103787

The Islamic University Gaza Higher Education Deanship Faculty of Engineering Civil Engineering Department Design and Rehabilitation of Structures /

Fresh and Hardened Properties of Ultra High Performance Self Compacting Concrete

" "

By

Mohammed Wael Abu Shaban

Supervised By

Dr. Mohammed Arafa Dr. Mamoun Al Qedra

A Research Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Civil Engineering Design and Rehabilitation of Structures

June 2012

I

ABSTRACT The main goal of this research is to produce Ultra High Performance Self Compacting Concrete (UHPSCC) in Gaza strip, using materials which are available at the local markets. Different trial mixes were used to obtain the acceptable fresh properties of Self compacting concrete with a compressive strength exceeding 140 MPa. The research includes also the use of a recognized manufacturer mineral admixture, basalt aggregate, quartz, and special type of fine aggregate (quartz powder).

The elimination of vibration for compacting concrete during placing through the use of Self Compacting Concrete leads to substantial advantages in terms of better homogeneity, enhancement of working environment and improvement in the productivity by increasing the speed of construction. The resulting concrete is characterized in the fresh state by methods used for Self Compacted Concrete, such as slump-flow, V-funnel and L- box tests.

The fresh and hardened mechanical properties of UHPSCC were studied, i.e., workability, viscosity, flowability, passing ability, self compacting, compressive strength, split cylinder strength, and flexural strength. The effect of using different superplasticizer and silica fume doses on these properties are obtained within research work.

The effect of adding different amounts of basalt aggregate (150%, 160%, and 170%) by cement weight on the fresh and hardened properties of UHPSCC, i.e., workability, viscosity, flowability, passing ability, compressive strength, and density is also investigated.

The results showed that the optimum mix is obtained by adding 160% basalt, 3% superplastisizer and 15.5% silica fume. The test results also revealed that it is possible to produce UHPSCC in Gaza Strip with compressive strength in excess of 140 MPa using (1%, 2%, and 3%) superplasticizer,10% to 16% silica fume, and 15.5% silica fume, with water cement ratio less than 0.33.

II

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III

DEDICATIONS To my Father, Mother, Joan, Hamam, and Belal, to my wife Alaa.

To my friends, and to whom I belong.

IV

ACKNOWLEDGMENT I would like to express my sincere appreciation to Dr. Mohamed Arafa and Dr.

Mamoun Al Qedra - Department of Civil Engineering, Faculty of Engineering,

The Islamic University of Gaza- for their help and guidance in the preparation

and development of this work. The constant encouragement, support and

inspiration they offered were fundamental to the completion of this research.

Special thanks go to the material and soil lab of the Islamic University of Gaza,

for their logistic facilitations and their continuous support. I would like to

express my deep thanks for my friends for their assistance during the practical

work of the research. Finally I would like to thank everyone who gave advice or

assistance that contributed to complete this research.

V

TABLE OF CONTENTS

ABSTRACT ..................................................................................................................................... I

ARABIC ABSTRACT .................................................................................................................... II

DEDICATIONS ............................................................................................................................ III

ACKNOWLEDGMENT ............................................................................................................... IV

TABLE OF CONTENTS ................................................................................................................ V

LIST OF TABLES ...................................................................................................................... VIII

LIST OF FIGURES ....................................................................................................................... IX

CHAPTER 1- INTRODUCTION ................................................................................................... 2

1.1 General Background .............................................................................................................. 2

1.2 Statement of the problem ....................................................................................................... 3

1.3 Scope of work ........................................................................................................................ 4

1.4 Research objectives ............................................................................................................... 4

1.5 Methodology ......................................................................................................................... 5

1.6 Thesis Layout ........................................................................................................................ 5

CHAPTER 2- LITERATURE REVIEW ........................................................................................ 8

2.1 Definition of Ultra High Performance Self Compacting Concrete ....................................... 8

2.2 History of developing UHPSCC ........................................................................................... 8

2.3 Advantages of UHPSCC ....................................................................................................... 9

2.4 New structural design and construction system .................................................................. 11

2.5 UHPSCC large scale application ......................................................................................... 13

2.6 Materials of UHPSCC ......................................................................................................... 14

2.6.1 Powder .......................................................................................................................... 14

2.6.2 Portland cement ............................................................................................................ 14

2.6.3 Silica fume .................................................................................................................... 17

2.6.4 Micro fine aggregates ................................................................................................... 19

2.7 Concluding Remarks ........................................................................................................... 20

CHAPTER 3- CONSTITUENT MATERIALS AND EXPERIMENTAL PROGRAM .............. 23

3.1 Introduction ......................................................................................................................... 23

3.2 Characterizations of constituent Materials .......................................................................... 24

3.2.1 Cement .......................................................................................................................... 24

VI

3.2.2 Aggregates (basalt, quartz sand, quartz powder) .......................................................... 25

3.2.3 Water ............................................................................................................................ 28

3.2.4 Admixture ..................................................................................................................... 28

3.2.5 Silica Fume ................................................................................................................... 29

3.3 Mix Design of UHPSCC ..................................................................................................... 30

3.4 UHPSCC Preparation .......................................................................................................... 31

3.5 Test Program ....................................................................................................................... 32

3.6 Equipment and testing procedure ........................................................................................ 34

3.6.1 Tests Applied On Fresh Concrete ................................................................................. 34

3.6.2 Tests Applied on Hardened Concrete ........................................................................... 41

CHAPTER 4- TEST RESULTS AND DISCUSSION .................................................................. 49

4.1 Introduction ......................................................................................................................... 49

4.2 Fresh properties tests results ................................................................................................ 50

4.3 Effect of silica fume and superplasticizer on slump flow results ........................................ 52

4.4 Effect of silica fume and superplasticizer on V-Funnel test results .................................... 53

4.5 Effect of silica fume and superplasticizer on L-Box test results ......................................... 54

4.6 Segregation in the trial mixes .............................................................................................. 55

4.7 Hardened properties tests results ......................................................................................... 56

4.7.1 Effect of silica fume and superplasticizer on UHPSCC density ................................... 56

4.7.2 Effect of silica fume and superplasticizer on UHPSCC compressive strength ............ 57

4.7.3 Compressive strength Time relationship ................................................................... 60

4.7.4 Effect of silica fume and superplasticizer on UHPSCC splitting strength ................... 64

4.7.5 Splitting tensile strength Time relationship ............................................................... 66

4.7.6 Effect of Basalt content ................................................................................................ 68

CHAPTER 5- CONCLUSIONS AND RECOMMENDATIONS ................................................ 74

5.1 Introduction ......................................................................................................................... 74

5.2 Conclusions ......................................................................................................................... 74

5.2.1 Generals ........................................................................................................................ 74

5.2.2 Fresh properties ............................................................................................................ 74

5.2.2 Hardened properties ...................................................................................................... 76

