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UNIVERSITI PUTRA MALAYSIA
MOSLIH AMER SALIH
FK 2015 164
NEW GEO-POLYMERIZATION PROCESS FOR HIGH STRENGTH ALKALI-ACTIVATED BINDER WITH PALM OIL FUEL ASH AND
GROUND GRANULATED BLAST FURNACE SLAG
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NEW GEO-POLYMERIZATION PROCESS FOR HIGH STRENGTH
ALKALI-ACTIVATED BINDER WITH PALM OIL FUEL ASH AND
GROUND GRANULATED BLAST FURNACE SLAG
By
MOSLIH AMER SALIH
Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia,
in Fulfilment of the Requirements for the Degree of Doctor of Philosophy
March 2015
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COPYRIGHT
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icons, photographs and all other art work, is copyright material of Universiti Putra
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the thesis for non-commercial purposes from copyright holder. Commercial use of
material may only be made with the express, prior, written permission of Universiti
Putra Malaysia.
Copyright ©Universiti Putra Malaysia
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DEDICATIONS
I dedicate this thesis to, my father, my mother, my brothers and my small family, my
wife and children Mina, Ameen and Dima.
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Abstract of thesis presented to the Senate of Universiti Putra Malaysia in fulfilment
of the requirement for the degree of Doctor of Philosophy
NEW GEO-POLYMERIZATION PROCESS FOR HIGH STRENGTH
ALKALI-ACTIVATED BINDER WITH PALM OIL FUEL ASH AND
GROUND GRANULATED BLAST FURNACE SLAG
By
MOSLIH AMER SALIH
March 2015
Chairman: Professor Dato’ Ir Abang Abdullah Abang Ali,PhD
Faculty: Engineering
This study investigated a new geopolymerization process for the production of high
strength alkali activated binder, using high volume palm oil fuel ash (POFA) mixed
with ground granulated blast furnace slag (GGBS). The experimental work was
designed for the geopolymer paste and mortar. In the paste, the optimum alkali
activation parameters of POFA were identified. These parameters included Sodium
Hydroxide concentration, Solid/Liquid ratio (S/L), and Sodium Silicate to Sodium
Hydroxide ratio (SS/SH). The role of curing regime and its effect on the alkali
activation of POFA was investigated at ambient and different temperatures. GGBS
was introduced as a partial replacement of POFA in five percentages (10-50%) to study
the role of Calcium ions and mechanisms to improve the load bearing capacity of the
resulting gel to a high strength geopolymer binder.
The production of high strength geopolymerized mortar cured at ambient temperature
was initially targeted by applying the activation parameters with the same replacement
levels of GGBS as in the paste. The durability of the proposed alkali activated binder
was investigated by exposing the mortar to extreme environments, namely elevated
temperatures and sulfate attack. The compressive strength test, microstructural and
chemical tests such as Scanning Electron Microscopy/Energy-Dispersive X-Ray
Spectroscopy (SEM/EDX), X-Ray Diffraction (XRD), Thermogravimetric
Analysis/Derivative Thermogravimetry (TGA/DTG), Differential Scanning
Calorimetry (DSC) and Fourier Transform Infra-Red (FTIR), were conducted to study
the underlying mechanisms of strength development.
The results showed that liquid Sodium Hydroxide at 12 Molarity, S/L ratio at 1.32,
and SS/SH ratio at 2.5 were applicable to alkali activate 100% POFA and produce
geopolymer paste with 32.84 MPa at the age of 28 days. One major finding was
identifying the Calcium Silicate Hydrate gel (C-S-H) as the main binding phase; with
no Calcium Hydroxide Ca(OH)2 detected in the system. The test results showed that
100% POFA geopolymer paste can set and harden at ambient temperature with a
comparable compressive strength to samples cured in the oven. Calcium ions dissolved
from GGBS participated in increasing the binder strength by the formation of more C-
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S-H gel. Aluminum ions provided by GGBS led to a higher degree of polymerization
and significant degree of crosslinking between C-S-H chains and shifting it to
C-(A)-S-H gel. The compressive strength for binary geopolymer paste was 78.12 MPa
at the age of 28 days.
The alkali activated binder from the alkali activation of POFA as the only
aluminosilicate material was able to produce geopolymer mortar with normal strength
of 33.91 MPa at the age of 28 days. Inclusion of GGBS with POFA was effective to
produce high strength geopolymer mortar with compressive strength of 70.25 MPa at
the age of 28 days. Results from residual compressive test at elevated temperatures
showed that samples maintained their dimensional stability at elevated temperatures
due to the presence of evacuation routes (pore system) in the mortar which allowed
water to be evaporated. Moreover, glass transition was detected between 600 ºC and
800 ºC which provided a relative increase in the strength of the geopolymer mortar.
Test results showed that the proposed geopolymer mortar performed better than
Portland cement mortar when exposed to sulfate attack. The results indicated that
although Sodium sulfate and Magnesium sulfate had deterioration effect due to
decomposing of Si and Ca ions from both C-S-H and C-A-S-H gels, the proposed
geopolymer mortar experienced less strength depletion which can be related to the
absence of calcium hydroxide in the matrix.
Keywords: POFA, Geopolymer binder, Geopolymer cement, GGBS, Alkali
activation, Geopolymer mortar.
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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai
memenuhi keperluan untuk ijazah Doctor Falsafah
PROSES GEO-POLIMERISASI BARU UNTUK PENGIKAT ALKALI
TERAKTIF BERKEKUATAN TINGGI DENGAN ABU SISA BAHAN API
KELAPA SAWIT DAN SANGA RELAU BAGAS BERBUTIR
Oleh
MOSLIH AMER SALIH
Mac 2015
Pengerusi: Professor Dato’ Abang Abdullah Abang Ali, PhD
Fakulti: Kejuruteraan
Kajian ini telah menyiasat proses geo-polimerisasi untuk penghasilan pengikat alkali
teraktif berkekuatan tinggi menggunakan abu sisa bahan api kelapa sawit (POFA)
berisipadu tinggi diadunkan dengan sanga relau bagas berbutir (GGBS). Ujian-ujian
telah dirancang untuk adunan dan mortar geopolimer. Dalam adunan, parameter-
parameter alkali teraktif optimum telah dikenalpasti. Parameter-parameter ini
termasuk kepekatan Sodium Hidroksida (kemolaran), nisbah pepejal kepada cecair
(S/L) dan nisbah Sodium Silika kepada Sodium Hidroksida (SS/SH). Peranan rejim
pengawetan dan kesannya terhadap alkali teraktif POFA telah dikaji dengan
menggunakan suhu ambien and suhu yang berlainan. GGBS telah diperkenalkan
sebagai gantian separa POFA sebanyak lima peratus (10-50%) untuk mengkaji
peranan ion-ion kalsium dan mekanisma-mekanisma untuk memperbaiki kapasiti
beban tahan galas gel yang terbentuk kepada pengikat geopolimer berkekuatan tinggi.
Penghasilan mortar geopolimer berkekuatan tinggi pada yang terawet pada suhu
ambien mulanya disasarkan dengan menggunakan parameter-parameter pengaktifan
dengan aras-aras gantian GGBS yang sama seperti dalam adunan. Ketahanlasakan
pengikat alkali teraktif yang dicadangkan telah dikaji selepas pendedahan mortar
tersebut kepada sekitaran melampau seperti suhu ternaik dan serangan sulfat. Ujian
kekuatan mampatan, ujian-ujian kimia dan mikrostruktur seperti XRD, SEM/EDX,
TGA/DTG, DSC dan FTIR telah dijalankan untuk mengkaji mekanisma-mekanisma
di sebalik perkembangan kekuatan. Hasil keputusan telah menunjukkan bahwa cecair
Sodium Hidroksida pada kemolaran 12, nibah S/L pada 1.32 dan nisbah SS/SH pada
2.5 telah digunakan untuk aktif alkali 100% POFA dan menghasilkan 32.84 MPa
kekuatan mampatan pada hari ke-28. Satu penemuan utama telah mengenalpasti
struktur gel yang dominan – gel Kalsium Silika Terhidrat gel (C-S-H) – sebagai fasa
pengikatan yang terhasil daripada 100% POFA alkali teraktif; lebih-lebih lagi tiada
Kalsium Hidroksida Ca(OH)2 telah dikesan di dalam sistem.
