STRENGTH AND DEFORMATION CHARACTERISTICS OF … · increasing fiber contents and did not depend on a cement content at a relatively low fiber content. In terms of flexural strength,

STRENGTH AND DEFORMATION CHARACTERISTICS OF CEMENTED

SAND IMPROVED WITH PALM FIBER

MISS CHUTKAMON DACHRUEANG

A THESIS SUBMITTED IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR

THE DEGREE OF MASTER OF ENGINEERING

(CIVIL ENGINEERING)

FACULTY OF ENGINEERING

KING MONGKUT’S UNIVERSITY OF TECHNOLOGY THONBURI

2018

ii

Thesis Title Strength and Deformation Characteristics of Cemented Sand

Improved with Palm Fiber

Thesis Credits 12

Candidate Miss Chutkamon Dachrueang

Thesis Advisor Asst. Prof. Dr. Sompote Youwai

Program Master of Engineering

Field of Study Civil Engineering (Geotechnical Engineering)

Department Civil Engineering

Faculty Engineering

Academic Year 2018

Abstract

This study presents the engineering properties of sand-cement improved with palm fiber.

The compressive and flexural strengths of non-reinforced cemented sand showed brittle

behavior with increasing cement content. Its brittle behavior decreased by increasing a

palm fiber content and a fiber length. The strain index (D) significantly increased by

increasing fiber contents and did not depend on a cement content at a relatively low fiber

content. In terms of flexural strength, adding fibers increased the load carrying capacity

of soil-cement after the first crack. The efficiency of fiber strongly depended on the fiber

length and fiber content. The residual strength and equivalent ductility ratio increased by

increasing fiber content and fiber length. The optimum fiber contents and fiber length for

the compressive and flexural strength were at 1.0% and 40 mm, respectively. The

proposed empirical equation can be successfully employed to predict unconfined

compressive strength and flexural strength with different mixing ratio.

Keywords: Cemented sand/ Compressive strength/ Flexural strength/ Palm fiber

iii

หวัขอ้วทิยานิพนธ์ ลกัษณะดา้นกาํลงัและการเสียรูปของทรายซีเมนตท่ี์ปรับปรุงดว้ยเส้นใยปาลม์

หน่วยกิต 12

ผูเ้ขียน นางสาวฉตัรกมล เดชเรือง

อาจารยท่ี์ปรึกษา ผศ. ดร.สมโพธิ อยูไ่ว

หลกัสูตร วศิวกรรมศาสตรมหาบณัฑิต

สาขาวชิา วศิวกรรมโยธา (วศิวกรรมเทคนิคธรณี)

ภาควชิา วศิวกรรมโยธา

คณะ วศิวกรรมศาสตร์

ปีการศึกษา 2561

บทคดัยอ่

การศึกษาคร้ังน้ีนาํเสนอคุณสมบติัทางด้านวิศวกรรมของทรายซีเมนต์ท่ีปรับปรุงดว้ยเส้นใยปาล์ม

การทดสอบกาํลงัรับแรงอดัและกาํลงัรับแรงดดัของทรายซีเมนตท่ี์ไม่มีการเสริมแรงดว้ยเส้นใยพบวา่

ตวัอยา่งการทดสอบมีความเปราะ ความเปราะของวสัดุจะลดลงเม่ือเพิ่มปริมาณเส้นใยและความยาว

ของเส้นใย ดชันีความเครียด (D) เพิ่มข้ึนอย่างมีนยัสําคญัเม่ือปริมาณเส้นใยเพิ่มข้ึนและไม่ข้ึนอยูก่บั

ปริมาณซีเมนต์ ค่ากาํลงัรับแรงดัดคงคา้งและความสามารถในการดูดซับพลงังานเพิ่มข้ึนเม่ือเพิ่ม

ปริมาณเส้นใยและความยาวของเส้นใย ปริมาณเส้นใยท่ีเหมาะสมสาํหรับค่ากาํลงัรับแรงอดัและกาํลงั

รับแรงดดัอยูท่ี่ร้อยละ1.0 และความยาวของเส้นใยท่ีเหมาะสมคือ 40 มิลลิเมตร สมการเชิงประจกัษท่ี์

นาํเสนอสามารถนาํไปใชใ้นการทาํนายค่าความแข็งแรงของกาํลงัรับแรงอดัท่ีไม่ไดก้าํหนดและกาํลงั

รับแรงดดัท่ีมีอตัราส่วนต่างกนั

คาํสาํคญั: กาํลงัรับแรงดดั/ กาํลงัรับแรงอดั/ ทรายซีเมนต/์ เส้นใยปาลม์

iv

ACKNOWLEDGEMENTS

I would like to express my sincere thanks to my thesis advisor, Asst. Prof. Dr. Sompote

Youwai for his invaluable help and constant encouragement throughout the course of this

research. Without his help in both academic and this thesis would not have been

completed without all the support that I have always received from his.

Sincere appreciation is also extended to the members of the committees, Assoc. Prof. Dr.

Pornkasem Jongpradist, Assoc. Prof. Dr. Pitthaya Jamasawang for their help,

encouragement, suggestions, constructive comments, and serving as members of my

thesis examination committees.

Thanks, are also extended to the student members of Geotechnical Engineering Division,

Department of Civil Engineering, King Mongkut’s University of Technology Thonburi

(KMUTT), for their kind help and invaluable encouragement. Finally, the author would

like to thank my lovely family and my lovely friends for their encouragement, constant

love, and strong support during studying at KMUTT. Moreover, I am very impressed by

geotechnical laboratory member for their warm welcome and make comfortable, able to

enjoy learning.

v

CONTENTS

PAGE

ENGLISH ABSTRACT ii

THAI ABSTRACT iii

ACKNOWLEDGEMENTS iv

CONTENTS v

LIST OF TABLES vii

LIST OF FIGTURES xi

LIST OF SYMBOLS xviii

LIST OF TECHNICAL VOCABULARY AND ABBREVIATIONS xx

CHAPTER

1. INTRODUCTION 1

1.1 Introduction 1

1.2 State of the Problem 3

1.3 Objective of Study 3

1.4 Scope and Limitation 3

1.5 Expected Benefit 3

2. LITERATURE REVIEW 4

2.1 Pavement 4

2.2 Soil Stabilization 8

2.3 Soil Cement Stabilization 10

2.4 Fiber Reinforcement 13

2.5 Case Studies of Fiber-Reinforced Soil 20

3. METHODOLOGY 23

3.1 Introduction 23

3.2 Materials in Laboratory Test 24

3.3 Test apparatuses 28

3.4 Measuring devices 28

3.5 Preparations of Tested Samples 30

vi

CONTENTS (Cont’d)

PAGE

3. METHODOLOGY 23

3.6 Evaluations of Geotechnical Engineering Properties 40

3.7 Indices for Verification of the Empirical Equation 45

3.8 Test Program 46

4. RESULTS AND DISCUSSION 47

4.1 Introduction 47

4.2 Unconfined Compression Test (UC) 47

4.4 Flexural Strength Test (FS) 65

4.5 Empirical Equations the Effect of Cement Water Ratio (C/W) 79

4.6 Evaluation of Proposed Empirical Equation 90

5. CONCLUSIONS 96

5.1 Conclusions 96

5.2 Recommendation for Future Research 97

REFERENCES 98

APPENDIX 105

A The results of unconfined compressive strength test (UC) 105

B The results of flexural strength test 111

C The results of empirical equations the effect of cement-water 114

ratio (C/W) and evaluation of proposed empirical equation

CURRICULUM VITAE 146

vii

LIST OF TABLES

TABLE PAGE

2.1 Difference between Flexible Pavements and Rigid Pavements 6

2.2 Showing the main proportion of cement 10

2.3 Showing how the Department of State Highways mixes cement 13

3.1 Properties of palm fiber 25

3.2 Index properties of Ayutthaya sand 26

3.3 Properties and Classifications of Cement 27

3.4 Detail of compaction used for cylinder mold in this study 32

3.5 Detail of compaction used for beam mold in this study 36

3.6 Test program implemented in the present study 46

4.1 The coefficients of associated compressive strength (qu) with variables

in regression models

83

4.2 The coefficients of associated flexural strength (f1) with variables in

regression models

87

A.1 Axial strain at peak strength (%) and Strain index (D) curing 28 days 106

A.2 Unconfined compressive strengths of sand cement improved with palm

fibers curing 28 days

109

A.3 Toughness of unconfined compressive strengths of sand cement

improved with palm fibers curing 28 days

110

B.1 Flexural performance of sand cement improved with palm fibers curing

28 days

112

C.1 Values of Aqu and Bqu from relationships UCS (qu) and cement-water ratio

(C/W) at fiber length 10 mm

117

C.2 Values of Aqu from the relationships between UCS (qu) and cement-water

ratio (C/W) using the average of Bqu of 1.5096 at fiber length 10 mm

117

C.3 Values of Aqu and Bqu from relationship between values of Aqu and

fiber content (FC) at fiber length 10 mm

118

C.4 Values of Aqu and Bqu from relationships UCS (qu) and cement-water ratio


120

viii

LIST OF TABLES (Cont'd)

TABLE PAGE



120



120

C.7 Values of Aqu and Bqu from relationships UCS (qu) and cement-water

ratio (C/W) at fiber length 40 mm

122



122



123

C.10 Values of Af1 and Bf1 from relationships FS (f1) and cement-water ratio


125

C.11 Values of Af1 from the relationships between FS (f1) and cement-water

average of Bqu of 2.1592 at fiber length 10 mm

125

C.12 Values of Af1 and Bf1 from relationship between values of Af1 and


126



128


ratio (C/W) using the average of Bf1 of 2.003 at fiber length 20 mm

128



128



130



130



131

ix


TABLE PAGE

C.19 Summary of the predicted and the measured values of peak strength (qu)

for non-reinforced by cement-water ratio (C/W)

132

C.20 Values of µ, σ, COV, RI, and RD obtained from comparison of peak

strength (qu) for non-reinforced

133


for fiber length 10 mm by cement-water ratio (C/W)

133


strength (qu) for fiber length 10 mm

134



135



136



136



137

C.27 Summary of the predicted and the measured values of flexural strength

(f1) for non-reinforced by cement-water ratio (C/W)

139

C.28 Values of µ, σ, COV, RI, and RD obtained from comparison of flexural

strength (f1) for non-reinforced

140

C.29 Summary of the predicted and the measured values flexural strength (f1)


140

C.30 Values of µ, σ, COV, RI, and RD obtained from comparison of flexural


141

C.31 Summary of the predicted and the measured values of flexural

strength(f1) for fiber length 10 mm by cement-water ratio (C/W)

142


strength (qu) for non-reinforced

143

x


TABLE PAGE

C.33 Summary of the predicted and the measured values of flexural strength

(f1) for fiber length 10 mm by cement-water ratio (C/W)

143


strength (qu) for fiber -reinforced

144

xi

LIST OF FIGURES

FIGURE PAGE

2.1 Flexible Pavement and Rigid Pavement Cross-Section 5

2.2 Typical stress distribution under a rigid and a flexible pavement 5

2.3 Methods of soil reinforcement 14

3.1 Schematic diagram following procedures to conduct the research 23

3.2 Palm fibers 24

3.3 The length of fiber in this study 25

3.4 Gradations of Ayutthaya in this study 27

3.5 Compression loading machine 28

3.6 Detail of load cell 29

3.7 LVDT which have capacity of 20 mm for global vertical displacement

measurement

29

3.8 Hammer for cylinder mold 33

3.9 Specimen preparation for unconfined compression test 34

3.10 Hammer for beam mold 36

3.11 Specimen preparation flexural strength test 38

3.12 The relationships between dry density , drymaxγ (g/cm3) and fiber content

(%) at UC and FS test

39

3.13 Unconfined compression test apparatuses and set up 41

3.14 The flexural strength test 43

3.15 Load-net deflection curve from flexural performance test (ASTMC1609) 44

3.16 Definition of equivalent ductility ratio DT,150R 45

4.1 The comparison of stress-strain relationships between different

cement content (%)

48

4.2 The comparison of stress-strain relationships between different fiber

length and different fiber content for cement content 3%

50



52



54

xii

LIST OF FIGURES (Cont'd)

FIGURE PAGE

4.5 The comparison of stress-strain relationships between samples this study

and previous researches

54

4.6 The relationships between strain index (D) and different fiber content

(%) at different cement content (%)

57

4.7 The comparison of strain index (D) at different fiber content between

samples this study and previous researches

57

4.8 The relationships between toughness ratio and different fiber content (%)

at different cement content (%) for different fiber length

59

4.9 Relationships between peak strength (qu) and different fiber content (%)

and different cement content (%)

62

4.10 Comparison of peak strength (qu) of the different fiber length (mm),

fiber content (%) and cement content (%)

63

4.11 The comparison of the peak (qu) with different fiber content (%) between


64

4.12 The comparison of the peak (qu) with different fiber length (mm) between


64

4.13 Relationships between load-deflection curves at different cement content 65

4.14 Relationships between load-deflection curves at different fiber length and

different fiber content for cement content 3%

67



69



71

4.17 The comparison of load-deflection curves between samples this study


72

4.18 The relationships between flexural strength, f1 (MPa) with

fiber content (%) at different fiber length (mm) and different cement

content (%)

73

xiii


FIGURE PAGE

4.19 The comparison of flexural strength f1 (MPa) between samples this study


74

4.20 The relationships between the residual strength at deflection of L/150,

RS150 (MPa) at different fiber length (mm) and different fiber content

(%)

76

4.21 The relationships between the toughness at deflection of L/150, TD150

(N-m) at different fiber length (mm) and different fiber content (%)

77

4.22 The relationships between the equivalent flexural strength, R D 150 (%)

at different fiber length (mm) and different fiber content (%)

78

4.23 The comparison of the equivalent flexural strength, R D 150 (%) between


79

4.24 Relationships between UCS (qu) and the cement-water ratio (C/W) for

non-reinforced specimen

80

4.25 Relationships between UCS (qu) and the cement-water ratio (C/W) for

fiber-reinforced specimen

82

4.26 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for non-reinforced specimen

84

4.27 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for fiber-reinforced specimen

86

4.28 The relationship between flexural strength (f1) and compressive

strength(qu)

89

4.29 The relationship between flexural strength (f1) ratio and compressive

strength (qu) ratio

89

4.30 Comparison of peak strength (qu) between the predicted and the

measured values at different fiber content (%), fiber length (mm) and

cement content (%)

91



cement content (%) R2 = 0.9816

91

xiv


FIGURE PAGE



cement content (%)

92




92

4.34 Comparison of flexural strength (f1) between the predicted and the


cement content (%)

94




94



cement content (%)

95




95

A.1 The relationships between strain index (D) and fiber content (%) various

fiber length (10mm, 20mm, and 40 mm) at different cement content 108

C.1 Relationships between UCS (qu) and the cement-water ratio (C/W) for


115

C.2 Relationships between UCS (qu) and the cement-water ratio (C/W) at

dfferent fiber content (0.5%, 1.0% and 2.0%) for fiber length 10 mm

116


different fiber content (0.5%, 1.0% and 2.0%) using the average of Bqu

of 1.5096 for fiber length 10 mm

116

C.4 Relationships between Aqu and fiber content for fiber length 10 mm (%) 117

xv


FIGURE PAGE


different fiber content (0.5%, 1.0% and 2.0%) for fiber length 20 mm

118




119

C.7 Relationships between Aqu and fiber content (%) for fiber length 20 mm 119

C.8 Relationships between UCS (qu) and the cement-water ratio (C/W)

different at fiber content (0.5%, 1.0% and 2.0%) for fiber length 40 mm

121


different fiber content (0.5%, 1.0% and 2.0%) using the average of

Bqu of 1.6617 for fiber length 40 mm

121

C.10 Relationships between Aqu and fiber content (%) for fiber length 40 mm 122

C.11 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for non-reinforced

123

C.12 Relationships between FS (f1) and the cement-water ratio (C/W) at


124


different fiber content (0.5%, 1.0% and 2.0%) using the average of Bf1


124

C.14 Relationships between Af1 and fiber content (%) for fiber length 10 mm 125



126




127




129

xvi


FIGURE PAGE




129


C.21 Comparison of peak strength (qu) between the predicted and the

measured values for non-reinforced

132


measured values for fiber length 10 mm

134



135



137


measured values at different fiber content (%) and fiber length (mm)

138



R2 = 0.9816

138

C.27 Comparison of flexural strength (f1) between the predicted and the

measured values

139



141



142



144


measured values between the predicted and the measured values at

different fiber content (%) and fiber length (mm)

145

xvii


FIGURE PAGE



different fiber content (%) and fiber length (mm) R2 = 0.9816

145

xviii

LIST OF SYMBOLS

SYMBOL

Unit

b the width of the specimen m

C weight of cement g

d the depth of the specimen m

F weight of fiber g

FC fiber content %

f flexural strength kPa

f1 first peak strength MPa

fp peak strength MPa

Gs specific gravity g/cm3

Gsf specific gravity of fibers g/cm3

L span length m

L0 length 10 mm mm

L/150 the deflection at the end of test mm

P load kN

P1 first peak N

Pp post-peak N

qu the maximum compressive stress kPa

R2 r-square equal

RDT,150 equivalent flexural strength ratio %

TD the toughness ratio

TD150 the area under the load-net deflection curve since the

origin until the end of test where deflection is L/150

N-m

TDfiber the toughness of the fiber-reinforced

TDno-fiber the toughness of no fiber

V the volume of cylindrical cm3

Ws weight of dry soil g

Ww weight of water g

X cement content %

xix

LIST OF SYMBOLS (Cont'd)

SYMBOL

Unit

fiber∆ axial strain at a peak strength of fiber-reinforced kPa

no-fiberΔ axial strain at a peak strength of no-fiber kPa

dry(max)ρ weight of maximum dry density

µ average

σ stard devition

σa axial stress

xx

LIST OF TECHNICAL VOCABULARY AND ABBREVIATIONS

ACI = american Concrete Institute

Al2O3 = aluminum oxide

ASTM = american Society for Testing and Materials

CAH = calcium aluminate hydrate

CaO = calcium oxide

Ca (OH) 2 = calcium hydroxide

C3A = calcium aluminate

C4AF = tetracalcium aluminoferrite

CBR = california bearing ratio

CCFS = cement-fiber-sand

CSH = calcium silicate hydrate

C2S = dicalcium silicate

C3S = tricalcium silicate

C/W = cement/water ratio

D = the strain index

DOH = standard for highway construction

Fe2O3 = ferric oxide

FS = flexural strength test

g = gram

HDPE = high density polyethylene

HMA = hot mix asphalt

LVDT = linear variable displacement transducer

MDD = maximum Dry Density

MgO = magnesium oxide

MPa = megapascal

m = metre

mm = milli metre

N = newton

OMC = optimum moisture content

PET = polyester fibers

PP = polypropylene fibers

xxi

LIST OF TECHNICAL VOCABULARY AND ABBREVIATIONS (Cont'd)

PVA = polyvinyl alcohol fibers

RD = ranking distance

RI = ranking index

SO3 = sulfur trioxide

SiO2 = silicon dioxide

UC = unconfined compression strength test

UCS = unconfined compression strength

1

CHAPTER 1 INTRODUCTION

1.1 Introduction In general, the construction of a roadway to be able to resist the weight of cars and a

heavy traffic load, the properties of the material should also meet the standard. The

roadway is consisting of different layers. For example, surface course, base course, sub-

base course, and selected material. Normally, there will be some soils as a part of the road

construction. Soil can often be considered as a combination of four basic types: gravel,

sand, clay, and silt. The soil can resist a certain degree of compression and shear stresses.

However, it can rarely sustain tensile stresses and some natural soils do not have tightness

such as sand. Sometimes, the poor soils are usually an unavoidable problem due to a lot

of the development of constructing projects. Cause the soils are not enough to adapt to

the growth rate in infrastructure. So civil engineers employ several techniques to deal

with these problems is soil stabilization. The methods of stabilization can be divided into

three groups that are chemical stabilization, mechanical stabilization or a combination of

both techniques (Tran, et al., 2018a; Tran, et al., 2018b). However, Chemical stabilization

is an extensively used soil improvement techniques inbound pavement applications. The

addition of chemical additives such as cement, lime and fly ash usually results in a

material with lower compressibility and higher strength in comparison with natural soil.

Portland cement is commonly used as a cementing agent for this stabilization. Even with

higher strength and lower compressibility after chemical stabilization (Chinkulkijniwat

and Horpibulsuk, 2012) the stabilized material exhibits brittle behavior under

compression and flexural loading (Sukontasukkul and Jamsawang, 2012; Onyejekwe and

Ghataora, 2014).