5.3 Recommendations ............................................................................................................... 77

5.3.1 The effect of Material ................................................................................................... 77

5.3.2 Durability of UHPSCC ................................................................................................. 78

VII

5.3.3 Short term mechanical properties ................................................................................. 79

5.3.4 Using UHPSCC in the Rehabilitation Works ............................................................... 79

CHAPTER 6- REFERENCES ...................................................................................................... 81

CHAPTER 7- APPENDIXES ....................................................................................................... 86

VIII

LIST OF TABLES Table 2.1: History of developing UHPSCC .................................................................................... 9

Table 2.2: Advantages of UHPSCC .............................................................................................. 11

Table 3.1: cement characteristics according to the manufacturer sheets ....................................... 24

Table 3.2: Physical property of basalt aggregate ........................................................................... 26

Table 3.3: Physical property of quartz sand .................................................................................. 26

Table 3.4: Water absorption of basalt aggregate ........................................................................... 27

Table 3.5: Water absorption of quartz sand ................................................................................... 27

Table 3.6: The technical data for the "Sika ViscoCrete - 10" (source: from supplier) .................. 28

Table 3.7: The technical data for the "Sika - Fume" (source: from supplier) ................................ 29

Table 3.8: Self Compacting Criteria .............................................................................................. 34

Table 3.9: Test program for compressive strength ........................................................................ 42

Table 4.1: Best mixture proportions of UHPSCC by weight of cement ....................................... 49

Table 4.2: One cubic meter components of UHPSCC mixture ..................................................... 50

Table 4.3: Changing in mixtures proportions per cement weight ................................................. 50

Table 4.4: Mixtures classification ................................................................................................. 51

Table 4.5: Mixtures mean density ................................................................................................. 56

Table 4.6: Mixtures mean compressive strength after 28 days ..................................................... 57

Table 4.7: Summary of compressive strength test results for first UHPSCC mix ........................ 60

Table 4.8: Summary of compressive strength test results for all mixes ........................................ 61

Table 4.9: Comparison of ratio of (fc)t /(fc )28 of UHPSCC with the prediction of ACI

Committee 209 of NSC ................................................................................................................. 63

Table 4.10: Summary of splitting tensile strength test results ....................................................... 65

Table 4.11: Summary of splitting strength test results for first UHPSCC mix ............................. 66

Table 4.12: Changing in mixtures proportions .............................................................................. 69

Table 4.13: Basalt different proportion mixes results ................................................................... 69

IX

LIST OF FIGURES

Figure 2.1: Advantages of UHPSCC ............................................................................................. 10

Figure 2.2: New Construction system achieved by making full use of UHPSCC ........................ 12

Figure 2.3: Sandwich structure for immersed tunnel .................................................................... 12

Figure 2.4: Burj Khalifa ................................................................................................................ 13

Figure 2.5: Microstructure development in Portland cement pastes ............................................. 15

Figure 2.6: Effect of micro silica in densifying the concrete mix ................................................. 18

Figure 3.1: Aggregates used in mixture preparations .................................................................... 25

Figure 3.2: The chemical admixture (Superplasticizer) used in mixture preparation ................... 29

Figure 3.3: Sika Fume ................................................................................................................ 30

Figure 3.4: Mix design procedure ................................................................................................. 30

Figure 3.5: The drum mixer ........................................................................................................... 32

Figure 3.6: Experimental program steps chart ............................................................................... 33

Figure 3.7: Slump cone and base plate .......................................................................................... 35

Figure 3.8: Slump flow test ........................................................................................................... 36

Figure 3.9: The largest diameter of the flow spread ...................................................................... 36

Figure 3.10: V-funnel test.............................................................................................................. 38

Figure 3.11: General assembly of L-box ....................................................................................... 39

Figure 3.12: Dimensions and typical design of L-box .................................................................. 40

Figure 3.13: Compression test specimens (100x100x100mm) ..................................................... 41

Figure 3.14: Compressive strength test machine ........................................................................... 42

Figure 3.15: Split cylinder test setup for cylinder 150 x 300mm .................................................. 44

Figure 3.16: Crack in a split cylinder tensile specimen ................................................................. 45

Figure 3.17: Diagrammatic view for flexure test of concrete by center-point loading ................. 46

Figure 3.18: Flexural test specimens (100*100*500mm) ............................................................. 46

Figure 4.1: Effect of silica fume and superplasticizer on UHPSCC slump flow .......................... 52

Figure 4.2: Effect of silica fume and superplasticizer on UHPSCC V-Funnel time ..................... 53

Figure 4.3: Effect of silica fume and superplasticizer on UHPSCC L-Box test ............................ 55

Figure 4.4: Effect of silica fume and superplasticizer on UHPSCC density ................................. 57

Figure 4.5: Effect of silica fume and superplasticizer on UHPSCC compressive strength ........... 58

Figure 4.6: Effect of silica fume dosage on compressive strength ................................................ 60

Figure 4.7: The variation of mean compressive strength with age for first UHPSCC mix ........... 61

Figure 4.8: Relation between the mean compressive strength and age for all mixes .................... 62

X

Figure 4.9: Comparison of ratio of (fc)t /(fc )28 for UHPSCC and NSC at different ages ........... 63

Figure 4.10: Compressive strength gain as a function of time after casting .................................. 64

Figure 4.11: Effect of silica fume and superplasticizer on UHPSCC splitting strength ................ 66

Figure 4.12: The variation of splitting strength with age for first UHPSCC mix.......................... 67

Figure 4.13: The ratio of fsp (t) to fsp (28days) with time for UHPSCC ...................................... 68

Figure 4.14: Effect of Basalt Content on UHPSCC Slump Flow .................................................. 70

Figure 4.15: Effect of Basalt Content on UHPSCC V-Funnel test................................................ 70

Figure 4.16: Effect of Basalt Content on UHPSCC Compressive Strength .................................. 71

Figure 4.17: Effect of Basalt Content on UHPSCC Splitting Tensile Strength ............................ 71

Figure 4.18: Effect of Basalt Content on UHPSCC Flexural Tensile Strength ............................. 72

CHAPTER 1 INTRODUCTION

1



2

CHAPTER 1- INTRODUCTION

1.1 General Background

Reinforced concrete is considered the most frequently used structural material,

not only because it has good mechanical proprieties after hardening, easy to use,

etc. but also its dominant advantage that it is considered as an economic

structural material.

Increasing the concrete strength is always one of the main desires of concrete

technology. Since more than 20 years, ultra high strength concretes with

compressive strength ranging from 50 MPa up to 130 MPa have been used

worldwide in tall buildings and bridges with long spans or buildings in

aggressive environments (Farhang and Arash,2008).

Building elements made of high strength concrete are usually densely

reinforced. The small distance between reinforcing bars may lead to defects in

concrete. If ultra high performance concrete is a self-compacting, the production

of densely reinforced building element from ultra high performance concrete

with high homogeneity would be an easy work (Jianxin and Jorg, 2002).

