performance evaluation of steel slag as substitute

PERFORMANCE EVALUATION OF STEEL SLAG AS NATURAL

AGGREGATES REPLACEMENT IN ASPHALTIC CONCRETE

by

TEOH CHERH YI

Thesis submitted as fulfillment of the requirements For the degree of Master of Science

November 2008

PENILAIAN PRESTASI SLAG BESI SEBAGAI PENGGANTI AGREGAT SEMULA JADI DALAM KONKRIT ASFALT

Disediakan oleh

TEOH CHERH YI

Tesis yang diserahkan untuk Memenuhi keperluan bagi

Ijazah Sarjana Sains

November 2008

Appendix A

Appendix B

Appendix C

PERFORMANCE EVALUATION OF STEEL SLAG AS NATURAL AGGREGATES REPLACEMENT IN ASPHALTIC CONCRETE

TEOH CHERH YI

UNIVERSITI SAINS MALAYSIA

2008

ii

Acknowledgement

First and foremost, I would like to express my utmost and sincere gratitude

to my supervisor Associate Professor Dr. Hj. Meor Othman Hamzah for his

guidance, advice and patience, encouragements and support throughout the

entire duration of this study and thesis writing. Not forgetting my second

supervisor Dr. Zaid Hj. Yusof for his guidance too.

I would like to express my appreciation and gratitude to every organization

and individual who lend me a hand in completing this study and my masters

degree. I wish to take this opportunity to express my appreciation to

Universiti Sains Malaysia and the School of Civil Engineering for providing

me with the best possible facilities, environment and materials for my

laboratory testing and also for providing the reference materials. Besides, I

would also like to take this opportunity to express my gratitude to RST

Technology Sdn. Bhd. for providing me with the steel slag aggregates used

for this study.

On the other hand, I would also like to express my gratitude to all the staffs

of the School of Civil Engineering for their kind cooperation. My appreciation

also extends to the technicians of Highway and Traffic Engineering

laboratory, Mr. Zulhairi Ariffin and Mr. Mohd Fouzi Ali for their assistance. I

would like to express my gratitude for the sincere friendship of the fellow

post graduate students in the School of Civil Engineering for being wonderful

friends and their support.

iii

Last but not least, I would like to pay my appreciation to my beloved

family and friends for their love and care, and also the encouragement all the

time.

iv

Table of Content

Content

Page Acknowledgement ii Table of Content iv List of Tables viii List of Figures xii List of Plates xvii List of Abbreviation xviii Abstrak xx Abstract xxi

Chapter One: Introduction

1.1 Introduction To Steel Slag 1 1.2 Objective 3 1.3 Justification of Research 3 1.4 Scope of Work 5 1.5 Organization of Thesis 6

Chapter Two: Literature Review

2.1 Introduction 9 2.2 Efforts in Utilizing Waste Materials as Construction

Materials 10 2.2.1 Utilization of Waste Materials in Road

Constructions 12 2.2.2 Advantages of Utilizing Waste Materials in Road

Construction 15 2.2.3 Problems Concerning Utilization of Recycled

Materials in Road Constructions 16 2.3 Material Description of Steel Slag 17 2.4 Source of Steel Slag 18 2.5 Production of Steel Slag 19 2.6 Properties of Steel Slag 22 2.6.1 Physical and Mechanical Properties 23 2.6.1.1 Particle Shape 27 2.6.1.2 Surface Texture 27 2.7 Chemical Properties of Steel Slag 28 2.8 Handling of Steel Slag Aggregates 30 2.9 Utilization of Steel Slag Aggregates in Road

Constructions 31 2.10 Performance of Steel Slag Asphalt Mixture 34 2.11 Advantages of Using Steel Slag as Road Construction

Aggregate 36 2.12 Disadvantages of Using Steel Slag as Road Construction

Aggregate 37 2.13 Effects of Climate Changes on Bituminous Mixtures 37 2.13.1 Permanent Deformation 38

v

2.13.2 Low Temperature Cracking 40 2.13.3 Moisture Susceptibility 41 2.14 Aging 42

Chapter Three: Materials and Methodology

3.1 Introduction 46 3.2 Aggregates 46 3.2.1 Granite 47 3.2.2 Steel Slag 48 3.3 Mineral Filler 50 3.3.1 Ordinary Portland Cement 50 3.3.2 Hydrated Lime 51 3.4 Mix Designation 52 3.5 Binder Preparation 53 3.6 Additive 53 3.6.1 Drain Asphalt Modified Additive 54 3.7 Methods for Preparation of Specimens and Testing

Procedures 55 3.7.1 Aggregate Preparation 57 3.7.2 Resistance to Abrasion 57 3.7.3 Aggregates Grading and Proportioning 58 3.7.4 Mix Preparation 59 3.7.4.1 Porous Mix Preparation 59 3.7.4.2 Dense Mix Preparation 60 3.7.5 Stripping Test 61 3.7.6 Bituminous Mix Mechanical Testing Methods 61 3.7.6.1 Marshall Stability and Flow Test 61 3.7.6.2 5-Pulse Resilient Modulus Test 62 3.7.6.3 Dynamic Creep Test 65 3.7.6.4 Water Permeability Measurement 66 3.7.6.5 Cantabro Test 68 3.7.6.6 Binder Drainage Test 69 3.7.6.7 Moisture Susceptibility Test 70 3.7.6.8 Aging of Bituminous Mixtures 73 3.8 Number of Specimens 75 3.9 Summary 76

Chapter Four: Mix Design

4.1 Introduction 77 4.2 Mix Design of Dense Mixtures 78 4.2.1 Volumetric Properties of Dense Mixtures 78 4.2.1.1 Mix Density 79 4.2.1.2 Voids in Total Mix 80 4.2.1.3 Voids in Mineral Aggregates 82 4.2.1.4 Voids Filled with Binder 83

vi

4.2.2 Marshall Stability Test Result 84 4.2.3 Resilient Modulus Test Result 85 4.2.4 Optimum Binder Content of Dense Mixtures 86 4.3 Mix Design of Porous Mixtures 89 4.3.1 Cantabro Test Result 89 4.3.2 Binder Drainage 91 4.3.3 Volumetric Properties of Porous Mixtures 92 4.3.3.1 Mix Density of Porous Mixture 93 4.3.3.2 Porosity of Porous Mixtures 94 4.3.3.3 VMA of Porous Mixtures 95 4.3.3.4 VFB of Porous Mixtures 96 4.4 Design Binder Content of Porous Mixtures 96 4.5 Comparison with Others’ Results 97

4.5.1 Comparison of Mix Design Parameters Between SSDA, SSGDA and GDA 97

4.5.1.1 Mix Density 97 4.5.1.2 Voids in Total Mix 98 4.5.1.3 Voids in Mineral Aggregates 99 4.5.1.4 Marshall Stability 100 4.5.1.5 Resilient Modulus 101