Tensile strength of soil could be improved by adding fibers into the soil. This method

consists of two general ways: random and oriented or systematic. In random addition,

fibers are added to the bulk of the soil and essentially disappear in the compound while

in the oriented method, they are positioned in an orderly manner in the soil. The second

method, which includes geo-synthetics, has been widely studied by researchers. A

conceptual study of the technical literature reveals that fibers are used in six civil

engineering practices: road construction, retaining walls, embankments, slope

2

stabilization, earthquake, and soil-foundation engineering (Tajdini, et al., 2017). The type

of fiber plays a significant role in soil stabilization properties because the different fiber

types lead to the differences in physical properties of fibers (e.g. length, diameter, surface,

and water absorption). According to original properties, fibers are divided into two groups

including synthetic fibers and natural fibers. Many researchers investigated the synthetic

fibers in soil reinforcement such as steel, polypropylene, cotton, nylon, etc. because of its

uniformity and reproducibility. However, it has been suggested that natural resources may

provide superior materials for improving soil structure, based on their cost-effectiveness

and environment-friendly aspects (Prabakar and Sridhar, 2002). Moreover, the surface

of the synthetic fibers is smooth. It results in weak bonding surface in soil stabilization.

In contrast, natural fibers have a rough surface, which produces better bonding strength

of fiber and soil particles in the fiber-soil matrix. Some types of natural fibers have been

indicated that they showed good performance in soil stabilization such as coir, flax, jute,

corn silk, straw, etc.

Palm fiber was chosen for this study due to its reliable strength and bulk availability in

Thailand. Oil palm belongs to the species Elaeis guineensis of the family Palmacea and

originated in the tropical forests of West Africa. Currently under intensive industrial in

cultivation in Southeast Asia, The palm fibers in date production have filament textures

with special properties such as low costs, plenitude in the region, durability, lightweight,

tension capacity and relative strength against deterioration (Yusoff, et al., 2010).

Unconfined compression strength (UCS), California Bearing Ratio (CBR) and

compaction tests were performed on neat and palm fiber reinforced soil samples by

(Marandi, et al., 2008). They found that at a constant palm fiber length, with increase in

fiber content (from 0% to 1%), the maximum and residual strengths were increased, while

the difference between the residual and maximum strengths was decreased. A similar

trend was observed for constant palm fiber inclusion and increase in palm fiber length

(from 20 mm to 40 mm). Ahmad, et al. (2010) mixed palm fibers with silty sand soil to

investigate the increase of shear strength during triaxial compression. The specimens

were tested with 0.25% and 0.5% content of palm fibers of different lengths (i.e. 15 mm,

30 mm and 45 mm). Reinforced silty sand containing 0.5% coated fibers of 30 mm length

exhibited approximately 25% increase in friction angle and 35% in cohesion compared

to those of unreinforced silty sand.

3

1.2 State of the Problem

From literature, a number of comprehensive researches have been conducted to

investigate the engineering properties of the palm fiber mixed silty sand (Ahmad, et al.,

2010). These researches were focusing on the engineering properties of palm fiber mixed

silty sand under static loading. However, there was few researches to investigate the

engineering properties of cemented sand mixed with palm fiber for using this mixed

material as a base or sub base layer of the pavement structure.

1.3 Objective of Study

1. To investigate the engineering properties of cement-sand with reinforced palm fiber.

2. To propose empirical equation to predict engineering properties of cement-sand with

reinforced palm fiber with different mixing ratios.

1.4 Scope and Limitation

A systematic series of unconfined compression test (UC) and flexural strength test (FS)

of cemented-sand with palm-fiber. The palm fiber is prepared with lengths 10 mm, 20

mm, and 40 mm at four different volume fractions: 0.0 %, 0.5 %, 1.0% and 2.0 %. Type

I Portland cement available in Thailand market is utilized as admixture by 3 %, 5 %, and

7 % by dry soil. The curing period of specimens is fixed at 28 days.

1.5 Expected Benefit 1. To know the deformation characteristics of cemented sand improved with palm fiber.

2. To forecast the engineering properties of cement-sand with reinforced palm fiber.

CHAPTER 2 LITERATURE REVIEW

2.1 Pavement The pavements can be classified based on the structural performance into two, flexible

pavements and rigid pavements. Difference between flexible and rigid pavements is based

on the manner in which the loads are distributed to the subgrade. Before we differentiate

between flexible pavements and rigid pavements, it is better to first know about them.

Details of these two are presented below.

2.1.1 Flexible Pavements Flexible pavement can be defined as the one consisting of a mixture of asphaltic or

bituminous material and aggregates placed on a bed of compacted granular material of

appropriate quality in layers over the subgrade. Water bound macadam roads and

stabilized soil roads with or without asphaltic toppings are examples of flexible

pavements. The design of flexible pavement is based on the principle that for a load of

any magnitude, the intensity of a load diminishes as the load is transmitted downwards

from the surface by virtue of spreading over an increasingly larger area, by carrying it

deep enough into the ground through successive layers of granular material. Thus for

flexible pavement, there can be grading in the quality of materials used, the materials with

a high degree of strength are used at or near the surface. Thus the strength of subgrade

primarily influences the thickness of the flexible pavement.

2.1.2 Rigid Pavements A rigid pavement is constructed from cement concrete or reinforced concrete slabs.

Grouted concrete roads are in the category of semi-rigid pavements. The design of rigid

pavement is based on providing a structural cement concrete slab of sufficient strength to

resists the loads from traffic. The rigid pavement has rigidity and high modulus of

elasticity to distribute the load over a relatively wide area of soil. Minor variations in

subgrade strength have little influence on the structural capacity of a rigid pavement. In

the design of a rigid pavement, the flexural strength of concrete is the major factor and

not the strength of subgrade. Due to this property of pavement, when the subgrade deflects

5

beneath the rigid pavement, the concrete slab is able to bridge over the localized failures

and areas of inadequate support from subgrade because of slab action.

Figure 2.1 Flexible Pavement and Rigid Pavement Cross-Section

(Source: Ruenkrairergsa, 2000)

2.1.3 Rigid and Flexible Pavement Characteristics The primary structural difference between a rigid and flexible pavement is the manner in

which each type of pavement distributes traffic loads over the subgrade. A rigid pavement

has a very high stiffness and distributes loads over a relatively wide area of subgrade a

major portion of the structural capacity is contributed by the slab itself. The load carrying

capacity of a true flexible pavement is derived from the load distributing characteristics

of a layered system Figure2.3 shows load distribution for a typical flexible pavement and

a typical rigid pavement.

Figure 2.2 Typical stress distribution under a rigid and a flexible pavement


6

Table 2.1 Difference between Flexible Pavements and Rigid Pavements


2.1.4 Pavements structure

1. Embankment Material

Embankment Material is earthen material which originally come from canal, road, or

from others places and has been used for purpose of raising the grade of a roadway. It has

no more than 4% of Lab C.B.R. and has 95% of the standard proctor density according

to the Department of Public Works and Town & Country Planning 2203-57: as well as

Flexible Pavement Rigid Pavement

1. It consists of a series of layers with the

highest quality materials at or near the

surface of pavement.

It consists of one layer Portland

cement concrete slab or relatively

high flexural strength.

2. It stability depends upon the aggregate

interlock, particle friction and cohesion.

It is able to bridge over localized

failures and area of inadequate

support.

3. Its stability depends upon the aggregate

interlock, particle friction and cohesion.

Its structural strength is provided by

the pavement slab itself by its beam

action.

4. Pavement design is greatly influenced by

the subgrade strength.

Flexural strength of concrete is a

major factor for design.

5. It functions by a way of load distribution

through the component layers.

It distributes load over a wide area of

subgrade because of its rigidity and

high modulus of elasticity.

6. Temperature variations due to change in

atmospheric conditions do not produce

stresses in flexible pavements.

Temperature changes induce heavy

stresses in rigid pavements.

7. Flexible pavements have self-healing

properties due to heavier wheel loads are

recoverable due to some extent.

Any excessive deformation

occurring due to heavier wheel loads

are not recoverable, i.e. settlements

are permanent.

7

the C.B.R. Standard Test or no less than the standard which has been set on the

construction plan.

2. Subgrade Course Subgrade is the in-situ material on which the pavement structure is placed. The subgrade

must be able to support loads transmitted from the pavement structure.

3. Subbase Course

Subbase course is between the base course and the subgrade. It functions primarily as

structural support but it can also: 1. Minimize the intrusion of fines from the subgrade

into the pavement structure. 2. Improve drainage. 3. Minimize frost action damage. 4.

Provide a working platform for construction. The subbase generally consists of lower

quality materials than the base course but better than the subgrade soils. A subbase course

is not always needed or used. For example, a pavement constructed over a high quality,

stiff subgrade may not need the additional features offered by a subbase course so it may

be omitted from design. However, a pavement constructed over a low quality soil such as

swelling clay may require the additional load low quality soil such as swelling clay may

require the additional load distribution characteristic that a subbase course can offer. In

this scenario the subbase course may consist of high quality fill used to replace poor

quality subgrade (over excavation). C.B.R. Standard Test shouldn’t be less than 25% out

of 95 of the Modified Proctor Density as referred on the Department of Public Works and

Town & Country Planning the standard 2203-57 as well as the C.B.R. Standard Test

which has been set on the construction

4. Base Course

Base course is the layer directly below the surface course and generally consists of

aggregate (either stabilized or unstabilized). The Material in this base course are crushed

limestone, soil aggregate - Use the High quality of Materials because this base course are

received by the high density of stresses. In certain situations where high base stiffness is

desired, base courses can be constructed using a variety of HMA mixes

5. Surface Course

Surface course is the top layer support descending load bearing capacity with the highest

load bearing capacity for supporting traffic loads. It provides characteristics such as

8

friction, smoothness, noise control, rut resistance and drainage. In addition, it prevents

entrance of surface water into the underlying base, subbase and subgrade.

2.2 Soil Stabilization

About 3000 years ago, soil improvement technique were employed by Babylonians to

build Babylon temples, In the same period Chinese utilized wood and straw to reinforce

the soil.

The soil available on a project site might not meet all the engineering requirements for

the intended purpose. In some cases, the soil might not even be desirable for simple

engineering construction. Engineers can avoid problematic soils by either changing the

project site or replacing the undesirable soil with suitable soils from a nearby site. In early

days of constructions of highways, bridges, and buildings, soil replacement methods were

widely employed. However, with increasing use of land and growth of cities, highways

and industrial zones, decisions to avoid the use of poor grounds are less frequently made

and ground improvement methods have been developed extensively (Lambe and

Whitman, 1979).

Hogentogler (1938) once said soil stabilization was processed that helping any kind of

natural soils being able to bare any surface and also be able to bear the weight of roadways

without disasters. We can better the soil’s quality by increasing the compaction or control

the visual image in the laboratory room, by far, the Optimum Moisture Content (OMC)

is the important part, and also with the admixture.

Improvement of soil quality (Ruenkrairergsa, 1982). There are several ways to improve

soil quality, each of which varies in practice, depending on the suitability and purpose of

use. Improvement of soil quality by cement is as follows.

1. Stabilization by Treatment

2. Mechanical Stabilization

3. Cement Stabilization

4. Lime and Lime Fly Ash Stabilization

5. Bituminous Stabilization

6. Lignin Stabilization

9

7. Molasses Stabilization

8. Chemical Stabilization

Soil improvement is a process carried out to achieve improved geotechnical properties

and engineering response of a soil or earth material at a site (Nicholson, 2014).

Hausmann (1990) asserts that, the process can be achieved by methods like

1. Mechanical Modification

In this technique, external mechanical forces are used to increase soil density, including

soil compaction by using methods like static compaction, dynamic compaction, and deep

compaction by heavy tamping (Hausmann, 1990; Nicholson, 2014).

2. Hydraulic Modification

In this technique, pore-water is forced out of the ground through drains or wells. Lowering

the groundwater level by pumping from trenches or boreholes can be applied for coarse-

grained or cohesion-less soils. However, for fine-grained or cohesive soils, application of

the long-term of external pressure (preloading) or electrical loads (electro kinetic

stabilization) is used (Nicholson, 2014).

3. Physical and Chemical Modification

One example of this method is soil stabilization by physically mixing/blending additives

with top layers at depth. Additives can be natural soils, industrial by-products or waste

materials; and other chemical materials that can react with the soil or ground: Other

applications are soil/ground modification by grouting and thermal modifications

(Hausmann, 1990; Nicholson, 2014).

4. Modification by inclusions and confinement

This technique is considered as strengthening soil by materials such as meshes, bars,

strips, fibers, and fabrics corresponding to the tensile strengths. Confining a site with

steel, or fabric elements can also form stable-earth retaining structures (Hausmann, 1990).

Soil reinforcement method falls under this category and it’s further elaborated in the next

section.

10

2.3 Soil Cement Stabilization

2.3.1 Physical and Chemical Properties of cement Cement that has been mostly used to stabilize soil is Portland cement. Type I but we can

also use other Portland cements or mixed cement which derived from mixing Portland

cement type I with an inert material like sand, or limestone approximately 25%. Cement

is very well-known and has been used world-wide because it is easy to find, has a steady

property, has its own standard both inland and abroad, and we can adapt it for the

construction very easily. That’s why the Department of State Highways always uses

cement. The main components of cement are C3S, C2S, C3A, and C4AF.

2.3.2 False Set and the Hardening of Cement Cement mixing with water will create cement paste which once was a liquid and we call

this process by dormant period, then, paste will gradually set even sometimes it quite soft

which we called Initial Set until then we will called it initial setting time. The paste’s

setting still working on, up until it transfers into solid cement or what we called Final Set

and the timing during this process called the Final Setting Time. Until then, paste will be

able to up lift the weight and all of these processes are called hardening

Table 2.2 Showing the main proportion of cement


Quality C3S C2S C3A C3F

Hydration ratio of

cement

Fast

(hour)

Slow

(day)

Immediately Very fast

(minute)

The development of

compression ratio

Fast

(day)

Slow

(Sunday)

Very fast

( 1day)

Very fast

(1 day)

Compressive Strength Medium Little Low Low

Heating from

hydration

Medium

(500J/g)

Little

(200J/g)

Very high

(850J/g)

Medium

(420J/g)

11

2.3.3 How to Increase Cement’s Compressive Strength Ways to increase cement’s Compressive Strength came mainly from Cement Hydration

which is pretty much the same as Cement Hydration that occurs in concrete. Whenever

cement touches the water, something will happen during the process and it’s called

Cement Hydration. The result from it will release Calcium Silicate Hydrate (CSH),

Calcium Aluminate Hydrate (CAH) and Calcium Hydroxide (Ca (OH) 2). Calcium

Silicate Hydrate (CSH), Calcium Aluminate Hydrate (CAH) is what will vise the cement.

While Calcium Hydroxide (Ca (OH) 2) which was released from Hydration will associate

with soil silica and soil alumina as follow. As a result, it will create Calcium Silicate

Hydrate (CSH) and Calcium Aluminate Hydrate (CAH). The Cement Hydration can be

explained in the term of equation as the following:

2 2Cement + H O CSH + CAH + Ca(OH)→ (2.1)

++ -2Ca(OH) Ca + 2(OH)→ (2.2)

++ -2Ca + 2(OH) + Soil Silica(SiO ) CSH→ (2.3)

++ -2 3Ca + 2(OH) + Soil Alumina(Al O ) CAH→ (2.4)

Therefore, we can notice that Cement Hydration in soil will create Calcium Silicate

Hydrate (CSH) and Calcium Aluminate Hydrate (CAH) which has collet ability as we

can see from the equation number (2.1), (2.3), and (2.4). The equation number (2.1)

showing us that Calcium Silicate Hydrate (CSH) and Calcium Aluminate Hydrate (CAH) are from Cement Hydration which we normally called Primary Reaction. On the other

hand, the equation number (2.3) and number (2.4) will create other substances later, so,

it will affect the capacity of each material to be gradually strong which is called Secondary

Reaction or Pozzolanic Reaction.

2.3.4 How to Design the Cement’s Mixture

Cement soil is considered one of the Cement Stabilization in order to be used as a material

is filling on the roadways like base and sub-base. The Department of State Highways has

12

been applied this method with roadways construction for longer than 30 years since it

help us solving problems like the lack of material to build roadways or streets and also to

help us increase the baring load of the road as well which could lead to the less disaster

in the future, by the way, at least the roadways will surely be longer lasting. The main

proportions of cement are consisting of aggregate, cement, and water. The way we mix

up each substance will help us find the right balance that suitable for the wanted

compressive strength or as required as on the plan which has to be done before the

construction get started. Whoever involves this method should have past experiences and

professional on this field to find the right amount of cement and the way we test it. In a

practical way, each of us who is doing this job might has different perspective, different

angle of detail, or even different way to test it. For example, the right amount of cement

proportion or the analysis of Unconfined Compressive Strength which each right for each

amount of cement; so as a result, it will give us the different kind of outcomes. How we

design the cement’s mixture is considered the very important part of the process as

required on the standard of the Department of State Highways, for instance.

- Standard No. DOH-S 203/2532 “Cement Modified Crushed Rock Base”

- Standard No. DOH-S 204/2533 “Soil Cement Base”

- Standard No. DOH-S 204/2533 “Soil Cement Subbase”

Ruenkrairergsa (2000) reported that as he has been studying under the topic of roadways

construction from cement since 1965-1972 and how he has been learned how to design,

testing the roadways during 1972-1982, and the balance of Unconfined Compressive

Strength after 7 days construction is 250 psi which is right in Thailand. The amount of

cements are around 3 -5 % and the construction should spend around 7 days and 200-

300 psi. The field compaction should not less than 95%, and modified compaction

should be around 15 cm. The protection of Reflective Crack is to allow people to use the

roadways after finishing the construction and left it with water for 3 days after finished

the prime coat and should covered it with asphalt, leave it there for 1-2 months. The

duration depends up on soil properties and how busy the traffic is.

13

Table2.3 Showing how the Department of State Highways mixes cement


Pavement Unconfined Compressive Strength

(Curing 7 day)

Standard No. DH-S 203/2532 “Cement

Modified Crushed Rock Base”

Not less than 350 psi (24.6 ksc.)

Standard No. DH-S 204/2533 “Soil

Cement Base”

Not less than 250 psi (17.5 ksc)

Standard No. DH-S 204/2533 “Soil

Cement Subbase”

Not less than 100 psi (7.0 ksc)

2.4 Fiber Reinforcement Soil reinforcement as one of the ground/soil improvement techniques, is a process of

using synthetic or natural additive materials to improve the soil/ground characteristics or

properties (Hausmann, 1990). Soil reinforcement with randomly distributed fibers can be

done by using either natural fibers or synthetic fibers

2.4.1 Soil Reinforcement Using Natural and Synthetic Fibers Soil can often be regarded as a combination of four basic types: gravel, sand, clay, and

silt. It generally has low tensile and shear strength and its characteristics may depend

strongly on the environmental conditions (e.g. dry versus wet). On the other hand,

reinforcement consists of incorporating certain materials with some desired properties

within other material which lack those properties. Therefore, soil reinforcement is defined

as a technique to improve the engineering characteristics of soil in order to develop

parameters such as shear strength, compressibility, density, and hydraulic conductivity.

Mainly, reinforced soil is a composite material consisting of alternating layers of

compacted backfill and man-made reinforcing material. So, the primary purpose of

reinforcing soil mass is to improve its stability, to increase its bearing capacity, and to

reduce settlements and lateral deformation. The standard fiber-reinforced soil is defined

as a soil mass that contains randomly distributed, discrete elements, i.e. fibers, which

provide an improvement in the mechanical behavior of the soil composite. Fiber

reinforced soil behaves as a composite material in which fibers of relatively high tensile

14

strength are embedded in a matrix of soil. Shear stresses in the soil mobilize tensile

resistance in the fibers, which in turn imparts greater strength to the soil. Mainly, the use

of random discrete flexible fibers mimics the behavior of plant roots and contributes to

the stability of soil mass by adding strength to the near-surface soils in which the effective

stress is low. In this way, laboratory and some in situ pilot test results have led to

encouraging conclusions proving the potential use of fibers for the reinforcement of soil

mass providing an artificial replication of the effects of vegetation (Abtahi, et al., 2009).

2.4.1.1 Classification

A comprehensive literature review shows that short fiber soil composite can be

considered as a coin with two sides. One side includes the randomly direct inclusion of

fibers into the matrix, i.e. soil mass. Another side comprises the oriented fibrous

materials, e.g. Geo-Synthetics family. It is emphasized that the former concept is not as

well-known as the second, not only in optimizing fiber properties, fiber diameter, length,

surface texture, etc. but also in reinforcing mechanism. McGown (1978) classified soil

reinforcement into two major categories including ideally inextensible versus ideally

extensible inclusions. The former includes high modulus metal strips that strengthen soil

and inhibits both internal and boundary deformations. Catastrophic failure and collapse

of soil can occur if reinforcement breaks. Ideally extensible inclusions include relatively

low modulus natural and/or synthetic fibers, plant roots; and geosynthetics. They provide

some strengthening but more importantly they present greater extensibility (ductility);

and a smaller loss of post-peak strength compared to the neat soil (Savastano, et al., 2000).

Figure 2.3 Methods of soil reinforcement

(Source: Hejazi, et al., 2012)

15

2.4.1.2 Natural fibers

At the present time, there is a greater awareness that landfills are filling up, resources are

being used up, the planet is being polluted and that non-renewable resources will not last

forever. So, there is a need for more environmentally friendly materials. That is why there

have been many experimental investigations and a great deal of interest has been created

worldwide on potential applications of natural fibers for soil reinforcement in recent

years. The term ‘‘eco-composite’’ shows the important role of natural fibers in the

modern industry. Mainly, what part of the plant the fiber came from, the age of the plant;

and how the fiber was isolated, are some of the factors which affect the performance of

natural fibers in a natural fiber reinforced soil. It is necessary to mention that natural fibers

have been used for a long time in many developing countries in cement composites and

earth blocks because of their availability and low cost (Li, 2005).