Keputusan ujian menunjukkan 100% POFA adunan geopolimer boleh set dan
menhgeras pada suhu ambien dengan perbandingan kekuatan mampatan dengan
sampel-sampel yang diawet di dalam ketuhar. Ion-ion kalsium terlarut daripada GGBS
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yang terlibat dalam peningkatan kekuatan pengikat dengan pembentukan lebih banyak
gel C-S-H. Ion-ion Aluminium yang juga terhasil daripada GGBS membawa kepada
tahap yang lebih tinggi polimerisasi dan tahap sambung-silang yang ketara di antara
rantaian C-S-H beralih kepada gel C-(A)-S-H. Kekuatan mampatan pada adunan
geopolimer binari adalah 78.12 MPa pada umur ke-28 hari.
Pengikat geopolimer yang terhasil daripada 100% POFA alkali teraktif sebagai bahan
aluminosilikat sahaja dapat menghasilkan mortar geopolimer dengan kekuatan normal
33.91 MPa pada umur ke-28 hari. Kemasukan GGBS ke dalam POFA telah
menunjukkan keberkesanan dalam penghasilan mortar geopolimer berkekuatan tinggi
dengan kekuatan mampatan sebanyak 70.25 MPa telah tercapai pada umur ke-28 hari.
Keputusan-keputusan daripada baki ujian mampatan pada suhu ternaik menunujukkan
sampel-sampel mengekalkan kestabilan dimensi pada suhu-suhu ternaik disebabkan
kehadiran laluan pemindahan yang sedia ada (sistem liang) dalam mortar di mana ia
membenarkan air disejat. Tambahan pula, transisi kaca telah dikesan di antara 600 ºC
dan 800 ºC yang menyediakan peningkatan relatif dalam kekuatan. Ujian-ujian
menunjukkan bahawa mortar geopolimer yang dicadangkan lebih baik daripada mortar
simen Portland apabila didedahkan kepada serangan sulfat. Keputusan menunjukkan
walaupun Sodium Sulfat dan Magnesium Sulfat telah merosot kesan akibat penguraian
ion-ion Si dan Ca daripada kedua-dua gel C-S-H dan C-A-S-H, geopolimer mortar
dicadangkan mengalami susutan kekuatan di mana boleh dikaitkan dengan kehadiran
Kalsium Hidroksida di dalam matriks.
Kata Kunci: POFA, pengikat Geopolimer, Simen Geopolimer, GGBS, Alkali teraktif,
mortar geopolymer
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ACKNOWLEDGEMENTS
First and foremost, I would like to thank ALLAH my God, without him I would never
have the faith, power, determination to live, work, and finish all the work involved in
my thesis.
All thanks to my supervisor, Prof. Dato Ir. Abang Abdullah Abang Ali, for his
guidance, help and support during my study. Special thanks to Prof. Ramazan
Demirboga for his support and directions. I warmly thank Dr. Nima Farzadina for his
generous guidance, invaluable advices for my research. I would like also to thank Dr.
Mohd Mustafa Al Bakri Abdullah for his kindness to have the training at University
Malaysia Perlis (UniMAP) and also special thanks to his staff for their support.
Thanks to Dr. Noor Azline for her support. Special thanks and appreciation to the
Housing Research Center (HRC) staff at Universiti Putra Malaysia (UPM), especially
Mrs. Erna and Miss Liayna, who were very kind and supportive during my study.
I would like to express my deepest appreciation to my beloved wife, and my children
for their sacrifices and the patience all the time I was away from them for the sake of
my study. Great thanks to my father, Mr. Amer Salih Hadi Al Khafagy for his great
encouragement and support all the way in my PhD journey.
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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been
accepted as fulfilment of the requirement for the degree of Doctor of Philosophy.
The members of the Supervisory Committee were as follows:
Abang Abdullah Abang Ali, PhD
Professor, Ir
Faculty of Engineering
Universiti Putra Malaysia
(Chairperson)
Ramazan Demirboga, PhD
Associate Professor
Faculty of Engineering
Universiti Putra Malaysia
(Member)
Noor Azline Mohd. Nasir, PhD
Lecturer
Faculty of Engineering
Universiti Putra Malaysia
(Member)
BUJANG BIN KIM HUAT, PhD
Professor and Dean
School of Graduate Studies
Universiti Putra Malaysia
Date:
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Declaration by graduate student
I hereby confirm that:
this thesis is my original work
quotations, illustrations and citations have been duly referenced
the thesis has not been submitted previously or comcurrently for any other degree
at any institutions
intellectual property from the thesis and copyright of thesis are fully-owned by
Universiti Putra Malaysia, as according to the Universiti Putra Malaysia
(Research) Rules 2012;
written permission must be owned from supervisor and deputy vice –chancellor
(Research and innovation) before thesis is published (in the form of written,
printed or in electronic form) including books, journals, modules, proceedings,
popular writings, seminar papers, manuscripts, posters, reports, lecture notes,
learning modules or any other materials as stated in the Universiti Putra Malaysia
(Research) Rules 2012;
there is no plagiarism or data falsification/fabrication in the thesis, and scholarly
integrity is upheld as according to the Universiti Putra Malaysia (Graduate
Studies) Rules 2003 (Revision 2012-2013) and the Universiti Putra Malaysia
(Research) Rules 2012. The thesis has undergone plagiarism detection software
Signature: Date:
Name and Matric NO.: Moslih Amer Salih (GS28688)
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Declaration by Members of Supervisory Committee
This is to confirm that:
the research conducted and the writing of this thesis was under our supervision;
supervision responsibilities as stated in the Universiti Putra Malaysia (Graduate
Studies) Rules 2003 (Revision 2012-2013) were adhered to.
