Study of Microstructure Properties of

Republic of Iraq Ministry of Higher Education And Scientific Research University of Baghdad College of Engineering Civil Engineering Department

Study of Microstructure Properties of Self Compacting Concrete Reinforced with Fibers and ISubiected to Elevated

Temperatures. A Thesis Submitted to the Department of Civil Engineering of the

University of Baghdad in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Building Materials Engineering

By

Ammar Saleem [lharzaal Bo Sc.1997 h4.Sc.2000

2013A.D

1434A.H

ク

Vノ

/

′ １１１

白 ′

(17:二 J:5コ

′げ

・ ●

ハ■日￨ふ 13ン

′ ′

To My parents For their love & support.

To MY wife For her Support, advice and encouragement

To My children Hamzaand Mustafa For their understanding and love

To My close friends For their love and suPPort

臨

2013

。

Aeknowledgrnent "In the name of Allah,

the Most Gracious, the Most

Merciful"

First all thanks go to Allah who enabled me to achieve this research work. I would especially like to express my deep appreciation and sincere gratitude to

prof. Dr. Nada M. Fawzi for her supervision and invaluable guidance and assistance that made the achievement

of this work possible. This Ph.D. thesis

could not have been completed without her wise direction.

I

also present my loyalty and thankfulness to every person who encouraged

and taught me. Undoubtedly, there is a share for every one of them in my career.

Special thanks are also due to the staff of the National Center for Construction

Laboratories

in Tikrit and to the staff of

Laboratory

in civil

Engineering

Department, University of Tikrit. Special thanks to all my faithful friends for their brotherly help throughout this work.

I also could not forget the patience of my wife during this long work'

Abstract Self-Compacted concrete (SCC) is the concrete poured into a

mold where it can flow under its own weight without any compaction. It was used for the first time in Japan

in

1980, and then was spread to the

Europe and then in the United States. Currently this type of concrete is used in a limited way in the Republic of lraq, but until now there are no

specific studies on the feasibility of using this type of concrete in large construction business.

This research presents an experimental study on the performance of SCC subjected to elevated temperature. Two SCC mixes were performed'

These concrete mixes were performed

in college of Engineering/Tikdt

University. Mechanical and microstructural properties were studied at ambient temperature and after heating. For each test, the specimens (Cubes,

Cylinders, and Prisms) were heated at a rate temperatures

of

I

Colmin up to target

(150,300,450 and 600 C")' In order to ensure a uniform

temperature throughout the specimen, the temperature was held constant at

the target temperature for

I h before cooling. In addition, the specimen

mass was measured before and after heating in order to determine the loss

of water during the test. The results were used to analyze the degradation of

SCC due to heating.

It

has noted an important increase

in

compressive

strength of about 11.22 % between 150 and 300 C" for RSCC (Reference Self Compacted Concrete) mix specimens at an age of 60 days, and 6.22

%o

for FRSCC (Fiber Reinforced Self Compacted Concrete) mix specimens

for the same age, while at an age of 90 days FRSCC mix specimens showed an increase of about 3.2Yo compared to 3.53% for FRSCC mix specimens.

It

has noted that for RSCC mix specimens, the compressive

strength for temperature rate of 450 Co decreased to

3

l.0l %

and

4l .25oh at

an ages of 60 and 90 days respectively compared to their relatives not

exposed to high temperature, and 4l.32Yo and 48.39o/o for temperature rate

of 600 Co at an ages of 60 and 90 days respectively. For FRSCC mix specimens, the compressive strength for temperature rates of 450 Co decreased to 37 .6gyo and 40.49Yo at an ages of 60 and 90 days respectively

compared to their relatives not exposed to high temperature, and and 48.26%o for temperature rate of 600 C" at an ages

47 '55oh

of 60 and 90

days

respectively, and this is mainly due to alteration of the porous network

(departure

of bond water and decomposition of

hydrates and

to

the

microcracking). Flexural behavior of both mixes of RSCC and FRSCC at age

of 90 days is similar to that of 60 days age but with lesser rates, and

this is due to continuous hydration which improves microstructure'

List of Contents Section No.

Subject

Page

No.

Chapter pne_Introduc● on

ξυ

16

4

ξυ

Fiber Reinforced SCC. ObiCCt市 e. Phases ofStJoy.

，

1.4

０

Typcs OfScc.

ξリ

1.3

1

う４

うる

General. SelfCompacting Concrete.

ξυ

Phasc I Phase II Phase III

1.6.1

1.6.2 1.6.3

5

6 6 6

Phase IV Thesis Layout. Chapter Two - Literature Review General Temperature Effects on SCC.

1.64 1.7 う‘

つ４

う４

Mechanical Propenies

2.3

of

8

10

Structural Self Cornpacting

Concrete.

2.4

つつ

Mechankal Bchavior of Fiber Reinforced Sdf

ξυ

2.4.1

2.4.2 2.4.3

First Crack Tensile Stress. First Crack Flexural Stress. Shape, Geometry, and Distribution of Fibers in Cernent Matrix. Interaction between Fibers and Matrix. Critical Fiber Volurne. Efficiency of Fiber Reinforcement.

2.5

Post‐ cracking State.

Ccment

3.2.2 3.2.3 3.2.4

Finc Aggregate Coarse Aggrcgatc.

3.24.2 3.2.4.3

32 33 35 35 36 37

Admixtures. High Range Water Reducing Admixture(llRWRA). High Performance Cohesion Agent. Silica Fume.

ffi

Fibers.

，

3.2.6

31 31

００ つ

3.2.5

26 ，

,

Fiber Orientation. Chapter Three - Materials and ExpErimental WorkGeneral. Materials.

う‘

Prc― cracking State.

3.2.1

32.41

23 24

り

う４

つつ

3.1

19

ξυ ξυ う‘ う４

2.5.2 2.5.3 2.5.4 2.5.4.1 2.5.4.2 2.5.5

16 つ ‘ つ‘

2.5.1

15

38

3.2.6.2 3.3

Trall Mixes. Reference Trail Mixes. Selection of a Suitable Mix.

3.4

3.4.1 3.4.1.1

Hybrid Fiber Trial Mix. Calculation of Fraction Weight. Mixing of Concrete.

3.4.2 3.4.2.1

3.5

Testing Program. Exposure to Elevated Temperature. Evaluation of Mechanical Properties. Compressive Strength. Tensile Splitting Strength. Flexural Toughness. Chapter Fou. - Bglqllq a!4 !l!ge!!l n General. Mechanical Properties.

3.6

3.6.1 3.6.2 3.6.2.1

3.6.2.2 3.6.2.3 4.1

4.2

50 50 50

4.2.1.1

4.2.2 4.22.1 4.2.3

′ヽ

Flexural Toughness. R6 Sample. H6 Sample.

ξυ

lhapterFive-Microst@

ξυ

り４

5.3

5.3. I 5.3.1.1

5.3.1.2 5.3.1.2.1

5.3.1.2.2 5.3.1.2.3

5.3.1.2.4

5.3.1.3.2

Effect of Admixture on Microstructure of Interfacial Zone.

91

of

l5rci

Temper4lulg.-

lV

91

92 92 93 93 93

of

● ０ソ ，

5.3.1.3.1

91

● ０ソ ，

5.3.1.3

90 90

General. Preparation Specimens for SEM Techniqqg. Microstructure Observation.

Reference Self Compacted Concrete R6 Mix. Reference Self Compacted Concrete R6 Mix at Age 60 Days Exposed to Elevated Temperature. Exposure to Temperature Rate of Exposure to Temperature Rate of 300 Co. Exposure to Temperature Rate of 450 C1 Exposure to Temperature Rate of 600 C". Reference Self Compacted Concrete R6 Mix at Age 90 Days Exposed to Elevated Exposure to Temperature Rate of 150 C'. Exposure to Temperature Rate of 300 Co.

ξυ ′

56 57 60 60

，

4.2.3.1

う乙 くυ

Compressive Strength. Elevated Temperature Effects. Tensile Spliuing Strength. Elevated Temperature Effects.

4.2.1

4.2.3.2

38 39 39 40 40 40 43 43 44 47 47 47 47 48 48

Polypropylene Fibers. Steel Fibers. Self Compactability Tests 04 l4CLIvIEgs.