1. Barely straw fibers

Barely straw is widely cultivated and harvested once or twice annually in almost all rural

areas in all over the world and could be used in producing composite soil blocks with

better characteristics, but relatively few published data is available on its performance as

reinforcement to soil or earth blocks (Hejazi, et al., 2012). It is important to know that

during the Egyptian times, straws or horsehairs were added to mud bricks, while straw

mats were used as reinforcements in early Chinese and Japanese housing construction

(Mansour, et al., 2007; Li, 2009). Abtahi, et al. (2010) showed that barley straw fibers are

most effective on the shear strength of the soil than Kenaf fibers. The optimized fiber

content was 1%.

2. Bamboo fibers

Bamboo fiber is regenerated cellulose fiber. It is a common fact that bamboo can thrive

naturally without using any pesticide. The fiber is seldom eaten by pests or infected by

pathogens. So, scientists found that bamboo owns a unique anti-bacterial and

bacteriostatic bio-agent named ‘‘Bamboo Kun’’. It is important to know that the root

rhizomes of bamboo are excellent soil binders which can prevent erosion. Bamboo fibers

are remarkably strong in tension but have a low modulus of elasticity about 33-40

kN/mm2 and high water absorption about 40-45% (Hejazi, et al., 2012). Ramaswamy, et

al. (1983) studied the behavior of concrete reinforced with bamboo fibers. The results

show that these fibers can be used with advantage in concrete in a manner similar to other

16

fibers. It seems that the combination of cement and the root rhizomes of bamboo open a

new window for soil reinforcement process (Khedari, et al., 2005).

3. Cane fibers

Cane or sugar cane belongs to grass family and grows up to 6 m high and has a diameter

up to 6 cm and bagasse is the fibrous residue which is obtained in sugarcane production

after extraction of the juice from the cane stalk. The fiber diameter is up to 0.2-0.4 mm.

However, waste cane fiber has limited use in most typical waste fiber applications

because of the residual sugars and limited structural properties within the fiber. But, the

residual sugars can result in a detrimental impact on the finished product, i.e. a stiffer

bonding phase generates in the composite structure. Therefore, ‘‘Cement Board’’

produced from sugar cane waste has been recently introduced to the market. The authors

recommend the application of these fibers in soil reinforcement as an empty research area

(Hejazi, et al., 2012).

4. Coconut (coir) fibers

The outer covering of fibrous material of a matured coconut, termed coconut husk, is the

reject of the coconut fruit. The fibers are normally 50-350 mm long and consist mainly

of lignin, tannin, cellulose, pectin, and other water-soluble substances. However, due to

its high lignin content, coir degradation takes place much more slowly than in other

natural fibers. So, the fiber is also very long lasting, with an infield service life of 4-10

years. The water absorption of that is about 130-180% and diameter are about 0.1-0.6

mm. Coir retains much of its tensile strength when wet. It has low tenacity but the

elongation is much higher. The degradation of coir depends on the medium of

embedment, the climatic conditions and is found to retain 80% of its tensile strength after

6 months of embedment in clay. Coir geo-textiles are presently available with wide ranges

of properties which can be economy economically utilized for temporary reinforcement

purposes. Mainly, coir fiber shows better resilient response against synthetic fibers by a

higher coefficient of friction. For instance, findings show that coir fiber exhibits greater

enhancements (47.50%) in resilient modulus or strength of the soil than the synthetic one

(40.0%). Ravishankar, et al. (2004) confirmed that for coir-stabilized lateritic soils, the

maximum dry density (MDD) of the soil decreases with the addition of coir and the value

of optimum moisture content (OMC) of the soil increases with an increase in the

percentage of coir. The compressive strength of the composite soil increases up to 1% of

17

coir content and the further increase in coir quantity results in the reduction of the values.

The percentage of water absorption increases with an increase in the percentage of coir.

The tensile strength of coir-reinforced soil (oven dry samples) increases with an increase

in the percentage of coir. Khedari, et al. (2005) introduced a new type of soil-cement

block reinforced with coir fibers with low thermal conductivity. Black cotton soil treated

with 4% lime and reinforced with coir fiber shows ductility behavior before and after

failure. An optimum fiber content of 1% (by weight) with aspect ratio of 20 for fiber was

recommended for strengthening the BC soil (Babu, et al., 2008).

5. Flax fibers

Flax is a slender, blue-flowered the plant is grown for its fibers and seeds in many parts

of the world. In an effort, (Segetin, et al., 2007) improved the ductility of the soil-cement

composite with the addition of flax fibers. An enamel paint coating was applied to the

fiber surface to increase its interfacial bond strength with the soil. ‘‘Uku’’ is a low-cost

flax fiber reinforced stabilized rammed earth walled housing system that has been

recently designed as a building material. In this way, a mobile flax machine is used

enabling the fast and mobile processing of flax leaves into flax fibers

6. Jute fibers

Jute is mainly environmental-friendly fiber that is used for producing porous textiles

which are widely used for filtration, drainage, and soil stabilization. For instance,

GEOJUTE is the commercial name of a product woven from jute fibers used for soil

stabilization in pavement engineering. Aggarwal, et al. (2009) used different lengths

(5 mm-20 mm) of jute fibers in different percentages (0.2%-1.0%) to reinforce soil.

7. Palm fibers

The palm fibers in date production have filament textures with special properties such as

low costs, plenitude in the region, durability, lightweight, tension capacity and relative

strength against deterioration. Fibers extracted from decomposed palm trees are found to

be brittle, having low tensile strength and modulus of elasticity and very high water

absorption.Unconfined compression strength (UCS), California Bearing Ratio (CBR) and

compaction tests were performed on neat and palm fiber reinforced soil samples by

(Marandi, et al., 2008). They reported that at a constant palm fiber length, with increase

in fiber inclusion (from 0% to 1%), the maximum and residual strengths were increased,

18

while the difference between the residual and maximum strengths was decreased.

A similar trend was observed for constant palm fiber inclusion and increase in palm fiber

length (from 20 mm to 40 mm). Ahmad, et al. (2010) mixed palm fibers with silty sand

soil to investigate the increase of shear strength during triaxial compression. The

specimens were tested with 0.25% and 0.5% content of palm fibers of different lengths

(i.e. 15 mm, 30 mm and 45 mm). Reinforced silty sand containing 0.5% coated fibers of

30 mm length exhibited approximately 25% increase in friction angle and 35% in

cohesion compared to those of unreinforced silty sand.

2.4.1.3 Synthetic (man-made) fibers

1. Polyethylene (PE) fibers

The feasibility of reinforcing soil with polyethylene (PE) strips and/or fibers has been

also investigated to a limited extent. It has been reported that the presence of a small

fraction of high-density PE (HDPE) fibers can increase the fracture energy of the soil.

Nowadays, GEOFIBERS, typically 2.5 cm-5 cm long discrete PP and/or PE fibrillated or

tape strands, are mixed or blended into sand or clay soils. But, it is important to know that

some researchers have applied the term ‘‘Geofiber’’ for PP fibers used in soil

reinforcement. Kim, et al. (2008) used PE waste fishing net (0%, 0.25%, 0.5%, 0.75%,

and 1%) to reinforce lightweight soil derived from the dredging process. They found that

the maximum increase in compressive strength was obtained for a waste fishing net

content of about 0.25%.

2. Polyester fibers (PET)

Kumar, et al. (2016) tested highly compressible clay in UCS test with 0%, 0.5%, 1.0%,

1.5% and 2.0% flat and crimped polyester fibers. Three lengths of 3 mm, 6 mm and 12

mm were chosen for flat fibers, while crimped fibers were cut to 3 mm long. The results

indicate that as the fiber length and/or fiber content increases, the UCS value will

improve. Crimping of fibers leads to increase of UCS slightly. These results are well

comparable to those found by (Tang, et al., 2007).

3. Polyvinyl alcohol fibers (PVA)

Polyvinyl alcohol (PVA) fiber is a synthetic fiber that has recently been used in fiber-

reinforced concrete, since its weather resistance, chemical resistance (especially alkaline

19

resistance), and tensile strength are superior to that of PP fiber. PVA fiber has a

significantly lower shrinkage from heat than nylon and/or polyester. It has a specific

gravity of 1.3 g/cm3, a good adhesive property to cement and high antalkali

characteristics. For this reason, it is suitable for using PVA fiber as a soil reinforcing

material. Therefore, the inclusion of PVA fiber seems to produce more effective

reinforcement in terms of strength and ductility when compared to other fibers under the

same cementation. Park (2011) found that the addition of 1% polyvinyl alcohol (PVA)

fiber to 4% cemented sand resulted in a two times increase in both the UCS and the axial

strain at peak strength when compared to non-fiber reinforced specimen.

4. Polypropylene fibers (PP)

Polypropylene fiber is the most widely used inclusion in the laboratory testing of soil

reinforcement (Yetimoglu, et al., 2005). Currently, PP fibers are used to enhance the soil

strength properties, to reduce the shrinkage properties and to overcome chemical and

biological degradation. Yetimoglu, et al. (2005) indicated that PP fiber reinforcement

enhanced the unconfined compressive strength (UCS) of the soil and reduced both

volumetric shrinkage strains and swell pressures of the expansive clays. From the

experiments on field test sections in which a sandy soil was stabilized with PP fibers.

5. Glass fibers

Consoli, et al. (1998) indicated that inclusion of glass fibers in silty sand effectively

improves peak strength. In another work, (Consoli, et al., 1998) examined the effect of

PP, PET and glass fibers on the mechanical behavior of fiber-reinforced cemented soils.

Their results showed that the inclusion of PP fiber significantly improved the brittle

behavior of cemented soils, whereas the deviator stresses at failure slightly decreased.

Unlike the case of PP fiber, the inclusion of PET and glass fibers slightly increased the

deviator stresses at failure and slightly reduced the brittleness. Studied the behavior of

kaolinite–fiber (PP and glass fibers) composites, and found that the increase in the UCS

was more pronounced in the glass fiber-reinforced specimens.

20

2.5 Case Studies of Fiber-Reinforced Soil There has been an evolution in the inclusion of fibers in the soil for reinforcement

purposes. Various researchers have conducted studies on fiber-reinforced soil and this

section summarizes some of the published research.

Tang, et al. (2007) reported increased unconfined compression strength and shear strength

of fiber reinforced uncemented/cemented low plastic clay soils with 0.05% to 0.25% short

polypropylene fibers. Unconfined compression strength of the fiber reinforced cemented

soil was found to be more than the sum of unconfined compression strength of fiber

reinforced uncemented soil and that of cemented soil. Unlike cement addition, fibers

decreased the stiffness of the treated specimens. Axial strain at failure was increased with

fiber addition posing a ductile behavior compared to brittle behavior of non-reinforced

specimen. In a similar study, (Park, 2011) also reported increased compression strength

and failure strain of fiber reinforced cemented sand.

Marandi, et al. (2008) studied the strength properties of palm fiber-reinforced sand at

different fiber contents and fiber lengths. They reported an increase in unconfined

compression peak strength, secant modulus, residual strength and failure strain with

increased fiber content and fiber length.

Sadek, et al. (2013) investigated the shear strength of fiber reinforced sand, by mixing

coarse or fine sand with nylon fishing wires as reinforcement fibers. The fibers were of

diameter 0.18mm and 0.7mm, of length ranging from 7mm to 27mm, and fiber content

inclusion ranging from 0% to 1.5% by weight of dry sand. Specific gravity and particle

size distribution tests were carried out to determine the physical properties of sand.

Whereas, nylon fishing fiber properties like length, diameter, Young’s modulus, tensile

strength, and specific gravity were determined. Furthermore, 150 direct shear tests were

performed on the fiber-sand composite at normal stress levels of 100, 150 and 200 kN/m2.

Results showed that the addition of 1% by dry sand weight of nylon fibers with an aspect

ratio of 150 and fiber length of 27mm, prepared at a relative density of 55% increased the

shear strength and ductility of the composite by 37% for coarse sand and 46.8% for fine

sand.

21

Jamsawang, et al. (2014) studied flexural strength test of sand cement improved with

polypropylene fibers. The cement content used 3%, 5% and 7% by weight of dry soil and

the fiber content was 0.5%, 0.75%, 1.0%, 1.5%, and 2.0% of the sand volume. The results

indicated the fiber inclusion significantly improves the post peak flexural behavior, which

is a requirement for bound pavement materials. The first peak flexural strength f1 and

stiffness of both compacted-cement-sand and cement-sand-fiber (CCFS) are essentially

the same for the same cement content. For low fiber content, the fiber inclusion primarily

prevents the sudden failure. The CCFS exhibits deflection-hardening behavior and the

peak flexural strength (fp) is higher than the first peak flexural strength (f1) for medium

to high fiber contents.

Jamsawang, et al. (2018) investigated the influence of seven different fiber types on the

flexural performance of compacted cement-fiber-sand (CCFS) with four fiber fractions

(0.5%, 1.0%, 1.5% and 2% by volume). The seven types of fibers are 12mm

polypropylene, 19mm polypropylene, 40mm polypropylene, 55mm polypropylene,

33mm steel, 50mm steel and 58mm polyolefin fibers. The overall CCFS performance was

divided into seven sub design performance indicators peak strength, peak strength ratio,

residual strength ratio, ductility index, toughness, equivalent flexural strength ratio, and

maximum crack width. The interaction mechanism of the fiber/cement-sand interface was

investigated by scanning electron microscopy. Finally, the effectiveness of each fiber type

was compared and rated in terms of the overall performance. The results show that the

50mm steel fiber provided the best overall sub performance, resulting in an excellent

overall flexural performance; in comparison, the 12mm polypropylene fiber exhibited

very poor performance. However, the 19mm polypropylene and 33mm steel fiber

specimens provided very good and good overall performances, respectively. The nature

of the fiber surface and the fiber length affects the overall performance of CCFS. The

surface of the steel fibers, compared to the other synthetic fiber types, is more hydrophilic

and is more compacted in a cemented sand matrix without separation of the interfacial

zone, providing the best overall flexural performance.

Tran, et al. (2018a) study considered the effect of the additive amount of fibers (0.5%,

1.0%, 1.5%, and 2.0%) as well as the fiber lengths (10 mm, 30 mm, and 50 mm) on the

mechanical properties of fiber reinforced soil by using compaction test, unconfined

compression test, and splitting tension test. The results indicated that the addition of

22

cornsilk fibers in soil improved mechanical properties including compressive strength,

splitting tensile strength, ductility, toughness, and stiffness. Typically, the highest

increase of maximum unconfined compressive strength was about 38% when using the

fiber content of 1% and the fiber length of 10 or 30 mm. The most increase of failure

splitting tensile strength was 210.5% with the fiber content of 2% and the fiber length of

50 mm. It can be concluded that cornsilk fibers showed good performance in soil

stabilization, seemed to be a good fiber material to modify soil, and should be concerned

in future.

Tran, et al. (2018b) study focused on exploring the effects of cornsilk fibers on

mechanical properties of cemented soil by conducting compaction, compression, and

splitting tension tests. The influences of fiber content (0%, 0.25%, 0.5%, and 1% by

weight of dry soil), cement content (4%, 8%, and 12% by weight of dry soil), and curing

time (7, 14, and 28 days) were investigated in the present work. The multiple nonlinear

regression models following the parameters including curing time, fiber content, and

cement content for predicting compressive strength as well as tensile strength were

established. The effective degree of each parameter on compressive and tensile strength

was also evaluated. The experimental results revealed that the addition of cornsilk fibers

in cemented soil improved the compressive and splitting tensile strength. The fiber

contents of 0.25%–0.5% are recommended to use in cemented soil reinforced by cornsilk

fibers. Splitting tensile strength equals to 0.148 times of compressive strength for both

cemented soil and fiber-cement stabilized soil. The compressive and tensile strength

could be predicted following the regression models with high accuracy. Based on the

proposed model and sensitivity analysis, the cement content is the most effective

parameter affecting on compressive strength and splitting tensile strength followed by

curing time and fiber content.

CHAPTER 3 METHODOLOGY 3.1 Introduction This research is to study the engineering properties of palm fibers mixed with sand and

cement for backfilling in the construction of road structure. It is necessary to study its

strength and deformation characteristics. In this study, the characteristics of palm-sand-

cement mixtures were investigated by a series of unconfined compression tests (UC) and

flexural strength test (FS). The mixtures in this study were prepared by mixing: a) Palm

fibers; b) Ayutthaya sand; and c) Portland cement, together at different mixing ratios.

Figure 3.1 shows the schematic diagram following procedures to conduct the research.

Figure 3.1 Schematic diagram following procedures to conduct the research

Methodology

Geotechnical laboratory tests

Research Study

Preparing sample - Cement content (by weight of dry soil) 3%, 5%, and 7% - Length (mm); 10 mm, 20mm, and 40mm - Fiber content (by volume); 0.0%, 0.5%, 2.0%, and 2.0%

Unconfined compression tests

Flexural strength tests

Test results

Analysis and Discussion

Conclusions

24

3.2 Materials in Laboratory Test

3.2.1 Palm Fibers Palm fibers were extracted from empty fruit bunches from oil palm by the retting process.

The palm fibers were brought from Chumphon province, Thailand as shown in Figure

3.2. In this study, palm fibers were prepared with different lengths of 10 mm, 20 mm, and

40 mm. The different volume fraction: 0.0%, 0.5%, 1.0%, and 2.0 % by volume were

according to (Sukontasukkul, et al., 2012; Jamsawang, et al., 2018). The properties of

these palm fibers given in Table 3.1.

(a) palm fruit (b) empty bunch

(c) palm fibers in this study

Figure 3.2 Palm fibers

25

Table 3.1 Properties of palm fiber

Palm fiber Value

Specific gravity (g/cm3) 1.91

Shape Straight

Section Circular

Length (mm) 10-80

Color White

Maximum Load (N) 234.10

Tensile strength (MPa) 4.80

Average diameter (mm) 0.60

Elongation at break (%) 29

*The samples was tested Bureau of Science and Technology Research and Service King- Mongkut's University of Technology Thonburi

(a) fiber length 10 mm (b) fiber length 20 mm

(c) fiber length 40 mm

Figure 3.3 The length of fiber in this study

26

3.2.2 Ayutthaya Sand Ayutthaya sand which is popularly used for mixing with cement and aggregate to make

concrete for construction in Thailand was used in this study. Specific gravity test of this

sand was determined following the recommended procedures given in ASTM D854-97.

Sieve analyses were performed to determine the particle size distribution of sand

following the procedures given in ASTM D422-63 and compaction test (modified

proctor) were performed to determine maximum dry density ( dry maxρ ) and optimum

moisture content (OMC) of sand following the procedures given in ASTM D1557-00.

Table 3.2 and Figure 3.4 summarize some index properties of this sand and its gradation,

respectively.

Table 3.2 Index properties of Ayutthaya sand

Soil Properties Values

D10 (mm) 0.27

D30 (mm) 0.47

D60 (mm) 0.86

Specific Gravity, Gs 2.66

Uniformity coefficient, Cu 3.24

Coefficient of gradation, Cc 0.97

USCS classification SP

Compaction Test ( modified proctor)

Maximum dry density, dry maxρ (g/cm3) 1.95

Optimum moisture content, OMC (%) 10.50

27

Figure 3.4 Gradations of Ayutthaya in this study

3.2.3 Portland Cement Portland cement used in this study is for Portland cement type I. The fraction of cement

in the mixture is 3%, 5% and 7% by weight of dry soil.

Table 3.3 Properties and Classifications of Cement

Parameter Cement

Silicon Dioxide, SiO2 (%) 20.61

Aluminum Oxide, Al2O3 (%) 5.03

Ferric Oxide, Fe2O3 (%) 3.03

Sulfur Trioxide, SO3 (%) 2.70

Calcium Oxide, CaO (%) 64.89

Magnesium Oxide, MgO (%) 1.43

Specific gravity 3.15

Loss of ignition (%) 1.23

Classification Ordinary Portland cement

type I-grade 53

0.1 1 100

20

40

60

80

100

Perce

nt Fin

er (%

)

Particle Size (mm)

28

3.3 Test apparatuses Displacement-controlled compression loading machine shown in Figure 3.5 with a

capacity of about 50 kN. Compression is provided by moving up the bottom plate of the

loading frame at a constant rate which can be selected at the speed control panel in front

of the apparatus. This apparatus was used in performing unconfined compression tests

(UC) and flexural strength tests (FS) by continuous monotonic loading at a constant rate

until the failure of the specimen to obtain the maximum vertical stress values.

Figure 3.5 Compression loading machine

3.4 Measuring Devices

3.4.1 Load cell A load cell was used for a measure of axial load applies to the specimen. The body of

load cell made from Phosphor Bronze (C5212P) having a shape as shown in Figure 3.6

Speed control panel

Bottom plate

Loading direction control panel

Power switch

29

(a). Four strain gages manufactured by Kyowa Co. Ltd., Japan were glued on the top of

the load cell’s body as shown in Figure 3.6 (b) with adhesive (Hirakawa, et al., 2002).