More over in recent years, premature deterioration of reinforced concrete

structures has given a considerable cause for concern where large numbers of

existing structures are currently in need of either strengthening or rehabilitation

due to various reasons.

Ultra high performance self compacting concrete can solve the problem of

casting in densely confined areas, and areas which need a large thickness of the

concrete.

Self compacting concrete is a concrete that flows and compacts only under

gravity. It fills the whole mold completely without any defects. The usual self-

compacting concretes have a compressive strength in the range of 30-50 MPa

(European Guidelines,2005).


3

1.2 Statement of the problem

This study deals with the issue of producing the ultra high performance self

compacting concrete (UHPSCC) in Gaza strip. This product is needed to

facilitate many difficulties.

Casting concrete in tall buildings, huge foundations, bridges, and long

spans, where ultra high performance concrete is needed at the same time

the self compacting prosperities required to make pumping process easy

and possible.

Due to large numbers of deteriorated structures which need

rehabilitation and strengthening, ultra high strength concrete is

recommended in such cases to provide small cross sections able to carry

existing or new loads, building elements strengthened with ultra high

strength concrete are usually densely reinforced. The small distance

between reinforcing bars and the small spaces provided by framework -

especially in the repair works, may lead to defects in concrete such as

honeycombing, and segregation, if high strength concrete is self-

compacting, the production of densely reinforced strengthened building

element from high strength concrete with high homogeneity would be an

easy work.


4

1.3 Scope of work

This research produces the UHPSCC in the IUG lab, and investigates the fresh

and hardened properties of this production.

1. Characteristics of fresh (UHPSCC) In order to obtain the characteristics of fresh UHPSCC, the following aspects are considered: Mix design. Workability. Outstanding flowability. Homogeneity (No separation/ segregation).

2. Characteristics of hardened (UHPSCC) The following test to be carried out to establish the mechanical properties of UHPSCC: Compressive strength. Splitting tensile strength. Flexural strength. Hardened density.

1.4 Research objectives

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

Compacting Concrete (UHPSCC) in Gaza strip using available materials, and to

study the mechanical prosperities of (UHPSCC), this will open a new

possibilities for the production of a new material, locally. This can be achieved

through the following objectives:

I. Identify the possible concrete mixes to produce several strengths with several

self compacting concrete (SCC) properties.

II. Obtaining the fresh properties of the UHPSCC (Slump, V-Funnel, L-Box).

III. Obtaining the mechanical prosperities of hardened UHPSCC including

compressive strength, splitting tensile strength, hardened density, and flexural

strength.


5

1.5 Methodology

In general terms, the following methodology was followed to achieve the

research objectives.

1- To conduct comprehensive literature review related to subject of

UHPSCC.

2- Selection of suitable ingredient materials required for producing

UHPSCC, including cement, silica fume, aggregates, water, and chemical

admixtures.

3- Determine the relative quantities of these materials in order to produce

UHPSCC mixes.

4- Performing physical and mechanical laboratory tests on UHPSCC

samples and compares the results to the available standards.

5- Analyze the results and draw conclusions.

1.6 Thesis Layout

The research entails six chapters organized as follows:

Chapter 1 (Introduction)

This chapter gives a general background about ultra high performance self

compacting concrete, research problem and scope of work, objectives and

methodology used to achieve the research objectives. Also it describes the

structure of the research.


6

Chapter 2 (Literature Review)

This chapter discusses the concept of producing ultra high performance self

compacting concrete, history of UHPSCC, Advantages, applications and

materials.

Chapter 3 (Constituent Materials and Experimental Program)

This chapter reviews the materials were used in producing ultra high

performance self compacting concrete and their properties, mix design of

UHPSCC, testing program, and equipments used in the testing procedures.

Chapter 4 (Test Results and discussion)

This chapter illustrates the test results including the fresh and hardened results,

visual inspection splitting and flexural test results.

Chapter 5 (Conclusions and Recommendations)

This chapter includes the concluded remarks, main conclusions and

recommendations drawn from this research.

Chapter 6 (References)

This chapter lists the reviewed references.

CHAPTER 2 LITERATURE REVIEW

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8

CHAPTER 2- LITERATURE REVIEW

2.1 Definition of Ultra High Performance Self Compacting Concrete

Ultra high Performance Self Compacting Concrete (UHPSCC) is a mix concrete which

possesses the fresh properties of the Self Compacting Concrete (SCC) and the hardened

properties of the Ultra High Performance Concrete (UHPC).

UHPSCC is a very dense structured fine or coarse aggregate concrete with a low water

/cement ratio smaller than 0.40, high cement content chemical and mineral admixtures

which are selected to increase the bond between the aggregates and the cement paste and

to facilitate flow and penetration through congested reinforcement zones (Okamura and

Ouchi, 2003).

The optimization of granular mix of UHPSCC leads to high performance concrete that

has excellent deformability in the fresh state, high resistance to segregation, and can be

placed and compacted under its self weight without applying vibration, also this mix

leads to minimizing the number of defects such as micro cracks and pore spaces that

allow achieving a greater percentage of the potential ultimate load carrying capacity

defined by its components and providing enhanced durability properties. Because of the

high compressive strength in hardened state and the excellent deformability in fresh state

this type of concrete is named Ultra High Performance Self Compacting Concrete

(EFNARC, 2005).

2.2 History of developing UHPSCC

Table (2.1) summarizes the process of developing the high strength concrete, self

compacting concrete and finally the ultra high performance self compacting concrete

(Richard and Cheyrezy, 1995) (Buitelaar, 2004) (EFNARC, 2005).


9

Table 2.1: History of developing UHPSCC

Year UHPC - History Year SCC - History 1950 Concrete with a compressive

strength of (34MPa) was considered high strength concrete

1988 The first time SCC was developed in Japan

1960 High strength concrete were developed in labs only(80MPa)

1993 The prototype of self-compacting concrete was first completed using materials already on the market

1980 High performance concrete were developed in Denmark -for special applications in the security industry and protective defense constructions (100MPa)

1997 The SCC was used for the first time in Europe in the civil works

1985 First research was conduct on the applications of UHPC

2002 European specification and guidelines were developed for SCC

More recently

Compressive strengths approaching (120MPa) is used

More recently

SCC is used commercially in

Japan, Europe, USA, etc.