Signature: Signature:
Name of Name of
Chairman of Member of
Supervisory Supervisory
Committee: Committee:
Signature:
Name of
Member of
Supervisory
Committee:
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TABLE OF CONTENTS
Page
ABSTRACT i
ABSTRAK iii
ACKNOWLEDGEMENTS v
APPROVAL vi
DECLARATION viii
LIST OF TABLES xv
LIST OF FIGURES xvii
LIST OF ABBREVIATIONS AND ACRONYMS xxvii
CHAPTER
1 INTRODUCTION
1.1 Background 1
1.2 Research Problem 2
1.3 Hypothesis of the Research 4
1.4 Research Objectives 4
1.5 Research Questions 4
1.6 Research Contribution 5
1.7 Significance of the Study 5
1.8 Scope and Limitations of the study 6
1.9 Thesis Layout 6
2 LITERATURE REVIEW
2.1 Introduction 8
2.2 Definition of the Alkali-Activated Materials and
Geopolymers
8
2.3 History of Alkali-Activated Materials 10
2.4 Binding Phase Structure in Alkali-Activated Materials 10
2.4.1 Binding Phase Structure in Alkali Activated
Aluminosilicate Materials Categorized with Low
Calcium Content
10
2.4.2 Binding Phase Structure in Alkali Activated
Aluminosilicate Materials Categorized with Higher
Calcium Content
13
2.5 The Most used Alkaline Activators in the Alkali Activation
Process
14
2.5.1 The Sodium Hydroxide (NaOH): Definition,
Manufacturing and the use in the Industry
15
2.5.2 The Sodium Silicate (Na2Si2O5): Definition,
Manufacturing and the use in the Industry
15
2.6 The Impact of a Combination of Two Activators on the
alkali activation process
16
2.7 The Most Used Activation Method-The Activation
Parameters
17
2.7.1 Sodium Ion Concentration and Sodium Oxide Content
In the Alkaline Activator as a Percentage of the
Aluminosilicate Material
17
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2.7.2 The Aluminosilicate Material to the Alkaline
Activator Ratio (Solid to Liquid) Coupled with
Sodium Silicate to Sodium Hydroxide Ratio (SS/SH)
17
2.8 Curing Conditions Associated with the Alkali Activation of
the Aluminosilicate Materials
19
2.9 The Most used Aluminosilicate Materials (Waste
Materials) to produce Geopolymer Binders
19
2.10 Palm Oil Fuel Ash (POFA) 22
2.10.1 POFA Classification as a Supplementary
Cementing Material
20
2.10.2 POFA as an Aluminosilicate Source in The Alkali
Activation Process
24
2.11 Alkali Activated Binders and the Strength Rate 25
2.12 Mechanisms of Participation of the Calcium Ions in The
Alkali Activation Process
27
2.13 Behavior of Alkali-Activated Materials Exposed to
Elevated Temperatures
27
2.14 Durability and Deterioration Mechanisms of Alkali-
Activated Materials Exposed to Sulfate Attack
28
2.15 Testing Techniques for Characterization of Alkali
Activated Materials
28
2.15.1 Compressive Strength 29
2.15.2 X-Ray Diffraction (XRD) 30
2.15.3 Scanning Electron Microscopy/Energy-Dispersive
X-Ray Spectroscopy Analysis (SEM/EDX)
33
2.15.4 Thermogravimetric Analysis/Derivative
Thermogravimetric Analysis (TGA/DTG)
35
2.15.5 Fourier Transform Infra-Red Spectroscopy
Analysis (FTIR)
37
2.16 Summary and the Research Gap 41
3 METHODOLOGY
3.1 Introduction 43
3.2 Preliminary Laboratory Work to Practice the Alkali
Activation Technology
45
3.3 Materials 45
3.3.1 Palm Oil Fuel Ash (POFA): Preparation and
Characterization
45
3.3.2 Portland Cement Used in Preparation of the
Reference Mortar
51
3.3.3 Sand 51
3.3.4 Tap Water 52
3.3.5 Ground Granulated Blast Furnace Slag (GGBS) 52
3.3.6 Alkaline Activators 54
3.3.6.1 Sodium hydroxide (NaOH) 54
3.3.6.2 Sodium Silicate Solution (Na2Si2O5) 54
3.3.7 Distilled Water 55
3.3.8 Sodium Sulfate (Na2SO4) 55
3.3.9 Magnesium Sulfate (MgSO4.7H2O) 55
3.4 Experimental Procedure 55
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3.4.1 Activation Parameters: S/L ratio and SS/SH ratio 55
3.4.2 S/L ratio and SS/SH ratio Calculations 56
3.4.3 Step by Step Activation Approach 56
3.4.4 Geopolymer Paste Production: Mixing Procedure 57
3.4.5 Activities Applied to Achieve the Study Objectives 57
3.4.5.1 Objective One 57
3.4.5.1.1 Investigating the Sodium
Hydroxide (NaOH) Concentration
57
3.4.5.1.2 Investigating the Solid to Liquid
ratio (S/L) and Sodium Silicate to
Sodium Hydroxide ratio (SS/SH)
58
3.4.5.2 Objective Two 59
3.4.5.2.1 Investigating the Curing Regime 59
3.4.5.3 Objective Three 59
3.4.5.3.1 High Strength Binder by Partial
Replacement of POFA with GGBS
59
3.4.6 The Mortar 60
3.4.6.1 Portland Cement Mortar Production
(Reference Mortar)
60
3.4.6.2 Objective Four 61
3.4.6.2.1 Production of the Geopolymer
Mortar
61
3.4.6.2.2 Exposure to Elevated Temperatures 61
3.4.6.2.3 Exposure to Sulfate Attack 63
3.4.6.2.3.1 Sodium Sulfate Attack 63
3.4.6.2.3.2 Magnesium Sulfate
Attack
64
3.5 Tests Applied in the Study 64
3.5.1 X-Ray Fluorescence (XRF) Spectroscopy 64
3.5.2 Setting Time 65
3.5.3 Flow Table Test 65
3.5.4 Bulk Density 66
3.5.5 Compressive Strength Test 66
3.5.6 Scanning Electron Microscopy/Energy-Dispersive
X-Ray Spectroscopy Analysis (SEM/EDX)
67
3.5.7 X-Ray Diffraction (XRD) 69
3.5.8 Thermo Gravimetric Analysis/Derivative
Thermogravimetriy (TGA/DTG)
70
3.5.9 Differential Scanning Calorimetry (DSC) 71
3.5.10 Fourier Transform Infra-Red Spectroscopy
(FTIR)
72
4 RESULTS AND DISCUSSIONS
4.1 Introduction 73
4.2 Preliminary Laboratory Work 73
4.3 Activation Parameters 73
4.3.1 Investigating NaOH Concentration (Molarity) 73
4.3.2 Qualitative Observations 74
4.3.2.1 Soundness in water 74
4.3.2.2 Color 75
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4.3.3 Effect of Different S/L Ratios and Different SS/SH
ratios
75
4.3.3.1 Efflorescence 75
4.3.3.2 Flowability 79
4.3.3.3 Bulk Density 80
4.3.4 Compressive Strength 81
4.3.5 Microstructural and Chemical Analysis 83
4.3.5.1 X-Ray Diffraction (XRD) 83
4.3.5.2 Scanning Electron Microscope (SEM) 86
4.3.5.3 Energy-dispersive X-Ray spectroscopy
analysis (EDX)
87
4.3.5.4 Fourier Transform Infra-Red (FTIR) 89
4.3.5.5 Differential Scanning Calorimetry (DSC) 91
4.4 Investigating Different Curing Temperatures 92
4.4.1 Compressive Strength 92
4.4.2 Hardening Time 94
4.4.3 Microstructural and Chemical Analysis 96
4.4.3.1 X-Ray Diffraction (XRD) 98
4.4.3.2 Energy-dispersive X-Ray Spectroscopy
Analysis (EDX)
100
4.4.3.3 Scanning Electron Microscope (SEM) 102
4.4.3.4 Fourier Transform Infra-Red (FTIR) 103
4.4.3.5 Thermo Gravimetric Analysis/Derivative
Thermogravimetric Analysis (TGA/DTG)
104
4.5 High Strength Alkali Activated Binder - Effect of GGBS 104
4.5.1 Setting Time 104
4.5.2 Compressive Strength 106
4.5.3 Microstructural and Chemical Analysis 108
4.5.3.1 X-Ray Diffraction (XRD) 108
4.5.3.2 Fourier Transform Infra-Red (FTIR) 110
4.5.3.3 Energy-Dispersive X-Ray spectroscopy
analysis (EDX)/Scanning Electron
Microscope (SEM)
111
4.5.3.4 Thermogravimetric Analysis/Derivative
Thermogravimetric Analysis (TGA/DTG)
116
4.5.3.5 Differential Scanning Calorimetry (DSC) 118
4.6 Geopolymer Mortar from POFA Blended with GGBS 119
4.6.1 Flowability 119
4.6.2 Bulk Density for Geopolymer Mortar 119
4.6.3 Compressive Strength 120
4.6.4 Microstructural and Chemical Analysis 123
4.6.4.1 X-Ray Diffraction (XRD) 123
4.6.4.2 Scanning Electron Microscope (SEM) 127