Figure 3.6 Detail of load cell

(a) the body of load cell

(b) attachment of four strain gages on the top

surface of load cell body

3.4.2 Linear variable displacement transducer (LVDT) The LVDT was used for the external measurement of vertical strain from the axial

displacement of the loading piston as shown in Figure 3.7. The calibration result is

presented as a relationship between the known displacement and the output voltage.

(a) (b)

Figure 3.7 LVDT which have capacity of 20 mm for global vertical displacement

measurement

30

3.5 Preparations of Tested Samples

3.5.1 Method preparation of sand cement and palm fiber The specimens were prepared in the laboratory, it can be achieved as the ratio of these

components. The derivation of mixing components can be described as followings; and

the amount of sand, water, cement and fiber used in Eq. (3.1), Eq. (3.2), Eq. (3.3) and Eq.

(3.4), respectively.

s dry(max)W = ρ ×V (3.1)

w dry(max)W = ρ × V × OMC (3.2)

dryXC = ρ × V ×

100 (3.3)

ffF = × V × Gs

100 (3.4)

Where: sW = weight of dry soil (g.)

wW = weight of water (g.)

C = weight of cement (g.) F = weight of fiber (g.) dry(max)ρ = weight of maximum dry density (g/cm3)

V = the volume of cylindrical (cm3) OMC = optimum moisture content (%) X = cement content (%)

f = fibers content (%)

fGs = specific gravity of fibers (g/cm3)

31

3.5.2 Test Preparations

3.5.2.1 Prepartion of sand-cement-palm fiber specimen for unconfined

compression test (UC)

Sand-cement-palm fibers mixture specimens were prepared by following procedures;

1. Cylinder molds having 75 mm in diameter and 150 mm in height were cleaned by

using tissue paper soaked with acetone. Then, inner surfaces (i.e., side and bottom)

were smeared with a thin layer of grease.

2. Assemble all the parts of the mold by fastening all fasteners of mold.

3. Prepare palm fiber, sand, and cement portions with resection to different ratios of

palm

fiber-sand-cement by weight each portion separately. Then, prepare tap water to attain

optimum water content as obtained from the modified proctor test according to

ASTM D1557-00.

4. The dry sand and cement were mixed until the mixture acquired a uniform consistency

(about 3 min). Then palm fibers add for mix together on an aluminum tray. After that

the water was added to the cement-fiber-sand mixture to attain optimum water content

(OMC) and mixed thoroughly for 5 min until a homogeneous paste was created.

5. Dividing the wet mixture into five portions

6. Pour the wet mixture in the prepared mold until the height of each lift becomes slightly

higher than one five of the mold’s height.

7. Compact the wet mixture by a rammer having a weight of 25 N and drop height of

0.45 m for 32 blows per lift (Table 3.4). Repeat steps 6 and 7 four lifts in total until

the wet mixture fulfils the mold. Therefore, the energy used in compaction for

preparing unconfined compression specimens in this study was about 2,700 kN-m/m3,

which is in accordance with ASTM D1557-00.

8. Smoothen the top surface of the specimen by using a sharp edge. Then, seal the

specimen within the mold by a sheet of plastic film with bands, then specimen was

cured inside the mold.

9. Carefully extract the specimen from the mold.

10. Warp the specimen again with additional layers of plastic film to ensure that the water

applied in the mixture is not lost due to evaporation.

11. Seal the plastic film together by glued-tap at both top and bottom ends of the

32

specimen.

12. Label each specimen with information on mixing ratio and date of preparation. Then,

keep all the prepared specimens in temperature and moisture-controlled room at

23 ±2°C for 28 days. (After 28 days, cementation products from hydration process

complete)

13. The specimens were considered suitable for testing if they met following tolerances:

the dry unit weight degree of compaction was between 99% and 101% shown in

Figure 3.12 (a) and diameter was within 5 mm, and the height was with 1 mm

proposed by (Festugato, et al., 2017; Moreira, et al., 2018)

Table 3.4 Detail of compaction used for cylinder mold in this study

Items Properties

Diameter (mm) 75

Height (mm) 150

Volume(m3) 6.627 x10-4

Weight of hammer (N) 25

Height of hammer drop (m) 0.45

Number of layers 5

Number of blows 32

Energy input (kN-m/m3) 2,700 (modified proctor)

33

Figure 3.8 Hammer for cylinder mold

(a) (b)

(c) (d)

Sand Water

Palm fibers Cement

0.45 m

25 N

34

(e) (f)

(g) (h)

Figure 3.9 Specimen preparation for unconfined compression test

(a) cylinder mold (b) surfaces were smeared with a thin layer of grease (c) portions of the specimen including palm fibers, sand, cement,

and water

(d) mixing all the mixing portions

(e) filling the wet mixture into the cylinder mold

(f) compaction the material

(g) wrap the specimen by plastic film

(h) specimen after cured 28 days

3.5.2.2 Prepartion of sand-cement-palm fiber specimen for flexural strength test

Sand-cement-palm fibers mixture specimens were prepared by following procedures;

35

1. Beam molds having 100 mm wide, 100 mm deep, and 350 mm long, were cleaned by

using tissue paper soaked with acetone. Then, inner surfaces (i.e., side and bottom)

were smeared with a thin layer of grease.

2. Assemble all the parts of the mold by fastening all fasteners of mold.

3. Prepare palm fiber, sand, and cement portions with resection to different ratios of palm

fiber-sand-cement by weight each portion separately. Then, prepare tap water to attain

optimum water content (OMC) as obtained from the modified proctor test according

to ASTM D1557-00.

4. The dry sand and cement were mixed until the mixture acquired a uniform consistency

(about 3 min). Then palm fibers add for mix together on an aluminum tray. After that

the water was added to the cement-fiber-sand mixture to attain optimum water content

(OMC) and mixed thoroughly for 5 min until a homogeneous paste was created.

5. Dividing the wet mixture into five portions.

6. Pour the wet mixture in the prepared mold until the height of each lift becomes slightly

higher than one five of the mold’s height.

7. Compact the wet mixture by a rammer having a weight of 50 N. and drop height of

0.45 m. for 84 blows per lift (Table 3.4). Repeat steps 6 and 7 four lifts in total until

the wet mixture fulfills the mold. Therefore, the energy used in compaction for

preparing unconfined compression specimens in this study was about 2,700 kN-m/m3,

which is in accordance with ASTM D1557-00.

8. Smoothen the top surface of the specimen by using a sharp edge. Then, seal the

specimen within the mold by a sheet of plastic film with bands, then specimen was

cured inside the mold.

9. Carefully extract the specimen from the mold.

10. Warp the specimen again with additional layers of plastic film to ensure that the water

applied in the mixture is not lost due to evaporation.

11. Seal the plastic film together by glued-tap at both top and bottom ends of the

specimen.

12. Label each specimen with information on mixing ratio and date of preparation. Then,

keep all the prepared specimens in temperature and moisture-controlled room for

28 days. (After 28 days, cementation products from hydration process complete)

13. The specimens were considered suitable for testing if they met following tolerances:

36

the dry unit weight degree of compaction was between 98% and 102% shown in

Figure 3.12 and diameter was within 5 mm, and the height was with 1 mm proposed

by (Festugato, et al., 2017; Moreira, et al., 2018).

Table 3.5 Detail of compaction used for beam mold in this study.

Items Properties

Wide (mm) 100

Deep(mm) 100

Long(mm) 350

Volume(m3) 3.5x10-3

Weight of hammer (N) 50

Height of hammer drop (m) 0.45

Number of layers 5

Number of blows 84

Energy input (kN-m/m3) 2,700 (modified proctor)

Figure 3.10 Hammer for beam mold

0.45 m

50 N

37

(a) (b)

(c) (d)

(e) (f)

Water Sand

Palm fibers Cement

38

(g) (h)

Figure 3.11 Specimen preparation flexural strength test

beam loading compression test

(a) beam mold (b) surfaces were smeared with a thin layer of grease (c) portions of the specimen including palm fibers, sand,

cement, and water

(d) mixing all the mixing portions

(e) filling the wet mixture into the cylinder mold

(f) compaction the material

(g) wrap the specimen by plastic film

(h) specimen after cured 28 days

39

(a) unconfined compression test (UC)

(b) flexural strength test (FS)

Figure 3.12 The relationships between dry density , drymaxγ (g/cm3) and fiber content (%)

at UC and FS test

0.0 0.5 1.0 1.5 2.01.85

1.90

1.95

2.00

2.05Cement content (%) Length (mm) nofiber 10 20 40 3 5 7

-2% lower-bound

+2% upper-bound

γdry max

Dry

dens

ity, γ

dry

max

(g/c

m3 )

Fiber content (%)

0.0 0.5 1.0 1.5 2.01.85

1.90

1.95

2.00

2.05

Cement content (%) Length (mm) nofiber 10 20 40 3 5 7

-2% lower-bound

+2% upper-bound

γdry max

Dry

dens

ity, γ

dry

max

(g/c

m3 )

Fiber content (%)

40

3.6 Evaluations of Geotechnical Engineering Properties 3.6.1 Unconfined Compression Test (UC) In order to perform unconfined compression tests on sand cement palm fiber mixture

specimens, the following procedures were employed when using compression loading

machine. This test was conducted in accordance with ASTM D2166-06 standard.

1. After specimens were cured for 28 days, the wrapped plastic films were removed.

Then, the diameter and height of the specimen were measured, each for three random

locations for one specimen, and then averaged. Then, the weight of each specimen

was determined.

2. The test equipment was set up as shown in Figure 3.10. Suspend the top cap of

specimen together with the load cell (20 kN) by locking the clamp. Then, input the

calibration factor of the load cell to the sampling program and perform zero-setting

on the physical value read from the load cell.

3. Place the sand-cement-palm fiber specimen on the pedestal. Then, apply small amount

of gypsum paste on the top end of specimen. Subsequently, lower the cap to place on

the gypsum paste. This provides the full contact between the top of specimen and

the cap.

4. Place the specimen in the loading device so that it is centered on the bottom platen.

Adjust the loading device carefully so that the upper platen just makes contact with

the specimen. zero the deformation indicator. apply the load so as to produce an axial

strain at the rate of ½ to 2% min. In this study use rate 1.50 min/mm

5. LVDT was used to measure the vertical displacement of specimen.

6. Start to let computer control such that the vertical stress acting on the specimen was

kept at 5kPa.

41

Figure 3.13 Unconfined compression test apparatuses and set up

3.6.1.1 Calculations Procedures of Unconfined Compression Test Results

Calculations of compressive stress and axial strain according to Eq. 3.5 and Eq. 3.6

a0

Fσ A

= (3.5)

Where: aσ = compressive stress (kPa)

F = vertical force measured by load cell (kN)

0A = cross-sectional area of specimen prior to compression (m3)

Strain values presented in this study were defined as:

aΔHε = -H

(3.6)

Where: aε = axial strain measured by LVDT (%)

LVDT

Load cell

Chamber

Specimen

Compression machine

42

ΔH = change in height of specimen (mm)

0H = initial height of specimen (mm)

3.6.2 Flexural Strength Test (FS) In order to perform flexural strength test on sand cement palm fiber mixture specimens,

the following procedures were employed when using apparatus A. This test was

conducted in accordance with ASTM C1609-10:

1. After specimens were cured for 28 days, the wrapped plastic films were removed.

Then, the wide, height and long of the specimen were measured, each for three

random locations for one specimen, and then averaged. Then, the weight of each

specimen was determined.

2. The test equipment was set up as shown in Figure 3.11(a) and Figure 3.11(b), the

applied load was measured using 20-kN load cell. Two linear variable differential

transducers (LVDTS) were attached to a reference beam to measure the deflection at

the middle of the tested beam.

3. Then, input the calibration factor of the load cell to the sampling program and perform

zero-setting on the physical value read from the load cell.

4. Started the test and the deflection rate of 0.05 mm/min was controlled by an electric

motor and the test was stopped at a net deflection of 4.0 mm.

(a) test specimen and setup

(Source: Jamsawang, et al., 2018)

43

(b) apparatuses for test

Figure 3.14 The flexural strength test

3.6.2.1 Calculations Procedures of Flexural Strength Test Results

Calculations of flexural strength according to Eq. 3.7, toughness and equivalent flexural

strength ratio according Eq. 3.8.

2

PLf = bd

(3.7)

Where: f = flexural strength (kPa)

P = load (kN)

L = span length (m)

Compression machine

Two LVDT

Load cell

Specimen Reference beam

Support

Ball bearing

44

b = the width of the specimen (m)

d = the depth of the specimen (m)

Figure 3.15 Load-net deflection curve from flexural performance test (ASTMC1609)

(Source: Kim, et al., 2008)

toughness or energy absorption based on the area under load-deflection curve up to

prescribed deflection by a plot from an origin to a target deflection at L/150, the method

by (ASTM C1018-97) as shown in Figure 3.15. The equivalent flexural strength ratio is

the ratio of the area under the load versus deflection relationship to the product of first

peak load (P1) times the deflection at L/150 as shown in Figure 3.16.

D

D 150T,150

1

TR = ×100%P (L/150)

(3.8)

Where: DT,150R = equivalent flexural strength ratio (%)

D150T = the area under the load-net deflection curve since the

origin until the end of test where deflection is

L/150 (N-m)

45

1P = first peak load (N)

L/150 = the deflection at the end of test

(a) D

T,150R < 100% (b) DT,150R > 100%

Figure 3.16 Definition of equivalent ductility ratio DT,150R

(Source: Jamsawang, et al., 2018)

3.7 Indices for Verification of the Empirical Equation There are two indices that can indicate the precision as well of the prediction which are

i) ranking index (RI) and ii) ranking distance (RD). The details of these indices are

explained as follows. K expressed the mean (µ) and the standard deviation (σ) statistics

of the ratio of the estimated compression index to the laboratory-determined compression

index, which is determined by the following equation:

predicted

measured

AK =

A (3.9)

If A is the value of interest, Apredicted and Ameasured are the corresponding values predicted

by the empirical equation and measured from the experiment, respectively. The ratio of

Apredicted to Ameasured is defined as K as follows Eq. 3.9. The mean of K has ability to

represent the accuracy of correlation (Briaud and Tucker, 1988). On the other hand,

precision of correlation could be defined by the standard deviation of K (Briaud and

Tucker, 1988). It has to remark that the minimum of K is 0 but the maximum is infinity

with an optimum value of one. The ranking index (RI) is the method to relieve the

46

problem of nonsymmetrical distribution of the K data. This RI was introduced by (Briaud

and Tucker, 1988). The RI expresses a whole judgment on the quality of correlation while

taking into consideration the mean value and the standard deviation of all K data. RI is

determined by the following equation:

(ln[K]) (ln[K])RI = μ +σ (3.10)

On the other hand, the ranking distance (RD) is the method that represents an overall

judgment on the quality of a calculation method that takes into consideration the mean

value and the standard deviation of all the K data. The particular concept was applied to

develop the RD formula. This formula consists of mean values (µK) and the standard

deviation (σK) which are plotted on the x-axis and y-axis, respectively. RD is the distance

from optimum condition coordinate (1, 0) which is determined by Eq. 3.11 (Cherubini

and Orr, 2000):

2 2K KRD = (1-μ ) +(σ ) (3.11)

3.8 Test Program The unconfined compression (UC) and the flexural strength test (FX), specimens with

different lengths of 10 mm, 20 mm, and 40 mm at three different volume fraction: 0.0%,

0.5%, 1.0%, and 2.0 % by volume.

Table 3.6 Test program implemented in the present study

Test Cement content

(%)

Fiber content

(%)

Fiber length

(mm.)

Number of

test

specimen

Unconfined compression

test (UC)

3 0, 0.5, 1.0, 2.0 10, 20, 40 30

5 0, 0.5, 1.0, 2.0 10, 20, 40 30

7 0, 0.5, 1.0, 2.0 10, 20, 40 30

Flexural

strength test (FS)

3 0, 0.5, 1.0, 2.0 10, 20, 40 30

5 0, 0.5, 1.0, 2.0 10, 20, 40 30

7 0, 0.5, 1.0, 2.0 10, 20, 40 30

Total 180

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Introduction This chapter presents the testing results and analysis of unconfined compression test (UC)

and flexural strength test (FS) of sand cement which are improved by palm fibers.

An empirical equation to predict engineering properties of mixed material was proposed.

4.2 Unconfined Compression Test (UC) The unconfined compression test (UC) of cement- sand improved with palm fibers under

controlled unit weights of 1.95 g/cm3 and were conducted for different cement content

(3%, 5% and 7% weight of dry soil), fiber content ( 0.0%, 0.5%, 1.0% and 2.0% of by

volume) and fiber lengths (10 mm, 20 mm and 40 mm).

4.2.1 Stress-Strain Behaviors

Figure 4.1 showed the relationships between stress-strain curves for non-reinforced

cemented sand at cement content 3%, 5% and 7%. The result showed the axial stress

increases with axial strain up to maximum peak then the axial stress decreases with

increasing axial strain (sharp strain softening). It can be seen the axial stress increase with

an increase in axial strain until the peak value after that the axial stress sudden drop. It is

indicated that the brittle behavior is presented. For the maximum compressive stress (qu)

of adding cement 5% and 7%, it increases in the range of 6.2-10.3 times when compared

to the cement ratio of 3%. It can be said that the peak strength (qu) increases with the

cement content increase for cement 3%, 5%, and 7%.

48

Figure 4.1 The comparison of stress-strain relationships between different

cement content (%)

Figure 4.2 (a) to 4.2 (c) showed the relationships between stress-strain curves for fiber-

reinforced at cement content 3% with different fibers content (0.5%, 1.0%, and 2.0%)

and different fiber length (10 mm, 20 mm, and 40 mm). In this study, the axial strain at

the end of the test which is equal to 6 % was defined as the residual strain. Figure 4.2 (a)

showed the adding of fiber content 0.5%. After reaching peak stress, the axial stress

rapidly decreases with the increasing axial strain (sharp strain softening). However, the

residual stress increases with increasing fiber length (10 mm < 20 mm < 40 mm). For

samples with adding fiber 1.0 % (Figure 4.2 (b)) and 2.0 % (Figure 4.2 (c)), the sharp

softening behavior can still be seen. However, the residual stress (post-peak) increased

with increasing fiber content (0.5 % < 1.0 % < 2.0%). The maximum compressive stress

(qu) of adding fiber 0.5% to 2.0% increased in the range of 1.1-2.8 times when compared

to the no-fiber case.

0 1 2 3 4 50

500

1000

1500

2000

2500

3000non-reinforced

Cement 7%

Cement 5%

Cement 3%

Axia

l stre

ss, σ

a (kP

a)

Axial strain, εa (%)

Cement content 3% Cement content 5% Cement content 7%

49

(a) fiber content 0.5%

(b) fiber content 1.0%

0 1 2 3 4 5 60

100

200

300

400

500

600

700

800

no fiber

Cement content 3%, Fiber content 0.5%Length, L (mm) no fiber 10 20 40

L 20 mm

Axia

l stre

ss, σ

a (kP

a)


L 40 mm

L 10 mm

0 1 2 3 4 5 60

100

200

300

400

500

600

700

800

no fiber


Axia

l stre

ss, σ

a (kP

a)


L 10 mm

L 20 mm

L 40 mm

50

(c) fiber content 2.0%

Figure 4.2 The comparison of stress-strain relationships between different fiber length

and different fiber content for cement content 3%

Figure 4.3 (a) to 4.3 (c) stress-strain curves for fiber-reinforced at cement content of 5%

with different fibers content (0.5 %, 1.0%, and 2.0%) and different fiber length (10 mm,

20 mm, and 40 mm). In this study, the axial strain at the end of the test which is equal to

6 % was defined as the residual strain. The sharp softening behavior occurred for samples

with adding fiber 0.5% to 2.0%. Moreover, the maximum compressive strength decreases

with increasing fiber content. It decreased in the range of 0.7-0.9 times when compared

to the no-fiber specimen. These results indicated that increasing the fiber content leads to

a slight reduction in the strength of reinforced soil-cement. However, adding fiber to soil-

cement causes the brittleness of soil-cement to be decreased and its ductility is increased

by increasing the fiber length (10mm < 20 mm < 40 mm). It can be seen from

Figure 4.2 (b) to 4.4 (c), the initial slopes of stress-strain curves for samples reinforced

with fiber lengths of 20 mm and 40 mm are less than that of no-fiber.