4.5.2 Comparison of Mix Design Criteria between SSPA and GPA 102

4.5.2.1 Mix Density 102 4.5.2.2 Porosity 103 4.5.2.3 VMA 104 4.5.2.4 VFB 105 4.5.2.5 Abrasion Loss 106 4.5.2.6 Binder Drainage 108 4.5.2.7 Stability 109 4.6 Summary 110

Chapter Five: Mechanical Properties and Moisture Susceptibility of Dense and Porous Asphalt Mixes

5.1 Introduction 112 5.2 Resilient Modulus 112 5.2.1 Resilient Modulus of Dense Steel Slag Mixes 112 5.2.2 Resilient modulus of Porous Steel Slag Mixes 113 5.2.3 Effects of Temperature on Resilient Modulus 114 5.3 Dynamic Creep 119 5.3.1 Creep Modulus of Dense Steel Slag Mixes 119 5.3.2 Creep Modulus of Porous Steel Slag Mixes 121 5.3.3 Effects of Temperature on Creep Stiffness 125 5.4 Indirect Tensile strength 132 5.4.1 Indirect Tensile Strength of Dense Steel Slag

Mixes 132 5.4.2 Moisture Susceptibility 133 5.5 Permeability 135

vii

5.6 Evaluation of Stripping Potential of Steel Slag Aggregate-Asphalt Bonding 136

5.7 Cantabro Test on Water Soaked SSPA Specimens 137 5.8 Comparison with Other Test Results 139 5.8.1 Resilient Modulus of Dense Asphalt Mixes 139

5.8.2 Resilient Modulus of Porous Asphalt Mixes 140 5.8.3 Creep Modulus of Dense Asphalt Mixes 141

5.8.4 Creep Modulus of Porous Asphalt Mixes 142 5.8.5 Indirect Tensile Strength 144 5.8.6 Permeability 146 5.9 Summary 147 Chapter Six: Effects of Aging on Bituminous Mixture

Incorporating Steel Slag Aggregates

6.1 Introduction 149 6.2 Effects of Aging on Dense Mixture 150 6.2.1 Effects of Aging on Resilient Modulus 150

6.2.2 Aging Effects on Creep Stiffness of Dense Mixtures 156

6.3 Effects of Aging on porous Mixtures 163 6.3.1 Effects of Aging on Resilient Modulus of SSPA 163 6.3.2 Effects of Aging on Creep Stiffness of SSPA 164

6.3.3 Effects of Aging on Water Permeability and Abrasion Loss of SSPA 168

6.4 Comparison with Others Studies 171 6.5 Summary 176

Chapter Seven: Conclusions

7.1 Summary 177 7.2 Recommendations for Future Studies 181

References

183

Appendices

Appendix A Appendix B Appendix C

viii

List of Tables

Table 2.1: Steel Slag Properties and JKR Specifications

Table 2.2: Steel Slag Mechanical Properties and JKR Specifications

Table 2.3: Typical Physical Properties of Steel Slag

Table 2.4: Mechanical Properties of Steel Slag

Table 2.5: Typical Chemical Compositions of Steel Slag Used in this

Research and Granite

Table 2.6: Chemical Composition of Steel Slag Released by Natsteel,

FHWA and NSA

Table 3.1: Specific Gravity and Water Absorption of Steel Slag Aggregates

Table 3.2: Mix Designations of Specimens

Table 4.1: Volumetric Properties of SSDA

Table 4.2: Volumetric Properties of SSGDA

Table 4.3: Dense Mix Design Criteria

Table 4.4: Binder Drainage Test Result of SSPA

Table 4.5: Volumetric Properties of SSPA

Table 5.1: Percentage of Increment in Resilient Modulus of SSDA

Table 5.2: Percentage of Increment in Resilient Modulus of SSGDA

Table 5.3: Correlation between Resilient Modulus and Temperature

Table 5.4: Dynamic Creep Results of SSDA.

Table 5.5: Dynamic Creep Results of SSGDA

Table 5.6: Coefficients and Correlations of the Linear Relationships between

Creep Stiffness and Loading Cycle (SSPA)

ix


Accumulated Strain and Loading Cycle (SSPA)

Table 5.8: Dynamic Creep Test Results of SSDA (3600 Load Cycles)

Table 5.9: Dynamic Creep Test Results of SSDA (10000 Load Cycles)

Table 5.10: Dynamic Creep Test Results of SSGDA (3600 Load Cycles)

Table 5.11: Dynamic Creep Test Results of SSGDA (10000 Load Cycles)

Table 5.12: Coefficients of the Linear Relationships between Creep stiffness

and Load Cycle of SSDA at 40°C and 60°C

Table 5.13: Coefficients of the Linear Relationships between Creep stiffness

and Load Cycle of SSGDA at 40°C and 60°C

Table 5.14: Coefficients of the Linear Relationships between Accumulated

Strain and Load Cycle of SSDA at 40°C and 60°C

Table 5.15: Coefficients of the Linear Relationships between Accumulated

Strain and Load Cycle of SSGDA at 40°C and 60°C

Table 5.16: Determination of Degree of Stripping for SSDA and SSGDA

Table 5.17: Average Coefficients of the Linear Relationships between Log-

Creep stiffness and Log-Load Cycle (SSPA)


Creep stiffness and Log-Load Cycle (GPA)


Accumulated Strain and Log-Load Cycle (SSPA)


Accumulated Strain and Log-Load Cycle (GPA)

Table 6.1: Resilient Modulus at OBC (SSDA and SSGDA Mixes)

x

Table 6.2: Effect of Aging on Resilient Modulus of SSDA Mixes after STOA

and LTOA

Table 6.3: Effect of Aging on Resilient Modulus of SSGDA Mixes after STOA

and LTOA

Table 6.4: Creep Modulus of Aged SSDA and SSGDA Specimens


Accumulated Strain and Loading Cycle of Unaged and Aged

SSDA Mixes


Accumulated Strain and Loading Cycle of Unaged and Aged

SSGDA Mixes


Creep Stiffness and Loading Cycle (SSPA Mixes, STOA)


Creep Stiffness and Loading Cycle (SSPA Mixes, LTOA)


Accumulated Strain and Loading Cycle (SSPA Mixes, STOA)

Table 6.10: Coefficients and Correlations of the Linear Relationships

between Accumulated Strain and Loading Cycle (SSPA Mixes,

LTOA)

Table 6.11: Effects of Aging on Abrasion Loss and Water Permeability of

SSPA Mixes

Table 6.12: Correlation between Coefficient of the Linear Relationship

between Permeability and Binder Content for Unage and Aged

SSPA Mixes

xi

Table 6.13: Comparison of Resilient Modulus Results for SSPA, SSDA,

SSGDA and GDA Mixes

Table 6.14: Percentage of Increment for Resilient Modulus of Dense Asphalt

Mixes Subjected to Aging

Table 6.15: Comparison of Creep Stiffness and Axial Strain between SSDA,

SSGDA and GPA Mixes

xii

List of Figures

Figure 2.1: Overview of Steel Slag Production in A Modern Intergrated Steel

Plant.