2002-2008 Some researches takes place on matching the UHPC and SCC in one mix in order to develop the UHPSCC, which is used recently in many special tall buildings and tunnels

2.3 Advantages of UHPSCC

In general terms, the UHPSCC holds the advantages of the UHPC and SCC, so the main

advantage that UHPSCC is an innovative concrete that does not require vibration for

placing and compaction. It is able to flow under its own weight, completely filling

formwork and achieving full compaction, even in the presence of congested

reinforcement. It also has over standard concrete is its high compressive strength. Other

advantages include low porosity, improved microstructure and homogeneity, high

flexibility without the addition of fibers. As a result of its superior performance,

UHPSCC has found application in the storage of nuclear waste, bridges, roofs, piers,

seismic-resistant structures and structures designed to resist impact loading. Owing to its

high compression resistance, precast structural elements can be fabricated in slender form

to enhance aesthetics. Durability issues of traditional concrete have been acknowledged


10

for many years and significant funds have been necessary to repair aging infrastructure.

UHPSCC possesses good durability properties and lower porosity and capillaries account

for its endurance. UHPSCC construction requires lower maintenance costs in its service

life than conventional concrete. UHPSCC has enhanced ductility, high temperature

performance and improved impact resistance.

Figure (2.1) and Table (2.2) shows the advantages of UHPC, SCC and UHPSCC as one

mixture respectively.

Figure 2.1: Advantages of UHPSCC

Advantages of SCC

Advantages of UHPC

Homogeneous

Durable

Low porosity

High compressive strength

Homogeneous & Durable

Less sensitivity to temp. change

Flowability & Rapid placement

Does not require vibration

Advantages of UHPSCC


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Table 2.2: Advantages of UHPSCC A

dvan

tage

s of

UH

PSC

C

High compressive strength Flowability (No separation and No Segregation) Can be easily pumped Low noise-level in the plants and construction sites Eliminated problems associated with vibration Less labor involved Faster construction Improved quality and durability Less sensitivity to temperature change Low porosity

2.4 New structural design and construction system

Adding the self compacting properties to the ultra high performance concrete saves the

cost of vibrating compaction and ensures the compaction of the concrete in the structures.

However, total construction cost cannot always be reduced, except in large scale

constructions. This is because conventional construction systems are essentially designed

based on the assumption that vibrating compaction of concrete is necessary.

UHPSCC can greatly improve construction systems previously based on conventional

concrete that required vibrating compaction. This sort of compaction, which can easily

cause segregation, has been an obstacle to the rationalization of construction work. Once

this obstacle is eliminated, concrete construction can be rationalized and new

construction systems including formwork, reinforcement, support and structural design,

can be developed (Okamura and Ouchi, 2003), this can be summarized in the following

figure.


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Ultra High performance Self compacting Concrete High Compressive Strength

No Vibration Resistant to Segregation

Less Restriction to Design Less Restriction to Practice

New Type of Structures Rational Construction System

Rational Combination of Concrete & Steel

Figure 2.2: New Construction system achieved by making full use of UHPSCC

One example of this is the so-called sandwich structure Figure (2.3), where concrete is

filled into a steel shell. Such a structure has already been completed in Kobe, and could

not have been achieved without development of UHPSCC.

Figure 2.3: Sandwich structure for immersed tunnel (EFNARC, 2005)


13

2.5 UHPSCC large scale application The Burj Khalifa Figure (2.4), the worlds tallest building, has a laundry list of superlatives. Greatest number of stories, highest occupied floor, longest travel distance elevator, worlds highest swimming pool. Perhaps none of these would have been achievable without the great advances that have been made in concrete technology over the past 20 to 30 years. Most of the Burj Khalifa is a reinforced concrete structure, except for the top, which consists of a structural steel spire with a diagonally braced lateral system. 330,000 m3 of high-performance self compacting concrete is used throughout the building. The Burj Khalif a One of the major requirements for the successful completion of this project was the ability to pump the concrete slurry up to a height of 600 meters in a short enough time span (around 30 minutes) to ensure the concrete remained workable and retained its high performance properties. To decrease construction time, the concrete was designed to be self-compacting (SCC), meaning a concrete mix that leveled itself solely due to its own weight, with little or no vibration. It spread into place, filled formwork, and packed tightly into even the most congested reinforcement, all without any mechanical vibration.

Figure 2.4: Burj Khalifa


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2.6 Materials of UHPSCC

The constituent materials used for the production of UHPSCC are the same as those for

conventionally ultra high performance concrete except that UHPSCC contains lesser

aggregate and greater powder (cement and filler particles). Limestone powder, silica

fume, quartz powder, etc are used as the filler materials. To improve the strength, self

compatibility, without segregation, a high dosage of superplasticizer along with stabilizer

is added (Arafa et.al, 2010).

2.6.1 Powder

The term powder used in UHPSCC refers to a blended mix of cement and filler

particles smaller than 0.125 mm. The filler increases the paste volume required to achieve

the desirable workability of UHPSCC. The addition of filler in an appropriate quantity

enhances both workability and durability without sacrificing early strength.

2.6.2 Portland cement

Portland cement concrete is foremost among the construction materials used in civil

engineering projects around the world. The reasons for its often use are varied, but among

the more important are the economic and widespread availability of its constituents, its

versatility, and adaptability, as evidenced by the many types of construction in which it is

used, and the minimal maintenance requirements during service life.

2.6.2.1 Hydration of Portland cement

When Portland cement is mixed with water, its constituent compounds undergo a series

of chemical reactions that are responsible for the eventual hardening of concrete.

Reactions with water are designated hydration, and the new solids formed on hydration

are collectively referred to as hydration products. Figure (2.5) shows schematically the

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

water that separates individual cement grains in the fluid paste Figure (2.5.a) with solid

hydration products that form a continuous matrix and bind the residual cement grains

together over a period of time, as illustrated in Figure (2.5):(b-d).The calcium silicates

provide most of the strength developed by Portland cement. C3S provides most of the


15

early strength in the first three to four weeks and both C3S and C2S contribute equally to

ultimate strength (Mindess, Young and Darwin, 2002).

The hydration reactions of the two calcium silicates are very similar, differing only in the

amount of calcium hydroxide formed as seen in the following equations (Mindess, Young

and Darwin, 2002):

23Tricalcium silicate + 11 328Calcium silicate hydrate + 3 calcium hydroxide

(Mindess, Young and Darwin, 2002)

22Dicalcium silicate + 9 328C S H + calcium hydroxide

C-S-H or C3S2H8 is called calcium silicate hydrate and is the principal hydration

product. The formula C3S2H8 is only approximate because the composition of this

hydrate is actually variable over quite a wide range. In Portland cement, the hydration of

Figure 2.5: Microstructure development in Portland


16

tricalcium aluminate C3A involves reactions with sulfate ions that are supplied by the

dissolution of gypsum, which is added to temper the strong initial reaction of C3A with

water that can lead to flash set. The primary initial reaction of C3A is as follows:

2Tricalcium aluminate + 3 2Gypsum + 26 6332Ettringite Where S is equivalent to SO3 and ettringite is a stable hydration product only while there

is an ample supply of sulfate available.