4.6.4.3 Energy-dispersive X-Ray spectroscopy
analysis (EDX)
131
4.6.4.4 Fourier Transform Infra-Red (FTIR) 132
4.6.4.5 Thermogravimetric Analysis/Derivative
Thermogravimetric Analysis (TGA/DTG)
134
4.6.4.6 Differential Scanning Calorimetry (DSC) 137
4.7 POFA Geopolymer Mortar Exposed to Elevated 139
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Temperatures
4.7.1 Compressive Strength 139
4.7.2 Microstructural and Chemical Analysis 143
4.7.2.1 X-Ray Diffraction (XRD) 143
4.7.2.2 Scanning Electron Microscope (SEM) 145
4.7.2.3 Fourier Transform Infra-Red (FTIR) 146
4.7.2.4 Thermogravimetric Analysis/ Derivative
Thermogravimetric Analysis(TGA/DTG)
148
4.7.2.5 Differential Scanning Calorimetry (DSC) 152
4.8 Durability of Geopolymer Mortar Exposed to Sodium
Sulfate and Magnesium Sulfate Attack
154
4.8.1 Compressive Strength 154
4.8.2 Microstructural and Chemical Analysis 159
4.8.2.1 Scanning Electron Microscope/Energy-
Dispersive X-Ray Spectroscopy Analysis
(SEM/EDX)
159
4.8.2.2 Fourier Transform Infra-Red (FTIR) 169
4.8.2.3 Thermogravimetric Analysis/ Derivative
Thermogravimetric Analysis(TGA/DTG)
173
4.8.2.4 Differential Scanning Calorimetry (DSC) 177
4.9 The relation of the results with the hypothesis used in
this study
180
5 CONCLUSIONS AND RECOMMENDATIONS
5.1 The Effect of the Activation Parameters on the
Compressive Strength, Microstructure and Chemical
Properties
182
5.2 The Effect of Curing Temperatures on the Compressive
Strength, Microstructure and Chemical Properties of
POFA Geopolymer Binder
183
5.3 The Effect of the Binary Mix of POFA-GGBS and its
Underlying Mechanisms in Order to Produce High
Strength Geopolymer Binder at Ambient Temperature
184
5.4 High Strength POFA-GGBS Mortar and its Compressive
Strength and Durability
185
5.5 Recommendations for Future Research 186
BIBLIOGRAPHY 187
BIODATA OF STUDENT 206
LIST OF PUBLICATIONS 207
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LIST OF TABLES
Table Page
2.1 Sialate and Poly (sialate) terminology (Davidovits, 2011)
9
2.2 The chemical composition for different aluminosilicate
materials used in alkali activation
21
2.3 FTIR characteristic bands (Panias et al. 2007; Ahmari et al.
2012; Davidovits, 2011; Nath and Kumar, 2013)
40
3.1 Chemical composition of POFA by XRF test
46
3.2 Chemical composition and physical properties of cement
used. Data provided by the company
51
3.3 River sand sieve analysis and grading according to ASTM
C 33-2004
51
3.4 Chemical composition of ground granulated blast furnace
slag
53
3.5 NaOH weight related to each concentration
54
3.6 Sodium silicate chemical composition
54
3.7 Sodium silicate physical properties
55
3.8 Mixes proportions for selecting the sodium hydroxide
concentration.
58
3.9 Mixes proportions for selecting the right solid to liquid
ratio and right sodium silicate to sodium hydroxide ratio
58
3.10 Mixes for selecting the curing temperature
59
3.11 Mix design for POFA geopolymer paste and POFA
blended with GGBS as partial replacement by weight
59
3.12 Mix proportion for Portland cement mortar according to
ASTM C 109/C 109M-2012
61
3.13 Mix design for POFA geopolymer mortar and POFA
blended with GGBS as partial replacement by weight
61
4.1 Bulk density for POFA geopolymer paste (group one and
two) at different sodium silicate to sodium hydroxide ratios
80
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4.2 Compressive strength for POFA geopolymer paste
106
4.3 Bulk density (kg/m3) for POFA geopolymer mortar and
POFA blended with GGBS
120
4.4 Compressive strength results for POFA geopolymer mortar
and Portland cement mortar
121
4.5 Relative residual compressive strength for mortar after one
hour of exposure to elevated temperatures
140
4.6 Residual compressive strength and reduction percentage
after six months exposure to sulfate attack
158
4.7 EDX Spectrum spots analysis for 100% POFA geopolymer
mortar after six months of exposure to 8.0% sodium sulfate
161
4.8 EDX Spectrum spots analysis for 100% POFA geopolymer
mortar after six months of exposure to 8.0% magnesium
sulfate
162
4.9 EDX Spectrum spots analysis for (70% POFA+30%
GGBS) geopolymer mortar after six months of exposure
to 8.0% sodium sulfate
165
4.10 EDX Spectrum spots analysis for (70% POFA + 30%
GGBS) geopolymer mortar after six months of exposure to
8.0% magnesium sulfate
165
4.11 EDX Spectrum spots analysis for (50% POFA + 50%
GGBS) geopolymer mortar after six months of exposure to
8.0% sodium sulfate
168
4.12 EDX Spectrum spots analysis for (50% POFA + 50%
GGBS) geopolymer mortar after six months of exposure to
8.0% magnesium sulfate
169
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LIST OF FIGURES
Figure Page
2.1 Tetrahedral configuration of ionic concept (Davidovits,
2011)
9
2.2 Conceptual model for geopolymerization process (Duxson
et al., 2007a)
12
2.3 Conceptual model for alkali activation of low Ca
aluminosilicate sources (Provis, 2014a)
13
2.4 Dissolution mechanism of an aluminosilicate glass during
early stages of reaction (Duxson and Provis, 2008)
14
2.5 XRD pattern of Fly ash and ground waste concrete powders
and geopolymer specimens prepared with 0% and 50%
GWC at 10 M NaOH and SS/N=2.0 and cured at ambient
temperature for 7 days (A: anorhite, M: mullite, P:
portlandite, Q: quarts, T: 1.1-nm tobermorite) (Ahmari et
al., 2012)
32
2.6 XRD pattern of fly ash blended with slag, GFACS10=fly
ash blended with 10% slag, GFABF25=fly ash blended
with 25% slag, GFABF40=fly ash with 40% slag,
GFABF50=fly ash blended with 50% slag, M=Mulite,
X=Quartz, *=C-S-H (Nath and Kumar, 2013)
32
2.7 SEM image of paste having (a) 10% GGBS and (b) 50%
GGBS, where A=un-reacted or partially reacted slag
particles, B=un-reacted or partially reacted fly ash
particles, C=aluminosilicate geopolymer gel containing
calcium as indicated in EDX spectrum and D=pure
aluminosilicate geopolymer gel (Nath and Sarker, (2014)
34
2.8 SEM Micrograph showing the microstructure of
geopolymer cured at (a) 23 ºC, (b) 30 ºC, (c) 60 C, and (d)
70 ºC (Nasvi et al., 2014)
35
2.9 DTG curve generated from TGA/DTG test for metakaolin
and fly ash-based geopolymer paste. MK=Metakaolin,
FA=Fly Ash (Kong et al., 2007)
36
2.10 TGA curve showing the thermal behavior of
geopolymerised paste prepared from metakaolin (Elimbi et
al., 2014)
36
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2.11 FTIR Spectra for fly ash, ground waste concrete and
geopolymer specimens prepared with 100% fly ash and
50% ground waste concrete at 10 M NaOH and SS/SH=2.0
and cured at ambient temperature at the age of 7 days
(Ahmari et al., 2012)
38
2.12 FTIR Spectra analysis of ground fly ash (GFA) and
geopolymer paste (Somna et al., 2011)
39
3.1 Research Methodology Flowchart
44
3.2 Palm Oil Shells, husk and fibers before burning
46
3.3 Raw POFA as a wet ash coming out of the incinerator at
Palm Oil Mill
47
3.4 XRD pattern for POFA
47
3.5 SEM micrograph showing irregular particles of raw POFA
48
3.6 SEM micrograph showing porous cellular particles of raw
POFA
48
3.7 SEM micrograph for ground POFA