Figure 2.2: Flow Diagram of Steel Slag Production Through BOF and EAF.

Figure 3.1: Flow of Methodology Carried Out in This Research

Figure 3.2: ACW 14 gradation for SSDA, SSGDA and GDA

Figure 3.3: Gradation for SSPA and GPA (Samat, 2006)

Figure 4.1: Mix Density versus Binder Content (SSDA and SSGDA Mixes)

Figure 4.2: VTM versus Binder Content (SSDA and SSGDA Mixes)

Figure 4.3: VMA versus Binder Content (SSDA and SSGDA Mixes)

Figure 4.4: VFB versus Binder Content (SSDA Mixes)

Figure 4.5: Marshall Stability versus Binder Content (SSDA and SSGDA

Mixes)

Figure 4.6: Flow versus Binder Content (SSDA and SSGDA Mixes)

Figure 4.7: Resilient Modulus versus Binder Content (SSDA and SSGDA

Mixes)

Figure 4.8: Determination of OBC for SSDA and SSGDA Mixes

Figure 4.9: Abrasion Loss versus Binder Content (SSPA Mixes)

Figure 4.10: Retained Binder versus Mix Binder Content (SSPA Mixes)

Figure 4.11: Density versus Binder Content (SSPA Mixes)

Figure 4.12: Porosity versus Binder Content (SSPA Mixes)

Figure 4.13: VMA versus Binder Content (SSPA Mixes)

Figure 4.14: VFB versus Binder Content (SSPA Mixes)

xiii

Figure 4.15: Density versus Binder Content (SSDA, SSGDA and GDA

Mixes)

Figure 4.16: VTM versus Binder Content (SSDA, SSGDA and GDA Mixes)

Figure 4.17: VMA versus Binder Content (SSDA, SSGDA and GDA Mixes)

Figure 4.18: Marshall Stability versus Binder Content (SSDA, SSGDA and

GDA Mixes)

Figure 4.19: Resilient Modulus versus Binder Content (SSDA, SSGDA and

GDA Mixes)

Figure 4.20: Density versus Binder Content (SSPA and GDA Mixes)

Figure 4.21: Porosity versus Binder Content (SSPA and GDA Mixes)

Figure 4.22: VMA versus Binder Content (SSPA and GPA Mixes)

Figure 4.23: VFB versus Binder Content (SSPA and GPA Mixes)

Figure 4.24: Abrasion Loss versus Binder Content (SSPA and GPA Mixes)

Figure 4.25: Binder Drainage Test Results of SSPA and GPA Mixes

Figure 4.26: Stability versus Binder Content (SSPA and GPA Mixes)

Figure 5.1: Resilient Modulus versus Binder Content (SSDA and SSGDA

Mixes)

Figure 5.2: Resilient Modulus versus Binder Content (SSPA Mixes)

Figure 5.3: Resilient Modulus versus Binder Content (SSDA Mixes)

Figure 5.4: Resilient Modulus versus Binder Content (SSGDA Mixes)

Figure 5.5: Resilient Modulus versus Temperature (SSDA Mixes)

Figure 5.6: Resilient Modulus versus Temperature (SSGDA Mixes)

Figure 5.7: Resilient Modulus versus Temperature (OBC)

Figure 5.8: Creep Stiffness versus Binder Content (SSDA Mixes)

Figure 5.9: Creep Stiffness versus Binder Content (SSGDA Mixes)

xiv

Figure 5.10: Creep Stiffness versus Binder Content (SSPA Mixes)

Figure 5.11: Creep Stiffness versus VTM (SSPA Mixes)

Figure 5.12: A Typical Graphical Illustration of the Creep Stiffness versus

Load Cycle Relationship (SSPA Mixes)

Figure 5.13: A Typical Graphical Illustration of the Accumulated Strain

versus Load Cycle Relationship (SSPA Mixes)

Figure 5.14: A Typical Graphical Illustration of the Creep Stiffness versus

Load Cycle Relationship (SSDA at 40°C and 60°C)

Figure 5.15: A Typical graphical Illustration of the Creep Stiffness versus

Load Cycle Relationship (SSGDA at 40°C and 60°C)


versus Load Cycle Relationship (SSDA at 40°C and 60°C)


versus Log-Load Cycle Relationship (SSGDA at 40°C and

60°C)

Figure 5.18: Tensile Strength versus Binder Content (SSDA and SSGDA

Mixes)

Figure 5.19: Tensile Strength versus Binder Content (SSDA Mixes)

Figure 5.20: Tensile Strength versus Binder Content (SSGDA Mixes)

Figure 5.21: Coefficient of Permeability versus Binder Content (SSPA Mixes)

Figure 5.22: Coefficient of Permeability versus Porosity (SSPA Mixes)

Figure 5.23: Abrasion Loss versus Number of Rotation (Fresh and

Conditioned SSPA Mixes)

Figure 5.24: Resilient Modulus versus Binder Content (SSDA, SSGDA and

GDA Mixes)

xv

Figure 5.25: Resilient Modulus versus Binder Content (SSPA and GPA

Mixes)

Figure 5.26: Creep Stiffness versus Mixture Type (SSDA, SSGDA and GDA

Mixes)

Figure 5.27: Creep Modulus versus Binder Content (SSPA and GPA Mixes)

Figure 5.28: ITS comparison between SSDA, SSGDA and GDA Mixes

Figure 5.29: Water Permeability versus Binder Content (SSPA and GPA

Mixes)

Figure 5.30: Coefficient of Permeability versus Porosity (SSPA and GPA

Mixes)

Figure 6.1: Resilient Modulus at 10°C versus Binder Content (Unaged and

Aged SSDA Mixes)


Aged SSDA Mixes)


Aged SSDA)


Aged SSGDA)


Aged SSGDA)


Aged SSGDA)

Figure 6.7: Creep Modulus versus Binder Content (Aged SSDA Mixes)

Figure 6.8: Creep Modulus versus Binder Content (Aged SSGDA Mixes)

xvi

Figure 6.9: A Typical Graphical Illustration of Creep Modulus versus Load

Cycle Relationship for Aged SSDA and Aged SSGDA Mixes

Figure 6.10: A Typical Graphical Illustration of Accumulated Strain versus

Load Cycle Relationship (Aged SSDA and Aged SSGDA Mixes)

Figure 6.11: A Typical Graphical Illustration of Axial Strain versus Load

Cycle Relationship (Unaged and Aged SSDA Mixes)

Figure 6.12: A Typical Graphical Illustration of Axial Strain versus Load

Cycle Relationship (Unaged and Aged SSGDA Mixes)