0 1 2 3 4 5 60

100

200

300

400

500

600

700

800

900

no fiber


Axia

l stre

ss, σ

a (kP

a)


L 10 mm

L 20 mm

L 40 mm

51



0 1 2 3 4 5 60

500

1000

1500

2000Cement content 5%, Fiber content 1.0%Length, L (mm) no fiber 10 20 40

no fiber

Axia

l stre

ss, σ

a (kP

a)


L 40 mm

L 20 mm

L 10 mm

0 1 2 3 4 5 60

500

1000

1500

2000Cement content 5%, Fiber content 0.5%Length, L (mm) no fiber 10 20 40

no fiber

Axia

l stre

ss, σ

a (kP

a)


L 40 mm

L 20 mm

L 10 mm

52




Figure 4.4 (a) to 4.4 (c) showed the relationships between stress-strain curves for fiber-

reinforced at cement content 7% with different fibers content (0.5%, 1.0%, and 2.0%)

and different fiber length (10 mm, 20 mm and 40 mm). In this study, the axial strain at

the end of the test which is equal to 6 % was defined as the residual strain. The results are

consistent with the cement ratio of 5%. The maximum compressive strength decreases

with increasing fiber content. It decreased in the range of 0.6-1.1 times when compared

to the no-fiber specimen. However, both the rate of softening decreases and residual stress

increases with increasing fiber content (0.5 %< 1.0 %< 2.0%) and fiber length (10 mm<

20 mm< 40 mm). In detail, the sharp softening behavior appeared for samples with adding

fiber of 0.5 % whereas the rate of softening decreases and residual stress slightly increases

from the non-fiber samples. The residual stress is larger and clearly seen when fiber

content reached 2.0% with fiber length 40 mm. Moreover, comparing the same fiber

content and fiber length at different cement content, the fiber provides more effective for

the samples with lower cement. While higher cement content samples tend to present a

lower performance when increasing the fiber length and fiber content.

0 1 2 3 4 5 60

500

1000

1500

2000


no fiber

L 10 mm

L 20 mm

Axia

l stre

ss, σ

a (kP

a)


L 40 mm

53

A comparison of a stress-strain curve with previous research is shown in Figure 4.5. The

results indicate that the efficiency of fiber on ductility improvement of cemented sand

strongly depends on the fiber content. As it is seen in this Figure, both of the residual

stress and the strain at failure increased with increasing fiber content. This reduction is

increased with increasing the fiber length.



0 1 2 3 4 5 60

500

1000

1500

2000

2500

3000

no fiber


L 10 mm

L 20 mm

L 40 mm

Axia

l stre

ss, σ

a (kP

a)


0 1 2 3 4 5 60

500

1000

1500

2000

2500

3000

no fiber


Axia

l stre

ss, σ

a (kP

a)


L 40 mm

L 10 mm

L 20 mm

54




Figure 4.5 The comparison of stress-strain relationships between samples this study


0 1 2 3 4 5 60

500

1000

1500

2000

Mahapo P et al., (2015)

Sadek et al., (2013)

Tang C et al., (2007)

Axia

l stre

ss, σ

a (kP

a)


Fiber Content (%) Fiber Cement (%) Length (mm)This study., SP 0.50 2.00 Palm 5 20Tang C et al., (2007), CL 0.05 0.25 Polypropylene 5 12Sadek S et al., (2013), SP 0.25 1.00 Polypropylene 1 20Mahapo P., (2015), SP 0.50 2.00 Polypropylene 5 19

This study

0 1 2 3 4 5 60

500

1000

1500

2000

2500

3000

no fiber


Axia

l stre

ss, σ

a (kP

a)


L 40 mm

L 20 mm

L 10 mm

55

4.2.2 Effect of Fiber on Stiffness Figure 4.6 (a) to 4.6 (c) showed the relationships between axial strain index (D) of sample

with different fiber content (0.5%, 1.0% and 2.0%) and the different cement content 3%,

5% and 7% at different fiber length (10 mm, 20 mm and 40 mm). The strain index is

useful when either peak stress or a residual stress state is not clearly observed. However,

its applications are limited to the cemented specimens that have the same cement ratio

(Park, 2011). The concept of stain index (D) can be applied to evaluate the ductility or

deformability of cemented sand that is reinforced by various fibers and maybe indicate

the degree of fiber extensibility in cemented sand and aid in the selection of suitable fibers

for a given cementation (Park, 2011). The ductility measures the ability of a material to

sustain inelastic deformation prior to the collapse without a significant loss in the

resistance. The strain index (D) can be calculated by axial strain at a peak strength of

fiber-reinforced divided by axial strain at a peak strength of no-fiber ( fiber∆ / no-fiberΔ ).

Details of each data are shown in Appendix A. This results indicates that the stiffness of

the specimen was affected by addition of fiber delays failure and improves the brittle

behavior. Figure 4.6 (a) to 4.6 (c) shows the value of strain index (D) increased with

increasing both fiber content and fiber length. However, the strain index values do not

depend on the cement ratio. In other words, the lower cement content 3%, the strain index

value is higher than the strain index of cement ratio at 5% and 7 %. It concluded that the

strain index can be applied to the same cement ratio and it is not significant to cement

content. A comparison of a stain index (D) with previous research is shown in Figure 4.7.

Tang, et al. (2007) and Park (2011) studied the strain index(D) by UCS tests on cement

clays with PP fiber. It indicated that the value of strain index (D) increase with increasing

fiber content. However, it does not depend on cement content so, the result shows the

same as this study.

56

(a) fiber length 10 mm

(b) fiber length 20 mm

0.5 1.0 1.5 2.00

1

2

3

4

5

Length 10 mmCement content (%) 3 5 7

Stra

in in

dex,

D (%

)

Fiber content (%)

Cement 3%R2=0.8390

R2=0.8698

Cement 5%R2=0.6568

Cement 7%

0.5 1.0 1.5 2.00

1

2

3

4

5

6


Stra

in in

dex,

D (%

)

Fiber content (%)

Cement 3%R2=0.6433

Cement 7%

Cement 5%R2=0.6723

R2=0.8626

57

(c) fiber length 40 mm

Figure 4.6 The relationships between strain index (D) and different fiber content (%)

at different cement content (%) for different fiber length

Figure 4.7 The comparison of strain index (D) at different fiber content between


0.5 1.0 1.5 2.00

2

4

6

8

10


Stra

in in

dex,

D (%

)

Fiber content (%)

Cement 3%R2=0.6380

Cement 7%R2=0.8119

Cement 5%R2=0.8700

Fiber Length (mm) cement (%)This study, SP palm 20 3 5 7Park (2011), SP PVA 12 2 4 6

0.0 0.5 1.0 1.5 2.00

1

2

3

4

5

6

7

Stra

in in

dex,

D

Fiber content (%)

58

4.2.3 Toughness of Unconfined Compressive Strength ratio The stress-strain curves are useful to evaluate the ductility, which indicates the strain-

energy-absorption capability. This value provides the determination of specimen

toughness based on the area under the stress-strain curve up to the prescribed strain. In

this study, the area under the stress-strain curve since the origin until 5% of strain. The

toughness ratio (TD) can be calculated by the toughness of the fiber-reinforced divided by

the toughness of no fiber ( D Dfiber no-fiberT / T ). The normalized energy for these samples is 1 or

less. Details of each data are shown in Appendix A. Figure 4.8 (a) to 4.8 (c) shown the

relationships between toughness ratio with different fiber content, fiber length and

different cement content. The result indicated that the toughness ratio increases with

increasing both fiber content and fiber length for 3% cement ratio. For higher cement

ratio of 5% and 7%, the toughness increases with increasing fiber length (10mm <20 mm

<40 mm). However, for fiber content, the toughness increases with increasing fiber

content from 0% to 1% and obviously decreased at the fiber content of 2%. It concluded

that the toughness of the specimen with increases in accordance with the relationship

stress-strain occurred (Mahapo, 2015).

(a) cement content 3%

0.0 0.5 1.0 1.5 2.00

5

10

15

20

Cement content 3 %Length (mm) 10 20 40

Toug

hnes

s of

UCS

ratio

, TD fib

er/ T

D no-fi

ber

Fiber content (%)

Length 40 mm

Length 20 mm

Length 10 mm

59

(b) cement content 5%

(c) cement content 7%

Figure 4.8 The relationships between toughness ratio and different fiber content

(%) at different cement content (%) for different fiber length

0.0 0.5 1.0 1.5 2.00

1

2

3

4

5

6


Toug

hnes

s of

UCS

ratio

, TD fib

er/ T

D no-fi

ber

Fiber content (%)

Length 40 mm

Length 20 mm

Length 10 mm

0.0 0.5 1.0 1.5 2.00

1

2

3

4

5

6


Toug

hnes

s of

UCS

ratio

, TD fib

er/T

D no-fi

ber

Fiber content (%)

Length 40 mm

Length 20 mm

Length 10 mm

60

4.2.4 Influence of Fiber Content and Fiber Length on Unconfined

Compressive Strength value Figure 4.9 (a) to 4.9 (c) shown the relationships between peak strength (qu) with different

fiber content, fiber length and different cement content. It observed that the peak strength

(qu) increase with an increase in cement content. At the cement content of 3% (Figure 4.9

(a)), the results showed the peak strength (qu) slightly increases with an increase in fiber

content (from 0% to 1.0 %). Then, it started to decrease and was constant at fiber content

2%. For the higher cement content of 5% ( Figure 4.9 (b)) and 7% ( Figure 4.9 (c)), the

strength increased with an increase in fiber content (from 0.5% to 1.0%) and obviously

decreased at fiber content of 2%. It can be concluded that fiber inclusion could be easily

distributed in the specimens and bear the pulling stress inside when the fiber content is

relatively low (0.5%-1.0%). However, it would be hard to combine the fiber at the fiber

content 2% because of excessive fiber inclusion can muddle together in some parts of the

specimens (Sadek, et al., 2013; Chen, et al., 2015; Sharma, et al., 2015). Furthermore, the

fiber bonds and tensile strength provided by fibers were the main sources of improvement

for specimens with low cement contents (3%). Nevertheless, for the specimens with a

higher cement content (5% and 7%) appears that the cementation effect became the

dominant source of improvement. So, excessive fiber does not further assist in increasing

the strength of improved soil. This could be explained that at low cement content or early

age. The hydration reaction products are low in quality as well as quantity. Thus, the

fibers in cement-soil matrix play an important role in the increase of compressive

strength. On the other hand, with the increase of cement content or curing time, the

number and quality of hydration reaction products increase. As a result, the effect of fibers

on improving compressive strength decreases (Chen, et al., 2015; Tran, et al., 2018a; Wei,

et al., 2018).

Strengh of reinforced cemented sand increased with increasing fiber length as shown in

Figure 4.9 (a) to 4.9 (c). At the low cement content (cement 3%) shown in Figure 4.9 (a),

the peak strength clearly increased with increasing fiber length because the fiber can be

to the bonds between soil particles provided by fiber reinforcement (Chen, et al., 2015).

However, for the higher cement content (cement 5% and 7%) are shown in Figure 4.9 (b)

to 4.9 (c). The cement ratio effect was the main influencing factor on the ductility of

61

specimen and more than the effects of a fiber length. Details of each data are shown in

Appendix A.



0.0 0.5 1.0 1.5 2.00

200

400

600

800

1000


Length 40 mm

Length 20 mm

Length 10 mm

Peak

stre

ngth

, qu

(kPa

)

Fiber content (%)

0.0 0.5 1.0 1.5 2.00

500

1000

1500

2000


Length 10 mm

Length 20 mm

Length 40 mm

Peak

stre

ngth

, qu

(kPa

)

Fiber content (%)

62


Figure 4.9 Relationships between peak strength (qu) and different fiber content (%)

and different cement content (%)

Comparison of peak strength (qu) of the different fiber length, fiber content and cement

content show in Figure 4.10. To obtain the highest strength, the optimum fiber length and

fiber content for the different cement ratio (3%, 5% and 7%) is 40 mm and 1.0%,

respectively.

0.0 0.5 1.0 1.5 2.00

500

1000

1500

2000

2500

3000

3500


Length 10 mm

Length 20 mm

Length 40 mm

Peak

stre

ngth

, qu

(kPa

)

Fiber content (%)

63

Figure 4.10 Comparison of peak strength (qu) of the different fiber length (mm),

fiber content (%) and cement content (%)

A comparison of peak strength (qu) of different type of fiber reinforced soil at different

fiber content (%) with previous researches is shown in Figure 4.11. The peak strength

increased with from 0.5% to 1.0% of fiber inclusion. Then, strength gradually decreased

when a fiber content was higher than 1.0 %. Figure 4.12 shows a comparison of peak

strength (qu) of different type of fiber reinforced soil at different fiber length with previous

researches. At similar fiber content, the longer fiber could improve strength more than

the specimen with a shorter fiber. However, the excessive fiber length will cause the

compressive strength slightly reduced. Figure 4.10 and 4.11 conclude that the type of fiber

has a greater effect than fiber attending into soil cement fiber matrix. The matrix depends

on various physical factors, such as the internal friction of the fibers with soil-cement and

mechanical factors such as the modulus of elasticity of the fibers, which vary with a

change in the fibers and, therefore, affect the tensile strength of the materials (Tajdini, et

al., 2017).

0.0 0.5 1.0 1.5 2.0

0

500

1000

1500

2000

2500

3000

3500Cement Content, C Length, L (mm) (%) 10 20 40 3 5 7

Peak

stre

ngth

, qu

(kPa

)

Fiber content (%)

C7%L40mm

C7%L10mm

C5%L10mm

C3%L10mmC3%L20mm C3%L40mm

C5%L20mm

C5%L40mm

C7%L20mm

64

Figure 4.11 The comparison of the peak (qu) with different fiber content (%) between


Figure 4.12 The comparison of the peak (qu) with different fiber length (mm) between


0.5 1.0 1.5 2.0

0

500

1000

1500

2000

2500

3000

Sharma, et al.(2015), Grewia

Mahapo P.(2015), steelMahapo P.(2015), Polypropylene

Tran, et al.(2018), CornsilkSharma, et al.(2015), Pinus

This study, palm

Anggraini, et al.(2015), Coir

Peak

stre

ngth

, qu

(kPa

)

Fiber content (%)

Fiber Length(mm) This study, SP palm 20 cement 3% This study, SP palm 20 cement 3% Anggraini, et al.(2015), Soft Clay coir 5-15 lime 5% Sharma, et al.(2015), SC Grewia Optivia 730 cement 2.5% Sharma, et al.(2015), SC Pinus Roxburghii 324 cement 2.5% Mahapo P. (2015), SP polypropylene 19 cement 5% Mahapo P. (2015), SP steel 33 cement 5% Tran, et al. (2018), Clay conrnsilk 30 -

5 10 15 20 25 30 35 40

0

250

500

750

1000

1250

Chen, et al. (2015), F0.5C1.0Chen, et al. (2015), F0.5C0.5

Chen, et al. (2015), F1.0C0.5

This study F0.5C5Chen, et al. (2015), F1.0C1.0

This study F1.0C5

Sadek S, et al. (2013), F0.5C8

Peak

stre

ngth

, qu

(kPa

)

Length (mm)

Fiber Fiber content, F (%) Cement, C (%) This study,SP palm 0.5 1.0 5.0 Sadek S, et al. (2013),SP polypropylene 0.5 1.0 0.5 0.5 1.0 1.0 Chen, et al. (2015), soft soil polypropylene 0.5 8.0

65

4.3 Flexural Strength Test (FS) The flexural strength test (FS) has been done by using four-point bending test. Curing

time is 28 days. The specimens of cement-sand improved with palm fibers under

controlled unit weights of 1.95 g/cm3 and were conducted for different cement content

(3%, 5% and 7% weight of dry soil), fiber content ( 0.0%, 0.5%, 1.0%, and 2.0% of by

volume) and fiber lengths (10 mm, 20 mm and 40 mm).

4.3.1 Behavior of Load-Deflection Curves Figure 4.13 showed the relationships between loads versus net deflection at different

cement content (3%, 5% and 7%). The result showed the load non-reinforced at cement

3%, 5%, 7% increased linearly with increasing net defection. It increases until the first

peak load (P1). After that, the load suddenly decreased and no residual load after the first

crack occurred. The Figure shows the shape softening behavior so, the first peak (P1) and

post-peak (Pp) are the same values.

Figure 4.13 Relationships between load-deflection curves at different cement content

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

500

1000

1500

2000

2500

Cement 5%

Cement 7%


Load

, P1 (

N)

Net deflection (mm)

Cement 3%

L/600 L/150 L/100

non-reinforced

66

Figure 4.14 (a) to 4.14 (c) show the relationships between loads versus net deflection with

different fiber content (%), fiber length (mm) at cement content 3%. For the samples with

adding fiber content shows the load-deflection are two-stage addressed. The first stage

represented by the linear part before the crack occurred, while the second stage shows the

sample behavior after samples cracked. It indicated to see the effect of fiber reinforcement

on the soil cement. In the first stage, the load was applied and increases linearly with the

net deflection until the load hits the maximum after this point, there is a sudden drop of

the load with increases net defection (P1 = PP). However, the load for adding fiber started

to increases again. It did not exceed the maximum load in the first stage (softening). It

illustrates the fiber bridging effect helped to control the rate of energy release which is

characteristic of ductile response (Anggraini, et al., 2015). The behavior shows defection-

softening at the same of non-reinforced. Figure 4.14 (a) to 4.14 (c) shows the loads versus

net deflection after the post-peak (PP) increases with increasing fiber content (0.5% <

1.0% < 2.0%) and fiber length (10 mm < 20 mm< 40 mm).

(a) length 10 mm

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

200

400

600

800

1000

no fiber

F 2.0%

F 1.0% F 0.5%

L/100L/150

Load

, P1 (

N)

Net deflection (mm)

L/600

Cement content 3 % , Length 10 mm Fiber content, F (%) no fiber 0.5 1.0 2.0

67

(b) length 20 mm

(c) length 40 mm

Figure 4.14 Relationships between load-deflection curves at different fiber length


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

200

400

600

800

1000

no fiber

F 2.0%

L/100L/150L/600

Load

, P1 (

N)

Net deflection (mm)

F 1.0%

F 0.5%


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

200

400

600

800

1000

no fiber

L/100L/150L/600

Load

, P1 (

N)

Net deflection (mm)

F 2.0%

F 1.0%

F 0.5%


68

Figure 4.15 (a) to 4.15 (c) showed the relationships between loads versus net deflection

with different fiber content (%), fiber length (mm) at cement content 5%. The results

show a similar with specimen with cement 3%. The load carrying capacity depend on

fiber length (10 mm < 20 mm < 40 mm) and fiber content (0.5% < 1.0% < 2.0%).The

deformation behavior exhibited defection-softening.

(a) length 10 mm

(b) length 20 mm

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

500

1000

1500

2000

Load

, P1 (

N)

Net deflection (mm)

L/600 L/150 L/100

F 2.0%

F 1.0%F 0.5%

no fiber


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

500

1000

1500

2000

F 0.5%

Load

, P1 (

N)

Net deflection (mm)

L/600 L/150 L/100


F 2.0%

F 1.0%

no fiber

69

(c) length 40 mm



Figure 4.16 (a) to 4.16 (c) showed the relationships between loads versus net deflection

with different fiber content (%), fiber length (mm) at cement content 7%. It is presented

softening behavior as well as cement ratio 3% and 5%. Before the first peak (fp), the

tension occurred at the bottom side of the beam, then it extended up over the beam

thickness until the beam cracks. These the cracks are caused by the sand-cement matrix.

For the post-peak (Pp), the fiber-reinforced started to work which calls the residual

strength (Alskif, 2016).

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

500

1000

1500

2000

2500

3000

no fiber

F 0.5%

F 1.0%

F 2.0%

Load

, P1 (

N)

Net deflection (mm)

L/600 L/150 L/100


70

(a) length 10 mm

(b) length 20 mm

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

1000

2000

3000

4000

no fiber

F 0.5%F 1.0%

Load

, P1 (

N)

Net deflection (mm)

L/600 L/150 L/100

F 2.0%


0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

1000

2000

3000

4000

no fiber

F 0.5%F 1.0%

Net deflection (mm)

Load

, P1 (

N)

L/600 L/150 L/100

F 2.0 %


71

(c) length 40 mm



Figure 4.17 shows a comparison of load-deflection curves between samples in this study

and previous researches. The type of fiber, fiber content and fiber length effected to the

behaviors of the beam. This may indicate the behavior of hardening or softening. Due to,

bond plays an important role in improving the flexural behavior. However, the bond is

influenced by various factors such as the orientation, the shape of fiber and the surface

area of fiber.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

1000

2000

3000

4000

5000

no fiber

F 0.5%

F 1.0%

F 2.0%

Load

, P1 (

N)

Net deflection (mm)

L/600 L/150 L/100


72

Figure 4.17 The comparison of load-deflection curves between samples this study


4.3.2 First Peak Strength (f1) and Peak Strength (fp) The relationships between flexural strength (f1) with fiber content (%) at different fiber

length (10 mm, 20 mm, and 40 mm) and different cement content (3 %, 5%, and 7%) are

shown in Figure. 4.18. Detail of each data group for flexural strength (f1) calculation is

shown in Appendix B. The flexural strength (f1) refers to the stress caused by bending

along the bottom face of the beam when the first crack being formed. The results both

non-reinforced and fiber- reinforced shown the load behavior deflection-softening. Thus,

the first- peak (f1) and the post-peak (fp) are the same values. This Figure showed the

flexural strength peak (f1) values at the both non-reinforced and fiber-reinforced. The

flexural strength peak (f1) values increased with increasing cement content. To obtain the

highest strength, the optimum fiber content is 1.0 % and fiber length is 40 mm. The

strength slightly decreased when fiber content was higher than 2.0%. The f1 value is the

support of the matrix (cementation bond). It can be seen from the increase in fiber content

has an insignificant impact for the first crack because of the f1 values of fiber-reinforce

depends mainly on the strength of the cement-sand matrix rather than the fiber bridging

capacity. For example, the f1 values of the fiber slightly increased compared with no-

fiber.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

500

1000

1500

2000

2500

Anggraini, et al. (2017)

Sukontasukkul, et al.(2012)

This study

This study

Jamsawang, et al.(2018)

Jamsawang, et al.(2018)

Load

, P1 (

N)

Net deflection (mm)

Fiber Fiber content (%) Length (mm) Cement (%)This study,SP palm 1.0 2.0 40 5Sukontasukkul, et al. (2012), soft clay coir 0.0 1.0 13-15 10Anggraini, et al.(2017), clay polypropylene 0.5 1.0 58 20Jamsawang, et al.(2018), SP polypropylene 1.0 2.0 40 5

73

Figure 4.18 The relationships between flexural strength, f1 (MPa) with

fiber content (%) at different fiber length (mm) and different cement

content (%)

A comparison of flexural strength (f1) of different type of fiber reinforced soil at different

fiber content (%) with previous researches is shown in Figure 4.19. The flexural strength

(f1) increases with increasing fiber content from 0.5% to 1.5%. However, the flexural

strength slightly decreased with increasing fiber content at 2.0%. From Figure, it can be

concluded that the flexural strength values (f1) do not depend on the type of fiber, because

the first crack occurred between sand-cement matrixes wherein the amount of fiber or

type of fiber has little effect. From previous research said that the stress standard, the

segregation of the fibers from the matrix occurred when the maximum shear stress

reached its critical value in their interface.