49
3.8 SEM micrograph for ground POFA with particle size
49
3.9 POFA stored after sieving and grinding-ready to be used
for experimental work
50
3.10 Particle size distribution for POFA after grinding
50
3.11 Clean graded river sand used in mortar production
52
3.12 XRD pattern for ground granulated blast furnace slag
(GGBS)
53
3.13 SEM micrograph for GGBS showing crushed shape
particles
53
3.14 GGBS particle size distribution
54
3.15 Hobart mixer
60
3.16 Example of heating rate and the thermal steady state
demonstrated by the furnace
62
3.17 Placing specimens before exposure to elevated
temperatures
62
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3.18 Nabertherm high temperature laboratory furnace
63
3.19 Geopolymer mortar and Portland cement mortar immersed
in sulfates
64
3.20 Vicat Needle Apparatus for setting time
65
3.21 Flow Table
66
3.22 Compression machine, Unit Test Scientific
67
3.23 Hitachi S-3400N for SEM images and EDX spots elements
analysis
68
3.24 Gold coating of samples using Emitech K550X Sputter
Coater
68
3.25 SEM/EDX sample holder
68
3.26 Shimadzu XRD 6000
69
3.27 Thermogravimetric analyzer (TGA/DTG) (Mettler Toledo,
TGA/SDTA 851, Switzerland)
70
3.28 Differential Scanning Calorimetry instrument (Mettler
Toledo, DSC 832e/500)
71
3.29 Perkin Elmer Spectrum 100, FT-IR Spectometer
72
4.1 Compressive strength results for POFA geopolymer paste
with different concentration of NaOH
74
4.2 POFA geopolymer paste specimens-Black Color
75
4.3 Visual percentage of efflorescence in group one (S/L=1.0)
with SS/SH ratio of a) 1.0, b) 1.5, c) 2.0, d) 2.5, e) 3.0 at
28 days
77
4.4 Visual percentage of efflorescence in group two (S/L=1.32)
with SS/SH ratio of a) 1.0, b) 1.5, c) 2.0, d) 2.5, e) 3.0 at 28
days
78
4.5 Flow of POFA geopolymer paste (S/L=1.0) with different
SS/SH ratios
79
4.6 Flow of POFA geopolymer paste (S/L=1.32) with different
SS/SH ratios
79
4.7 Compressive strength results for POFA geopolymer paste
group one, S/L ratio 1.0
81
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4.8 Compressive strength results for POFA geopolymer paste
group two, S/L ratio 1.32
81
4.9 XRD patterns for POFA geopolymer paste group one,
(S/L=1.0) with different SS/SH ratios a) 1.0, b) 1.5, c) 2.0,
d) 2.5, e) 3.0
84
4.10 XRD patterns for POFA geopolymer paste group two,
(S/L=1.32) with different SS/SH ratios a) 1.0, b) 1.5, c) 2.0,
d) 2.5, e) 3.0
85
4.11 SEM image of geopolymerised POFA
86
4.12 EDX spot analysis of POFA geopolymer paste with S/L
ratio 1.32, SS/SH ratio 2.5 at different points
87
4.13 EDX spectrum of points 1 to 7 (pt1 to pt7)
88
4.14 Ca/Si ratio in different points (pt1 to pt 7) from EDX test
89
4.15 FTIR spectra of raw POFA and geopolymerised POFA of
group 2.0 S/L ratio 1.32
90
4.16 DSC diagrams of raw POFA and alkali activated POFA
(S/L=1.32)
91
4.17 Compressive strength results of POFA geopolymer paste
cured at different curing temperatures measured at 7, 28,
90, and 180 days
92
4.18 Strength development rates for POFA geopolymer pastes
from 7-28, 28-90, and 90-180 days
93
4.19 Hardening time for POFA geopolymer pastes cured at 60
ºC, 70 ºC, and 80 ºC and ambient temperature
94
4.20 Cracks generated in POFA geopolymer paste specimens at
60 ºC after 24 hours curing time, a) Top View, b) Side View
95
4.21 XRD patterns for POFA geopolymer pastes cured at a)
ambient temperature, b) 60 ºC, c) 70 ºC, d) 80 ºC at 7 and
28 days
96
4.22 Energy-dispersive X-Ray Spectrums (EDX) for POFA
geopolymer pastes cured at ambient temperature, 60 ºC, 70
ºC, and 80 ºC
98
4.23 Ca/Si ratio resulted from EDX test
99
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4.24 SEM images for POFA geopolymer pastes cured at
different curing temperatures, A) ambient temperature, B)
70 ºC, C) 80 ºC
101
4.25 FTIR Spectra for raw POFA and alkali activated POFA
cured at different curing temperatures
102
4.26 TGA Spectra for raw POFA and POFA geopolymer pastes
cured at different curing temperatures
104
4.27 Initial and final setting time
105
4.28 Compressive strength results for POFA geopolymer paste
and POFA blended with GGBS as partial replacement by
weight
107
4.29 XRD patterns for alkali activated POFA blended with
GGBS
109
4.30 FTIR Spectra for raw POFA, raw GGBS, and POFA
blended with GGBS in different percentages after alkali
activation
110
4.31 Energy-dispersive X-ray spectroscopy (EDX), A) 100%
POFA, B) 10% GGBS, C) 20% GGBS, D) 30% GGBS, E)
40% GGBS, F) 50% GGBS
112
4.32 Si/Al ratio at the age of 28 days resulted from EDX test
analysis
113
4.33 Ca/Si ratio at the age of 28 days resulted from EDX test
113
4.34 SEM images and EDX spot points elements analysis
115
4.35 TGA results for POFA geopolymer paste blended with 10,
20, 30, 40 and 50% GGBS
116
4.36 DTG results for POFA geopolymer paste blended with 10,
20, 30, 40 and 50% GGBS
117
4.37 Peak temperatures resulted from the analysis of TGA/DTG
test
117
4.38 DSC thermograms of POFA geopolymer paste and POFA
blended with GGBS
118
4.39 Flow results for POFA geopolymer mortar by flow table
test
119
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4.40 Compressive strength of POFA geopolymer mortar and
POFA blended with GGBS geopolymer mortar
121
4.41 XRD pattern for POFA geopolymer mortar blended with
GGBS at the age of 7 days
124
4.42 XRD pattern for POFA geopolymer mortar blended with
GGBS at the age of 28 days
126
4.43 SEM images for geopolymer mortar at the age of 7 days: a)
100% POFA, b) 10% GGBS, c) 20% GGBS, d) 30%
GGBS, e) 40% GGBS, f) 50% GGBS
128
4.44 SEM images for geopolymer mortar at the age of 28 days:
a) 100% POFA, b) 10% GGBS, c) 20% GGBS, d) 30%
GGBS, e) 40% GGBS, f) 50% GGBS
129
4.45 SEM images for geopolymer mortar at the age of 90 days:
a) 100% POFA, b) 10% GGBS, c) 20% GGBS, d) 30%
GGBS, e) 40% GGBS, f) 50%
130
4.46 SEM/EDX images for geopolymer mortar at the age of 90
days: a) 100% POFA, b) 10% GGBS, c) 20% GGBS, d)
30% GGBS, e) 40% GGBS, f) 50% GGBS
131
4.47 FTIR Spectra for geopolymer mortar at the age of 7 days
132
4.48 FTIR Spectra for geopolymer mortar at the age of 28 days
133
4.49 TGA results analysis for geopolymer mortar at the age of 7
days
135
4.50 TGA results analysis for geopolymer mortar at the age of
28 days
135
4.51 DSC Spectra for geopolymer mortar at the age of 7 days
137
4.52 DSC Spectra for geopolymer mortar at the age of 28 days
138
4.53 Compressive strength results for geopolymer mortar and
Portland cement mortar at the age of 28 days cured at
ambient temperature before exposure to elevated
temperatures
139
4.54 Residual compressive strength for geopolymer mortar and
Portland cement mortar after exposure to elevated
temperatures
140
4.55 Geopolymer mortar and Portland cement mortar cubes after
exposure to 700 ºC (left group) and 800 ºC (right group)
142
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4.56 Geopolymer mortar maintained its shape and dimensions
after exposure to 700 ºC for one hour
142
4.57 XRD patterns for 100% POFA geopolymer mortar before
and after exposure to elevated temperatures.