Figure 6.13: Resilient Modulus versus Binder Content (Aged and Unaged

SSPA Mixes)

Figure 6.14: A Typical Graphical Illustration of Creep Modulus versus Load

Cycle Relationship (Unaged and Aged SSPA Mixes)

Figure 6.15: A Typical Graphical Illustration of Accumulated Strain versus

Load Cycle Relationship (Unaged and Aged SSPA Mixes)

Figure 6.16: Coefficient of Permeability versus Binder Content (Aged and

Unaged SSPA Mixes)

Figure 6.17: Abrasion Loss versus Binder Content (Aged and Unaged SSPA

Mixes)

Figure 6.19: Resilient Modulus versus Temperature (Aged Dense Mixes)

Figure 6.20: Comparison of Axial Strain between Unaged and Aged SSDA,

SSGDA and GDA Mixes

xvii

List of Plates

Plate 3.1: Darin Asphalt Modified Additive Used in This Research

Plate 3.2: Adding DAMA in Dry Mix Process

Plate 3.3: Material Testing Apparatus (MATTA) Used in this Research

Plate 3.4: Testing Jig Used for Resilient Modulus Testing

Plate 3.5: Permeameter at Highway Engneering Laboratory, USM

Plate 3.6: Arrangement of Loose Mix in the Force Draft Oven

Plate 4.1: Fresh Specimen (left) and Specimen after Going Through the

Cantabro Test (right)

Plate 4.2: Granite Aggregates (left) and Steel Slag Aggregates (right)

xviii

List of Abbreviations

AASHTO American Association of State Highway and Transportation

Officials

ACV Aggregate Crushing Value

ACW Asphaltic Concrete Wearing Course

AIV Aggregate Impact Value

ASTM American Society of Testing and Material

BOF Basic Oxygen Furnace

CaCO3 Calcium Carbonate

Ca (OH2) Calcium Hydroxide

CaCO3 Carbon Dioxide, Calcite

DAMA Darin Asphalt Modified Additive

DBC Design Binder Content

EAF Electric Arc Furnace

FEhS Forschungsgemeinschaft Eisenhϋttenschlacken e.V.

(Research Association for iron and Steel Slags)

FHWA Federal Highway Administration

GDA Granite Dense Asphalt

GPA Granite Porous Asphalt

HMA Hot Mix Asphalt

JIS Japan Industrial Standards

LAAV Los Angeles Abrasion Value

LTOA Long Term Oven Aging

NSA Nippon Slag Association

xix

OBC Optimum Binder Content

PG Penetration Grade

SG App Apparent Specific Gravity

SG Dry Dry Specific Gravity

SG SSD Surface Saturated Specific Gravity

SSDA Steel Slag Dense Asphalt

SSGDA Steel Slag/ Granite Dense Asphalt

SSPA Steel Slag Porous Asphalt

STOA Short Term Oven Aging

USA United States of America

USEPA United States Environmental Protection Agency

USGS United States Geological Survey

VFB Voids Filled with Bitumen

VMA Voids in Mineral Aggregate

VTM Voids in Total Mix

xx

Penilaian Prestasi Slag Besi Sebagai Pengganti Agregat Semula Jadi

dalam Konkrit Asfalt

Abstrak

Slag besi ialah salah satu bahan buangan industri yang dijadikan agregat

pembinaan jalan raya. Penyelidikan ini dijalankan untuk mengkaji prestasi

agregat slag besi sebagai bahan pembinaan jalan raya serta

membandingkan prestasinya dengan agregat granit. Slag besi yang

digunakan diuji untuk mendapatkan sifat fizikal dan mekanikalnya. Dua reka

bentuk campuran tumpat dengan bitumen gred penusukan 80/100 dan satu

reka bentuk campuran berliang dengan bitumen gred penusukan 60/70 juga

digunakan dalam penghasilan spesimen ujian. Spesimen campuran tumpat

dirujuk sebagai Asfalt Padat Slag Besi 100% (SSDA) dan Asfalt Padat 50%

Slag Besi 50% Granit (SSGDA) manakala campuran berliang dirujuk

sebagai Asfalt Berliang Slag Besi (SSPA). Dalam fasa pertama

penyelidikan, SSDA dan SSGDA diuji untuk menilai prestasinya melalui ciri

modulus kebingkasan, rayapan dinamik, kestabilan Marshall dan kekuatan

tegangan tak langsung. Selain ujikaji yang dinyatakan (kecuali kekuatan

tegangan tak langsung), SSPA juga dinilai melalui ujikaji Cantabro dan ujikaji

kebolehtelapan air. Untuk fasa kedua penyelidikan, ujikaji dalam fasa

pertama dijalankan ke atas spesimen yang melalui proses penuaan.

Rintangan campuran tumpat dan campuran berliang terhadap rayapan dan

retakan pada suhu rendah diperbaik selepas proses penuaan. Keputusan

ujikaji menunjukkan bahawa slag besi berpotensi besar untuk dijadikan

bahan pembinaan jalan raya.

xxi

Performance Evaluation of Steel Slag as Natural Aggregates

Replacement in Asphaltic Concrete

Abstract

Steel slag is one of the industry wastes engineered into road construction

material. This study was carried out to evaluate the performance of steel

slag aggregates as road construction material and its performance

compared to granite aggregates. The steel slag aggregates were tested for

its physical and mechanical properties. Two dense mix designs

incorporating penetration grade 80/100 bitumen and one porous mix design

incorporating penetration grade 60/70 bitumen were used to produce the

specimens for testing. The dense mix specimens are referred to as 100%

Steel Slag Dense Asphalt (SSDA) and 50% Steel Slag 50% Granite Dense

Asphalt (SSGDA) while the porous mix specimens are referred to as Steel

Slag Porous Asphalt (SSPA). During the first phase of the study, SSDA and

SSGDA were tested for performance evaluation through resilient modulus,

dynamic creep, Marshall stability and indirect tensile strength. Apart from

the tests stated (except for indirect tensile strength), SSPA were also tested

for abrasion loss and water permeability. In the second phase of the study,

the same tests as those carried out in the first phase were carried out on

aged specimens. Resistant against permanent deformation and low

temperature cracking improved after aging for both dense mixes and porous

mixes. Test results revealed that steel slag inhibits great potential as road

construction material.

1

Chapter 1

Introduction

1.1 Introduction to Steel Slag

Enormous quantities of waste materials are generated every year in

Malaysia. As the country’s population and industries grow, so do the amount

and type of waste materials generated. Schroeder (1994) reported that

many of these waste materials were non-decaying elements and will remain

in the environment for hundreds and perhaps thousands of years. This

situation combined with the ever increasing consumer population and

demand, has resulted in a waste disposal crisis. The facts about reduced

cost on extracting and processing new raw material and consumption of

virgin materials through reusing these materials are stated in various studies

since the past decades. Engineering waste materials innovatively and

effectively into road construction materials can address concerns about the

vast quantities of useful materials being discarded and wasted. One of

these waste materials which could be made into good use for road

construction is steel slag.