3.2.6.1

94

5.3.1 3.3

Exposure to Temperature Rate of 450 Co. 94 5.3.1.3.4 Exposure to Temperature Rate of 600 C.. 94 Hybrid Fiber Self Compacted Concrete H6 Mix at Age of 5.3.1.4 94 60 Days. Hybrid Fiber Self Compacted Concrete H6 Mix at Age of 5.3.1.5 95 60 Days Exposed to Elevated Temperature. 5.3.1.5.1 Exposure to Temperature Rate of 150 C". 95 5.3.1.5.2 Exposure to Temperature Rate of 300 C'. 95 5.3.1.5.3 Exposure to Temperature Rate of 450 Co. 95 5.31.54 Exposure to Temperature Rate of 600 C' 96 Hybrid Fiber Self Compacted Concrete H6 Mix at Age of 5.3.1.6 96 90 Days Exposed to Elevated Temperature. 5.3.1.6.1 Exposure to Temperature Rate of 150 Co. 96 5.3.1.6.2 Exposure to Temperature Rate of 300 Co. 96 5.3.1.6.3 Exposure to Temperature Rate of 450 C'. 96 5.3.1.6.4 Exposure to Temperature Rate of 600 C'. 97 Chapter Six - Conclusions and Recommendations for Future Works 6.1 General 108 6.2 Conclusions 108 63 Recommendations for Further Studies. 110

V

List of Tables Table No.

Table(2-1) Table(2‐ 2) Table(3‐

2)

Table(3‐ 4)

Table(3-5) Table(3-6)

Physical Droperties of cement. Chemical composition and main compounds of cement. Grading of fine aggregate. Chemical and physical properties offine aggregate. Selected grading of coarse aggregate. Chemical and physical properties of coarse aggregate.

Technical description ofhigh range water reducing admixture. Technical description of high performance cohesion Table(3-8) agent admixture. Table(3-9) Technical description of silica fume. Table(3-10) Chemical analysis results of silica fume. Table(3-11) Physical properties of polypropylene fibers. Table(3-12) Physical DroDerties of steel fi bers. Table(3‐ 13) Details of trail mixes. Results of the self compactibility and strength tests Table (3-14) conducted on eight trail mixes. Table(3-15) Details of aber■ actions. Results of the self compactibility and strength tests Table(3‐ 16) conducted on hybrid trail mix. Table(3-7)

Table(4-1

Table(4-2) Table(4-3) Table(4‐ 4)

Compressive strength results of R6 and H6 mixes. Residual compressive strength results of R6 and H6 mixes versus exposure to elevated temperature rates. Tensile splitting strengh results ofR6 and H6 mlxes. Residual tensile splitting strength results of R6 and H6 mixes versus exposure to elevated temperature rates.

V:

20 27 31 ● つ′ ，

Table(3-3)

Typical properties of cement-based matrices and fibers. Summary of Literature Review.

Page No.

う４ ● ，

Table(3‐

1

Title

33 34

34 36 36 37 37 38 39 40 41

43 43 51

53

57 58

Fie. (2-l)

Fis. (2-2)

Fie. Q-4\

Fig.(2-s)

angle (d).

Fig. (3-l) Fig. (3-2)

Fie.(3-3)

(a-l)

Fig. (a-a) Fie. (4-5)

Fig. (a-6) Fig. (a-7)

Fig. (a-10) Fig. (a-l Fig.

l)

g-r2)

Fig. (a-13) Fig. (a-la)

VII

27

42 44

49

56 57 59 60 61

ξυ ∠υ

Fie. (4-8) Fie. (4-9)

26

く ξυ ，

Fig. (a-3)

Compressive strength versus curing age of R6 and H6 mixes. Heating and cooling curves. Variation of residual compressive strength versus temperature exposure at age of60 days. Variation of residual compressive strength versus temperature exposure at age of90 days. Tensile splitting strength versus curing age. Variation ofresidual tensile splitting strength versus temperature exposure at age of60 days. Variation of residual tensile splitting strength versus temperature exposure at age of90 days. Stress-strain curve. Load-Deflection curyes of R6 mix versus curing age. Load-Deflection curves of R6 mix at age of 60 days versus temperature exposure. Load-Deflection curves of R6 mix at age of 90 days versus temperature exposure. oZ of Difference in ultimate load versus temperature exposure at age of 60 days. 04 oflncrease in deflection at first crack versus temperature exposure at age of60 days. 0/o of Decrease in deflection at ultimate load versus temperature exposure at age of60 days.

14

う４ ξυ

Fie. (4-2)

Variation of compressive strength of reference trial mixes versus curing age. Variation of compressive strength of hybrid fiber H6 trial mix versus curing age Load Deflection Curve.

10

ξυ

Fig.

Effect of superplstisizer on viscosity. Stress/strain curve for the fiber reinforced concrete composite. Pullout geometry to simulate the interaction between fibers and cement matrix. Definition of critical length. Intersection ofan oriented fiber across a crack with an

つ４ つ４

Fig. (2-3)

Title

ｅ   ・

Figure No.

。 晦Ｎ

List of Figures

66 66 67 67 68

0/o

Fig.

(a-ls)

Fie. (a-16) Fig. (a-17) Fig. (a-18) Fie. (4-19) Fie. (4-20) Fie. (a-21) Fig. (a-22) Fig. (a-23)

Fig. (a-2s) Fig. (a-26)

Fie.@27) Fie. (4-28) Fig. @-2e)

Fig. (a-30) Fig. (a-31) Fig. (a-32) Fig. (a-33) Fig. (4-34) Fig. (a-3s) Fig. (a-36)

V‖

l

68 69 69 70 70 71 71

72

72

73

74 74 78 78 79 79 80 80 81 81

82 つ‘ ００

Fig. (a-37)

at age of60 days. oZ of Decrease in ductility versus temperature exposure at age of60 days. o/o of Increase in toughness at first crack versus temperature exposure at age of60 days. %o of Decrease in toughness at ultimate load versus temperature exposure at age of60 days. Development of stiffrress of R6 ryI rglg5 JgMg-399. Ductility versus curing age of R6 mix. oZ of Decrease in ultimate load versus temperature exposure at age of90 days. 0Z of Increase in deflection at first crack versus temperature exposure at age of90 days. o/o of Decrease in deflection at ultimate load versus temperature exposure at age of90 days. 0/o of Increase in stiffiress versus temperature exposure at age of90 days. %o of Decrease in ductility versus temperature exposure at age of90 days. 7o of Increase in toughness at first crack versus temperature exposure at age of90 days. oZ of Decrease in toughness at ultimate load versus temperature exposure at age of90 days. Load-Deflection curves of H6 mix versus curing age. Load-deflection curves ofH6 mix at age of60 days versus temperature exposure. Load-deflection curves ofH6 mix at age of90 days versus temperature exposure. oZ of Difference in ultimate load versus temperature exposure at age of 60 days. 0/o of Increase in deflection at first crack versus temperature exposure at age of 60 days. % of Difference in deflection at ultimate load versus temperature exposure at age of60 days. % of Difference in stiffrtess versus temperature exposure at age of 60 days. %o of Decrease in ductility versus temperature exposure at age of60 days. o/o of Difference in toughness at first crack versus temperature exposure at age of60 days. oZ of Decrease in toughness at ultimate load versus temperature exposure at age of60 days.

つつ ７′

Fig. $-2a)

of Increase in stiffrress versus temperature exposure

Fig. (a-38)

Fig. (a-a0) Fig. (a-al) Fig. (a-az) Fig. (a-a3) Fig. @aa) Fie. (4-45) Fig. (a-a6)

Fis. $-a7)

Fig. (a-49) Fig. (a-50)

of 90 days versus temperature exposure. Development oftoughness Index versus curing age of H6 mix. % of Difference in toughness Index Iroof H6 mix at

of60

days versus temperature exposure. % of Difference in toughness Index Iroof H6 mix at age of90 days versus temperature exposure. age

84 84 85 85

86 86 87 87 ００ ００

Fig. (a-48)

of90

days. 0/o oflncrease in toughness at first crack versus temperature exposure at age of90 days. % of Difference in toughness at ultimate load versus temperature exposure at age of90 days. Development of stiffiress versus curing age of H6 mix. % of Difference in toughness Index I: of H6 mix at age of 60 days versus temperature exposure. %o of Difference in toughness Index Is of H6 mix at age at age

83 ● ００ ，

Fig. (a-39)

% of Difference in ultimate load versus temperature exposure at age of90 days. o/o of Increase in deflection at first crack versus temperature exposure at age of90 days. 0/o of Decrease in deflection at ultimate load versus temperature exposure at age of90 days. 0Z of Increase in stiffiress versus temperature exposure at age of90 days. o/o of Decrease in ductility versus temperature exposure

88

89

List Of Plates

(2-l)

Plate (3-1) Plate (3-2) Plate (3-3)

ｅ   ・

Plate

。 晦Ｎ

Plate No.

Subject

Small pipes used as obstacles in formwork.

8

Short12 mm PPF.

38 39 47

Steel fibers. Oven view and layout of samples.

Plate

(4-l)

Spalling ofconcrete cubes upon exposure to elevated temperafure.

Plate

(5-l)

SEM equipment. Microstructure development of R6 mix sample at age

Plate (5-2) Plate (5-3) Plate (5-4) Plate (5-5) Plate (5-6) Plate (5-7) Plate (5-8) Plate (5-9) Plate (5-10) Plate (5-11) Plate (5-12) Plate (5-13)

of60

days.

Microstructure development of R6 mix sample at age

of90

days.

