performance evaluation of steel slag as substitute
TRANSCRIPT
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
Table 5.7: Coefficients and Correlations of the Linear Relationships between
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)
Table 5.18: Average Coefficients of the Linear Relationships between Log-
Creep stiffness and Log-Load Cycle (GPA)
Table 5.19: Average Coefficients of the Linear Relationships between Log-
Accumulated Strain and Log-Load Cycle (SSPA)
Table 5.20: Average Coefficients of the Linear Relationships between Log-
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
Table 6.5: Coefficients and Correlations of the Linear Relationships between
Accumulated Strain and Loading Cycle of Unaged and Aged
SSDA Mixes
Table 6.6: Coefficients and Correlations of the Linear Relationships between
Accumulated Strain and Loading Cycle of Unaged and Aged
SSGDA Mixes
Table 6.7: Coefficients and Correlations of the Linear Relationships between
Creep Stiffness and Loading Cycle (SSPA Mixes, STOA)
Table 6.8: Coefficients and Correlations of the Linear Relationships between
Creep Stiffness and Loading Cycle (SSPA Mixes, LTOA)
Table 6.9: Coefficients and Correlations of the Linear Relationships between
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)
Figure 5.16: A Typical Graphical Illustration of the Accumulated Strain
versus Load Cycle Relationship (SSDA at 40°C and 60°C)
Figure 5.17: A Typical Graphical Illustration of the Accumulated Strain
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)
Figure 6.2: Resilient Modulus at 25°C versus Binder Content (Unaged and
Aged SSDA Mixes)
Figure 6.3: Resilient Modulus at 40°C versus Binder Content (Unaged and
Aged SSDA)
Figure 6.4: Resilient Modulus at 10°C versus Binder Content (Unaged and
Aged SSGDA)
Figure 6.5: Resilient Modulus at 25°C versus Binder Content (Unaged and
Aged SSGDA)
Figure 6.6: Resilient Modulus at 40°C versus Binder Content (Unaged and
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%
SPJ88 (JKR, 1988)Arahan Teknik
8/85 (JKR, 1985)
Flakiness Index 4 19 Not exceeding 30
SPJ88 (JKR, 1988)Arahan Teknik
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.