See and Hamzah (2002) also reported that steel slag amounts to

approximately 10% of liquid steel output in a typical steel producing plant

and represents the major waste item generated from the steel making

industry. The cost for committing to an environmental friendly disposal plan

can add tremendous burden to the industry. The solutions to this crisis lie in

2

recycling and engineering these waste materials into useful products and

reuse them for constructions and developments of the nation.

Steel slag is a by-product of the steel producing process, containing

fused mixtures of oxides and silicates. Its highly compressed structure

resulted in a very dense and hard material. It is the coarse portion of the

residues produced during the separation of the molten steel from impurities

in steel making furnaces (See and Hamzah, 2002). Steel slag occurs to be

in liquid melt of complex solution containing silicates and oxides, primarily

calcium, iron, unslaked lime and magnesium and solidified upon cooling

(TFHRC, 2002)

Ali et al (1992) pointed out that steel slag asphalt concrete mixes

have been used in countries such as the United States, England, Japan and

Canada, particularly in areas with high concentration of iron and steel

production. The use of steel slag as an aggregate substitute to natural

aggregates is considered a standard practice in many jurisdictions, with

applications that include its use in granular base, embankments, engineered

fill, highway shoulders, and hot mix asphalt pavement. Experience gained in

southern Ontario since early 1970’s has shown that the use of steel slag in

asphalt concrete provides the advantageous features of the steel slag which

results in high quality mix.

3

1.2 Objectives

The aim of this research is to study the performance of steel slag as

road pavement aggregates compared to the conventional use of granites for

the same purpose. The detailed objectives are outlined below:

(1) To assess the performance of dense bituminous mix prepared using

100% steel slag (SSDA) and dense bituminous mix incorporating a

combination of 50% granite and 50% steel slag (SSGDA).

(2) To appriase the performance of porous asphalt incorporating steel

slag (SSPA) as road pavement aggregates compared to the

performance of conventional porous asphalt incorporating granite

aggregates (GPA).

(3) To evaluate the effect of moisture, temperature and aging on the

performance of mixes incorporating steel slag.

(4) To compare the performance of SSDA and SSGDA with dense

bituminous mix incorporating 100% granite aggregates (GDA) and to

compare the performance of SSPA with porous bituminous mix

incorporating 100% granite (GPA) .

1.3 Justification of Research

Steel slag aggregate is a 100% recycled and engineered product with

great potential as replacement to naturally occurring aggregates in road

construction projects due to its physical and chemical properties. Most

projects involving steel slag aggregate were incorporating this aggregate

type in lower quality applications such as road base rather than wearing

4

course. However, steel slag aggregate was reported to exhibit higher

porosity, superior adhesion with binder due to its surface structure and

chemical content, and favorable shapes. Pores continuity in steel slag

aggregate may improve the water permeability in asphalt mixes and improve

the skid resistance and aquaplaning, while the superior adhesion with

bitumen may address the problem of stripping and moisture related damage

on pavement. These characteristics may improve the performance of

asphalt mixes and road safety level. Previous studies also suggested that

asphalt mixtures incorporating steel slag aggregate may also improve the

resistance against rutting and cracking.

From the economic point of view, utilization of steel slag as road

construction aggregate may reduce the cost of extracting and processing

naturally occurring aggregates. The steel producing industry may also

reduce their cost for treating and disposing the vast number of steel slag

stockpiles. Since the early days of Malaysian roads development, economic

factor had played a major role in deciding the routes and qualities of paved

roads. Malaysian road authorities activated a huge amount of funding to

preserve the road structures in this country. Hundreds of millions Ringgit

Malaysia had been allocated for road constructions and maintenances in

every Malaysian Plan. While the lifespan of a pavement may be increased,

the maintenance cost for pavements may also reduce, thus providing more

funds for other development projects.

On its impact at preserving the environment, utilization of steel slag

aggregate in various ways may directly reduce both the dependent on

5

naturally occurring aggregate and the number of raw material-extracting

projects. On the other hand, incorporating steel slag in road construction

projects may reduce the area used as landfill.

1.4 Scope of Work

The scope of work for this research is to develop bituminous mixes

compatible or out performing existing conventional bituminous mixes, using

steel slag and a combination of 50% steel slag and 50% granite as

aggregates.

The mix type investigated was a dense mix confirming to the JKR

ACW14 gradation using 100% steel slag (SSDA), 100% granite (GDA) and

combination of 50% steel slag and 50% granite (SSGDA). Bitumen

penetration grade 80/100 was incorporated as the binder for all dense mix

design. The performance of GDA stated in this study was obtained from

Mohamed (2007) and used as a comparison to the performance of SSDA

and SSGDA. Besides, porous mixes confirming to the gradation developed

by Samat (2006) using 100% steel slag (SSPA) and 100% granite (GPA)

were also studied. For porous mixes, the binder type used was penetration

grade 60/70. Darin Asphalt Modified Additive (DAMA) was also incorporated

in both mixes in the form of a dry process. DAMA was developed by Darin

Tech Corporation Ltd., Korea. A detailed description of DAMA is available

elsewhere (Samat, 2006).

Steel slag aggregates were obtained from the Natsteel plant at the

Prai Industrial Area. These aggregates were selected from two different

6

stockpiles of coarse aggregates (> 10mm) and fine aggregates (< 10mm).

These aggregates were then crushed and sieved into their designated bins.

A range of tests was carried out to evaluate the mix properties and

performance, including obtaining volumetric properties, the optimum binder

content, stability, potential of cracking and permanent deformation,

susceptibility to moisture, water permeability and abrasion loss. These

testing procedures were repeated for specimens subjected to accelerated

ageing process in a force draft oven to evaluate their performance under

service. The test results of mixes incorporating steel slag aggregates were

then compared with those of conventional mixes.

1.5 Organization of the Thesis

An introduction to this research is presented in chapter one. This

chapter briefly outlined the objectives and scope of work to fulfill the

necessary evaluation of steel slag aggregates as road construction material.

The studies on steel slag as road construction material had been

continuously carried out in an advancing manner. An overview of previous

studies on the feasibility, performance and suitability of steel slag aggregates

as road construction material is summarized in the next chapter. Various

topics regarding aggregates properties, mix designs, testing methods and

test results compiled in laboratory and field tests from these studies and

researches are related in this chapter.