0.0 0.5 1.0 1.5 2.0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

C7%L40 mm

C7%L20 mmC7%L10 mm

C5%L40 mm C5%L20 mmC5%L10 mm

C3%L40 mmC3%L20 mm

Flex

ural

stre

ngth

, f1 (

MPa

)

Fiber content (%)

Cement content, C (%) Length, L (mm) 10 20 40 3 5 7

C3%L10 mm

74

Figure 4.19 The comparison of flexural strength, f1 (MPa) between samples this study


4.3.3 Residual Strength at net deflection of L/150 Residual strength is another indicator that can describe the deformation characteristic of

the material, which is closely related to the first crack (f1). In this study, the net deflection

at the end of the test which is 4 mm according to (Jamsawang, et al., 2014; Jamsawang,

et al., 2018). The residual strength values read from load versus net deflection curve at

L/600, L/150 and L/100. It was calculated from Eq.3.7 and details of each data are shown

in Appendix B. The Figure 4.20 (a) to 4.20 (c) show the relationships between residual

strength (RS150) at net deflection of L/150 (2 mm) with different fiber content (0.5%,

1.0%, and 2.0%) and different fiber length (10 mm, 20 mm, and 40 mm). For cement

content 3%, 5%, and 7%, the specimen adding fiber demonstrated that the residual

strength increased with increasing fiber content (0.5% <1.0% < 2.0%) and fiber length

(10 mm < 20 mm < 40 mm). Most of all optimal values are obtained from the sample

with the fiber content of 2.0 % at fiber length 40 mm. This situation shows the fiber effect

helps to control the rate of energy release. Thus, the samples with fiber inclusion remain

their ability to carry the load after first peak (residual load) (Jamsawang, et al., 2014;

Jamsawang, et al., 2018).

0.0 0.5 1.0 1.5 2.00.0

0.2

0.4

0.6

0.8

1.0

Jamsawang, et al. (2018), Polyolefin

Jamsawang, et al. (2018), steel

Anggraini, et al. (2014), Coir

Flex

ural

stre

ngth

, f1 (

MPa

)

Fiber content (%)

Fiber Cement content (%) Length, L (mm)This study, SP palm 5 40Anggraini, et al. (2014), clay coir 10 13-15Jamsawang, et al. (2018), SP polypropylene 5 19Jamsawang, et al. (2018), SP polypropylene 5 40Jamsawang, et al. (2018), SP polypropylene 5 55Jamsawang, et al. (2018), SP polyolefin 5 58Jamsawang, et al. (2018), SP steel 5 33Jamsawang, et al. (2018), SP steel 5 50

This study

Jamsawang, et al. (2018), Polypropylene

75


(b) cement content 5 %

0.5 1.0 1.5 2.00.0

0.1

0.2

0.3

0.4

0.5


Resid

ual s

treng

th a

t def

lect

ion

of L

/150

, RS 15

0 (M

Pa)

Fiber content (%)

Length 20 mm

Length 10 mm

Length 40 mm

0.5 1.0 1.5 2.00.00

0.05

0.10

0.15

0.20

0.25

0.30

Length 10 mm

Length 20 mm

Length 40 mm


Resid

ual s

treng

th a

t def

lect

ion

of L

/150

, RS 15

0 (M

Pa)

Fiber content (%)

76

(c) cement content 7 %

Figure 4.20 The relationships between the residual strength at deflection of L/150,

RS150 (MPa) at different fiber length (mm) and different fiber content (%)

4.3.4 Flexural Toughness at L/150 (TD150) Figure 4.21 showed the relationships between toughness at L/150 (TD

150) with fiber

content (%) at different fiber length (mm) and cement content 3%, 5% and 7%. The

toughness or energy absorption is the ability to persist a large deformation of the material.

This value provides the determination of specimen toughness based on the area under the

load-deflection curve up to prescribed deflection. In this study was considered at net

deflection point of 2 mm (from 0 to L/150) because of (Jamsawang, et al., 2014) suggests

that “the peak load (Pp) increases with increasing fiber content (%) and cement content

(%) and is found to be at approximately L/150 (2 mm)”. Details of each data are shown

in Appendix B. It can be seen that the toughness of the non-reinforced increased with

increasing cement content (3% <5% < 7%). The toughness of fiber-reinforced specimen

increased with an increasing cement content for short fiber (10 mm, 20 mm). The

toughness of long fiber (40 mm) reinforced specimen did not depend on the cement ratio.

However, the samples of fiber-reinforce, the toughness increased with increasing the fiber

content (0.5% < 1.0% < 2.0%) and fiber length (10 mm < 20 mm < 40 mm). It concludes

that the cement content, fiber content and fiber length has a significant effect on flexural

0.5 1.0 1.5 2.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


Resid

ual s

treng

th a

t def

lect

ion

of L

/150

, RS 15

0 (M

Pa)

Fiber content (%)

Length 40 mm

Length 20 mm

Length 10 mm

77

toughness, in other words, higher cement content, higher fiber content and fiber length

results in higher toughness because of the external load could be transferred to the palm

fibers through the interfacial bonding between the fibers and cemented soil matrix.

Furthermore, the fibers were able to restrain the crack propagation and traverse across the

cracks to transfer internal force (Jamsawang, et al., 2014; Anggraini, et al., 2017)

Figure 4.21 The relationships between the toughness at deflection of L/150, TD150

(N-m) at different fiber length (mm) and different fiber content (%)

4.3.5 Equivalent strength ratio Figure 4.22 showed the relationships between equivalent flexural strength ratio, RD

T,150

(%) with different fiber content (%) at different fiber length (mm) and cement content

3%, 5% and 7%. Details of each data are shown in Appendix B. The equivalent flexural

strength ratio (RDT,150) indicates the ductility performance or ability to persist a

deformation of cemented sand improves palm fiber which represents the area under the

load-deflection curve from 0 to L/150 (2 mm). This is considered the toughness

performance of fiber-reinforced after the first crack which does not consider the first crack

caused by sand cement matrix. However, RDT,150 values can be represented both of

hardening or softening behaviors. If the RDT,150 is less than 100 % shows softening

behavior but higher 100 % shows hardening behavior. As seen by Figure, the RDT,150

0.0 0.5 1.0 1.5 2.0

0

1

2

3

4

5

C3%L40 mm

C3%L20 mmC3%L10 mm

Cement content, C (%) Length, L (mm) 10 20 40 3 5 7

Toug

hnes

s at

L/1

50, T

D 150 (N

-m)

Fiber content (%)

C5%L40 mm

C5%L20 mm

C5%L10 mm

C7%L10 mm

C7%L20 mm

C7%L40 mm

78

values increase with increasing the fiber content and fiber length. It can be seen that the

fiber length and fiber content at different cement ratio 3%, 5% and 7% shows the

softening behavior whereas the cement ratio 3% with fiber content 2% at fiber length 20

mm and 40 mm show the hardening behavior. It is said that if the RDT,150 values show

softening behavior. The area under the load-deflection is lower than the first peak (P1).

However RDT,150 hardening behavior has represented the area under the load-deflection

will be higher or lower than the first peak (P1).

Figure 4.22 The relationships between the equivalent flexural strength, RDT,150 (%)

at different fiber length (mm) and different fiber content (%)

A comparison of equivalent flexural strength ratio, RDT,150 (%) of different type of fiber

reinforced soil at different fiber content (%) with previous researches is shown in Figure

4.23. The RDT,150 values increase with increasing fiber content and different type of fiber.

Nevertheless, RDT,150 values do not depend on the different cement ratio. It can be seen

the RDT,150 values of different cement ratio (3%, 5% and 7%) is similar to the same fiber

content. Therefore the RDT,150 values are not significantly at different cement ratio but are

significant in fiber content and different type of fiber.

0.0 0.5 1.0 1.5 2.0

0

30

60

90

120

150 Cement content, C (%) Length, L (mm) 10 20 40 3 5 7

Softening

Equi

vale

nt fl

exur

al s

treng

th ra

tio, R

D T,15

0 (%

)

Fiber content (%)

C7%L40 mmC5%L40 mm

C5%L20 mm

C5%L10 mm

C7%L20 mm

C7%L10 mm

C3%L40 mm

C3%L20 mm

C3%L10 mm

Hardening

79

Figure 4.23 The comparison of the equivalent flexural strength, R D 150 (%) between


4.4 Empirical Equations the Effect of Cement Water Ratio (C/W) This section attempts to propose an empirical equation to predict engineering properties

of cemented sand with palm fiber as an internal reinforcement with different mixing ratio.

4.4.1 Unconfined Compression Test (UC) Figure 4.24 showed the fitted lines from the unconfined compression test (UC) for non-

reinforced specimen as a function of cement/water ratio (C/W). The strength increased

with increasing the C/W ratio. It was fitted through the experiment data of peak strength

(qu) with cement/water (C/W) values described by the following Eq.4.1. Its trend line of

the equation has an accuracy of R-square equal to (R2) 0.9215

1.8131uq (MPa) = 4.5858(C/W) (4.1)

Where: qu = unconfined compressive strength (MPa)

f1 = flexural strength (MPa)

0.0 0.5 1.0 1.5 2.0

0

40

80

120

160

200

This study

Jamsawang, et al., 2014

Equi

vale

nt fl

exur

al s

treng

th ra

tio, R

D T,15

0 (%

)

Fiber content (%)

Fiber type Cement(%) Length(mm)

This study, SP Plam 3 10 20 5 10 20 7 10 20Jamsawang, et al., 2014 Polypropylene 3 58 5 58 7 58 Jamsawang, et al., 2018 Polyolefin 5 58 Steel 5 50

Hardening

Softening

Jamsawang, et al., 2018

80

C/W = cement-water ratio

Figure 4.24 Relationships between UCS (qu) and the cement-water ratio (C/W) for


Figure 4.25(a) to Figure 4.25(c) showed the fitted lines from the unconfined compression

test (UC) for fiber-reinforced specimen at different fiber content (%) and different length

(mm) as a function of cement/water ratio (C/W). It can be seen that the influence of the

cement/water ratio (C/W) effect of compressive strength (qu). The strength increased with

increasing the C/W ratio. For the fiber-reinforced and non-reinforced materials, the

compressive strengths (qu) increased approximately linearly with an increase in the

cement content. In other words, the cement content has a great effect on the compressive

strength of non-reinforced (Figure 4.22) and fiber-reinforced (Figure 4.23).

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

non-reinforced

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)

Cement-Water Ratio, C/W Ratio

qu(MPa) = 4.5858(C/W)1.8131

R2 = 0.9215

81

(a) length 10 mm

(b) length 20 mm

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 10 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)


Fiber Content (%) Aqu Bqu,avg. R2

0.5 2.7705 1.5096 0.9073 1.0 3.6948 1.5096 0.9867 2.0 2.9593 1.5096 0.9880

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 20 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.5 4.4180 1.7064 0.9954 1.0 4.8483 1.7064 0.9990 2.0 3.7938 1.7064 0.9932

82

(c) length 40 mm

Figure 4.25 Relationships between UCS (qu) and the cement-water ratio (C/W) for

fiber-reinforced specimen

The regression parameters for predicting compressive strength (qu) of different fiber

content and fiber length are shown in Table 4.1. The nonlinear regression equations for

predication of compressive strength are shown in Eq. (4.2), Eq. (4.3) and Eq. (4.4) as

follows:

qu,avg.Bu quq (MPa) = A (C/W) (4.2)

2qu qu qu quA (MPa) = ( C (FC) +D (FC)+E ) (4.3)

qu,avg.B2u qu qu quq (MPa) = ( C (FC) +D (FC)+E )(C/W) (4.4)


FC = fiber content (%)


0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 40 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.5 4.5760 1.6617 0.9825 1.0 4.9360 1.6617 0.9982 2.0 3.9634 1.6617 0.9358

83

Table 4.1 The coefficients of associated compressive strength with variables in regression

models.

Fiber length

(mm)

coefficient R2

Cqu Dqu Equ Bqu,avg.

10 -1.7230 4.4354 0.9806 1.5096 0.9849

20 -1.2845 2.7979 3.3365 1.7064 0.9849

40 -1.1308 2.4216 3.6473 1.6617 0.9849

The nonlinear regression equations for prediction of compressive strength (qu) of different

fiber content and fiber length are shown in Eq. (4.5), Eq. (4.6), Eq. (4.7), Eq. (4.8) and

Eq. (4.9) as follows:

qu,avg.1Bu qu,1q (MPa) = A (C/W) (4.5)

qu,avg.2Bqu,1 qu,2 0A (MPa) = ( A )(L/L ) (4.6)

2qu,2 qu qu quA (MPa) = ( C (FC) +D (FC)+E ) (4.7)

qu,avg.2 qu,avg.1B B2u qu qu qu 0q (MPa) = (C (FC) +D (FC)+E )(L/L ) (C/W) (4.8)

2 0.1894 1.6259u 0q (MPa) = (-1.16815(FC) +2.7095(FC)+2.3486)(L/L ) (C/W) (4.9)



L = length (mm)

L0 = length 10 mm


84

4.4.2 Flexural strength test (FS) Figure 4.26 showed the fitted lines from the flexural strength test (FS) for non-reinforced

specimen as a function of cement/water ratio (C/W). The strength increases with

increasing the C/W ratio. It was fitted through the experiment data of flexural strength

(f1) with cement/water (C/W) values described by the following Eq.4.10. It trend line of

the equation has an accuracy of R-square equal to (R2) 0.9789

2.12511f (MPa) = 1.524(C/W) (4.10)

Where: f1 = flexural strength (MPa)


Figure 4.26 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for non-reinforced specimen

Figure 4.27 (a) to Figure 4.27 (c) showed the fitted lines from the flexural strength test

(FS) for fiber-reinforced specimen at different fiber content (%) and different length (mm)

as a function of cement/water ratio (C/W). It can be seen that the influence of the

cement/water ratio (C/W) effect of flexural strength (f1). The strength increased with

increasing the C/W ratio. For the fiber-reinforced and non-reinforced materials, the

0.3 0.4 0.5 0.6 0.7

0.0

0.2

0.4

0.6

0.8

f1 (MPa) = 1.524(C/W)2.1251

non-reinforced

Flex

ural

stre

ngth

, f1 (

MPa

)


R2= 0.9789

85

flexural strength (f1) increased approximately linearly with an increase in the cement

content. In other words, the cement content has a great effect on the flexural strength (f1)

of non-reinforced (Figure 4.22) and fiber-reinforced (Figure 4.23) similar to compressive

strength (qu) of unconfined compression test (UC).

(a) length 10 mm

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Fiber Content (%) Af1 Bf1,avg. R2

Length 10 mm

Fl

exur

al s

treng

th, f

1 (M

Pa)


0.5 1.7265 2.1592 0.9940 1.0 1.8449 2.1592 0.9889 2.0 1.7898 2.1592 0.9978

86

(b) length 20 mm

(c) length 40 mm

Figure 4.27 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for fiber-reinforced specimen

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 20 mm

Flex

ural

stre

ngth

, f1 (

MPa

)



0.5 1.7209 2.003 0.9942 1.0 1.8368 2.003 0.9781 2.0 1.7855 2.003 0.9913

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 40 mm

Flex

ural

stren

gth,

f 1 (M

Pa)



0.5 1.5916 1.7676 0.9931 1.0 1.7904 1.7676 0.9886 2.0 1.7031 1.7676 0.9912

87

The empirical parameters for predicting of flexural strength (f1) with different fiber

content and fiber length are shown in Table 4.3. The Proposed regression equations for

compressive are shown in Eq. (4.11), Eq. (4.12) and Eq. (4.13) as follows:

f1,avg.B1 f1f (MPa) = A (C/W) (4.11)

2f1 f1 f1 f1A (MPa) = ( C (FC) +D (FC)+E ) (4.12)

f1,avg.B21 f1 f1 f1f (MPa) = (C (FC) +D (FC)+E )(C/W) (4.13)

Where f1 = flexural strength (MPa)



Table 4.2 The coefficients of associated flexural strength (f1) with variables in regression

models.

Length

(mm)

coefficient R2

Cf1 Df1 Ef1 Bf1,avg.

10 -0.1947 0.5289 1.5107 2.1592 1.0000

20 -0.1886 0.5152 1.5107 2.0030 0.9992

40 -0.2802 0.8183 1.2526 1.7676 1.0000

The nonlinear regression equations for prediction of flexural strength (f1) of different fiber

content and fiber length are shown in Eq. (4.14), Eq. (4.15), Eq. (4.16), Eq. (4.17) and

Eq. (4.18) as follows:

f1,avg.1B1 f1,1f (MPa) = A (C/W) (4.14)

f1,avg.2Bf1,1 f1,2 0A (MPa) = ( A )(L/L ) (4.15)

88

2f1,2 f1 f1 f1A (MPa) = ( C (FC) +D (FC)+E ) (4.16)

f1,avg.2 f1,avg.1B B21 f1 f1 f1 0f (MPa) = (C (FC) +D (FC)+E )(L/L ) (C/W) (4.17)

2 0.1016 1.97661 0f (MPa) = (-0.22(FC) +0.618(FC)+1.31(L/L ) (C/W) (4.18)



L = length (mm)

L0 = length 10 mm

C/W= cement-water ratio

4.4.3 The relationship between flexural strength and compressive strength The relationship between flexural strength (f1) and compressive strength (qu) based on the

experimental data for both non-reinforced and fiber-reinforced with variations of fiber

content, fiber length and cement content. As can be obviously seen in this Figure, a linear

relationships with coefficients of accuracy of R-square equal to (R2) 0.9658 and 0.9213

are presented for non-reinforced and fiber-reinforced, respectively. It was fitted through

the experiment data of flexural strength (f1) with compressive strength (qu) values

described by the following Eq. 4.19 and Eq. 4.20.

Non-reinforced

1 uf (MPa) = 0.2792(q ) (4.19)

Fiber-reinforced

1 uf (MPa) = 0.3623(q ) (4.20)

Fiber-reinforced ratio

1 uf (MPa) = 0.4536(q ) + 0.819 (4.21)

89


qu = compressive strength (MPa)

Figure 4.28 The relationship between flexural strength (f1) and compressive

strength(qu)

Figure 4.29 The relationship between flexural strength (f1) ratio and compressive

strength (qu) ratio

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.2

0.4

0.6

0.8

1.0

fiber-reinforced f1(MPa) = 0.3623qu

R2= 0.9213

Flex

ural

stre

ngth

, f1(M

Pa)

Compressive strength, qu(MPa)

non-reinforced f1(MPa) = 0.2792qu

R2= 0.9658

0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5

3.0

non-reinforced

fiber-reinforced f1= 0.4536qu+ 0.819 R2= 0.7174

Flex

ural

stre

ngth

ratio

, f1

Compressive strength ratio, qu

90

4.5 Evaluation of Proposed Empirical Equations Empirical equations were developed to correlate the engineering properties obtained

experimentally with the peak strength (qu) and flexural strength (f1) and different fiber

content (FC) of fiber length (10 mm, 20 mm, and 40 mm). Verification of these predictive

equations was performed by comparing the predicted values on the y-axis with the

measured values on the x-axis. Here it is necessary to introduce an index(s) to indicate

the degree of prediction satisfaction. There are two indices that can indicate the accuracy

and precision which are: i) ranking index (RI); and ii) ranking distance (RD).

4.5.1 Unconfined Compression Test (UC) Figure 4.30-4.31 shows comparison of peak strength (qu) between the predicted and the

measured values for non-reinforced and fiber-reinforced (10mm, 20mm and 40mm). It

trend line of the equation has an accuracy of R-square equal to (R2) 0.9816.

The followings may be seen:

1. The predicted values of peak strength (qu) at non-reinforced are within the range of

±20% error. The values of RI and RD are 0.128 and 0.183, respectively. These values

are close to zero, which indicate a good performance of accuracy and precision.