Microstructure development of R6 mix sample at age

of60 days exposed to temperature rate of

150 Co. Microstructure development of R6 mix sample at age of60 days exposed to temperature rate of300 Co. Microstructure development of R6 mix sample at age of60 days exposed to temperature rate of450 C'. Microstructure development of R6 mix sample at age of60 days exposed to temperature rate of600 Co. Microstructure development of R6 mix sample at age of90 days exposed to temperature rate of 150 Co. Microstructure development of R6 mix sample at age of90 days exposed to temperature rate of300 C'. Microstructure development of R6 mix sample at age of90 days exposed to temperature rate of450 Co. Microstructure development of R6 mix sample at age of90 days exposed to temperature rate of600 Co. Microstructure development of H6 mix sample at age of60 days.

Microstructure development of H6 mix sample at age

of90

days.

Plate (5-14)

Microstructure development of H6 mix sample at age of 60 days exposed to temperature rate of 1 50 Co.

Plate (5-15)

Microstructure development of H6 mix sample at age

of60 days exposed to temperature rate of300

Co.

54 91

98 98 99 99 100 100 101

l0l 102 102 103

103

104 104

Microstructure development of H6 mix sample at age of60 days exposed to temperature rate of450 C'. Microstructure development of H6 mix sample at age Plate (5-17) of60 days exposed to temperature rate of600 Co. Microstructure development of H6 mix sample at age Plate (5-18) of90 days exposed to temperature rate of 150 Co. Microstructure development of H6 mix sample at age Plate (5-19) Plate (5-16)

of90 days exposed to temperature rate of300

Plare (5-20)

Plate (5-21)

Co.

Microstructure development of H6 mix sample at age

of90 days exposed to temperature rate of450

Co. sample at age

Microstructure development of H6 mix of90 days exposed to temperature rate of600 C".

105 105

106 106 107 107

Notations.

SCC RSCC FRSCC VNIA

Self compacting concrete. Reference self compacting concrete. Fiber reinforced self compacting concrete. European guidelines for testing self compacting r9!9l91e. High range water reducing admixture. Viscosity modiffing agent.

SF

Silica nlme.

EFNARC IIRWRA

SEM

Ec

Scanning electronic microscope. Water cementitious materials. Superplasticizer. High performance concrete. Polypropylene fibers. Concrete modulus of elasticity.

E″

Modulus of elasticity of the matrix.

w/cm SP IIPC

PPF

Volume fraction of matrix

臨 ηl

length efficiency factor

ηθ

orientation effi ciency factor

E′

Modulus of elasticity of fiber

/y

Volume fraction of the fiber

σ

First crack tensile strength ofthe fiber reinforced composite

鷹

σ

Tensile strength of the matrix at point of first crack

″ “

σ

Tensile strength ofthe fiber at point

/

σ

offirst crack

First crack flexural strength ofthe fiber reinforced composite

′

ニ

Stress in the matrix (modulus of rupture of the plane concrete).

′/′ ′

Fiber aspect ratio (ratio of length to diameter).

Critical/minimum fiber volume fraction.

p/c.′

σ

´ 'フ

レ

Ultimate tensile strength of the fiber. Stresses on the fibers when concrete fail at its first crack.

`ア

グ τ

Fiber diameter Interfacial bond strength

′ c

Critical length

ε″″

Strain ofthe fiber (at point

offirst crack).

ノ

Embedded length of the fiber in the cement matrix

ε

Ultimate strain of the fiber

′

θ

NCCL IQS

Angle of load orientation or applied stress National Center of Construction Laboratories. Iraqi Standards

C4AF SSD

Reference Guide Directory Loss on Ignition. Lime Saturation Factor. Tri-calcium silicate. Di-calcium silicate. Tri-calcium aluminate. Tetra calcium aluminate ferrite Saturated Surface Dry.

ASTM

American Society for Testing Materials

Cf

Failure strain

σ

Stress

∈

Strain

R.G.D

L.O.I L.S.F CrS CzS

CrA

∈y

Yicld strain

R

Reference (without fi ber)

H

Hvbrid fiber

R6

Reference mix no. 6

H6

Hybrid fiber mix no. 6

Df

Dm

Density of fiber. Density of matrix.

B.S

British Standards.

FRSCC

Fiber Reinforced Self Compacting Concrete.

ACI

American Concrete Institute.

RILEM

Intemational Union of Laboratories and Experts in Construction Materials, Systems and Structures.

CH

Calcium Hydrate

CSH

Calcium Silicate Hydrate

XIII

pterOne

Introduction

Introduction

Chapter One

1

1.1 General Self-compacting concrete (SCC), developed first in Japan in the

late 1980s, represents one of the most significant advances in concrete technology in the last two decades. SCC was developed to ensure adequate compaction through self-consolidation and facilitate placement of concrete

in structures with congested reinforcement and in restricted areas. SCC can be described as a high performance material which flows under its own

weight without requiring vibrators to achieve consolidation by complete

filling of the formworks even when access is hindered by narrow gaps between reinforcement bars according to W. Zhu at al., (2001) and K.H.

Khayat etal.,(2004). The constituent materials used for the production of SCC are the same as those for conventionally vibrated normal concrete except that SCC

contains

a

lesser amount

of

aggregates and larger amount

of

powder

(cement and filler particles smaller than 0. 125 mm) and special plasticizer

to enhance flowability. Fly ash, glass filler, limestone powder, silica fume, etc. are used as the filler materials. High flowability and high segregation resistance

of

SCC are obtained by using:

(i) a

larger quantity

of

fine

particles, i.e. a limited aggregate content (coarse aggregate: 50% of the

of the mortar volume); (ii) a low water/powder ratio; and (iii) a higher dosage of superplasticizer and concrete volume and sand: 40%o

stabilizer according to H. Okamura and K., (1995), Ozawa H., Okamura, (2003), and M. Ouchi and K. Audenaert et al., (2002). Stabilizer is needed

for SCC mixes for maintaining proper cohesiveness so that highly flowable SCC would not segregate. Typical ranges of proportions and quantities

of

the constituent materials for producing SCC are reported by K.H. Khayat et

al., (2004), N. Su et al., (2001), and Kapoor et al., (2003). Relevant information regarding design of SCC mixtures are reported by N. Su et al., (2001), R. Patel et al., (2004), and Sonebi, M., (2004b). Various tests for

Chapter One

Introduciion 2

assessment

of compatibility and flowability are described by EFNARC,

(2002,2005). Self-Compacted Concrete can also be regarded as "the most revolutionary development in concrete construction for several decades".

Originally developed to offset a growing shortage of skilled labor, it is now taken up with enthusiasm across European countries for both site and precast concrete work. It has been proved beneficial economically because

of the factors noted below according to Krieg, W., (2003):

) ) )

reduction in site manpower,

D

uniform and complete consolidation,

) ) )

faster construction,

easier placing,

better surface finishes, improved durability, increased bond strength,

D

greater freedom in design,

)

reduced noise levels due to absence of vibration.

D

safe working environment.

1.2 Self Compacting Concrete The method for achieving self-compactability involves not only

high deformability of paste or mortar, but also resistance to segregation between coarse aggregate and mortar when the concrete flows through the

confined zone of reinforcing bars according to H. Okamura and M. Ouchi, (2003). SCC has the ability to remain un-segregated during transport and

placing. High flowability and high segregation resistance

of SCC are

obtained by:

1. A larger quantity of fine particles, i.e., a limited coarse aggregate content.

Introduction

Chapter One

2. A low water/cementitious materials (powder is defined as cement plus the filler such as fly ash, silica fume etc.).

3. The use of superplasticizer according to H. Okamura and M. Ouchi, (2003), K. Audenaert et al., (2002).

be produced using standard cements and additives. It consists mainly of cement, coarse and fine aggregates, and filler, such as fly ash or Super-pozz@, water, super Self-compacting concrete can

plasticizer and stabilizer.

Three basic characteristics that are required to obtain SCC are:

high deformability, restrained flowability and

a

high resistance

to

segregation K. H. Khayat et al., (2004). High deformability is related to the

capacity space

ofthe concrete to deform and spread freely in order to fill all

the

in the formwork. It is usually a function of the form, size, and

quantity

of the

aggregates and the friction between the solid particles,

which can be reduced by adding a high range water-reducing admixture (HRWRA) to the mixture. Restrained flowability represents how easily the concrete can flow around obstacles such as reinforcement, and is related to

the member geometry and the shape of the formwork. Segregation is usually related to the cohesiveness of the fresh concrete, which can be enhanced by adding a viscosity-modifuing admixture

(VMA) along with

HRWRA, by reducing the free-water content, by increasing the volume of paste or by combining some of these constituents.

1.3 Types of SCC Two general types ofSCC can be obtained:

l.

The first type is with a small reduction in the coarse aggregates, containing a MV{A.