7

A description of the materials used in this research is narrated in

chapter three. Included in the discussions are the naturally occurring granite

aggregate, the engineered steel slag aggregate, fillers and additive used to

produce the test specimens. The different properties inhibited by steel slag

aggregate and their relationship to the acceptability of steel slag as road

construction material is also detailed in this section. On the other hand, the

handling of the materials and methods used for mixture design and testing of

the test specimens are crucial to obtain consistent outcome. The

procedures for preparing SSPA, SSDA and SSGDA specimens are outlined

in the fourth chapter of this thesis. Once the specimens are designed, their

engineering properties and performances need to be determined. These

testing methods and analysis techniques are also related in this chapter.

The mix design parameters including the volumetric properties of

mixes incorporating steel slag are evaluated, and analysis of the results is

discussed in chapter four. The patterns of these results, including the

advantages and shortcomings are then studied and compared between steel

slag bituminous mixes and granite bituminous mixes. Through the

compilation of results in the form of figures and tables, the analysis provides

the optimum binder content for the steel slag mixes and a better view of the

best possible way to cooperate these mixes into practical usage.

Apart from the tests mentioned in chapter four, there are several

other tests conducted to thoroughly evaluate the mechanical properties of

mixes incorporatng steel slag aggregates. These test results in chapter five

8

provides a prediction on the performance of these mixes including the tensile

strength and creep behaviour under simulation of the service conditions.

The effects of moisture susceptibility and temperature on the specimens

tested are also available. Moisture is one crucial factor which influences the

performance and lifespan of a pavement. In places with very cold climate,

the presence of moisture in the pavement structure could mean intensive

damage due to ice and cracking. Besides, there are also discussion on the

matter of possible loss of bonding between aggregate and asphalt due to

moisture. Temperature changes affected the viscosity of asphalt hence

playing a role in affecting the performance of the mixes.

The durability of steel slag mixes are put to the test through the

accelerated aging process and the results obtained are discussed in chapter

six. The simulated performance of steel slag mixes after seven to ten years

in service is evaluated and detailed in this part of the thesis.

The conclusions provided a clear view of the achieved objectives and

justifications of this research. Besides, a list of scope and possibility of

improvements related to this study for further researches is also enclosed in

chapter seven.

9

Chapter 2

Literature Review

2.1 Introduction

Asphalt mixture designs around the world were developed on the

basis of producing the most suitable combination of aggregate and binder

which provides the best performing roads with the longest possible lifespan.

The designated mixture must suits the respective geological and climate

conditions, traffic and economy demands, and interpolations of future

developments. A good design of bituminous mix was expected to result in a

mix which is adequately strong, durable, and resistive to damages due to

either traffic loads or climate changes, environmental friendly, economical

and any other related criteria.

Mix designs were achieved by putting test mix specimens with varied

proportions through numerous tests and finalized the best one which

complied with the set requirements. This process often resulted in a balance

mixture incorporating mutually conflicting parameters. One of the most

crucial aspects of mix design is to obtain the most qualified materials and

engineered it into an ideal aggregate for road construction. For centuries,

the aggregates used for road constructions were naturally occurring rocks

and the most frequently used were granites. Nevertheless, contemporary

studies have unearthed more synthetic and artificial materials fit to qualify as

aggregates for road construction.

10

2.2 Efforts in Utilizing Waste Materials as Construction Materials

The United States of America had been one of the earliest nations

utilizing waste and recycled materials in the construction field. These efforts

were continuously documented since decades ago. A recent report entitled

‘Transportation: Leading in Recycling’ (AASHTO, 2003) reported the

following efforts by various road authorities in the United States on the

matter of utilizing recycled materials in road constructions:

(a) The Texas Department of Transportation (TxDOT) had spent more

than USD 506 million on ‘green products’ and diverted more than 13

million tons of materials from the landfill since launching its recycling

program in 1994.

(b) Pennsylvania Department of Transportation (PennDOT) started the

Strategic Recycling Program as a comprehensive effort to

systematically identify, evaluate, and implement recycling

opportunities throughout Pennsylvania. They also worked in hand

with the state Department of Environmental Protection to reduce

waste materials from transportation operations and to encourage use

of recycled materials throughout transportation applications in the

state.

(c) The Massachusetts State Transportation Agency (MassHighway)

reported an impressive statistics, including recycling more than

15,000 tons of waste and more than 111,000 tons of recycled

11

materials were used in construction projects. Overall, nearly USD 27

million was spent on recycled-content and environmentally preferable

materials and products.

(d) The California Department of Transportation (Caltrans) recycled

asphalt and concrete pavement by converting it into base and sub-

base under the new road surface, and at the same time the agency is

looking for new ways to use recycled materials in road surfaces.

In an effort to study the utilization of recycled materials in road

constructions, the University of Texas in Austin, United States of America

(USA) undertook three substantial and creative research initiated by their

Center of Transportation Research (CTR) from the Cockrell School of

Engineering on behalf of the Texas Department of Transportation (TxDOT)

involve old tires, used copier and printer toner, and fly ash (CTR, 2002).

Combs (2001) quoted in a fiscal note that recycled materials

commonly used by TxDOT included recycled asphalt pavement (RAP),

which was made by taking the top layer of existing asphalt during road

expansion or replacement and separated it, dried it and mixed it with new

asphalt pavement and according to the United States Environmental

Protection Agency, more than 80 million tons of RAP were placed back into

new roads, shoulders and embankments in the USA each year.

12

Efforts in minimizing the wastage of reusable materials in construction

projects were evenly comparable across the Atlantic Ocean. The Europeans

had started using recycled materials especially in road constructions since

the 1970s. A number of countries in Europe had been routinely using

recycled materials with a high degree of success. The most remarkable

thing about the European experience was that the recycling rate of materials

in the highway environment frequently reaches 100 percent. The utilization

of recycled materials in Europe had even matured beyond the standard set

by the Americans. Remarkable efforts in utilizing recycled materials were

reported in Germany, Sweden, Denmark and Netherland due to respective

social, economy and geological requirements. These efforts were

mentioned by Holtz and Eighmy (2000) in a report for Federal Highway

Administration (FHWA).

2.2.1 Utilization of Waste Materials in Road Constructions

Noureldin and McDaniel (1989) mentioned that the demand for good

quality highway materials continued to increase whereas economical

sources were becoming more limited. This demand became more critical,

especially with the policy (adopted by some USA state highway

departments) of banning some aggregate types that had been frequently

used in the past for producing paving mixtures.

Davio (2000) stated that according to the United States Geological

Survey (USGS), more than 330 million tons (300 million metric tons) of

crushed stone were used in road base during 1996. The mining of such

13

stone, however, was being constrained by urbanization, zoning regulations,

increased costs, and environmental concerns. In some parts of the United

States, the supply of local stone was exhausted, requiring long hauls and

higher prices

Davio (2000) also reported that several alternative materials were

incorporated into the mix design of road construction projects besides

naturally occurring aggregates since decades ago and among them were

blast furnace slag, steel slag, plastic, glass, ashes, reclaimed concrete,

reclaimed asphalt concrete or reclaimed asphalt pavement and scrap tires.