143
4.58 XRD pattern for POFA replaced with 30% GGBS
geopolymer mortar before and after exposure to elevated
temperatures.
144
4.59 XRD pattern for POFA replaced with 50% GGBS
geopolymer mortar before and after exposure to elevated
temperatures.
144
4.60 SEM images for geopolymer mortars before and after
exposure to elevated temperatures: a) 100% POFA before
exposure, b) 100% POFA after exposure to 800 ºC, c) 50%
GGBS replacement before exposure, d) 50% GGBS
replacement after exposure to 800 ºC
145
4.61 FTIR Spectra for geopolymer mortar before exposure to
elevated temperatures
146
4.62 FTIR Spectra for geopolymer mortar after exposure to 400
ºC elevated temperature
147
4.63 FTIR Spectra for geopolymer mortar after exposure to 600
ºC elevated temperature
147
4.64 FTIR Spectra for geopolymer mortar after exposure to 800
ºC elevated temperature
148
4.65 TGA results for geopolymer mortar and Portland cement
mortar before exposure to elevated temperatures
149
4.66 TGA results for geopolymer mortar and Portland cement
mortar after exposure to 400 ºC elevated temperatures
150
4.67 TGA results for geopolymer mortar and Portland cement
mortar after exposure to 600 ºC elevated temperatures
150
4.68 TGA results for geopolymer mortar and Portland cement
mortar after exposure to 800 ºC elevated temperatures
151
4.69 DSC results for geopolymer mortar at ambient temperature
152
4.70 DSC results for geopolymer mortar after exposure to 400
ºC
153
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4.71 DSC results for geopolymer mortar after exposure to 600
ºC
153
4.72 DSC results for geopolymer mortar after exposure to 800
ºC
153
4.73 Residual compressive strength after 6 months of exposure
to 3.0% sulfates
155
4.74 Residual compressive strength after 6 months of exposure
to 5.0% sulfates
156
4.75 Residual compressive strength after 6 months of exposure
to 8.0% sulfates
157
4.76 SEM images for 100% POFA geopolymer mortar after 6
months exposure to 8% sodium sulfate solution
159
4.77 SEM images for 100% POFA geopolymer mortar after 6
months exposure to 8% magnesium sulfate solution
160
4.78 SEM/EDX spectrum spot analysis for 100% POFA
geopolymer mortar after 6 months exposure to 8%
magnesium sulfate solution
161
4.79 SEM/EDX spectrum spot analysis for 100% POFA
geopolymer mortar after 6 months exposure to 8%
magnesium sulfate solution
162
4.80 SEM images for geopolymer mortar (70% POFA+30%
GGBS) after 6 months of exposure to 8% sodium sulfate
163
4.81 SEM images for geopolymer mortar (70% POFA+30%
GGBS) after 6 months of exposure to 8% magnesium
sulfate
163
4.82 SEM/EDX spectrum spot analysis for geopolymer mortar
(70% POFA+30% GGBS) after 6 months exposure to 8%
sodium sulfate
164
4.83 SEM/EDX spectrum spot analysis for geopolymer mortar
(70% POFA+30% GGBS) after 6 months exposure to 8%
magnesium sulfate
165
4.84 SEM images for geopolymer mortar (50% POFA+50%
GGBS) after 6 months exposure to 8% sodium sulfate
166
4.85 SEM images for geopolymer mortar (50% POFA+50%
GGBS) after 6 months exposure to 8% magnesium sulfate
166
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4.86 SEM/EDX spectrum spot analysis for geopolymer mortar
(50% POFA+50% GGBS) after 6 months exposure to 8%
sodium sulfate solution
167
4.87 SEM/EDX spectrum spot analysis for geopolymer mortar
(50% POFA+50% GGBS) after 6 months exposure to 8.0%
magnesium sulfate
168
4.88 FTIR Spectra for 100% POFA geopolymer mortar after 6
months exposure to sulfate attack
170
4.89 FTIR Spectra for geopolymer mortar (70% POFA+30%
GGBS) after 6 months exposure to sulfate attack
170
4.90 FTIR Spectra for geopolymer mortar (50% POFA+50%
GGBS) after 6 months exposure to sulfate attack
170
4.91 FTIR Spectra for Portland cement mortar after 6 months
exposure to sulfate attack
172
4.92 TGA results for 100% POFA geopolymer mortar after 6.0
months exposure to sulfate attack
173
4.93 TGA results for geopolymer mortar (70% POFA+ 30%
GGBS) after 6.0 months exposure to sulfate attack
173
4.94 TGA results for geopolymer mortar (50% POFA+ 50%
GGBS) after 6.0 months exposure to sulfate attack
174
4.95 TGA results for Portland cement mortar after 6 months
exposure to sulfate attack
175
4.96 DTG results analysis for Portland cement mortar after six
months of normal curing and six months of exposure to
sodium sulfate and magnesium sulfate
176
4.97 DSC thermograms for 100% POFA geopolymer mortar
after six months of normal curing and six months of
exposure to sodium sulfate and magnesium sulfate
177
4.98 DSC thermograms for geopolymer mortar (70% POFA+
30% GGBS) after six months of normal curing and six
months of exposure to sodium sulfate and magnesium
sulfate
177
4.99 DSC thermograms for geopolymer mortar (50% POFA+
50% GGBS) after six months of normal curing and six
months of exposure to sodium sulfate and magnesium
sulfate
178
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4.100 DSC thermograms for Portland cement mortar after six
months of normal curing and six months of exposure to
sodium sulfate and magnesium sulfate
179
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LIST OF ABBREVIATIONS AND ACRONYM
POFA Palm oil fuel ash
GGBS Ground granulated blast furnace slag
S/L Solid to liquid ratio
SS/SH Sodium silicate to sodium hydroxide ratio
SEM Scanning Electron Microscope
EDX Energy-dispersive X-Ray spectroscopy analysis
XRD X-Ray Diffraction
TGA Thermal Gravimetry Analyzer
DTG Derivative Thermogravimetry
DSC Differential Scanning Calorimetry
FTIR Fourier Transform Infra-Red
C-S-H Calcium Silicate Hydrate
C-A-S-H Calcium Aluminate Silicate Hydrate
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CHAPTER ONE
INTRODUCTION
1.1 Background
The development of alkali activated materials has been addressed by many researchers
as a competitive friendly alternative to ordinary Portland cement (OPC) (Provis and
Van Deventer, 2009; Provis and Van Deventer, 2014; Van Deventer et al., 2010; Li et
al., 2010). Alkali activated binders are classified as the third generation cements in
addition to lime and ordinary Portland cement (Shi et al., 2011; Li et al., 2010; Van
Davidovits, 2011). The alkali activation process is gaining a great recognition and
interest because of its low CO2 emissions where carbon footprint is of concern (Provis,
2014a). Recently, scientific and technological development being made at a rapid pace
due to their low energy consumption and qualities (Provis, 2014a; Villa et al., 2010;
Provis et al., 2012; Chindaprasirt et al., 2007; Provis and Van Deventer, 2009).