2. The second type is with a significant reduction in the aggregates without any

VMA.

coarse

Chapter One

lntroduction 4

Chemical admixtures may also be used properties such as the workability

to

enhance certain

of fresh concrete and the strength of

concrete. The most command chemical admixture

is water reducing

admixture. This chemical admixture was developed

to

improve the

workability of the concrete at a low water/cement ratio. The workability of cement matrix is normally reduced with the addition of fibers. With the use

of water reducing admixtures, it is possible to maintain the workability of fiber reinforced concrete without adding extra water. In addition, extra water reduces the strength, increases shrinkage and has the tendency to develop cracks according to Mohammed A. Hameed, (2005).

1.4 Fiber Reinforced SCC. Two types offibers have been used to reinforce the cement-based matrices. The selection of the type of fibers is guided by the properties

of

the fiber such as diameter, specific gravity, young's modulus, tensile strength, etc., and the extent of these fibers affects the properties of the cement matrix.

The use of highly active pozzolanic material silica fume (SF) in

conjunction

with high range water reducing admixture (HRWRA)

produced high performance Self Compacted concrete (FIPSCC) with special features in both fresh and hardened states.

Self-Compacting Concrete was used for the wall of a large tank

belonging

to the Osaka Gas Company,

whose concrete casting was

completed in June 1988. The volume of SCC used in the tank amounted to 12,000 cubic meters.

lntroduction

Chapter One

5

1.5 Objective: This research presents an experimental study on the properties of self-compacting concrete (SCC) subjected to high temperature to gain more

understanding and knowledge regarding exposure temperature. Then, the influence

of high

of

SCC

temperature

on

to

elevated

mechanical

characteristics, by studying the changes in microstructure before and after

exposure

to a

certain range

Microscope (SEM).

A

of

temperature using Scanning Electronic

further aim is in particular to study, analyze, arld

explain the behavior of self-compacted concrete reinforced with a mix of

two different types of fibers under the influence of a certain range of temperafures.

1.6 Phases of Study: 1.6.1 Phase

I:

In phase

I

several experimental trail mixes of SCC to test the three

key factors distinguishing SCC which are filling ability, passing ability, and resistance to segregation

will

mixes with the specifications

be made, the results obtained from trail

will be compared, and then the ideal

experimental mix according to predetermined volumetric ratios

will

be

chosen.

1.6.2 Phase Fibers

II: will

be added to the SCC obtained from Phase

propylene or polyethylene and steel fibers experimental rates determined specifications of SCC.

till

I, a mix of

will be added according

to

obtaining a trail mix that matches the

Chapter One

1.6.3 Phase

Introduction

III:

As can be seen and according to the logical sequence ofphases mentioned earlier, a mixture of SCC reinforced with a mix of two different

types

of

fibers and mineral admixtures

of

reliable mechanical and

engineering properties as compared to normal concrete needs to be vibrated by machines

will

1.6.4 Phase

be obtained.

IV:

The effect of a certain range of high temperatures on the microstructure and behavior of SCC obtained from the phases mentioned earlier

will be studied. The term proposed for the temperatures will be 300 Co, 450 C', and 600 Co, and the temperature

of I

will

150 C",

be increased at a rate

Co per minute until reaching the target temperature for each stage. So a

wider range of temperatures while providing the fumace that meets the requirements

of the higher

temperatures could be studied. Thus,

it

can

evaluate the viability of the residual compressive strength as a function

of

temperature.

1.7 Thesis Layout: The achievement of the objectives described above requires the research to be made in a number ofstages. A general introduction and aim

ofresearch are presented in Chapter One. The review of literature regarding SCC production, mix design,

affecting factors, using

of

admixtures, applications

of

SCC, high

temperature behavior, hybrid fiber reinforcing, testing methods and workability are presented in Chapter Two. The detailed schedule of experimental work which includes the materials used, trail mixes casting, curing of concrete, tests performed and

Chapter One

I

ntroduction 7

heating

of

specimens up

to target temperatures is presented in

Chapter

Three.

Chapter Four demonstrates the results of the experimental work and the graphical representation

Chapter Five consist

of

ofthe results and its interpretations

microstructural analysis

unreinforced self-compacted concrete,

it

of fiber reinforced

discusses

and

a brief outline of

microscopic investigation performed on the samples

by using SEM

(Scanning Electronic Microscope). Chapter Six gives the summary and conclusions of this research.

It

also provides possible recommendations

improvement.

for further research

and

apterTwo

Literature Review

Chapter Two

Literature Review 8

2.

I

General A type of concrete, which can be compacted into every comer of

formwork purely by means of its own weight. The self-compactability of this concrete can be largely affected by the characteristics of materials and the mix proportions. It has fixed the coarse aggregate content to 50% ofthe

solid volume and the fine aggregate content to

40%o

of the mortar volume,

so that self-compactability could be achieved easily by adjusting the w/cm

ratio and superplasticizer dosage only. A model formwork, comprised of two vertical sections (towers) at each end of horizontal trough, was used to observe how well self-compacting concrete could flow through obstacles. Plate (2-1) shows the ends

of small pipes mounted across the horizontal

trough and used as obstacles. The concrete was placed into a right-hand

tower, flowed through the obstacles and rose

in the left-hand

tower

according to Hwang et al., (2006) and Okamura, H. and Ouchi, M., ( 1999).

Plate

(2-l) Small pipes

rk (Okamura, H. and Ouchi, M., 1999).

The obstacles were chosen to simulate the confined zones of an actual structure. The concrete in the left-hand tower rose to almost the same

level as in the right-hand tower. Similar experiments of this type were

Chapter Tlt'o

Literature Review 9

carried out over a period of about one year and the applicability of selfcompacting concrete for practical structures was verified.

It

has thought

that would be easy to create this new concrete because anti-washout underwater concrete was already in practical use. Anti-washout underwater concrete is cast underwater and segregation is strictly inhibited by adding a

large amount of a viscous agent (anti-washout admixture), which prevents the cement particles from dispersing in the surrounding water. However, it

was found that anti-washout underwater concrete was not applicable for structures in open air for two reasons: First, entrapped air bubbles could not

be eliminated due to the high viscosity and second, compaction in the confined areas ofreinforcing bars was difficult. Thus, for the achievement

of

self-compactability,

superplasticizer,

a

super plasticizer was indispensable. With

a

the paste can be made more flowable with little

concomitant decrease in viscosity, compared to the drastic effect of the water, when the adhesion between the aggregate and the paste is weakened

as in Figure (2-1). The w/cm ratio was taken between 0.4 and depending on the properties

of the cement. The super plasticizer

0.6

dosage

and the final w/cm ratio were determined to ensure the self-compactability

evaluated subsequently by using the U+ype test according to Bentur, A. and Mindess, S., (2005).On the other hand, the use of polypropylene fiber,

steel fiber in SCC with optimum dosage of (HRWRA) and (SF) admixture

is most likely to ensure optimized performance of SCC and to improve compression, tension, flexural toughness and impact loads over that

of

ordinary concrete. Also the presence of highly active pozzolan affects the microstructure characteristics of the concrete through the pore size and grain size refinement processes which strengthen the transition

zone and eliminate the micro cracking between the aggregate and the cement paste.

Literature Review

Chapter Two

10

The Hole of Superplastlclzer ﹂ ｆ‘Ｂ ５

Flowsblllty

Figure (2- I ) Effect of superplasticizer on viscosity (Okamura, H. and Ouchi, M., 1999).

2.2 Temperature Effects on SCC Concrete is non-combustible and does not support the spread

flames.

It

produces no smoke, no toxic gases

or no

of

emissions when

exposed to fire and does not contribute to the fire load. Concrete has a slow

rate of heat transfer which makes

it an effective fire shield for

adjacent

compartments and under typical fire conditions, concrete retains most of its strength. The European Commission gave concrete the highest possible fire

designation,

Al

according to M. Kanema, (2007).

The fire resistance of SCC is similar to normal concrete. In general, a low permeability concrete may be more prone to spalling but the

severity depends upon the aggregate type, concrete quality and moisture content Steffen Grunewald and Joost C., (2009). SCC can easily achieve

the requirements for high strength, low permeability concrete and will perform in a similar way to any normal high strength concrete under fire conditions according to Selc, T. et al., (2009). The use of polypropylene fibers in concrete has been shown to be

effective in improving its resistance to spalling. The mechanism is believed

Chapter Two

Literature Review 11

to be due to the fibers melting and being absorbed in the cement matrix. The fiber voids then provide expansion chambers for steam, thus reducing the risk of spalling. Polypropylene fibers have been successfully used with SCC according to AL-Rubiy, N.H., (2002).

Up

to

150 oC, the surface

of the observed concrete did not present any features of deterioration. No visible cracking could be distinguished. At 300 oC, few cracks appeared, notably in the interfacial transition zone between aggregates and paste. The cracks aspect was more pronounced for the samples heated to 450 oC and especially to 600 oC. At

these temperatures, many cracks could be observed not only

in

the

interfacial transition zone between aggregates and paste, but also in the paste and aggregates, notably at 600 "C. These cracks through aggregates observed at this temperature certainly resulted from the presence of quartz

(SiOz)

in the aggregates.

transformation

of

Indeed, towards 570 oC, the allotropic

quartz-o

in

quartz-B occurred.