Schroeder (1994) reported that in 1992, 6.9 million metric tons (7.6

million tons) of steel slag was sold in the United States at a total value of

USD21.9 millions. The average selling price for steel slag at the plant was

USD3.02 per metric ton. Besides, Schroeder (1994) also quoted a

statement from the Bureau of Mines reporting that some 14 million metric

tons of blast furnace slag were sold in the United States in 1992 and out of

this value, 90% were air-cooled slag primarily used in road constructions. In

other cases, plastics were recycled and used as polyethene additive in

asphalt mix designs.

Holtz and Eighmy (2000) stated that in the United States, the process

of recycling waste materials were estimated to be producing between 352

million tons (320 million metric tons) and 859 million tons (780 million metric

tons) recycled materials per year. When compared to the use of new

14

materials in highway construction which was estimated to be about 350

million tons (317.5 million metric tons) per year of which 320 million tons

(290 million metric tons) were used as aggregate in the mid-1990s, Holtz

and Eighmy (2000) mentioned it was obvious that there were potentially a

number of recycled materials that could be considered as substitutes

provided that they were economical, met engineering and environmental

specifications, and performed as well as traditional materials in the field.

In Sweden, a large country with a relatively low population density

and high aggregate availability, 45% blast furnace slag, 100% steel slag and

95% RAP were reused in road constructions. Germany, a larger country

with much industry and high aggregate availability, incorporated 100% blast

furnace slag, 92% steel slag, 97% coal bottom ash, 88% coal fly ash, 69%

municipal solid waste combustion bottom ash, and 55% RAP into road

constructions. While, Denmark, with a high population density and low

natural aggregate availability, utilized 100% steel slag, 81% crushed

concrete, 100% coal bottom ash, 100% coal fly ash, 100% RAP in road

constructions and finally, the Netherlands, a populous country with more

limited aggregate resources and a high degree of industrialization, had a

100% recycling rate in several categories. 100% of all recycled materials

were engineered into construction materials due to their close loop recycling

policy where recycled and waste materials were continually reused without

wastage (Holtz and Eighmy, 2000).

The utilization of recycled materials in road construction started to

gain attentions in country which previously considered these secondary

15

materials as inferior products only fitted for marginal applications. New

Zealanders, due to less availability of natural sources in recent times,

initiated their first stretch of pavement incorporating 100% recycled materials

through Fulton Hogan in 2003 (Slaughter, 2005).

In Japan, the Japan Iron and Steel Federation (JISF) and Nippon Slag

Association (NSA) have promoted the institution and widespread adoption of

Japan Industrial Standards (JIS). As a result, 99% of slag was useful

material and employed by national agencies such as the Ministry of Land,

Infrastructure and Transport and by local governments and other users, and

it had gained both high acclaim and certification (NSA, 2006).

Using recycled materials in road construction offered opportunities to

use huge quantities of recycled materials while extending the supply of

traditional construction materials and ensuring good-quality roads. The

United States Geological Survey (USGS) calculated that even though the

use of recycled crushed concrete aggregates increased by 170 percent

between 1994 and 1996, it still constituted only 0.4 percent of the total

aggregates consumed in 1995 (Davio, 2000).

2.2.2 Advantages of Utilizing Waste Materials in Road Construction

Recycled materials can be a source of good quality, cost effective

road materials that also benefit the environment. Using recycled materials

can frequently improve materials performance and reduce the rate of natural

resources depletion. Using recycled materials may also cut costs because

16

materials costs may be less than new materials; transportation/delivery costs

may be less; and disposal costs for job-site materials may be less.

Utilization of recycled materials benefits the environment by extending the

life of limited natural resources, reducing air and water pollution, and

extending landfill life. The use of waste materials (recycling) in the

construction of pavements has benefits in not only reducing the amount of

waste materials requiring disposal but can provide construction materials

with significant savings over new materials. The use of these materials can

actually provide value to what was once a costly disposal problem (USACE,

1999 and, Wilburn and Goonan, 1998).

2.2.3 Problems Concerning Utilization of Recycled Materials in Road

Constructions

Utilization of recycled materials might address the problems

concerning the environment and exhaustion of naturally occurring

aggregates, but there are still a few concerns raised by researchers

regarding leaching, future reusable value, production cost and availability,

properties, quality control and consistency as mentioned by Kandhal (1992).

The United States Environmental Protection Agency (USEPA) Office

of Solid Waste mentioned their concern over the potential environmental

damage caused by mishandling of recycled materials in a very recent report.

The concerns included leaks, spills, dumps or other types of hazardous

substances released into the environment, which were serious enough to

require some type of cleanup actions (USEPA, 2007).

17

Wilburn and Goonan (1998) mentioned that comprehensive planning

should be done before recycling operation began to avoid premature failure.

They feared that without proper site layout, equipments, operator efficiency

and creative marketing, the whole project may go into abrupt.

2.3 Material Description of Steel Slag

The German Research Association for Iron and Steel Slag described

steel slag as a non-metallic by-products generated from the non-metallic

constituents of the raw materials ore, coke and fluxes during the production

of steel. After slow cooling in air they form an artificial crystalline rock. Their

formation was comparable to that of natural magmatic rocks like basalt or

granite. Molten slag fulfilled important metallurgical functions and must be

distinguished from ashes which were residues of incineration processes.

Steel slag was separated from the liquid metal at the end of the metallurgical

treatment by means of their lower density. The separated slag underwent

appropriate heat treatment processes followed by mechanical processing to

provide the specific properties required by standards and regulations (FEhS,

2004).

The Japan Iron and Steel Federation and Nippon Slag Association

narrated that the steel-making process consists of refining pig iron, scrap

and other material to produce steel, either in a basic oxygen furnace or an

electric arc furnace. Steel slag (basic oxygen furnace slag and electric arc

furnace slag) was the by-product generated from this steel-making process,

in amounts of 110 to 120 kg per ton of crude steel (NSA, 2006).

18

See and Hamzah (2002) on the other hand described steel slag as a

by-product generated during steel making due to addition of flux such as

lime during the melting process. The flux reacted with the oxides or any

inorganic non-metallic components present in the metallic scrap and formed

complex minerals comprising of various forms of metal oxides silicates,

ferrites and others.

2.4 Source of Steel Slag

Steel slag could normally be obtained from slag processors who

collected the slag from steel-making facilities. Slag processors handled a

variety of materials such as steel slag, ladle slag, pit slag, and used

refractory material to recover steel metallic. These materials were source

separated, and well-defined handling practices were in place to avoid

contamination of the steel slag aggregate. The slag processors were also

aware of the general aggregate requirements of the end user (Liz Hunt and

Boyle, 2000).