2. The predicted values of peak strength at fiber length 10 mm are within the range of









Figure 4.32 - 4.33 shows comparison of peak strength (qu) between the predicted and the

measured values for non-reinforced and fiber-reinforced. It was fitted through the

experiment data of compressive strength (qu) values described by the following Eq.4.9. It

trend line of the equation has an accuracy of R-square equal to (R2) 0.9495. The values

of RI and RD are 0.127 and 0.115, respectively. The followings may be seen:

91

Figure 4.30 Comparison of peak strength (qu) between the predicted and the


cement content (%)

Figure 4.31 Comparison of peak strength (qu) between the predicted and the measured

values at different fiber content (%), fiber length (mm) and cement

content (%) R2 = 0.9816

0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5

3.0C3L0FC0C5L0FC0C7L0FC0

C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40

-20%

+20%+10%

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)

Measured Peak strength, qu measured (MPa)

1:1

-10%

*C = Cement Content*L = Length*FC = Fiber Content

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0

no-fiber fiber content 0.5% fiber content 1.0% fiber content 2.0%

R2 = 0.9816

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


92



cement content (%)




0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5

3.0


C3L0FC0C5L0FC0C7L0FC0

C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


+20%+10%

-10%

-20%

1:1

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0 Cement (%) Length (mm) Fiber Content (%) 0.5 1.0 2.0 3, 5, 7 10 3, 5, 7 20 3, 5, 7 40 3, 5, 7 0

qu predicted (MPa) = 0.979qu measured

R2 = 0.9495

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


93

4.5.2 Flexural strength test (FS) Figure 4.24-4.25 shows comparison between flexural strength (f1) the predicted and the

measured values for non-reinforced and fiber-reinforced (10mm, 20mm and 40mm). It

trend line of the equation has an accuracy of R-square equal to (R2) 0.9901.

The followings may be seen:

1. The predicted values of flexural strength (f1) at non-reinforced are within the range of



2. The predicted values of flexural strength (f1) at fiber length 10 mm are within the range

of ±10% error. The values of RI and RD are 0.183 and 0.169, respectively. These

values are close to zero, which indicate a good performance of accuracy and precision.







Figure 4.34 - 4.35 shows comparison of peak strength (qu) between the predicted and the

measured values for non-reinforced and fiber-reinforced. It was fitted through the

experiment data of compressive strength (qu) values described by the following Eq.4.18.

It trend line of the equation has an accuracy of R-square equal to (R2) 0.9867. The values

of RI and RD are 0.160 and 0.137, respectively. The followings may be seen:

94

Figure 4.34 Comparison of flexural strength (f1) between the predicted and the


cement content (%)




0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0


Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)

Measured Flexural strength, f1 measured (MPa)

+10%1:1

-10%

-20%

+20% C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40


0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0


R2 = 0.9901

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


95



cement content (%)




0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0

1.2


+40% 1:1C3L0FC0C5L0FC0C7L0FC0

C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


+10%

-10%

-20%

+20%

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0 Cement (%) Length (mm) Fiber Content (%) 0.5 1.0 2.0 3, 5, 7 10 3, 5, 7 20 3, 5, 7 40 3, 5, 7 0

qu predicted (MPa) = 0.9879qu measured

R2 = 0.9867

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


CHAPTER 5 CONCLUSION

5.1 Conclusions This research presents the effects of soil-cement improved with palm fiber. They were

investigated by conducting a series of unconfined compression test (UC) and flexural

strength test (FS). It can be seen that the addition of the palm fiber caused beneficial

changes in the engineering properties of soil used in this investigation. The experimental

and analytical results, some conclusions can be drawn as follows:

1. The compressive strength and flexural strength for the non-reinforced cemented sand

shows a brittle failure with increasing cement contents. However, its brittle behavior

decreased with increasing a palm fiber content and a fiber length.

2. The strain index (D) significantly increases with increasing fiber contents. However,

the strain index (D) value seems not to depend on a cement ratio at relatively low

fiber ratios.

3. The compressive strength of reinforced cemented sand increased with increasing the

length of fiber up to about 40 mm. When fiber length being more than 40 mm, the

rate of the strength increment was reduced.

4. The strength of reinforced specimen increased with increasing a fiber content up to a

particular mixing ratio. When a fiber content was more than an optimum fiber content,

strength of reinforced specimen decreased. In this study, the optimum fiber contents

should be used at 0.5%-1.0% depending on fiber content and fiber length.

5. In terms of flexural strength, the adding fibers increased the load carrying capacity of

soil-cement after the first crack. It is seen from the residual strengths at both L/600

and L/150 found to increases after the first crack (f1). However, the residual strength

is less than the first peak (f1), thus behavior shows softening.

6. The efficiency of fiber strongly depends on the fiber length and fiber content. In other

words, the greater length of the fiber gives better performance than short fiber length.

It can be seen from the residual strength increases with increasing fiber content and

fiber length increases. Moreover, the equivalent ductility ratio also increased.

7. At the same of cement content and fiber content, the optimum fiber contents should

be used at 1.0% and fiber length 40mm.

97

8. The proposed empirical equation can be successfully employed to predict unconfined

compression strength and flexural strength with different mixing ratio.

5.2 Recommendation for Future Research 1. As the scope of the present study covers the only natural palm fiber. The further

researches performed with other types of fiber are necessary.

2. This research is limited to test the unconfined compression test (UC) and flexural

strength test (FS). Resilient Modulus is also an important value in the design

pavement. Therefore, in the future, Resilient Modulus tests will also be performed.

REFERENCES

Abtahi, M., Sheikhzadeh, M. and Hassani, Y., 2009, “Compressive behavior of composite

soils reinforced with recycled waste tire cords and polypropylene fibers”, 1st

International and conference text engineering, Rasht, Iran.

Aggarwal, P. and Sharma B., 2010, “Application of jute fiber in the improvement of

subgrade characteristics”, International Conference on Civil Engineering

Technologies, September 27-30, Trabzon, Turkey.

Ahmad, F., Bateni, F. and Azmi, M., 2010, “Performance evaluation of silty sand

reinforced with fibers”, Geotextiles and Geomembranes, Vol. 28, No. 1, pp. 93-99.

Alskif, A., 2016, An Investigation of the Effect of Different Additives on the

Compressive and Flexural Strength of Rammed Earth, Master of Engineering Thesis,

Department of Science in Engineering, The University of Wisconsin-Milwaukee, pp.49-

68.

Anggraini, V., Asadi, A., Huat, B.B.K. and Nahazanan, H., 2015, “Effects of coir fibers

on tensile and compressive strength of lime treated soft soil”, Measurement, Vol. 59,

pp. 372-38.

Anggraini, V., Asadi, A., Syamsir, A. and Huat, B.K.B., 2017, “Three point bending

flexural strength of cement treated tropical marine soil reinforced by lime treated natural

fiber”, Measurement, Vol. 111, pp. 158-168.

ASTM C1018-97, “Standard Test Method for Flexural Toughness and First-Crack

strength of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading)”, ASTM

International, West Conshohocken, PA, USA.

ASTM C1609-10, “Standard Test Method for Flexural Performance of Fiber- Reinforced

Strength of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading)”, ASTM


99

ASTM D422-63, “Standard Test Method for Particle-Size Analysis of Soil”, ASTM


ASTM D854-97, “Standard Test Method for Specific Gravity of Soil by Water

Pycnometer”, ASTM International, West Conshohocken, PA, USA.

ASTM D1557-00, “Standard test methods for Laboratory Compaction Characteristics of

Soil Using Modified Effort”, ASTM International, West Conshohocken, PA, USA.

ASTM D2166-06, “Standard test methods for unconfined compressive strength”, ASTM


Babu, S. and Vasudevan, K., 2008, “Strength and stiffness response of coir fiber-

reinforced tropical soil”, American Society of Civil Engineers, Vol. 20, pp. 571-7.

Briaud, J.L. and Tucker, L.M., 1988, “Measured and predicted axial load response of 98

piles”, Journal of Geotechnical Engineering, Vol. 114, No. 9, pp. 984-1001.

Chen, M., Shen, S.L., Arul, A., Wu, H.N., Hou, D.W. and Xu, Y.S., 2015, “Laboratory

evaluation on the effectiveness of polypropylene fibers on the strength of fiber-reinforced

and cement-stabilized Shanghai soft clay”, Geotextiles and Geomembranes, Vol. 43,

No. 6, pp. 515-523.

Cherubini, C. and Orr, T.L.L., 2000, “A rational procedure for comparing measured and

calculated value in geotechnics”, Proceeding of International Symposium on Coastal

Geotechnical Engineering in Practice, Yokohama, pp. 261-265.

Chinkulkijniwat, A. and Horpibulsuk, S., 2012, “Field strength development of repaired

pavement using the recycling technique”, Quarterly Journal of Engineering Geology

and Hydrogeoly, Vol. 45, pp. 221-229.

Consoil, N.C., Prietto, P.D.M. and Ulbrich, L.A., 1998, “Influence of Fiber and Cement

Addition on Behavior of Sandy Soil”, Journal of Geotechnical and Geoenvironmental

Engineering, Vol. 124, No. 12, pp. 1211-1214.

100

Festugato, L., Menger, E., Benezra, F., Kipper, E.A. and Consoli, N.C., 2017, “Fibre-

reinforced cemented soils compressive and tensile strength assessment as a function of

filament length”, Geotextiles and Geomembranes, Vol. 45, pp. 77-82.

Hausmann, M.R., 1990, Engineering principles of ground modification, New York,

McGraw-Hill, p. 5-7

Hejazi, S.M., Sheikhzadeh, M., Abtahi, S.M. and Zadhoush, A., 2012, “A simple review

of soil reinforcement by using natural and synthetic fibers”, Construction and Building

Materials, Vol. 30, pp. 100-116.

Hirakawa, D., Uchimura, T., Shibata, Y. and Tatsuoka, F., 2002, “Time-Dependent

Deformation of Geosynthetics and Geosynthetics-Reinforced Soil Structure”,

Proceedings of the 7th International Conference on Geosynthetics, Vol. 4, pp. 1427-

1430.

Hogentogler, C.A., 1938, Engineering Properties of the Soils, New York, McGraw-

Hill, p. 3.

Jamsawang, P., Voottipruex, P. and Horpibulsuk, S., 2014, “Flexural Strength

Characteristics of Compacted Cement-Polypropylene Fiber Sand”, Journal of Materials

in Civil Engineering, Vol. 27, No. 9.

Jamsawang, P., Suansomjeen, T., Sukontasukkul, P., Jonpradist, P. and Bergado, D.T.,

2018, “Comparative flexural performance of compacted cement-fiber-sand”, Geotextiles

and Geomembranes, Vol. 46, pp. 414-425, pp. 212-220

Khedari, J., Watsanasathaporn, P. and Hirunlabh, J., 2005 “Development of fiber-based

soil-cement block with low thermal conductivity”, Cement Concrete Composites, Vol.

27, pp. 111-6.

Kim, D.J., Naaman, A.E. and Tawil, S.E., 2008, “Comparative flexural behavior of four

fiber reinforced cementations composites”, Cement & Concrete Composites, Vol. 30,

pp. 917-928.

101

Kumar, A. and Gupta, D., 2016, “Behavior of cement-stabilized fiber-reinforced pond

ash, rice husk ash-soil mixtures”, Geotextiles and Geomembranes, Vol. 44, No. 3, pp.

466-474.

Lambe, T.W. and Whitman, R.V. 1979, Soil Mechanics, New York Wiley, pp. 12-13.

Li, C., 2005, Mechanical Response of Fiber-Reinforced Soil, The Degree of Doctor of

Philosophy, Civil Architectural and Environmental Engineering, The University of Texas

at Austin.

Mahapo, P., 2015, Effects of Fiber Types on Unconfined Compressive and Tensile

Strength Characteristics of Compacted-Cement Fiber-sand, Master of Civil

Engineering Thesis, Department of Civil Engineering, King Mongkut’s University of

Technology North Bangkok, pp. 56-57

Mansour, A., Srebric, J. and Burley, J., 2007, “Development of straw-cement composite

sustainable building material for low-cost housing in Egypt”, Journal of Applied

Sciences, Vol. 3, pp.1571-80

Marandi, M., Bagheripour, H., Rahgozar, R. and Zare, H., 2008, “Strength and ductility

of randomly distributed palm fibers reinforced silty-sand soils”, American Journal of

Applied Sciences, Vol. 5, No. 3, pp. 209-220.

McGown, A., Andrawes, Z. and Hasani, M., 1978, “Effect of inclusion properties on the

behavior of sand, Geotechnique, Vol. 28, pp. 327-46.

Moreira, E.B., Baldovino, J.A., Rose J.L. and Izzo, L.R., 2018, “ Effects of porosity, dry

unit weight, cement content and void/cement ratio on unconfined compressive strength

of roof tile waste-sility soil mixtures”, Journal of Rock Mechanics and Geotechnical

Engineering, Vol. 11, pp. 369-378.

Nicholson, P.G., 2014, Soil Improvement and Ground Modification Methods,

Elsevier Science, Fourth Edition, Elsevier.

102

Onyejekwe, S. and Ghataora, G.S., 2014, “Effect of Fiber Inclusions on Flexural Strength

of Soils Treated with Nontraditional Additives”, Journal of Materials in Civil

Engineering, Vol. 26.

Park, S.S, 2011, “Unconfined compressive strength and ductility of fiber-reinforced

cemented sand”, Construction and Building Materials, Vol. 25, No. 2, pp.1134-1138.

Prabakar, J. and Sridhar, R.S., 2002, “Effect of random inclusion of sisal fibre on strength

behavior of soil” Construction and Building Materials, Vol. 16, No. 2, pp.123-131.

Ramaswamy, S., Ahuja, M. and Krishnamoorthy, S., 1983, “Behavior of concrete

reinforced with jute, coir, and bamboo fibres”, Cement Concrete Composites, Vol. 5,

pp. 3-13.

Ravishanker, U. and Raghavan, S., 2004, “Coir stabilized lateritic soil for pavements”,

Indian Geotechnical Conference, Ahmedabad, India, pp. 45-52.

Ruenkrairergsa, T., 1982, “Principle of Soil Stabilization”, Group Training in Road

Construction, Bangkok, Thailand, pp. 17-26.

Ruenkrairergsa, T., 2000, “Unconfined Compressive Strength and California Bearing

Ratio of Cement Stabilized Silty Sand”, Research and Development and Department

of Highways, Vol. 178, pp. 3-10.

Sadek, S., Najjar, S. and Abboud, A., 2013, “Compressive Strength of Fiber-Reinforced

Lightly-Cement Stabilized Sand”, The 18th International Conference on Soil

Mechanics and Geotechnical Engineering, Paris, pp. 2593-2596.

Savastano, H., Warden, G. and Coutts, P., 2000, “Brazilian waste fibers as reinforcement

for cement-based composites”, Cement Concrete Composites, Vol. 22, pp. 379-84.

Segetin, M., Jayaraman, K. and Xu, X., 2007, “Harakeke reinforcement of soil-cement

building materials manufacturability and properties, Building Environment, Vol. 66, pp.

369-378.

103

Sharma, V., Vinayak, K.H. and Marwaha, M.B., 2015, “Enhancing compressive strength

of soil using natural fibers”, Construction and Building Materials, Vol. 93,

pp. 943-949.

Sukontasukkul, P. and Jamsawang, P., 2012, “Use of steel and polypropylene fibers to

improve flexural performance soil-cement column”, Construction and Building


Tajdini, M., Bonab, M.H. and Golmohamadi, S., 2017, “An Experimental Investigation

on Effect of adding Natural and Synthetic Fibers on Mechanical and Behavioural

Parameters of Soil-Cement Materials”, International Journal Civil Engineering

Technology, Vol. 16, No. 4, pp. 353-370.

Tang, C., Shi, B., Gao, W., Chen F. and Cai, Y., 2007, “Strength and mechanical behavior

of short polypropylene fiber reinforced and cement stabilized clayey soil”, Geotextiles

and Geomembranes, Vol. 25, pp. 194-202.

Tran, Q.K., Satomi, S.T. and Takahashi, H., 2018a, “Effect of waste cornsilk fiber

reinforcement on mechanical properties of soft soils”, Transportation Geotechnics, Vol.

16, pp. 76-84.

Tran, Q.K., Satomi, S.T. and Takahashi, H., 2018b, “Improvement of mechanical

behavior of cemented soil reinforced with waste cornsilk fibers”, Construction and

Building Materials, Vol. 178, pp. 204-210.

Wei, L., Chai, S.X., Zhang, H.Y. and Shi, Q., 2018, “Mechanical properties of soil

reinforced with both lime and four kinds of fiber”, Construction and Building


Yetimoglu, T., Inanir, M. and Esatinanir, O., 2005 “A study on bearing capacity of

randomly distributed fiber-reinforced sand fills overlying soft clay”, Geotextiles and

Geomembranes, Vol. 23, No. 2, pp. 174-183.

104

Yusoff, M., Salit, M., Ismail N. and Wirawan, R., 2010, “Mechanical properties of short

random oil palm fiber reinforced epoxy composites”, Sains Malaysiana, Vol. 39, No. 1,

pp. 87-92.

APPENDIX A

The results of unconfined compressive strength test (UC)

106

Table A.1 Axial strain at peak strength (%) and Strain index (D) curing 28 days

Cement

content

(%)

Fiber

content

(%)

Axial strain at peak strength

(%)

Strain index , D

Fiber length (mm.) Fiber length (mm.)

0 10 20 40 0 10 20 40

3

0.5

0.3643

0.557 1.085 1.618

1

1.529 2.978 4.442

1.0 0.995 1.098 1.585 2.732 3.014 4.351

2.0 1.246 1.654 2.995 3.337 4.539 8.220

5

0.5

0.4613

0.600 0.7021 1.092

1

1.302 1.522 2.367

1.0 0.610 1.180 1.663 1.322 2.559 3.605

2.0 0.936 1.296 1.895 2.029 2.808 4.108

7

0.5

0.347

0.3813 0.617 0.620

1

1.109 1.795 1.804

1.0 0.453 1.119 1.601 1.319 3.255 4.658

2.0 0.999 1.399 2.277 2.909 4.073 6.626

107



Cement content 3%Length (mm) 10 20 40

0.5 1.0 1.5 2.00

2

4

6

8

10

Length 40 mm

Length 20 mm

Stra

in in

dex,

D (%

)

Fiber content (%)

Length 10 mm


0.5 1.0 1.5 2.00

1

2

3

4

5

Length 10 mm

Length 20 mm

Length 40 mm

Stra

in in

dex,

D (%

)

Fiber content (%)

108


Figure A.1 The relationships between strain index (D) and fiber content (%) various

fiber length (10mm, 20 mm, and 40 mm) at different cement content


0.5 1.0 1.5 2.00

2

4

6

8

Length 40 mm

Length 20 mm

Length 10 mm

Stra

in in

dex,

D

Fiber content (%)

109

Table A.2 Unconfined compressive strengths of sand cement improved with palm fibers

curing 28 days

Cement

content

(%)

Fiber

content

(%)

Unconfined compressive strength (kPa)

Fiber length (mm.)

0 10 20 40

3

0.5

228.628

268.128 457.793 508.168

1 448.368 547.045 569.231

2 410.746 489.066 644.147

5

0.5

1437.499

1098.804 1201.415 1192.296

1 1268.658 1398.141 1412.660

2 1040.159 1124.455 1284.625

7

0.5

2136.840

1426.790 2251.774 2429.087

1 1995.881 2415.677 2542.689

2 1569.773 1858.786 1910.005

110

Table A.3 Toughness of unconfined compressive strengths of sand cement improved

with palm fibers curing 28 days

Cement

content

(%)

Fiber

content

(%)

Toughness of UCS (kPa)

Fiber length (mm.)