2.6.2.2 Cement grains Size Distribution, Packing and Dispersion

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

about 1 m to about 80 m. Cements are ground slightly finer, but not much. The mean

size being of the order of 9 to 10 m. In visualizing the state of the flocculated mass of

cement grains in fresh Portland cement mixes, it appears that the variation in particle size

between larger and smaller cement particles does not result a dense packing. To a

considerable extent this is due to the flocculated character particles once bumped together

are "stuck" together by forces of attraction cannot readily slide to accommodate each

other better. However, even if they could, they are far too close to being of the same

order of size to be able to form dense local mixes. Water filled pockets of roughly the

same size as the cement particles exist throughout the mass (Neville, 1993).

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

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

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

0.2 m. When micro silica is added to ordinary cement paste a denser packing that may

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

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

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

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

they can separate from each other and pack individually between and around the cement

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


17

than the relatively usual mixing done in ordinary concrete production. High shear mixers

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

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

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

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

2.6.3 Silica fume

Silicon, ferrosilicon and other silicon alloys are produced by reducing quartz, with coal

and iron or other ores, at very high temperatures (2000C) in electric arc furnaces. Some

silicon gas or fume is produced in the process, which reaches the top of the furnace with

other combustion gases, where it becomes oxidized to silica in contact with the air and

then condenses as 0.1 m to 1 m spherical particles of amorphous silica. This material

is usually known as silica fume. It is also referred to as microsilica or more properly,

condensed silica fume (CSF). Silica fume is an ultra fine powder, with individual particle

sizes between 50 and 100 times finer than cement, comprising solid spherical glassy

particles of amorphous silica (85-96 percent SiO2). However, the spherical particles are

usually agglomerated so that the effective particle size is much coarser (ACI 548.6R-96).

2.6.3.1 The pozzolanic reactions

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

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

the silica to form a calcium-silicate hydrate through the pozzolanic reaction. See Figure

(2.6). (3 + 2)Portland cement + + + ( )

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

hydroxide solutions.

(Grutzeck and Roy, 1995) studied the reactivity of silica fume with calcium hydroxide in

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

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


18

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

days was required to consume the CH.

Figure 2.6: Effect of micro silica in densifying the concrete mix

(Grutzeck and Roy, 1995) suggest a gel model of silica fume-cement hydration.

According to this model, silica fume contacts mixing water and forms a silica-rich gel,

absorbing most of the available water. Gel then agglomerates between the grains of

unhydrated cement, coating the grains in the process. Calcium hydroxide reacts with the

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

the C-S-H produced by cement hydration, thus producing a very dense structure.

2.6.3.2 The physical effects

The strength at the Interfacial Transition Zone (ITZ) between cement paste and coarse

aggregate particles is lower than that of the bulk cement paste. The transition zone

contains more voids because of the accumulation of bleed water underneath the aggregate

particles and the difficulty of packing solid particles near a surface. Relatively more

calcium hydroxide (CH) forms in this region than elsewhere. Without silica fume, the CH


19

crystals grow large and tend to be strongly oriented parallel to the aggregate particle

surface (Monteiro and Maso, 1985). CH is weaker than calcium silicate hydrate (C-S-

H), and when the crystals are large and strongly oriented parallel to the aggregate surface,

they are easily cleaved. a weak interfacial transition zone (ITZ) results from the

combination of high void content and large, strongly oriented CH crystals.

According to (Mindess, 1988), silica fume increases the strength of concrete largely

because it increases the strength of the bond between the cement paste and the aggregate

particles.

(Jiaxnin and Jorg, 2002) pointed out .The increased coherence (cohesiveness) will

benefit the hardened concrete structure in terms of reduced segregation and bleed water

pockets under reinforcing bars and coarse aggregate.

(Monteiro and Mehta,1990) stated that silica fume reduces the thickness of the

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

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

during the early stages.

(Buitelaar, 2004) showed that addition of silica fume could reduce water demand

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

between the cement grains. This reduction only applies for systems with enough

admixtures to reduce surface forces.

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

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

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

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

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

2.6.4 Micro fine aggregates

Microfine aggregates defined as the materials passing sieve 75 m. In manufactured fine

aggregate these microfines are most likely smaller size fractions of the crushed aggregate,

while in natural sands the microfines can be clays, quartz powder or other deleterious

particles that harm the concrete.


20

The micro fine aggregate is an important parameter for gaining the self compacting

properties and the rheological properties which improved with increasing the micro fine

aggregates ratio. If the aggregate content in a UHPSCC mixture exceeds a certain limit,

blockage would occur independently of the viscosity of the mortar. Superplasticizer and

water content then determined to ensure desired self compacting characteristics

(Okamura and Ozawa, 1995).

Although most materials smaller than sieve 75 m increase the water demand of the

concrete, some experimental results claim that these fine particles can act as a lubricant

and enhance workability without a significant increase in the water demand for a given

workability (Hudson, 2007). Fillers such as microfines can have a positive effect on

concretes, influencing both particle packing and physiochemical reactions in the interface

zone (Kronlof, 1994).

Some positive effects of including fine fillers in mixtures are: smaller water requirement

due to improved particle packing; increased strength due to smaller water requirement

and improved interaction between paste and aggregate; decreased porosity; and better

workability (Kronlof, 1994).

2.7 Concluding Remarks

Ultra High Performance Self Compacting Concrete (UHPSCC) is one of the latest

developments in concrete technology. UHPSCC refers to materials with a cement matrix

and a characteristic compressive strength in excess of 120MPa. The hardened concrete

matrix of Ultra High Performance Self Compacting Concrete (UHPSCC) shows

extraordinary strength and durability properties, and the fresh concrete matrix shows

extraordinary workability allow it to flow under its own weight and without the need of

vibration.

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

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

dense microstructure. The sufficient workability is obtained by using superplasticizer.

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


21

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

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

particles.

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

nuclear waste, bridges, tall buildings, immersed constructions.

CHAPTER 3 CONSTITUENT MATERIALS AND EXPERIMENTAL PROGRAM

22



23

CHAPTER 3- CONSTITUENT MATERIALS AND EXPERIMENTAL PROGRAM

3.1 Introduction

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

produce UHPSCC associated with this research work.

The laboratory investigation consisted of testing both fresh and hardened concrete

properties. Fresh concrete was tested to ensure the self compacting ability of various

mixes, slump and V-funnel to ensure filling ability in the plastic state, L-box to ensure

the passing ability of UHPSCC, and V-funnel to test the segregation resistance. The tests

for hardened concrete included compression tests for strength and indirect tensile tests

(split cylinder and flexural strength tests).

The influence of the silica fumes dosage, superplasticizer, cement/ultra fine ratio and the

mixing procedures on the compressive strength concrete together with the workability

and density of UHPSCC were studied by preparing several concrete mixes.

The properties of several constituent materials used to produce UHPSCC are also

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

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

are illustrated in the following sections.