This

reversible

transformation had important effects on the physical properties of quartz

and induced

in a

particular expansion (0.8%

in

volume).

These

observations could be done on each concrete. Similar cracks appeared at the same temperatures for all the concretes according to Hanaa Fares et al., (2010).

2.3 Mechanical Properties of Structural Self Compacting

Concrete Up to 1940, the maximum concrete strength at constructions sites was of the order of 20 MPa which rose to 40 Mpa

by 1970 and now more

than 100 MPa is used in structures. This quantum jump in attainable strength was possible only due to the superylasticizers (Sp) which were simultaneously developed in Germany and Japan in the late gO's of the

Chapter Two

Literature

Revierry

previous century. The utilization of high performance concrete (HPC) and

self-compacting concrete (SCC) has been possible only due

to

SP

availability. In general when such high strengths with suffrcient workability are desired, the maximum size of aggregates should be around 10-12 mm

though aggregate size

in

12-20 mm range has also been used with w/cm

ratio in the range of 0.3-0.40. Using SP, sufficient powder and continuous aggregate grading

is the other main ingredients of any HPC or

SCC.

Continuous grading improves particle packing and hence reduces the voids according to Wafa, F. F., and Ashor, S. A., (1999).

In the last decades, the development ofconcretes with enhanced mechanical performance and durability has become an aspect concern

to fulfill new challenges and long service lives of

of

great

constructions.

The addition of fibers to concrete has contributed to the improvement of mechanical properties

of concrete. On the other hand, many efforts have

in building up conuete with improved workability by the application of self-compacting concrete (SCC) technology. Then SCC reinforced with polypropylene fibers (SCC+PPF) results in a very interesting technologic material with many advantages associated to

been made

durability and mechanical properties. The workability properties of selfconsolidating concrete (SCC) leads

to an important potential for

the

application of this material; however, even though multiple advantages are associated

to the use of SCC, its real market in situ application is much

lower than what consequence

it would

be expected. In some way, this limitation is a

ofthe lack ofknowledge related to durability and degradation

mechanisms with time. The addition of fibers to reinforced self-compacting

concrete improves compressive strength or strain, the impact resistance, reduces the cracking and spalling risk at high temperatures. Although the

behavior of SCC against fire is still under debate, the addition of polymeric fibers to this material should have a synergic effect, on why polypropylene

Chapter Two

Literature Reyiew 13

fibers (PPF) are well considered as an effective method to improve the response

of

concrete

to high temperatures. The addition of fibers

to

reinforced self-compacting concrete improves compressive strength or strain; the impact resistance reduces the cracking and spalling risk at high temperatures according to M. C. Alonsoi et al., (2008).

The viscosity of cement-based material can be improved by

the water/cementitious material ratio (w/cm) or using a viscosity-enhancing agent. It can also be improved by increasing the decreasing

cohesiveness of the paste through the addition

of filler, such as limestone.

However, excessive addition of fine particles can result in a considerable

in the specific surface area of the powder, which results in an increase of water demand to achieve a given consistency. On the other increase

hand, for fixed water content, high powder volume increases interparticle

friction due to solid-solid contact. This may affect the ability of the mixture to deform under its own weight and pass through obstacles according to Selc, T. et al., (2007').

2.4 Mechanical Behavior of Fiber Reinforced Self Compacting

Concrete The mechanical behavior of fiber reinforced concrete can be illustrated by three stages of the tensile stress versus strain curve was shown in Fig. (2-2) according to Danied, J. I., et al., (1998):

o

Elastic stage: In this stage, the load was carried by both of fibers

and matrix. The stress was transferred to the fibers when the deformation in the matrix occurred, while the stress would transfer

back to the matrix when the deformation stopped. This eventually happened till the point offirst crack.

stage

Literature Review

Chapter Two

14

.

Multiple cracking stages: The concrete strain exceeded

the

ultimate strain of its composite, which was above the strain value

of 0.003,

as the cracking and energy absorption took place in this

stage. When the stress continued to increase between the fibers and

matrix, formation of fine cracks were developed'

o

Post-multiple cracking stage: In this stage, the matrix no longer carried the load, where stress was transferred to the bridging fibers, as the

pullout and stretch occurred to fibers.

箸 .Vr

∽ ∽ ］α 卜 の

載 詞 卜巌上

,fV,

Ec` "

c"円

C.c

Cc.

STRA:N Fig. (2-2): Stress/strain curve for the fiber reinforced concrete composite (Danied et al., 1998). The prediction of modulus of elasticity, E" and first crack tensile stress of the composite o

P.' mu were developed by Ziad, B. and Gregory,

Chapter Two

Literature Review 15

(1989),while the flrst crack fractural stress,σ ′and was developed by

Nawy,E.G.,(2001). 2.4。 l

Modulus of Elasticity Modulus of elasticity can be determined using in below equation;

E, = E*V^(matrix)

*

,t,n

eEfVf

(f iber).......................(2-1)

Where;

E": Modulus of elasticity of the fiber reinforced composite.

E-: Modulus of elasticity of the matrix. 7-: Volume fraction of the matrix. a

,:

Fiber length efficiency factor.

a, : Fiber orientation efficiency factor. E1: Modulus of elasticity of fiber. 71: Volume fraction of the fiber.

2.4.2First Crack Tensile Stress First crack tensile stress can be determined using in below equation; o

^u

= o.^uV^(matrix) *

n

,n

uo

,v

1(Jiiber)...................(2-2)

Where o

-r:

First crack tensile strength of the fiber reinforced composite.

Chapter Two

Literature Review 16

o

Tensile strength of the matrix at point of first crack. mu :

o r: Tensile strength of the fiber at point of first crack. 2.4.3 First Crack Flexural Stress

First crack flexure stress can be determined using in below equation;

o

f

= 0.843f,V*(matr ix) + 42sVf (, t o r)

ff ib er) .. ......... (2-3 )

Where;

or:

First crack flexural strength of the fiber reinforced composite.

/: Stress in the matrix (modulus of rupture of the plane concrete).

('t or),Fiber aspect ratio (ratio of length to diameter). The mechanism of fiber reinforcement of cement matrices was first

explained by Romualdi, J. P. and Beston, G. B., (1963). It has suggested that fibers act as crack arrestors by producing pinching force, which tends to close a crack. By considering a direct tensile stresses field and applying the principles of linear elastic fracture mechanics. It has showed that the

first crack tensile strength was inversely proportional to the geometrical spacing of fibers for a given fiber volume content.

The use of fiber in brittle matrix material has a long history going back at least 3500 year when sun-backed bricks reinforced with straw were used to build the 57 m high

hill of AqarQuf, which is located near Baghdad

according to Hannant, D. J., (1978).

Literature ReYiew

Chapter Two

17

The introducing of fiber was brought in as a solution to develop concrete in view of enhancing its flexural and tensile strength, which is a

new form of binder that combines Portland cement in the bonding with

cement matrices. Fiber

is

most generally discontinuous, randomly

distributed throughout the cement matrices according to Rizwan et al., (2006). Reinforcement of SCC with short randomly distributed fibers can address some of the concerns related to SCC brittleness and poor resistance

to crack growth. Fibers used as reinforcement, can be effective in arresting cracks at both micro and macro levels. At the micro level, fibers inhibit the

initiation and growth of cracks, and after the micro-cracks, coalesce into

macro cracks, fibers provide mechanisms that abate their unstable propagation, provide effective bridging, and impart sources gain, toughness

& ductility

of

strength

according to Bentur, A. and Mindess, S. and

Balagura, P. N., and Saha S. P., (1992).

Although short fibers cannot replace conventional steel reinforcement, they create supplementary reinforcement used to achieve increase

in strength, a higher ductility, greater reduction shrinkage, crack

control, fatigue, and impact and abrasion resistance.

However,

development and advances in technologies have led to the discovery of

more effects

of fibers behavior, and mechanical

properties

of

concrete

according to Balagura, P. N., and Saha S. P., (1992).

Concrete is considered a brittle material as

strength and failure strain, the incorporating

it

has low tensile

of fiber into vulnerable

concrete is useful and effective, but reinforcing effects of only one type

of

fiber are limited. For concrete consisting of hardened cement, aggregates pore and micro-cracks of different sizes, hybrid fibers of different types

Chapter Tlro

Lit€rature ReYiew 18

and sizes may play important roles in resisting crack-opening at different scales to achieve high performance.