0 10 20 40

3

0.5

180.000

397.100 1236.000 1593.000

1 962.000 1338.000 2258.000

2 1246.000 1807.000 2528.000

5

0.5

1253.000

1199.000 1761.000 3899.000

1 2655.000 4844.000 5456.000

2 2317.000 3347.000 4654.000

7

0.5

2548.000

2168.000 3900.000 5858.000

1 4950.000 5815.000 9281.000

2 3197.000 6975.000 7847.000

111

APPENDIX B

The results of flexural strength test (FS)

112 Table B.1 Flexural performance of sand cement improved with palm fibers curing 28 days

Specimen First peak load

Peak load

L/600 (0.5 mm) L/150 (2.0 mm) L/100 (3.0 mm) TD

150 (N-m)

RDT,150 (%)

P1 (N) Pp (N) PD600 (N) fD

600(MPa) PD600 (N) fD

600(MPa) PD600 (N) fD

600(MPa) Cement3%

SC3F0 0.075 0.075 0.027 5.296 SC3F0.5L10 0.081 0.081 85.443 0.027 82.500 0.025 65.539 0.0197 0.177 32.732 SC3F1.0L10 0.114 0.114 141.321 0.042 101.779 0.031 71.841 0.022 0.271 35.764 SC3F2.0L10 0.105 0.105 239.561 0.072 149.924 0.045 134.343 0.040 0.409 58.313 SC3F0.5L20 0.110 0.110 134.952 0.040 118.08 0.035 106.893 0.0321 0.272 37.155 SC3F1.0L20 0.129 0.129 261.992 0.079 253.423 0.076 227.931 0.068 0.547 63.735 SC3F2.0L20 0.120 0.120 424.344 0.128 427.828 0.128 397.202 0.119 0.855 106.706 SC3F0.5L40 0.149 0.149 370.526 0.111 360.764 0.108 352.539 0.106 0.716 72.148 SC3F1.0L40 0.185 0.185 506.022 0.152 538.396 0.162 562.676 0.169 1.050 85.071 SC3F2.0L40 0.176 0.176 732.079 0.220 671.239 0.201 654.773 0.196 1.413 120.447 Cement5%

SC5F0 0.341 0.341 0.228 10.029 SC5F0.5L10 0.345 0.345 135.047 0.040 104.817 0.031 126.410 0.038 0.280 12.153 SC5F1.0L10 0.414 0.414 490.487 0.147 162.924 0.049 180.391 0.054 0.730 26.446 SC5F2.0L10 0.375 0.375 670.999 0.201 587.301 0.176 548.495 0.165 1.289 51.537 SC5F0.5L20 0.374 0.374 252.415 0.076 239.343 0.072 245.860 0.074 0.521 20.888 SC5F1.0L20 0.476 0.476 497.538 0.149 354.970 0.106 351.033 0.105 1.022 32.217 SC5F2.0L20 0.437 0.437 812.063 0.244 759.612 0.227 705.767 0.212 1.662 56.985 SC5F0.5L40 0.406 0.406 453.533 0.136 416.587 0.125 289.471 0.086 0.912 33.680 SC5F1.0L40 0.527 0.527 855.652 0.257 726.520 0.218 681.473 0.204 1.697 48.341 SC5F2.0L40 0.496 0.496 1581.705 0.475 1459.897 0.438 1311.165 0.393 3.044 92.112

106

113 Table B.1 (Cont’d) Flexural performance of sand cement improved with palm fibers curing 28 days

Specimen First peak load

Peak load

L/600 (0.5 mm) L/150 (2.0 mm) L/100 (3.0 mm) TD

150 (N-m)

RDT,150 (%)

P1 (N) Pp (N) PD600 (N) fD

600(MPa) PD600 (N) fD

600(MPa) PD600 (N) fD

600(MPa) Cement7%

SC7F0 0.636 0.636 0.489 11.526 SC7F0.5L10 0.726 0.726 311.235 0.093 143.770 0.043 171.200 0.051 0.774 15.990 SC7F1.0L10 0.780 0.780 608.308 0.182 286.683 0.086 238.695 0.072 1.088 21.766 SC7F2.0L10 0.741 0.741 720.723 0.216 612.258 0.184 339.865 0.102 1.334 26.998 SC7F0.5L20 0.777 0.777 386.463 0.116 254.700 0.076 189.732 0.057 1.030 19.876 SC7F1.0L20 0.789 0.789 614.886 0.184 356.593 0.107 433.368 0.130 1.246 23.702 SC7F2.0L20 0.780 0.780 1008.336 0.302 637.430 0.191 572.693 0.171 1.927 37.050 SC7F0.5L40 0.795 0.795 625.309 0.188 435.257 0.131 376.782 0.113 1.173 22.119 SC7F1.0L40 0.852 0.852 1013.707 0.304 845.262 0.254 732.052 0.220 2.040 35.899 SC7F2.0L40 0.814 0.814 2124.5593 0.637 1839.013 0.558 1729.730 0.519 4.135 69.657

APPENDIX C

The results of empirical equations the effect of cement water ratio (C/W) and evaluation

of proposed empirical equation

115

Figure C.1 Relationships between UCS (qu) and the cement-water ratio (C/W) for


0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

non-reinforced

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)


qu(MPa) = 4.5858(C/W)1.8131

R2 = 0.9215

116

Figure C.2 Relationships between UCS (qu) and the cement-water ratio (C/W) at

dfferent fiber content (0.5%, 1.0% and 2.0%) for fiber length 10 mm




0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 10 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)


Fiber Content (%) Aqu Bqu R2 0.5 2.7234 1.4777 0.8151 1.0 3.8677 1.5953 0.9770 2.0 2.8748 1.4557 0.9778

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 10 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.5 2.7705 1.5096 0.9073 1.0 3.6948 1.5096 0.9867 2.0 2.9593 1.5096 0.9880

117

Figure C.4 Relationships between Aqu and fiber content (%) for fiber length 10 mm

Table C.1 Values of Aqu and Bqu from relationships UCS (qu) and cement-water ratio


C/W Fiber content

(%)

Coefficients from the linear relation Bqu,avg.

Aqu Bqu R2

0.2857 0.5 2.7234 1.4777 0.8151

1.5096 0.4762 1.0 3.8677 1.5953 0.9770

0.6667 2.0 2.8748 1.4557 0.9778

Table C.2 Values of Aqu from the relationships between UCS (qu) and cement-water ratio

(C/W) using the average of Bqu of 1.5096 at fiber length 10 mm

C/W Fiber content

(%)

Coefficients from the linear relation

Aqu R2

0.2857 0.5 2.7705 0.9073

0.4762 1.0 3.6948 0.9867

0.6667 2.0 2.9593 0.9880

0.5 1.0 1.5 2.00.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

A qu

Fiber content, FC (%)

Aqu= -1.7230(FC)2+4.4354(FC)+0.9806

R2 = 0.9849

118

Table C.3 Values of Aqu and Bqu from relationship between values of Aqu and



Cqu Dqu Equ R2

-1.7230 4.4354 0.9806 0.9849



0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 20 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



119


different fiber content (0.5%, 1.0% and 2.0%) using the average of Bqu of

1.7064 for fiber length 20 mm

Figure C.7 Relationships between Aqu and fiber content (%)for fiber length 20 mm

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 20 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.5 4.4180 1.7064 0.9954 1.0 4.8483 1.7064 0.9990 2.0 3.7938 1.7064 0.9932

0.5 1.0 1.5 2.03.0

3.5

4.0

4.5

5.0

5.5

Aqu= -1.2845(FC)2+2.7979(FC)+3.3365

R2 = 0.9849

A qu


120



C/W Fiber content

(%)


Aqu Bqu R2

0.2857 0.5 4.8152 1.8739 1.0000

1.7064 0.4762 1.0 4.8313 1.6996 0.9981

0.6667 2.0 3.4893 1.5457 0.9990



C/W Fiber content

(%)


Aqu R2

0.2857 0.5 4.4180 0.9954

0.4762 1.0 4.8483 0.9990

0.6667 2.0 3.7938 0.9932




Cqu Dqu Equ R2

-1.2845 2.7979 3.3365 0.9849

121

Figure C.8 Relationships between UCS (qu) and the cement-water ratio (C/W)

different at fiber content (0.5%, 1.0% and 2.0%) for fiber length 40 mm


different fiber content (0.5%, 1.0% and 2.0%) using the average of

Bqu of 1.6617 for fiber length 40 mm

0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 40 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.3 0.4 0.5 0.6 0.70.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 40 mm

Unco

nfin

ed c

ompr

essiv

e st

reng

th, q

u (M

Pa)



0.5 4.5760 1.6617 0.9825 1.0 4.9360 1.6617 0.9982 2.0 3.9634 1.6617 0.9358

122

Figure C.10 Relationships between Aqu and fiber content (%)for fiber length 40 mm



C/W Fiber content

(%)


Aqu Bqu R2

0.2857 0.5 5.3706 1.9730 0.9939

1.6617 0.4762 1.0 5.1887 1.7579 1.0000

0.6667 2.0 3.1926 1.2541 0.9972



C/W Fiber content

(%)


Aqu R2

0.2857 0.5 4.5760 0.9825

0.4762 1.0 4.9360 0.9982

0.6667 2.0 3.9634 0.9358

0.5 1.0 1.5 2.03.5

4.0

4.5

5.0

5.5

A qu


Aqu= -1.1308(FC)2+2.4216(FC)+3.6473

R2 = 0.9849

123



Coefficients from the linear relation Cqu Dqu Equ R2

-1.1308 2.4216 3.6473 0.9849

Figure C.11 Relationships between flexural strength (f1) and the cement-water ratio

(C/W) for non-reinforced

0.3 0.4 0.5 0.6 0.7

0.0

0.2

0.4

0.6

0.8

f1 (MPa) = 1.524(C/W)2.1251

non-reinforced

Flex

ural

stre

ngth

, f1 (

MPa

)


R2= 0.9789

124

Figure C.12 Relationships between FS (f1) and the cement-water ratio (C/W) at


Figure C.13 Relationships between FS (f1) and the cement-water ratio (C/W) at different

fiber content (0.5%, 1.0% and 2.0%) using the average of Bf1 of 2.1592 for

fiber length 10 mm

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 10 mm

Flex

ural

stre

ngth

, f1 (

MPa

)


Fiber Content (%) Af1 Bf1 R2

0.5 1.8934 2.3505 0.9946 1.0 1.6913 1.9809 0.9856 2.0 1.7786 2.1462 0.9958

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0


Length 10 mm

Flex

ural

stre

ngth

, f1 (

MPa

)


0.5 1.7265 2.1592 0.9940 1.0 1.8449 2.1592 0.9889 2.0 1.7898 2.1592 0.9978

125

Figure C.14 Relationships between Af1 and fiber content for fiber length 10 mm

Table C.10 Values of Af1 and Bf1 from relationships FS (f1) and cement-water ratio


C/W Fiber content

(%)

Coefficients from the linear relation Bf1,avg.

Af1 Bf1 R2

0.2857 0.5 1.8934 2.3505 0.9946

2.1592 0.4762 1.0 1.6913 1.9809 0.9856

0.6667 2.0 1.7786 2.1462 0.9958

Table C.11 Values of Af1 from the relationships between FS (f1) and cement-water

average of Bqu of 2.1592 at fiber length 10 mm

C/W Fiber content

(%)


Af1 R2

0.2857 0.5 1.7265 0.9940

0.4762 1.0 1.8449 0.9889

0.6667 2.0 1.7898 0.9978

0.5 1.0 1.5 2.01.5

1.6

1.7

1.8

1.9

2.0

A f1


Af1 = -0.1886(FC)2+0.5152(FC)+1.5107

R2 = 1.0000

126

Table C.12 Values of Af1 and Bf1 from relationship between values of Af1 and



Cf1 Df1 Ef1 R2

-0.1886 0.5152 1.5107 1.0000



0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 20 mm

Flex

ural

stre

ngth

, f1 (

MPa

)


Fiber Content (%) Af1 Bf1 R2 0.5 1.9251 2.2312 0.9991 1.0 1.6812 1.8251 0.9660 2.0 1.7414 1.9527 0.9832

127




Figure C.17 Relationships between Af1 and fiber content (%)for fiber length 20 mm

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 20 mm

Flex

ural

stre

ngth

, f1 (

MPa

)



0.5 1.7209 2.003 0.9942 1.0 1.8368 2.003 0.9781 2.0 1.7855 2.003 0.9913

0.5 1.0 1.5 2.01.5

1.6

1.7

1.8

1.9

2.0

A f1


Af1= -0.1886(FC)2+0.5152(FC)+1.5107

R2 = 0.9992

128



C/W Fiber content

(%)

Coefficients from the linear relation Bf1,avg.

Af1 Bf1 R2

0.2857 0.5 1.9251 2.2312 0.9991

2.003 0.4762 1.0 1.6812 1.8251 0.9660

0.6667 2.0 1.7414 1.9527 0.9832



C/W Fiber content

(%)


Aqu R2

0.2857 0.5 4.4180 0.9954

0.4762 1.0 4.8483 0.9990

0.6667 2.0 3.7938 0.9932




Cf1 Df1 Ef1 R2

-0.1886 0.5152 1.5107 0.9992

129






0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 40 mm

Flex

ural

stre

ngth

, f1 (

MPa

)


Fiber Content (%) Af1 Bf1 R2

0.5 1.7800 1.9878 0.9999 1.0 1.6834 1.6479 0.9831 2.0 1.6173 1.6671 0.9866

0.3 0.4 0.5 0.6 0.70.0

0.2

0.4

0.6

0.8

1.0

Length 40 mm

Flex

ural

stre

ngth

, f1 (

MPa

)



0.5 1.5916 1.7676 0.9931 1.0 1.7904 1.7676 0.9886 2.0 1.7031 1.7676 0.9912

130

Figure C.20 Relationships between Af1 and fiber content (%)for fiber length 40 mm



C/W Fiber content

(%)


Aqu Bqu R2

0.2857 0.5 1.7800 1.9878 0.9999

1.7676 0.4762 1.0 1.6834 1.6479 0.9831

0.6667 2.0 1.6173 1.6671 0.9866



C/W Fiber content

(%)


Aqu R2

0.2857 0.5 1.7800 0.9999

0.4762 1.0 1.6834 0.9831

0.6667 2.0 1.6173 0.9866

0.5 1.0 1.5 2.01.5

1.6

1.7

1.8

1.9

2.0

Length 40 mm

A f1


Af1 = -0.2802(FC)2+0.8183(FC)+1.2526

R2 = 1.0000

131




Cqu Dqu Equ R2

-0.2802 0.8183 1.2526 1.0000

132

Table C.19 Summary of the predicted and the measured values of peak strength (qu) for

non-reinforced by cement-water ratio (C/W)

Cement

content

(%)

Length

(mm)

Measured

peak strength (qu)

(MPa)

Predicted

peak strength (qu)

(MPa)

3

0

0.229 0.274

5 1.438 1.195

7 2.137 2.199

Figure C.21 Comparison of peak strength (qu) between the predicted and the

measured values for non-reinforced

0.0 0.5 1.0 1.5 2.0 2.50.0

0.5

1.0

1.5

2.0

2.5

non-reinforced


Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


1:1+20%

-20%

133

Table C.20 Values of µ, σ, COV, RI, and RD obtained from comparison of peak strength

(qu) for non-reinforced

Statistical approach Values

Average (µ) 1.018

Std. Dev. (σ) 0.182

COV 0.179

RI 0.189

RD 0.182


fiber length 10 mm by cement-water ratio (C/W)

Cement

content

(%)

Length

(mm)

Fiber

content

(%)

Measured

peak strength (qu)

(MPa)

Predicted

peak strength (qu)

(MPa)

3

10

0.5 0.268 0.418

1.0 0.448 0.557

2.0 0.411 0.447

5

0.5 1.099 0.903

1.0 1.269 1.205

2.0 1.040 0.966

7

0.5 1.427 1.501

1.0 1.996 2.003

2.0 1.570 1.605

134




(qu) for fiber length 10 mm


Average (µ) 1.008

Std. Dev. (σ) 0.064

COV 0.063

RI 0.069

RD 0.064

0.5 1.0 1.5 2.0 2.5

0.5

1.0

1.5

2.0

2.5

Length 10 mm

1:1

-20%

+20%

Cement content (%) Fiber content (%) 0.5 1.0 2.0 3 5 7

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


135



Cement

content

(%)

Length

(mm)

Fiber

content

(%)

Measured

peak strength (qu)

(MPa)

Predicted

peak strength (qu)

(MPa)

3

10

0.5 0.458 0.521

1.0 0.547 0.572

2.0 0.489 0.447

5

0.5 1.201 1.245

1.0 1.398 1.367

2.0 1.124 1.070

7

0.5 2.252 2.210

1.0 2.417 2.428

2.0 1.859 1.900

Figure C.23 Comparison of peak strength (qu) between the predicted and the measured

values for fiber length 20 mm

0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5

3.0Cement content (%) Fiber content (%) 0.5 1.0 2.0 3 5 7

Length 20 mm

-10%

+10% 1:1

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


136




Average (µ) 1.018

Std. Dev. (σ) 0.182

COV 0.179

RI 0.189

RD 0.182



Cement

content

(%)

Length

(mm)

Fiber

content

(%)

Measured

peak strength (qu)

(MPa)

Predicted

peak strength (qu)

(MPa)

3

10

0.5 0.508 0.571

1.0 0.569 0.615

2.0 0.644 0.495

5

0.5 1.192 1.334

1.0 1.413 1.439

2.0 1.285 1.156

7

0.5 2.429 2.333

1.0 2.543 2.518

2.0 1.910 2.023

137






Average (µ) 1.008

Std. Dev. (σ) 0.064

COV 0.063

RI 0.069

RD 0.064

0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5

3.0

Length 40 mm

+20%

-20%

1:1Cement content (%) Fiber content (%) 0.5 1.0 2.0 3 5 7

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


138





R2 = 0.9816

0.5 1.0 1.5 2.0 2.5 3.0

0.5

1.0

1.5

2.0

2.5


C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40

-20%

+20%+10%

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


1:1

-10%


0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

0.5

1.0

1.5

2.0

2.5

3.0


R2 = 0.9816

Pred

icted

Pea

k st

reng

th, q

u pr

edict

ed (M

Pa)


139

Table C.27 Summary of the predicted and the measured values of flexural strength (f1)

for non-reinforced by cement-water ratio (C/W)

Cement

content

(%)

Length

(mm)

Measured

flexural strength (f1)

(MPa)

Predicted


(MPa)

3

0

0.076 0.106

5 0.341 0.315

7 0.636 0.644

Figure C.27 Comparison of flexural strength (f1) between the predicted and the

measured values

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0

1.2

non-reinforced

-10%

+10% 1:1


Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


140

Table C.28 Values of µ, σ, COV, RI, and RD obtained from comparison of flexural


Statistical approach Values Average (µ) 1.113 Std. Dev. (σ) 0.254

COV 0.228 RI 0.309 RD 0.278

Table C.29 Summary of the predicted and the measured values flexural strength (f1) for


Cement

content

(%)

Length

(mm)

Fiber

content

(%)

Measured


(MPa)

Predicted


(MPa)

3

10

0.5 0.081 0.115

1.0 0.114 0.123

2.0 0.105 0.120

5

0.5 0.345 0.348

1.0 0.414 0.372

2.0 0.375 0.361

7

0.5 0.726 0.719

1.0 0.750 0.769

2.0 0.741 0.746

141



Table C.30 Values of µ, σ, COV, RI, and RD obtained from comparison of flexural



Average (µ) 1.060

Std. Dev. (σ) 0.154

COV 0.145

RI 0.183

RD 0.165

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0

1.2

Length 10 mm


1:1

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


+10%

-10%

142



Cement

content

(%)

Length

(mm)

Fiber

content

(%)

Measured


(MPa)

Predicted


(MPa)

3

10

0.5 0.110 0.140

1.0 0.129 0.149

2.0 0.120 0.145

5

0.5 0.374 0.389

1.0 0.476 0.416

2.0 0.437 0.404

7

0.5 0.777 0.764

1.0 0.789 0.816

2.0 0.780 0.793



0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0

1.2

Length 20 mm


1:1

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


+20%

-20%

143


(qu) for non-reinforced


COV 0.125 RI 0.173 RD 0.144



Cement content

(%)

Length (mm)

Fiber content

(%)

Measured peak strength (qu)

(MPa)

Predicted peak strength (qu)

(MPa) 3

10

0.5 0.149 0.173 1.0 0.185 0.196 2.0 0.176 0.193

5

0.5 0.406 0.429 1.0 0.527 0.482 2.0 0.496 0.476

7

0.5 0.795 0.777 1.0 0.852 0.874 2.0 0.814 0.863

144




(qu) for fiber -reinforced


COV 0.073 RI 0.106 RD 0.084

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0

1.2

Length 40 mm

-10%

+10% 1:1Cement content (%) Fiber content (%) 0.5 1.0 2.0 3 5 7

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


145



different fiber content (%) and fiber length (mm)



different fiber content (%) and fiber length (mm) R2 = 0.9816

0.0 0.2 0.4 0.6 0.8 1.0 1.20.0

0.2

0.4

0.6

0.8

1.0


Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


+10%1:1

-10%

-20%

+20% C (%) L (mm) FC (%) 0.5 1.0 2.0 3 10 5 10 7 10 3 20 5 20 7 20 3 40 5 40 7 40


0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0


R2 = 0.9901

Pred

icted

Fle

xura

l stre

ngth

, f1

pred

icted

(MPa

)


146

CURRICULUM VITAE

NAME Miss Chutkamon Dachrueang

Date of Birth 27 April 1993

EDUCATIONAL RECORD

HIGH SCHOOL High School Graduation

Ampornpaisarn School, 2011

BACHELOR’S DEGREE Bachelor of Science in Industrial Education

(Civil Engineering)

King Mongkut’s University of Technology,

Thonburi, 2016

MASTER’ S DEGREE Master of Engineering (Civil Engineering)

King Mongkut’s University of Technology

Thonburi, 2018

PUBLICATION Dachrueang, C. , Youwai, S. , and Buathong, P. ,

2018, “Strength characteristics of cement sand

improved with palm fiber”, Proceeding of the 23rd

National Convention on Civil Engineering, GTE-

170, 18-20 July 2018, Nakhon Nayok, Thailand.

Documents

STRENGTH AND DEFORMATION CHARACTERISTICS OF … · increasing fiber contents and did not depend on a cement content at a relatively low fiber content. In terms of flexural strength,