24

3.2 Characterizations of constituent Materials

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

grey silica fume, crushed Quartz. Quartz powder and basalt aggregate, in addition to

superplasticizer are used to ensure suitable workability. Proportions of these constituent

materials have been chosen carefully in order to optimize the packing density of the

mixture.

3.2.1 Cement

Cement paste is the binder in UHPSCC that holds the aggregate (coarse, fine, micron

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

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

the most active component of UHPSCC and usually has the greatest unit cost, its

selection and proper use is important in obtaining most economically the balance of

properties desired of UHPSCC mixture.

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

Ultra High Performance Self Compacting Concrete (UHPSCC). The cement met the

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

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

relevant ASTM specifications for comparison purposes.

Table 3.1: cement characteristics according to the manufacturer sheets

Test type Ordinary Portland Cement Results ASTM C 150 Setting time (Vicat test) hr min

Initial 1 hr 30 min More than 60 min Final 4 hr 40 min Less than 6 hrs 15 min

Mortar Compressive Strength (MPa)

3 Days 25.7MPa Min. 12MPa 7 Days 36.9MPa Min. 19MPa

28 Days

53.4MPa No limit

Fineness (cm2/gm) 3006MPa Min. 2800 Water demand 27.5 % No limit


25

3.2.2 Aggregates (basalt, quartz sand, quartz powder)

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

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

High Performance Self Compacting Concrete are gradation, maximum size, and strength.

Providing that concrete is self compacting, the large particles of aggregate are

undesirable for producing Ultra High Performance Self Compacting Concrete. For

producing UHPSCC, selection of very strong aggregate with rough texture is

significantly more important the crushed basalt (coarse aggregate). The nominal size

ranges from 2 to 5 mm, quartz sand (fine aggregate) in the range of 0.3 to 0.8 mm which

is locally available in Gaza markets as shown in Figure (3.1), and quartz powder (micro

fine aggregate) in the range of 0 to 10 m. In addition, it is important to ensure that the

aggregates are clean, since a layer of silt or clay will reduce the cement aggregate bond

strength, in addition to increasing the water demand.

Figure 3.1: Aggregates used in mixture preparations

a- Quartz powder range of 0 to 10 m. b- Crushed basalt size ranges from 2 to 5 mm. c- Quartz range of 0.3 to 0.8 mm.


26

3.2.2.1 Specific gravity and Unit weight

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

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

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

gravity of basalt and quartz sand was done according to ASTM C127 and ASTM C128.

The specific gravity was calculated at two different conditions which are the dry

condition and the saturated surface dry condition (SSD). Table (3.2) and Table (3.3) show

the physical properties of basalt and quartz sand.

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

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

UHPSCC .The determination of unit weight was done according to ASTM C556. Table

(3.2) and Table (3.3) illustrate the unit weight of basalt and quartz.

Table 3.2: Physical property of basalt aggregate

Aggregate Size(mm)

Specific Gravity(dry)

Specific Gravity(SSD)

Unit Weight (kg/m3) (dry)

Unit Weight (kg/m3) (SSD)

5 3.02 3.06 3053 3076 4.75 3.04 3.08 3065 3092 2.3 3.07 3.11 3085 3112 2 3.11 3.15 3097 3120

Average 3.06 3.1 3075 3100

Table 3.3: Physical property of quartz sand

Aggregate Size(mm)

Specific Gravity(dry)

Specific Gravity(SSD)

Unit Weight (kg/m3) (dry)

Unit Weight (kg/m3) (SSD)

0.8 2.65 2.666 1661 1671.614 0.6 2.658 2.675 1662.15 1672.588 0.4 2.668 2.685 1663.13 1673.416 0.3 2.68 2.697 1663.95 1674.1

Average 2.67 2.68 1662.56 1672.93


27

3.2.2.2 Moisture content

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

either inside pores or at the surface. Moisture content of the coarse and fine aggregate

was done according to ASTM C127 and ASTM C128, but the final moisture content was

zero because the coarse and fine aggregates were dried in an oven at temperature (110o

C5). Table (3.4) and Table (3.5) illustrate the absorption percentages of basalt and

quartz sand.

Table 3.4: Water absorption of basalt aggregate

Aggregate Size(mm)

Water Absorption (%)

5 1.43 4.75 1.45 2.3 1.48 2 1.52

Average 1.47

Table 3.5: Water absorption of quartz sand

Aggregate Size(mm)

Water Absorption (%)

0.8 0.61 0.6 0.619 0.4 0.628 0.3 0.639

Average 0.62

From the previous results, it can be observed that the specific gravity of all aggregates

ranges from 3.02 to 3.1 for basalt, and from 2.65 to 2.68 for quartz sand. For aggregates,

the water absorption tends to increase with the size reduction. In addition, when the

aggregate size decreases, the unit weight of the aggregates increases.


28

3.2.3 Water

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

The water source was used from the soil and material laboratory at IUG which is

considered safe to drink.

3.2.4 Admixture

The chemical admixture used is superplasticizer which is manufactured to confirm to

ASTM-C-494 specification types G and F. When added to concrete mix, it shows a

strong self compacting behavior therefore suitable for the production of self compacting

concrete and improves the properties of fresh and hardened concrete. This plasticizing

effect can be used to increase the workability of fresh concrete, extremely powerful water

reduction (resulting in high density and strengths), excellent flowability (resulting in

highly reduced placing and compacting efforts, reduce energy cost for stream cured

precast elements, improve shrinkage and creep behavior, also it reduce the rate of

carbonation of the concrete and finally Improve Water Impermeability.

This type is known as "Sika ViscoCrete -10" delivered from SIKA Company (Product

data sheet 2010), shown in Figure (3.2). Some technical data for the "Sika ViscoCrete -

10" are shown in Table (3.6).

Table 3.6: The technical data for the "Sika ViscoCrete - 10" (source: from supplier)

Type Property Appearance Turbid liquid Density 1.08 kg/It. 0.005 PH value 7.5 Toxicity Non-Toxic


29

Figure 3.2: The chemical admixture (Superplasticizer) used in mixture preparation

3.2.5 Silica Fume

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

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

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

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

spherical particles (ACI 548.6R-96).

The silica fume was supplied by SIKA Company .It is known as "Sika -Fume". Figure

(3.3) shows the appearance of used silica fume, while Table (3.7) shows the technical

data, as supplied by the SIKA Company.

Table 3.7: The technical data for the "Sika - Fume" (source: from supplier)

Type Property Appearance Grey powder Specific gravity 2.20 Chloride Content Nil Toxicity Non-Toxic


30

Figure 3.3: Sika Fume

3.3 Mix Design of UHPSCC

The design process is graphically summarized in the following figure (3.4)

Figure 3.4: Mix design procedure

Accordingly the mix design in this research were developed pursuant to the standard

design procedure starting with determining the amount of aggregates required using the

other parameters such as densities of fine and coarse aggregates in SSD condition,

volume ratio of fine aggregate to the total aggregate, then determination of the cement

content for a target design compressive strength.