It is a natural evolution that one single

type of fibers develops into hybrid fibers. Concrete, as the most commonly

construction material is developing towards high performance, so that a number ofresearch works have been carried out on hybrid fiber reinforced concrete, however, most of the studies

of hybrid fiber reinforcement are

about composites with hybrid fibers of steel fiber and synthetic micro-fiber,

especially, concrete combined with hybrid fibers

of

steel fiber and

polypropylene fiber. Using hybrid macro-fibers as reinforcement to improve the performance of concrete is seldom reported. Fibers affect the characteristics of SCC in the fresh state. They are needle-like particles that increase the resistance to flow and contribute to an intemal structure in the

fresh state. Steel fiber reinforced concrete

is stiffer than conventional

concrete. In order to optimize the performance of the single fibers, fibers

need

to be homogeneously distributed;

clustering

of

fibers has to

be

avoided. The effect of fibers on workability is mainly due to four reasons.

First, the shape of the fibers is more elongated than the aggregates; the surface area at the same volume is higher. Second, stiff fibers change the

structure of the granular skeleton, whereas flexible fibers

fill

the

space

between them. Stiff fibers push apart particles that are relatively large compared to the fiber length, which increases the porosity of the granular

skeleton. Third, the surface characteristics

of fibers differ from that of

cement and aggregates, e.g. plastic fibers might be hydrophilic or hydrophobic. Finally, steel fibers are often deformed (i.e. have hooked ends

or are

to improve the anchorage between them and the surrounding matrix. To be effective in the hardened state, it is wave-shaped)

recommended

to choose fibers not shorter than the maximum aggregate

size. Usually, the fiber length is 2-4 times that of the maximum aggregate size according to Steffen Grunewald and Joost C., (2009).

Chapter Two

Literature Review 19

The interactions between the fiber and cement matrix, as well as

the structure of fiber reinforced cementitious material are the essential properties that affect the performance

of cement based fiber

composite

material. However, understanding these properties and the need for estimating the fiber contribution and the predication

of the composite

behavior are necessitated. Such considerations include:

o

The matrix composition.

r The uncracked and crack condition ofthe matrix. . Type, geometry and surface characteristics ofthe fibers. o The length efficiency and orientation of fibers through the cement matrix.

o o

Critical volume fraction of fibers. Predication

of the behavior and properties of fiber

reinforced

concrete.

The mechanical behavior of fiber reinforced concrete materials is dependent on the structure of the composite, which are both properties

of

the concrete and the properties of the fiber type used in the cement mix. Hence, composite analysis and prediction of their performance in various

loading conditions, such as intemal structure on the composite, must be characterized according to Romualdi, J. P. and Beston, G. B., (1963).

2.5 Shape, Geometry, and Distribution of Fibers in Cement

Matrix The largest influences on the fiber reinforced Concrete however

were the shape, geometry and mechanical properties

of fibers and the

dispersion of fibers in the cementitious matrix. The knowledge on the fiber properties is important for design purpose.

Literature Review

Chapter Two

,-

It

has been stated that the high value

of fiber

20

modulus of

elasticity would have direct influences on the matrix modulus of elasticity where this facilitated the stress transfer from the matrix to the fiber. Fiber

which has a higher tensile strength is essential to reinforcing action. Furthermore, fibers that had large values of failure strain would tend to have high extend or a prolongation in the composites according to Jemes, J., ( 1999). The properties and respective types of fibers are shown in Table

(2-\).

Table (2-1): Typical properties of cement-based matrices and fibers (ACI

Commltee 363,2010).

Diameter

Material or

Specilic

or

Length,

Fiber

GraYily

Thickness,

mm

Volume in

Elastic

Tensile

Modulus,

Strength,

GPa

MPa

10-30

l-10

20-40

I-4

164

200-1800

2-3

5-15

30-390

600-2700

05-24

3-5

10-50

300-1000

70

600-2500

Failure

Composite,

Strain, 7o

microns

Mortar Matrir

18-20

Concrete Matrix

18-24

Asbestos

255

116Carbon

195

1000020000

002-30

7-18

5-40

3-

001005

001002

85-97

97-999

continuous

20-120

Cellulose

05-50 10-50

27

5-15 ´０

Glass

300-5000

3-7

Polypropylene

Ilonofilament

091

20-100

5-20

01-02

Literature Revi€w

Chapter Two

2L

Continued, Table (2-l ).

Specific

or

Length,

Fiber

Grsvity

Thickness,

mm

ｅ ︲ ｉ ｓ 山 ｎ 中 ｅ Ｔ

Mal€rial or

ｓ ｃ ｕ ｉ ︲ ａ ｔ ｓ ｕ Ｐ ａ ｄ Ｃ ︲ ｏ Ｅ Ｍ

Diameter

Failure

Strain,

Volume in Composite,

To

microns

Chopped Film

01-10

091

20-100

5-50

5

300-500

l-3

3-8

2-6

12-40

700-1500

2-3

10-60

200

2000

03-20

10

Polyvinyl Alcohol

(PvA, PVOH) Steel

1

.86

100‐

600

2.5.1 Interaction between Fibers and

700‐

Matrix

Many detailed analytical prediction and models have developed

in the interaction of

been

fiber-matrix stress transfer and crack

bridging, as well as analyzing the shear stresses that develop across the

fiber-matrix interface. Most

of the models were done by

simulating

analyical solution on fiber-matrix interaction, which is based on a simple pullout geometry shown in Fig. (2-3). These analltical models involve the shear stresses and fractional stresses which are developed between the fiber

and cement matrix, offering predications on the efficiency

of

short,

randomly oriented fibers in the concrete matrix. The effectiveness of fibers

in the mechanical properties of the fiber reinforced concrete is influenced in two ways according to Nawy, E. G., (2001):

o

Processes where load is transferred from the cement matrix to the

fibers, and

.

The bridging effect ofthe fibers in the concrete cracks.

Literature Review

Chapter Two

ト ト ‘ ﹁

一 Ｐ

F18RE ρ

l,{ATRtX

↓一

r(

^'

au)

a$) + da

P(x)

P(■ )■ 一

曲

dP

一

Fig. (2-3): Pullout geometry to simulate the interaction between fibers and cement matrix (NawY, E. G., 2001).

2.5.2 Critical Fiber Volume The load bearing capacity of the fiber reinforced concrete depends on the volume dosage rate applied into the concrete matrix. In this fiber cement composite, the failure strain

of hber is normally greater than the

failure strain of the concrete. As to prevent the failure of fiber, the load bearing capacity

ofthe fiber must be greater than the load applied on the

concrete when the first crack appears. This was assumed that the concrete

did not contribute any further strength beyond the point of first crack,

the load was fully transferred to the fiber contained in the

as

concrete.

Furthermore, the fibers were able to carry more loads, resulting in that the

ultimate strength of the fiber cement composite was higher than the matrix strength itself. In this case, an equation for minimum fiber volume fraction,

(trzcr), was developed

to set to

equal the load bearing capacity

of

the

Literature Review

Chapter Two

23

fiber/cement composite and the fiber load bearing capacity. The minimum

or critical fiber volume dosage rate,, (vcr), that needs to be added to concrete for its loading bearing capacity or to sustain the load after the concrete cracks was given as in below according to Ziad, B. and Gregory, P.,

(le8e):

vr, >

o^u (2‐

4)

Where:

Vn: Criticallminimum fiber volume fraction.

o-r:

Ultimate tensile strength of the concrete in MPa.

orr:

Ultimate tensile strength of the fiber in MPa.

o /u: Stresses on the fibers when concrete fail at its first crack in MPa.

2.5.3 Efficiency of Fiber Reinforcement

The fiber reinforced

self-compacted concrete consists of

distribution of shot fibers in the cement matrix. Such contribution of short, inclined fibers on the mechanical properties of fiber reinforced concrete is usually less than long fibers placed parallel to the load. This means that the

efficiency ofthe short and inclined fibers is less. However, the efficiency of the fibers in the cement matrix to enhance the mechanical properties of concrete can be judged in two ways:

The property enhancement in the strength ofthe concrete, and The property enhancement in the toughness ofthe concrete.

Chapier Two

Literalure Review

__

24

fiber These effects on the properties ofconcrete depended on the and the shear length, and the orientation of fibers distributed in the concrete factors were bond strength of the fiber/cement composite. All of these three largely affect not independent as the effects on the fiber length orientation of efficiency the bond between the fibers and cement matrix. Determination

canbeobtainedbyempiricaloranalyticalcalculationsonthefactorsfor

a

, length efficiency

and 40 ', orientation

efficiency according to Ziad' B'

and Gregory, P.' (1989).

2.5.4 Length EfficiencY

fiber

minimum The critical length parameter, /"' can be defined as the in the fiber from the length which needs to build up ofa stress or load

to its failure strength fractional and shear stresses transfer and is equal in Fig' Q-a)' (load). The definition of the critical length of fiber is shown 2 fractional stresses transfer mechanism and curve curve

I

represents

l'

For curve the fiber represents an elastic stresses transfer mechanism' is no sufficient embedded length is less than the critical length, where there If the length of the length to produce stresses equal to the fiber strength'

fiberexceedslc,thestressesonmostofthelrberswillreachitsyield strength,asthiswasshownoncurve2'Thecriticallengthofthefibercan be calculated as:

,uzr-df L--

o

f

Where

dy: Fiber diameter (mm).

or:

Ultimate strength of the fiber (MPa)'

(2-s)

ChaPter

r: Interfacial bond

Two

Literature Review

strength (MPa).

