tentative Work 9

Mix Design Ratio ( 1 : 1 : 2 )

Cement 19 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1330g
Water Cement Ratio 0.23
Quantity of Water Aggregates used in SSD condition. No 4370 ml
additional water is added.
Admixture (Sp-303) 20 ml/kg of Cementations Material 380 ml
Coarse Aggregate ½ Inch Down 19 Kg
¾ Inch Down 19 Kg
Fine Aggregate Fineness Modulus = 2.4 19 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
Good Results were obtained. Also there was late gain of Strength. Table 4.18 indicates the
test results.
Table 4.18: Test Results for Tentative Work 9

Density 2482 kg/m3

Slump 75 mm 3 Inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 48.1 MPa 6974.5 Psi
28-days 66.6 MPa 9657 Psi
56-days 70 MPa 10150 Psi
90-days 94 MPa 13630 Psi

100
COMPRESSIVE STRENGTH OF CONCRETE(MPA)

94
90
80
66.6 70
70
60 7-days
48.1
50
28-days
40
56-days
30
90-days
20
10
0
7-days
28-days
56-days
90-days

Observations
 7th day strength: 48.1 MPa

 56th Day Strength: 70 MPa

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CHAPTER 4 RESULTS AND DISSCUSSION

Tentative Work 10
Special Size equal or smaller than 3/8'' is introduced in this mix. Aggregates (Fine &Coarse)
were washed and used in SSD state no additional water is added. No sharp increase is seen in
7 - days. Table 4.19 indicates the concrete mix design.

Tentative Work 10 Dated: January 1, 2017.

Mix Design Ratio 1: 1 : 2
Cement Brand Fauji, Type-1, Grade-53
Coarse Aggregate Sargodha crush
Water Absorption of Coarse Aggregate 1%
Fine Aggregate Lawrencepur
Water Absorption of Fine Aggregate 1.2 %
No. of cylinders Prepared 4
No. of cubes prepared 2

Table 4.19: Concrete Mix Design Criterion for Tentative Work 10

Mix Design Ratio ( 1 : 1 : 2 )

Cement 19 Kg
Silica Fume Percentage Replacement 7% of Cement
Quantity 1330g
Water Cement Ratio 0.23
Quantity of Water Aggregates used in SSD condition. No 4370 ml
additional water is added.
Admixture (Sp-303) 20 ml/kg of Cementations Material 380 ml
Coarse Aggregate ½ Inch Down 19 Kg
¾ Inch Down 19 Kg
Fine Aggregate Fineness Modulus = 2.4 19 Kg

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CHAPTER 4 RESULTS AND DISSCUSSION

Test Results:
The results were quite satisfactory in this batch. Test results are indicated in Table 4.20.
Table 4.20: Test Results for Tentative Work 10

Density 2482 kg/m3

Slump 75 mm 3 inch
Compressive Strength, 150 x 300-mm Moist Cured Cylinders
7-days 50 MPa 7250 psi
28-days 69 MPa 10005 psi
56-days 85 MPa 12325 psi
90-days 98 MPa 14210 psi

100 98
COMPRESSIVE STRENGTH CONCRETE(MPA)

90 85
80
69
70
60 50 7-days
50 28-days
40
56-days
30
90-days
20
10
0
7-days
28-days
56-days
90-days

Observations
 Curing Condition: Normal

 7th day strength: 50 MPa

 90th Day Strength: 98 MPa

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CHAPTER 4 RESULTS AND DISSCUSSION

There was observed different failure patterns for the concrete cubes specimens. The failure
pattern was different for specimens with variation of w/c ratio, Sp-303 amount, aggregate types
and curing conditions.
It was observed that for the concrete cylinder specimens exhibited a severe abrupt and splitting
failure in last trials. This indicates the less ductile concrete. Failure pattern of some specimens
is shown in the figures below.

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CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

CHAPTER 5

CONCLUSIONS
&
RECOMMENDATIONS

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CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

5. Conclusions and Recommendations

The results of this study demonstrate that high strength concrete can be produced in Pakistan
with readily available materials using conventional batching procedures. The following
conclusions have been made regarding the selection of materials, mix design, production, and
testing of high strength concrete.
1. The water-cement, or water-binder, ratio is the most influential parameter affecting the
compressive strength of high strength concrete. In general, to produce concrete having
a 56-day compressive strength of at least 9,000 psi, the water-binder ratio must be less
than 0.35.
2. A cement content of at least 10 sacks/cu.yd. is required to produce high strength
concrete having a slump of 4 to 7 in., if no chemical or mineral admixture is added to
the mix. A cement content of 8.5 sacks/cu.yd. is optimum for strength and workability
of high strength concrete mixes containing superplasticizer, for a water-cement ratio of
0.30 and a slump of 4 to 5 in.
3. Compressive strength of concrete increases as super plasticizer dosage increases, up to
a dosage which causes a concrete mix to become segregated and unworkable. The
addition of too much super plasticizer to a high strength concrete mix may result in
significant retardation of concrete hardening. The brand of super plasticizer used affects
both the workability and the compressive strength of high strength concrete.
4. High strength concrete can be produced using natural gravel or crushed stone. However,
higher compressive strengths are obtained with concrete made using crushed stone.
5. For concrete mixes made with cement contents of 8.5 sacks/cu.yd. or more but without
super plasticizers, using 1/2-in. max. Size coarse aggregate results in higher concrete
compressive strengths at 56 days for mixes having a similar slump. For concrete mixes
made with a super plasticizer, use of any size of coarse aggregate between 1/2-in. and
3/4-in. can result in high compressive strength. However, the highest compressive
strengths result from the use of 1/2-in. max. size coarse aggregate.
6. High strength concrete can be produced using a sand with a fineness modulus of from
2.4 to 2.7 for mixes containing no admixtures. Sands having a fineness modulus of as
low as 2.3 are satisfactory for producing high strength concrete when a super plasticizer
is used.
7. The 28-day compressive strength of high strength concrete which has been cured under
ideal conditions for 7 days after casting is not seriously affected by curing in hot and
dry conditions from 7 to 28 days after casting.
8. The compressive strength of high strength concrete specimens cast using 6-in. dia. x 6-
in. molds is 10 percent higher than that of concrete specimens cast using 6-in. dia. x 12-
in. molds, in general.
9. The type of capping compounds used to cap high strength concrete compressive
strength specimens for compression testing affects the test results. High strength
capping compounds should be used.
10. The modulus of rupture of high strength concrete falls between 8√fc’ and 12√fc’ .

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CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

11. High strength concrete having a slump of 4-in. or greater can be produced even when
mixing temperatures are of the order of 40 C and the total period of mixing is between
30 min. and 60 min.

Recommendations:
The recommendations are based on a study of the interaction among components of plain
concrete and its mix proportions and of their contribution to the compressive strength of high
strength concrete.
 It is recommended that results presented in this research will serve as a guideline to
resident engineers in selection of materials and proportions for producing high strength
concrete in Pakistan.
 Substantial improvements in strength and workability may be achieved simply by
experimenting with different brands of cement, chemical and mineral admixtures.
 Concrete producers should also encouraged to try larger coarse aggregates in concretes
with superplasticizers, and fine aggregates with finer gradations.

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CHAPTER 6 REFERENCES

CHAPTER 6

REFERENCES

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CHAPTER 6 REFERENCES

6. References

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A Nnadurai and A. Ravichandran, “Development of mix design for HSC with Admixtures”,
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