According to a recent rigorous and useful definition “Alkali activated materials are
produced through the reaction of an aluminosilicate-normally supplied in powder form
as an industrial by-product or other inexpensive martials-with an alkaline activator,
which is usually a concentrated aqueous solution of alkali hydroxide, silicate,
carbonate or sulfate” (Provis and Van Deventer, 2014; Provis, 2014a; Provis, 2009).
However, these materials, as new alternative binder to OPC in concrete technology,
are still at the beginning stages of development and need more investigations related
to the mechanisms of geopolymerization process (Pacheco-Torgal et al., 2012; Yip et
al., 2008). The activation methods, the type and dosage of alkali activators, curing
regime at the fresh state, and role of calcium in geopolymerization process are major
factors and still subjects of discussions for the researchers in this field (Nath and
Sarker, 2014; Nath and Kumar, 2013; Bernal et al., 2012; Bilim and Atiş, 2012; Yang
et al., 2012a; Liew et al., 2012a; Somna et al., 2011; Hajimohammadi et al., 2011).
The alkali activation process for an aluminosilicate source involves different
parameters. One of the governing factors on properties of the binding gel and its
formation is the type and dosage of alkali activators (Juenger et al., 2011). It has been
reported that different single activators were used in the activation process, such as
sodium hydroxide and sodium silicate (Somna et al., 2011; Rashad and Zeedan, 2011).
Combination of two different activators were also used in the alkali activation process
by using different liquid solutions (Luo et al., 2012; Altan and Erdoğan, 2012).
So far, a mix of liquid sodium silicate which is known as water glass and liquid sodium
hydroxide were the most used activating solutions in the geopolymers (Ryu et al.,
2013). This combination of activators were reported to have better performance in the
activation process comparing to single alkaline activators (Papa et al., 2014; Nath and
Sarker, 2014). The alkali hydroxide is required for dissolution of aluminosilicate
source while water glass solution acts as a binder, alkali activator and dispersant of
plasticizer (Komnitsas and Zaharaki, 2007). So far, different approaches have been
reported to measure the dosage of activators such as using sodium as a percentage of
the source material, or adding the total activator as a percentage of the binder (Bernal
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et al., 2012; Bilim and Atiş, 2012; Yang et al., 2012a). Nevertheless, previous works
have shown that solid to liquid (S/L) ratio and sodium silicate to sodium hydroxide
(SS/SH) ratio have tremendous effect on mechanical properties (Palomo et al., 1999;
Hardjito and Rangan, 2005a; Hardjito et al., 2004; Van Jaarsveld et al., 2002).
It has been reported that different factors affect the solid to liquid ratio and sodium
silicate to sodium hydroxide ratio in the alkali activation process. Firstly the shape and
particle size, and type of aluminosilicate precursor has an important effect on the
required quantity of the activator by which results in advanced dissolution (Kong et
al., 2007; Hardjito and Rangan, 2005a; Wang et al., 2005; Xu and Van Deventer,
2000b). The second factor affecting the geopolymerization process is the curing
regime at the fresh state of activation. In most cases the curing for alkali activated
materials is curried out at elevated temperatures ranging from 40 ºC to 90 ºC for a
period of 4 to 48 hours which is a limiting factor in construction industry (Lemougna
et al., 2013; Ryu et al., 2013; Rangan et al., 2005; Temuujin et al., 2009b). In order to
overcome the liming factors in geopolymerization process such as low reactivity, low
setting and slow strength development; calcium bearing materials or materials rich in
calcium oxide like GGBS were used to alter the reactivity of aluminosilicate precursors
(Oh et al., 2010; Guerrieri and Sanjayan, 2010; Yip et al., 2008; Nath and Sarker, 2014;
Kumar et al., 2010).
So far, different types of aluminosilicate materials such as Metakaolin (Yunsheng et
al., 2010; Liew et al., 2012b; Rashad, 2013; Pacheco-Torgal et al., 2011; Rovnaník,
2010), fly ash (Hardjito and Rangan, 2005b; Thomas et al., 2012; Provis et al., 2012)
and slag (Němeček et al., 2011; Luo et al., 2012; Fu et al., 2011; Bernal et al., 2011;
Bernal et al., 2010) were applied as alkali-activated cements.
Recently, researchers have incorporated palm oil fuel ash (POFA) as another potential
aluminosilicate source that can be used as an alkali activated cement. POFA is an agro-
waste produced in massive amounts from palm oil industry in South East Asia. POFA
has been used with a low content in binary mixes with other aluminosilicate materials
such as ground granulated blast furnace slag (GGBS), rice husk ash (RHA), and fly
ash in order to produce geopolymer paste, mortar and concrete while curing at oven
was the dominant regime in most of the studies.
This study intended to investigate the mechanisms by which calcium ions and
aluminum ions participate in the system in order to produce a high strength binder at
ambient temperature. It also studied the mechanism that governs the strength, chemical
composition, and microstructural change in the matrix after exposure to elevated
temperatures and sulfate attack.
1.2 Research Problem
The concept of alkali activated materials has been studied extensively as a promising
alternative to ordinary Portland cement (Provis, 2014a). However, the alkali activated
materials are still a complex class of binders (Provis and Van Deventer, 2009) and
there is still an increasing interest to improve the properties and microstructure of the
alkali activated binders. This is generated from the great need that is required to
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optimize the activation conditions in order to produce stronger, and more stable binder
(Bernal et al., 2014).
Furthermore, results from recent studies on the activation methods that being used in
alkali activation of different aluminosilicate sources have addressed the adverse effect
of oven curing as the dominant regime by which the production will be limited in the
real life situations comparing to Portland concrete.
There is also a consensus from some researchers regarding the use of Calcium bearing
materials or Calcium rich materials in binders with low calcium intake which results
in a better performance in terms of setting, hardening and also improving the load
bearing capacity of the gel; however, the mechanism of Calcium ion coupled with
Aluminum ion and their role in the system is still a complex subject.
Moreover, paucity has been noticed in the published studies and researches regarding
the behavior and degradation mechanism of alkali activated materials when exposed
to severe conditions such as heat exposure or sulfate attack. In this trend it is crucial
to investigate the change in compressive strength mechanism after exposure to such
environments.
Palm oil fuel ash (POFA) is one of the agricultural waste materials from the palm oil
industry in South East Asia. Malaysia is considered as the leading and the largest
producer of palm oil. It was estimated that only in Malaysia the wastes generated from
palm oil industry is 24.99 million tons per year (Hosseini and Wahid, 2013). The huge
amount of POFA is still a subject of wide criticisms and endless complaints because it
poses health hazard leading to various health problems. POFA needs large area to be
disposed which arising an environmental problem; in addition to the financial lost on
transportation of the waste and allocating hectares of lands for disposal. So far, some
studies have been conducted on low content POFA geopolymers although still a
comprehensive study on activation parameters, curing regime, its underlying
mechanism of geopolymerization, and its compatibility with other sources of
aluminosilicate is indispensable.
Recently, palm oil fuel ash (POFA) has been recognized as an aluminosilicate material
to be utilized in alkali activation technology. POFA was used as a supplementary
material in mixes with other aluminosilicate materials to produce geopolymer cement
paste, mortar and concrete. In all researches, a low content of POFA was kept to be
mixed with slag, fly ash and rice husk ash or other aluminosilicate materials to alter
POFA and increase its reactivity. Moreover, oven curing was associated to the
production process. Still, no study investigated the activation mechanism and the
microstructure of the resulted geopolymer binder from the activation of POFA as the
only aluminosilicate material source. Moreover, no study investigated the potential of
high volume of POFA to be activated with GGBS to produce high strength Geo-
polymerized paste and mortar at ambient temperatures.