Thelengthefficiencyfactorsareusedforthepredictionofthe

propertiesoffiberreinforcedconcreteinthepre.crackingandpost. of the cracking states. The length efficiency factors, which take accounts by critical fiber length on both pre-crack and post-crack states, are shown (1989) and the following equations according to Ziad, B' and Gregory' P'' Jemes, J., (1999):

2.5.4.1 Pre-cracking State Pre-cracking state can be evaluated as in below;

η

′

=1-考

(2-6)

2,5.4.2 Post-cracking State: Post-cracking state can be evaluated as in below;

,,=!-7

forl>2lc

n fort>2tc 't =0.25-'+ I ' t Where;

4

: Length efficiencY factor.

I.: Critical finally obtained from equation (2-5)'

e-r:

Strain of the fiber (at point of first crack)'

(2‐

7)

(2-8)

Literature Review

Chapter Two

/:

Embedded length of the fiber in the cement matrix.

e;rr: Ultimate strain of the fiber.

↓

０■ ３ ● ３ ■■ ■ ● ‘ ａｐ ● ０ ０ Ｊ Ｊ ０ ， ，

▲● マｌ ｌｌ ｉ︰ ︰

σ

ci4n

´‘         Ｌ

0S0rlHtr.l

Fig. (2-a): Definition of critical length: (a) Frictional stress distribution on fibers. (b) Intersection of fiber breaking load, with pullout load versus embedded length (Ziad, B. and Gregory, P.' 1989).

2.5.5 Fiber Orientation

If all fibers were placed parallel to the direction of stresses applied, the orientation efficiency is unity. However, the use of fibers in the concrete matrix is randomly distributed, where the orientation of the fiber

was unpredictable within the concrete with either in one, two or three dimensional arrays. In such distribution, some of the fibers were placed on an axis in an angle 1d)

ofthe load orientation or applied stresses shown in

Fig. (2-5). It shows that fiber at an angle can carry more load to those fiber

placed parallel

to the load direction by using vector analysis in

the

components of x, y and z. Furthermore, fibers at an inclined angle to the

ChaPter

Two

Literature Review

load direction carry more bending stresses during the bridging of a crack and decrease the fiber efficiency in carrying load applied to the concrete according toZiad,B. and Gregory, P., (1989) and Jemes, J'' (1999)'

Fig. (2-5): Intersection of an oriented fiber across a crack with angle d

(Ziad,B. and Gregory, P., 1989). A summary of literature review is tabulated as in Table (2-2) in below; Table (2-2) Summary of Literature Review' Reference

Conclusion

Hwang, S. D. et al.,

Self compactability could be achieved by fixing

(2006), Okamura, H.

the coarse aggregate content to 50Yo ofthe solid

and Ouchi, M., (1999),

volume and the fine aggregate content to 40yo

and Bentur, A. and

of the mortar volume and adjusting w/cm and

Mindess, (2005).

superplasticizer dosage only.

ChapterTwo

Literature Review 28

Continued, T able (2-2). Conclusion

Reference

M.Kanema, (2007). Steffen

Grunewald, Joost C.

The superplasticizer dosage and the final w/cm ratio

were determined

to

ensure the self compactability

evaluated subsequently by using the U-type test.

Low permeability concrete may be more prone to spalling under the effect of elevated temperature, but the severity depends upon the aggregate type, concrete

Walraven,

quality, and moisture content. (2009).

SCC can easily achieve the requirements for high Sclc Uk.T.et al,(2007).

strength, low permeability concrete, and

will

perform

in a similar way to any normal high strength concrete under fire conditions.

The use of PPF in concrete has been shown to be effective in improving its resistance to spalling. The AL― Rubiy,N.

mechanism is believed to be due to the fibers melting

H.,(2002).

and being absorbed in the cement matrix. The fiber voids then provide expansion chambers for steam and reducing risk of spalling.

Upon exposure to 300 Co temperature rate, few cracks appeared notably

in the interfacial

transition zone

Hanaa Fares et

between aggregates and paste, the cracks are more

J.,(2010).

pronounced for samples heated to 450 Co, and at 600

C" cracks could be observed not only in the interfacial zone, but also in the paste and aggregates.

ChaPter

Two

Literature Review

Continued, Table (2-2). Conclusion

Reference

@fficientworkabilitl

I

Wafa, F. F. and

are desired, the maximum size of aggregates should be

Ashor, S. A.,

around 10-12 mm, though aggregate size 12-20 mm range has also been used with w/cm in the range of

(teez).

0.3-

0.4 M. C. Alonsoi et

I

l I

|

strength

al., (2008).

I

or strain; the impact

resistance reduces the

cracking and spalling risk at high

temperatures.

I I

I

Ziad, B. and

more bending stresses during the bridging of a crack

Gregory, P., (l

and decrease

e8e).

Romualdi, J. P.

the fiber efficiency in carrying load

applied to the concrete. I ItIt

hus sho*ed that the first crack tensile strength was

I

and Beston, G.

linversely proportional to the geometrical spacing of I

B., (1e63).

| fibers for a given fiber volume content. I

Ef"

i"tr"d*ing of fiber was brought in as a solution

to

I

Rizwan, S. A. et al., (2006).

I

I I

Balagura, P. N. and Saha S. P.,

(ree2).

develop concrete in view of enhancing its flexural and

tensile strength, which is a new form of binder that combines Portland cement with cement matrix.

of SCC with short randomly distributed f n.infor..rn.nt | fib".. .un address some of the concems related to SCC I

I

b.inlen"rr and poor resistance to crack growth at both

I

.i".o

and macro levels.

I

Literature Re\ ierl

Chapter Two

30

Continued, T able (2-2). Conclusion

Reference

It Jemes, J.,

(leee).

has been stated that the high value

of fiber modulus of

elasticity would have direct influences on the matrix modulus

of

elasticity where this facilitated the

stress

transfer from the matrix to the fiber

The effectiveness of fibers in the mechanical properties of the fiber reinforced concrete is influenced by:

Nawy, E. G., (2001).

1. Processes where load is transferred from cement matrix to the fibers.

2. The bridging effect offibers in the concrete

cracks.

lterThree

Muterials and

Chapter Three

Materials and Experimental Work. つＪ

3.1 General This chapter describes preliminary design and planning such experimentation of coarse and fine aggregate, selection

as

of fiber with fiber

volume fraction, admixture effects, target strength of concrete specimens,

mix design and number of mix batches and concrete specimens required to meet the scope of this research. Test of fine and coarse aggregates have

been performed

at NCCL

(National Center

of

Construction

Laboratories)/Tikrit Branch.

3.2 Materials 3.2.1 Cement

Ordinary Portland cement type I, Iraqi manufacture was used in

all mixes throughout this investigation. It was stored in air-tight plastic containers to avoid exposure to atmospheric conditions like humidity. The physical and chemical properties of this cement are presented in Tables (3-

l) and (3-2)' respectively. Test results indicate that the adopted cement conformed to the Iraqi specification #

5/lg}4.

Table (3- l ): Physical properties of cement. Physical Properties

Limit ofIQs#

Specification

5/1984

Specific surface area (Blaine method), m2&g Setting dme(vicat

躍TTめ 'hHJ Semng, Final setting, hrs:min

230 m2lkg lower limit

R.G.D# 198/1990.

1:30

3:40

Not less than 45min Not more than

l0 hrs

Chapter Three

――――――――‐==================二

Table(3‐

Materials and Experimental Work.

=====三

二三二二

===二 =========二 ===========―

――――――-

32

1

Compressive strength MPa For 3-day For 7-day

21.5

R.G.D#

31.3

198/1990

Expansion by Autoclave method

0.36 l

15 νPalower limit

23 MPalower liml 0.80/O upper lim■

l

Table (3-2): Chemical composition and main compounds of cement.

Limits ofIQS# 5/1984

Oxides composition

Ca0

62.25

Si02

22.87

A1203

4.47

FezOr

3.07

MgO

RG.D#

S03

472/1993

238 247 う‘ つ４

LOI

127

Insoluble material

(L.SF)

C3S

38.14

C2S

37

C3A C4AF

6.65

ξυ ００

０

Lirne Saturatlon Factor,

5%Max. 2.80/O Max. 40/O Max. 1.50/O Max. (0.66-1.02)

9.34

3.2.2 Fine Aggregate Normal weight natural sand from Al-Tuz region east of Tikrit Area was used as fine aggregate. The grading of the sand conformed to the requirements of Iraqi specification # 4511984, as shown in Table (3-3). The

Chapter Three

Materials and Experimental Work.