Select the required performance based on related specification

Select constituent materials

Design mix composition

Adjust performance by laboratory testing

Verify or adjust performance by trials on lab


31

After that the filler and water content to be determined according to the selected

water/powder ratio and assumed air content, using the total absolute volume equation.

Then determination of the superplasticizer dosage based on the calculated total powder

content.

3.4 UHPSCC Preparation

The preparation of the UHPSCC specimens was made in the Soil and Material Lab at

IUG. After the required amounts of all constituent materials are weighed properly, the

next step is mixing them. The aim of mixing is that all aggregate particles should be

surrounded by the cement paste and silica fume, and all the materials should be

distributed homogeneously in the concrete mass. A power-driven tilting revolving drum

mixer is used in the mixing process (Figure 3.5). It has an arrangement of interior fixed

blades to ensure end-to-end exchange of material during mixing. Tilting drums have the

advantage of a quick and clean discharge.

The mixing procedure for UHPSCC included the following steps (Arafa et.al, 2010):

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

2) Placing all dry materials (cement, silica fume, crushed quartz and aggregate) in the mixer pan, and mixing for 2 minutes.

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

4) Waiting 1 minute then adding the remaining superplasticizer to the dry materials for 30 seconds.

5) Continuation of mixing as the UHPSCC changes from a dry powder to a thick paste. The time for this process will vary.

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

homogeneous concrete is poured into a clean plastic pan.

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

minutes after being done with mixing. All specimens were cast and covered to prevent

evaporation.


32

Figure 3.5: The drum mixer

3.5 Test Program

As stated in chapter one, the main aim of this research is to produce Ultra High

Performance Self Compacting Concrete (UHPSCC) in Gaza strip using available

materials. More specifically, and as stipulated in the first chapter, the test program to be

deployed in order to achieve the objectives of this assignment is depicted in Figure (3.6).


33

Figure 3.6: Experimental program steps chart


34

3.6 Equipment and testing procedure

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

concrete was tested to ensure the self compacting properties of UHPSCC. The tests for

hardened concrete include compressive strength, indirect tensile tests (Split cylinder test

and Flexural prism test).

3.6.1 Tests Applied On Fresh Concrete

To ensure the self compacting properties of the UHPSCC many test methods have been

developed. So far no single method or combination of methods has achieved universal

approval and most of them have their adherents. Similarly no single method has been

found which characterizes all the relevant workability aspects. Each mix design should be

tested by more than one test method for the different workability parameters.

For the initial mix design of SCC, all three workability parameters (filling ability, passing

ability and segregation) need to be assessed to ensure that all aspects are fulfilled as per

mentioned in table (3.8). A full-scale test should be used to verify the self compacting

characteristics of the chosen design for a particular application. While for site quality

control, two test methods are generally sufficient to monitor production quality. Typical

combinations are Slump-flow and V-funnel. With consistent raw material quality, a

single test method operated by a trained and experienced technician may be sufficient

(EFNARC, 2005).

Table 3.8: Self Compacting Criteria

Method Unit Minimum Range Maximum

Range Slump flow (Abram Cone) mm 550 850 T500 mm Slump flow S 2 9 V- funnel S 6 12 L Box (h2/h1) - 0.7 1.0


35

3.6.1.1 Slump flow and T500 test

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

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

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

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

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

suitable when the maximum size of the aggregate exceeds 40 mm.

The fresh concrete is poured into a cone as used for the normal slump test as shown in

figure (3.7). When the cone is withdrawn upwards the time from commencing upward

movement of the cone to when the concrete has flowed to a diameter of 500 mm is

measured; this is the T500 time, figure (3.8). The largest diameter of the flow spread of

the concrete and the diameter of the spread at right angles to it are then measured and the

mean is the slump-flow, figure (3.9).

Figure 3.7: Slump cone and base plate


36

Figure 3.8: Slump flow test

Figure 3.9: The largest diameter of the flow spread

The detailed procedure of this test was as mentioned in the European guidelines for SCC,

(EFNARC, 2005). The first step is to prepare the cone and base plate then place the

cleaned base in a stable leveled position, fill the cone without any agitation or rodding,

and strike off surplus from the top of the cone. Allow the filled cone to stand for not more

than 30s; during this time remove any spilled concrete from the base plate and ensure the

base plate is damp all over but without any surplus water.

Lift the cone vertically in one movement without interfering with the flow of concrete. If

the T500 time has been requested, start the stop watch immediately the cone ceases to be

in contact with the base plate and record the time taken to the nearest 0,1 s for the

concrete to reach the 500 mm circle at any point. Without disturbing the base plate or


37

concrete, measure the largest diameter of the flow spread and record it as dm to the

nearest 10 mm. Then measure the diameter of the flow spread at right angles to dm to the

nearest 10 mm and record as dr to the nearest 10 mm.

Check the concrete spread for segregation. The cement paste/mortar may segregate from

the coarse aggregate to give a ring of paste/mortar extending several millimeters beyond

the coarse aggregate. Segregated coarse aggregate may also be observed in the central

area. Report that segregation has occurred and that the test was therefore unsatisfactory.

Then the slump-flow is the mean of dm and dr expressed to the nearest 10 mm, and the

T500 time is reported to the nearest 0.1 s.

3.6.1.2 V-funnel test

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

concrete with a maximum size aggregate of 20mm. A V shaped funnel see Figure (3.10)

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

measured and recorded as the V-funnel flow time.

V-funnel, made to the dimensions (tolerance 1 mm), fitted with a quick release,

watertight gate at its base and supported so that the top of the funnel is horizontal. The V-

funnel shall be made from metal; the surfaces shall be smooth, and not be readily

attacked by cement paste or be liable to rusting. However container is needed to hold the

test sample and having a volume larger than the volume of the funnel and not less than 12

L.


38

Figure 3.10: V-funnel test

Clean the funnel and bottom gate, the dampen all the inside surface including the gate.

Then close the gate and pour the sample of concrete into the funnel, without any agitation

or rodding, then strike off the top with the straight edge so that the concrete is flush with

the top of the funnel. Place the container under the funnel in order to retain the concrete

to be passed. After a delay of (10 2) s from filling the funnel, open the gate and

measure the time tv, to 0,1 s, from opening the gate to when it is possible to see vertically

through the funnel into the container below for the first time. tv is the V-funnel flow time.

3.6.1.3 L-box test

The L-box test is used to assess the passing ability of self-compacting concrete to flow

through tight openings including spaces between reinforcing bars and other obstructions

without segregation or blocking. There are two variations; the two bar test and the three

bar test. The three bar test simulates more congested reinforcement.

The main concept of this test is to allow a measured volume of fresh concrete to flow

horizontally through the gaps between vertical, smooth reinforcing bars and the height of

the concrete beyond the reinforcement is measured.