FHWA mentioned that the processing of steel slag from metals

recovery was not only important to remove excess steel at the source for

reuse at the steel plant, but was also important to facilitate the use of the

nonmetallic steel slag as construction aggregate. This nonmetallic slag

could either be crushed, then screened for aggregate use (steel slag

aggregates), or sintered and recycled as flux material in the iron and steel

furnaces (TFHRC, 2002).

19

2.5 Production of Steel Slag

Steel Slag was generated as a melt at about 1650°C during

steelmaking from hot metal, direct reduced iron or scrap. It consisted of

oxidized co-elements of the hot metal and other metallic charges which

reacted with the added limestone and dolomite. Depending on the process

technology, one could distinguish Basic Oxygen Furnace (BOF), Open

Hearth, and Electric Arc Furnace (EAF) slag (FEhS, 2004).

There were several different types of steel slag produced during the

steel-making process. These different types were referred to as furnace or

tap slag, raker slag, synthetic or ladle slag, and pit or cleanout slag. Figure

2.1 presented a diagram of the general flow and production of different slag

in a modern steel plant. The steel slag produced during the primary stage of

steel production was referred to as furnace slag or tap slag. This was the

major source of steel slag aggregate. After being tapped from the furnace,

the molten steel was transferred in a ladle for further refining to remove

additional impurities still contained within the steel. This operation was

called ladle refining because it was completed within the transfer ladle.

During ladle refining, additional steel slags were generated by again adding

fluxes to the ladle to melt. These slags were combined with any carryover of

furnace slag and assist in absorbing deoxidation products (inclusions), heat

insulation, and protection of ladle refractories. The steel slags produced at

this stage of steel making were generally referred to as raker and ladle slags

(TFHRC, 2002).

20

Figure 2.1: Overview of Steel Slag Production in A Modern Intergrated Steel

Plant. (TFHRC, 2002)

According to See and Hamzah (2002), the most commonly found

steel slag in Malaysia is EAF slag. This slag was formed from re-melting of

steel and iron scrap. EAF method utilized high voltage current to melt the

scrap. This method involved the removal of excess carbon, silicon and other

elements from the molten iron. This process was aided by the addition of

lime as part of the flux which serves to combine the unnecessary

constituents contained in the iron source and separated them (i.e. the

resulting slag) from the molten steel.

In the basic oxygen process, hot liquid blast furnace metal, scrap, and

fluxes, which consist of lime (CaO) and dolomitic lime (CaO.MgO or

“dolime”), were charged to a converter (furnace). A lance was lowered into

Feedsback

Primary Steelmaking

(Furnace) Transfer

Ladle

Synthetic Flux

Addition

Ladle Waste & Dumped Residue

Furnace Slag

Raker Slag

Ladle Slag

Clean Out Or Pit Slag

Metals Recovery

Metals Recovery

Nonmetallic Steel Slag for Potential Aggregate Use Slag for

Disposal

21

the converter and high-pressure oxygen is injected. The oxygen combined

with and removed the impurities in the charge. These impurities consisted

of carbon as gaseous carbon monoxide, and silicon, manganese,

phosphorus and some iron as liquid oxides, which combined with lime and

dolime to form the steel slag. At the end of the refining operation, the liquid

steel is tapped (poured) into a ladle while the steel slag was retained in the

vessel and subsequently tapped into a separate slag pot (TFHRC, 2002).

Both EAF and BOF processes of producing steel slag are presented in

Figure 2.2.

Both BOF and EAF steel slag inhibited similar physical and chemical

properties. The chemical composition of steel slag varied with the steel

making practice and the quality of steel being produced. However, in

accordance with the description from FHWA, there were many grades of

steel that can be produced, and the properties of the steel slag can change

significantly with each grade. Grades of steel can be classified as high,

medium, and low, depending on the carbon content of the steel. High-grade

steels had high carbon content. To reduce the amount of carbon in the

steel, greater oxygen levels were required in the steel-making process. This

also required the addition of increased levels of lime and dolime (flux) for the

removal of impurities from the steel and increased slag formation (TFHRC,

2002).

22

Figure 2.2: Flow Diagram of Steel Slag Production Through BOF and EAF

(NSA, 2006).

2.6 Properties of Steel Slag

Different properties of various aggregates influenced their level of

performance and suitability for an application. The physical and mechanical

characteristic of an aggregate played an important role in providing the ideal

23

durability, permeability, stability and resistance against abrasion, cracking,

and permanent deformation. Besides, the chemical composition of an

aggregate was continuously studied and found to be a factor affecting its

adhesion with other construction material to form an ideal combination.

2.6.1 Physical and Mechanical Properties

Earlier tests by See and Hamzah (2002) on the 20 mm and 10 mm

steel slag stockpiles revealed the physical and mechanical properties

presented in Tables 2.1 and 2.2 respectively. These properties were

measured at the Highway Engineering Laboratory of the School of Civil

Engineering, Universiti Sains Malaysia following test procedures in the

appropriate British Standards (BS) and ASTM standards. The results were

then compared to the Jabatan Kerja Raya (JKR) or Public Works

Department specifications.

Table 2.1: Steel Slag and Granite Physical Properties and JKR

Specifications (See and Hamzah, 2002)

Parameter Steel Slag

Property Granite

Property JKR

Specifications Reference Document

Water absorption (20 mm)

1.2% 0.51% Not exceeding 2%

SPJ88 (JKR, 1988)Arahan Teknik

8/85 (JKR, 1985) Water

absorption (10 mm)

2.8% 0.75% Not exceeding 2%


8/85 (JKR, 1985)

Flakiness Index 4 19 Not exceeding 30


8/85 (JKR, 1985)

24

Table 2.2: Steel Slag and Granite Mechanical Properties and JKR

Specifications (See and Hamzah, 2002)

Parameter Steel Slag Property

Granite Property

JKR Specifications

Reference Document

ACV 26.05 26.10 Not exceeding 30

SPJ88 (JKR, 1988)

AIV 17.20 20.54 - -

LAAV 9.80 9.80 Not exceeding 60

Arahan Teknik 8/85 (JKR, 1985)

Soundness No disintegration 5.2 Not exceeding

12 SPJ88

(JKR, 1988)

PSV 56.6 52.7 Not less than 40 SPJ88 (JKR, 1988)

Resistance to Stripping

> 95% coated area - Not less than

95% coated area SPJ88 (JKR,

1988)

See and Hamzah (2002) commented on each property as the

following stated:

(a) The flakiness index at 4% for steel slag aggregates was considered

very low. This indicated that steel slag aggregates were largely

consisted of rounded shape aggregates. Such character together

with the high surface roughness of steel slag provided much improved

interlocking properties when the bitumen mixture of steel slag

aggregates is compacted compared to granite aggregates.

(b) The Aggregate Crushing Value (ACV) and Los Angeles Abrasion

Value (LAAV) of the steel slag aggregates were all within the JKR

specifications. These indicated that the material possess sufficient

strength for utilization as road construction aggregates.

performance evaluation of steel slag as substitute

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