33

physical and chemical tests of sand used throughout this work are shown in Table (3-4). Results also indicate that the fine aggregate grading and sulfate content are within the requirement of the Iraqi specification# 45119g4. Table (3-3): Grading of fine aggregate. Sieve size (mm)

Specification

Cum ulative passing 7o

specH騒 l:∬ J醤.984

Zone#3.

10

100

4.75

90-100

2.36

118

100

85‐

IQS# 30/1984

06 12‐

40

Table (3-4): Chemical and physical properties offine aggregate. Lirnits of lraqi

Properties

Specification

speciflcatiOn#

45/1984

(IQS)#3卜 84

Absorption %

(IQS)#31‐ 84

Sulfate content (as SO:), %

R.G.D#500/1994

Material finer than 0.075 mm sieve o%.

(IQS)#30-84

2.54 う４

︱ＩＬ

Specific gravity

上

0.25

0.5% (max. value)

(max. value)

5%o

3.2.3 Coarse Aggregate Local naturally river uncrushed gravel was used of nominal max. Size 14 mm as coarse aggregate. The aggregate for each batch was washed

Chapter Three

Materials and Experimental Work.

34

by water in order to remove the dust associated with coarse aggregate. High

proportion

of dust leads to

concrete according

segregation and causes crazing

to Taylor, W. H.,

aggregate conformed to the requirements

of

(1977).The grading

exposed

of

oflraqi Specifications #

coarse

4511994,

as shown in Table (3-5).

The coarse aggregate was dripped off and spread inside the laboratory in order to bring the aggregate particles to saturated surface dry

(SSD) condition. Physical and chemical properties were determined for coarse aggregate. Table (3-6) lists these properties and their corresponding

proper specifications. Table (3-5): Selected grading ofcoarse aggregate. Sieve size,

Cumulative passing o/o

Limit ofIQS#45/1984.

20

100

100

14

96

90‐ 100

73

50‐ 85

(nun)

Specification

10

IQS# 30/1984

つつ

5

0‐

10

236 Table (3-6): Chemical and physical properties ofcoarse aggregate. Limits of

Properties

Specification

Test Results

lraqi

Speciflcation

#45/1984 Specific gravity

(IQS)#31-84

2.6

Absorption %

(rQS) # 3l-84

1.5

￨

Chapter Three

Materials and Experimental Work.

35

Continued, Table (3-6).

Properties

Sulfate content (as SOr), %

Specification

Test Results

R.G.D#500/1994

0.06

Limits of Iraqi Specification # 45n984.

0.t%

_____-_____+_____

Material finer than 0.075 mm sieve, oZ

(rQS) # 30-84

t.2t

3.2.4 Admixtures 3.2.4.1 High Range Water Reducing Admixture (HRWRA)

The superplasticizer type is Structro 335; high performance concrete superplasticizer based on polycarboxylic technology was used throughout this investigation as a (HRWRA). Structuro 335, as its technical description presented in Table (3-7) and (Appendix A), is differentiated

from conventional superplasticizers in that

it is based on a unique

carboxylic ether polymer with rong lateral chains. This greatly improves cement dispersion. At the start of the mixing process, an electrostatic dispersion occurs but the presence

of the lateral chains, linked to

the

polymer backbone, generate a steric hindrance which stabilizes the cement particle's capacity to separate and disperse. This mechanism considerably reduces the water demand in flowable concrete. Structuro 335 combines the

properties

of

water reduction and workability retention. It allows the production of high performance concrete and/or concrete with high workability. Structuro 335 is a particularly strong superplasticizer alrowing production of consistent concrete properties around the required dosage. According to data in table (3-7), the Superprasticizer can be classified as type A, according to ASTM C 494,2004.

Chapter Three

Materials and Experimental Work.

36

Table (3-7): Technical description of high range water reducing admixture. Concrete Superplasticizer Appearance

Light yellow to reddish colored liquid

pH Volumetric Mass

l.l0 kg/ltr. @20"C r

url

i,oyS:t ta$.i C+-

-,1.

ful-,Jnil o:l cJJ-Yjl

ti ,d

l.a,r.-

.:r:i5-l ,':-

Jl it-*r

,.Jl fuLJill elE,oe er-lt e,'iti fuL-,,;S.ll ;i ,lC. J 'Jt - Jl ;.-f-Jl 6-1,:,ril.rll te r'r rlL c,-:,-,,.tgXt

,-.1S.:

rr-,,-ryt 'oJtill

Jl

u-.,lt j.i]i

6-J

ellS

.+t

1980 et" utr.l+ll .,s;JF

d3!

Oll i-l (JslJ 6l-1111 4:J-.F+ oi :3:.s-. dls.j,r ful.,Jijl (-F ECI hA dii-J IJI--J .'or.i.ll ir:.Liill dt"eYl d fuLJsll (J. eCl liA el\r1...1 dJ\ rje 6r:s-. drLl-,.r dltiA,',...11 .'t

"Sll

i+ (SCC) u-jl 4:61i fuLJ.iJl et:i ,rlc 1s,p r-,|-p '''-rll lra .FJ.-,9 l6Jl. ,'Usi ii.Llll c.rtlJiJl g,".lc'; ph-ii p,'':- ,i,!.b 6Jl-,,1r. drLrJJ k +F se aiJ{+-ll i:ritl, iril.. tSr^tl d-.lJill i-,lJr c-i .+F / i.-t+ 4-sdl iJS s's 4-,lJJl

.uj ',ni-lt 6-.11-.,p i.1-2: Gj-r Ol-; d+i .1" .('e 600 1450 ,300 ,150) &''cr''Jl ;Jl!l di+Ji J! c)-r-!t i.cL 6r"l i!r6:... ll ;-.11-.,pJl r-r-.,p se di+ll "EJ fi ,i+ll & .pt+:. r5.:{ 6JlJ,sll ;l:ii +:si $i g* OS;lt r+r d.,! i+lt & ,-*l+i d ,dli Jl lil;)trj .qJ.nll L!! 6Jrlj C-,16;.ll 4:qll \ri &Lil lgsll ql-J-:.JS+ aL-ri..*ll eiEill iJ.-ly .Jl+iYl eGi elll 300-r 150 a'/.ll.22Jl di.-il.li--bjll LrtL,rr;rq'raLx-,"'':-.'otl:nJl ','i'r .,5s

{$, / "p I

rJ:'-+ drUl'll igi*..]

t'

r-,1lJil dSl .O.ri..]ll

s,Lrr 60 ;nc ol (elLrl)t i-iL;i e3q::'+_.,;t a!!iJl) RSCC :J.lJl c.E:,I ef l..5 ,qJ*lt 4iill r*iil (.i!l)t u. ir;cy.+ q3lJt iJ.I;Jl) HSCC iJ"l.Jl .UJ"l '/.6.22

oe

c. tu:ti. 7.3.2v)Ji;:U RSCC iLlill .E.o c.,;6fi Lj; 90 -* d"J,.3 $o -tLi.-bj!l L3tL crLi-ii, RSCC il"lill cruyl i'p.:lt-r , HSCC il"lill

ot-iJ

'oJlJ,s

23.53

LJJ u:J.ill

r.oJ.oa 450 6-.rl> 4+'1ll

el"Eil 6UJ,l 0648.39

:

Cl 6Li'il l.,l"sr C. fuJtL LrtL ,',ui:ri oe 600 tr_rl:L

FJ,.ll

Yo4l.32:j.r-.,.J.1;.-::!l

C

e'/.48.26 s'147.55: , '/.40.49 :'/.31 l--eg

90

r 60 -rL"c)J3 HSCC

.69.,Jlrl & Ls 90 I 60 tt"c)lr RSCC r RSCC 6t+li o,' 600 t 450 6-.rl> drt+JJ,JbFl

crt-Ul ;r clJl 'o,pU-) 4yt "^tt U,.l d -*;tt Jl l.,Li 6+_l l:r3 ,dl!l ,,Jc rrF rirr .J,.,ll C^ euirYl L3tL ,J 6$j il.l-). i .(4lJ(+^lt r"r,ll -):+j 6l_2.r.taJl ah-:ll 'o.ll.Jj d.r+J',,;:r ,',..-: !-\ ,',:-,i-*;. el:JJl 3q; i-21 Jl crt:-.p ljs 6jli1l 4+ll

L!-iJ

;Jl!l

di+Jpl

uFFl

,'r^

i5;_p ".-+ elli :*.r_9 .e 300 Lr_tlrL

6-,;1-.,1,=

i-r,!

.-l_t

° L,9oン ・ J RSCC iLltm J」 .1島 ゝ￨」 井 .JIメ ￨。 ■ F600」 450 ｀ 憚口 ￨」 !け り ￨ゝ ・り ￨メ ゝ1ひ 6り _●り一 メリL夕 60″ ´ J=押 “ 出 ゃ夕 ‐ ♂ IJ=メロ .よ 鋤 16j J。 メ 』 ヽりヽ丼 ■ 1御 16jぃ 』」 出 一

￨

￨