L-box, have the general arrangement as shown in Figure (3.11) and the dimensions

(tolerance 1 mm) shown in Figure (3.12). The L-box shall be of rigid construction with

surfaces that are smooth, flat and not readily attacked by cement paste or be liable to


39

rusting. The vertical hopper may be removable for ease of cleaning. With the gate closed,

the volume of the vertical hopper shall be (12,6 12,8) L when filled level with the top.

The assemblies holding the reinforcement bars shall have 2 smooth bars of 12 mm

diameter with a gap of 59 mm for the two bar test and 3 smooth bars of 12 mm diameter

with a gap of 41 mm for the three bar test. These assemblies shall be interchangeable and

locate the bars in the L -box so that they are vertical and equidistant across the width of

the box.

Figure 3.11: General assembly of L-box


40

Figure 3.12: Dimensions and typical design of L-box

Support the L-box on a level horizontal base and close the gate between the vertical and

horizontal sections. Pour the concrete from the container into the filling hopper of the L-

box and allow standing for (60 10) s. Record any segregation and then raise the gate so

that the concrete flows into the horizontal section of the box. When movement has

ceased, measure the vertical distance, at the end of the horizontal section of the L-box,

between the top of the concrete and the top of the horizontal section of the box at three

positions equally spaced across the width of the box. By difference with the height of the

horizontal section of the box, these three measurements are used to calculate the mean

depth of concrete as H2 mm. The same procedure is used to calculate the depth of

concrete immediately behind the gate as H1 mm. The passing ability PA is calculated

from the following equation.

= 21


41

3.6.2 Tests Applied on Hardened Concrete

3.6.2.1 Compression Test for Hardened Concrete

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

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

were all completed nominally according to (ASTM C109, 2004) standard test method for

cubes. Numerous trial mixtures were manufactured. For each batch of UHPSCC made,

100x100x100 mm cube specimens were prepared, as shown in Figure (3.13). The cubes

were filled with fresh concrete in one layer without any compaction, after preparing the

specimens inside the cube were covered with plastic sheets for about 24 hours to prevent

moisture loss.

Figure 3.13: Compression test specimens (100x100x100mm)

Cubes stored in water until the time of the test. Before the tests, the specimens were air-

dried for 10 to15 minutes and any loose sand grains or incrustations from the faces that

will be in contact with the bearing plat of the testing machine are removed. The cubes are

placed in the testing machine so that the load is applied to opposite sides as cast and not

to the top and bottom as cast. Therefore, the bearing faces of the specimen are

sufficiently plane as to require no capping. If there is appreciable curvature, the face is

grinded to plane surface because, much lower results than the true strength are obtained

by loading faces of the cube specimens that are not truly plane surfaces.


42

The compressive strength machine in soil and material laboratory at the IUG was used for

determining the maximum compressive loads carried by concrete specimen cubes, as

shown in Figure (3.14).

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

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

the specimen.

comp =

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

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

considered as the compressive strength of the experiment. The test program for

compressive strength of UHPSCC is outlined in Table (3.9):

Table 3.9: Test program for compressive strength

Number of days Number of tested specimens

7 3 14 3 28 3

Figure 3.14: Compressive strength test machine


43

3.6.2.2 Splitting Cylinder Test

The splitting tensile strength of UHPSCC was measured based on ASTM C496(2004)

Standard test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens.

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

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

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

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

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

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

specimen, generating the bond failure between the aggregate particles and the cement

paste. Usually, splitting tensile strength test is used to evaluate the shear resistance

provided by concrete elements. However, the most important advantage is that, when

applying the splitting procedure, the tensile strengths are practically independent of either

the test specimen or of the test machine sizes, being only a function of the concrete

quality alone. Thus, much inconvenience is eliminated, particularly with respect to the

scale coefficient, which is involved in direct tensile tests. For this reason, this procedure

is considered to reproduce more exactly the real concrete tensile strength.

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

which a cylindrical specimen is placed on its side and loaded in diametrical compression,

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

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

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

by the two plane-parallel faceplates, situated at two diametrically opposite points on the

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

Figure (3.15), the major tensile stresses are developed which, at their limit, reach the

fracture strength value ASTM C496 indicates that the maximum fracture strength can be

calculated based on the following equation.

= 2


44

Where: P is the fracture compression force acting along the cylinder, D is the cylinder

diameter; = 3.14, L is the cylinder length.

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

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

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

owing to material deformations. So, over the cross section, horizontal compressive

stresses are developed too, in the close vicinity of the contact point between the press

plates and the material. Since the compressive stresses only develop to a small depth in

the cross section, it may be assumed that the tensile stresses are distributed evenly along

the diameter where the splitting takes place, see Figure (3.16). This test can be completed

in a standard concrete compression testing machine, with only one special requirement:

the bearing plates that load the specimen. Split cylinder tests were conducted on 6 x 12

in. (150 x 300mm) cylinders, tensile stress in the cylinder and the maximum tensile stress

occur at the center of the cylinder.

Figure 3.15: Split cylinder test setup for cylinder 150 x 300mm


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Figure 3.16: Crack in a split cylinder tensile specimen

All cylinder specimens were cast for testing at 28 days. Three of these cylinders were

tested for each period the mean values of the specimens were considered as split cylinder

strength of the experiment.

3.6.2.3 Flexural Test

The flexural strengths of concrete specimens are determined by the use of simple beam

with center point loading in accordance with (ASTM C293, 1994) as shown in figure

(3.17). The spacemen is a beam 100 x 100 x 500 mm. the mold is filled in one layer,

without any compacting or rodding, the beam casting and then immersing in water at

25C.

The cast beam specimens are tested turned on their sides with respect to their position as

molded. This should provide smooth, plane and parallel faces for loading if any loose

sand grains or incrustations are removed from the faces that will be in contact with the

bearing surfaces of the points of support and the load application. Because the flexural

strengths of the prisms are quickly affected by drying which produces skin tension, they

are tested immediately after they are removed from the curing basin as shown in Figure

(3.18).


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Figure 3.17: Diagrammatic view for flexure test of concrete by center-point loading

Figure 3.18: Flexural test specimens (100*100*500mm)

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

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

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

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

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

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

supports.

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

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

the bearing edge directly above the center line of the beam and at the center of the span

length. The load contacts with the surface of the specimen at the center. If full contact is

not obtained between the specimen and the load applying or the support blocks so that

there is a gap, the contact surfaces of the specimen are ground.


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

the maximum load indicated by the testing machine is recorded.

The flexural strength of the beam, Fr (in MPa), is calculated as follows:

= 322 Where: P = maximum applied load indicated by the testing machine, L = span length, B =

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

point of fracture).

The specimen beams tested after 28 days. At least three of these beams were tested for

each period and the mean values are determined.

3.6.2.4 Unit weight

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

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

cube specimens which are use

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