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1.3 Hypothesis of the Research
The hypothesis that this study was built on is the role of calcium ions provided by
GGBS in developing the chemical composition and the microstructure of the gel. The
abundant quantity of calcium ions has the ability to develop the load bearing capacity
of the formed binding phase of POFA. This will lead to enhance the compressive
strength of the geopolymer binder to higher strength. Furthermore, Calcium ions will
participate in changing the setting and the hardening of the developed binder to
ambient temperature. In other words, calcium ions will develop the binding phase
structure to be stronger and eliminate the need for higher temperature for curing and
hardening.
1.4 Research Objectives
The main aim of this research was to study the ability of alkali activated materials to
produce high strength binder at ambient temperature from high volume POFA blended
with GGBS. This was assimilated by studying the mechanical and microstructural
properties of alkali activated paste and mortar through the following four objectives:
1. To identify activation parameters, Sodium Hydroxide concentration
(Molarity), Solid to Liquid ratio (S/L) and Sodium Silicate to Sodium
Hydroxide ratio (SS/SH) in production of a geopolymer binder with POFA as
a single aluminosilicate source.
2. To investigate the appropriate curing temperature in geopolymerization of
100% POFA.
3. To investigate the production of high strength geopolymer binder by using
binary mixing of GGBS and POFA.
4. To assess the durability performance of the proposed geopolymer mortar when
exposed to elevated temperatures and sulfate attack.
1.5 Research Questions
This study focused on the compressive strength, microstructural, chemical and thermal
characteristics of POFA geopolymer paste and POFA geopolymer mortar produced
from a binary mixture of POFA and GGBS in order to answer the following questions:
How do the solid to liquid ratio and sodium silicate to sodium hydroxide ratio
affect the geopolymerization process?
What is the mechanism by which calcium ions available in the aluminosilicate
material affect geopolymerization process and help the geopolymer binder to
set at ambient temperature and produce high strength binder and high strength
mortar?
How do thermal and microstructural analysis differentiate between C-S-H and
C-A-S-H as the main binding phases in alkali activated materials?
How do elevated temperatures and sulfate attack deteriorate the C-S-H, and C-
A-S-H in mortar?
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1.6 Research Contribution
Palm oil fuel ash (POFA) is designated with a moderate content of silicate and a low
content of aluminum which reportedly can produce a low strength geopolymer binder
(less than 18 MPa) when POFA is the only alkali activated material. In the same time
oven curing at 65 ºC to 75 ºC for 24 hours was associated as a curing regime in the
production process of this binder.
The aim of this study is to produce a high strength geopolymer binder using high
volume of palm oil fuel ash at ambient temperature. This study exploits the role of
calcium ions coupled with aluminum ions provided by GGBS to investigate the
mechanisms by which the strength of binding phase can be improved and allow to the
binder to harden without oven curing. Investigating the degradation mechanisms
governing the alkali activated mortar after exposure to elevated temperatures and
sulfate attack is another major contribution of the present study.
1.7 Significance of the Study
The overarching purpose of this study is to activate POFA albeit its very low content
of aluminum. The finding of this research will also explain the mechanism by which
aluminosilicate with low aluminum content are involved in the geopolymerization
process. Also, the results of this study may encourage and promote further research
on the use of POFA in geopolymer technology in mortar and concrete as well as the
use of other aluminosilicate materials with low aluminum content which will
ultimately lead to development of more environmentally friendly products with low
energy consumption and very low CO2 emissions.
Furthermore, there is no comprehensive study on the effect of curing temperature on
alkali activation of mixes with 100% POFA. So, the other purpose of this study is to
investigate the microstructure and chemical composition of POFA geopolymer paste
binder cured at ambient temperature (25-30) ºC and oven cured at 60 ºC, 70 ºC, and
80 ºC. This study proposes the applicability of ambient temperature as a curing regime
in POFA geopolymer binders. Investigating the use of ambient temperature to produce
a geopolymer binder from agro waste materials such as POFA will contribute to a
development of mix design to be used in structural sector. It can lower the cost and
energy consumption; meanwhile enhances construction pace.
Moreover, ground granulated blast furnace slag was used as a partial replacement of
POFA in order to enhance the load bearing quality (capacity) of the binder. The
purpose is to produce high strength binder as an alternative to ordinary Portland
cement in high strength concrete using ambient temperature curing regime. The
finding of this work may facilitate the development of high strength geopolymer
concrete using higher calcium alkali activated materials at ambient temperature.
The last but not least, this study investigates the durability of alkali activated binder
using the binary mix of POFA and GGBS after exposure to severe environment namely
elevated temperatures and sulfate attack. The findings of this study assess the
acceptability of the binder in terms of durability and also clarify on the deterioration
mechanism.
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1.8 Scope and limitations of the study
The main purpose of this study is to investigate new geopolymerization process to
produce high strength alkali activated binder from high volume of POFA cured at
ambient temperature. In order to achieve the established objectives, the scope and
limitations of this study are summarized as follows:
In this study, activation parameters are limited to Sodium Hydroxide concentration
(NaOH molarity), Solid to Liquid ratio (S/L), and Sodium Silicate to Sodium
Hydroxide ratio (SS/SH). Furthermore, a combination of liquid Sodium Silicate
(Na2SiO3) mixed with liquid Sodium Hydroxide (NaOH) was chosen as alkaline
activators and represented by SS/SH ratio. As for the curing regime only for
temperatures were assigned in the second objective which are namely; ambient
temperature at (25-30) ºC, and oven curing at three different temperatures of 60 ºC, 70
ºC, and 80 ºC. In order to study the effect of Ca ions and to develop a high strength
binder, GGBS was chosen and replaced with POFA at different levels of 10%, 20%,
30%, 40% and 50%.
The durability of geopolymer mortar produced from 100% POFA and POFA-GGBS
geopolymerized mortar was limited to the performance of the geopolymerised mortar
at elevated temperatures and in sulfate environments. The heat exposure was for one
hour within the rates of 100 ºC, 200 ºC, 300 ºC, 400 ºC, 500 ºC, 600 ºC, 700 ºC, and
800 ºC. Furthermore; the durability of geopolymer mortar were investigated by
exposing the mortars to Sodium sulfate and Magnesium sulfate. Geopolymer mortars
were exposed for 6 months to three different concentrations 3%, 5%, and 8%.
All the tests were conducted on geopolymer paste and mortars and aggregate with size
bigger than 4.75 mm were excluded from this study in order to eliminate the effect of
the volume concentration factor in the matrix and to minimize the effect of the thermal
conductivity and specific heat of the resulted matrix.
In this study, X-Ray fluorescence spectrometry scanning (XRF), setting time, flow
table test, compressive strength, X-Ray diffraction (XRD), Scanning Electron
Microscope (SEM) coupled with Energy-dispersive X-Ray spectroscopy analysis
(EDX), Thermogravimetric Analysis/Derivative Thermogravimetric Analysis
(TGA/DTG), Differential scanning calorimetry (DSC), and Fourier transform Infra-
Red (FTIR) were the main tests conducted to trace properties of the materials before
and after alkali activation in geopolymer paste and mortar.
1.9 Thesis Layout
In this study, an experimental work has been carried out to achieve the required
objectives. The work presented in this thesis is spread across five chapters.
Chapter one includes a general introduction about the alkali activated materials and
geopolymer technology as an alternative binder to ordinary Portland cement. The
studied objectives were illustrated in general in this chapter. Chapter two initially
illustrated the definition of alkali activated materials and the term geopolymer.
History, geopolymerization mechanisms, activation methods, activators,
aluminosilicate materials and tests that have been used in this technology were all
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illustrated. Chapter two is considered as a reference that can give all the required
information and details about alkali activation technology and geopolymers. Figures
and images were used to explain the way that the required tests were used in identifying
the changes before and after alkali activation, and the changes in the paste and mortar
with different parameters in the study. In chapter three, the methodology that used in
the experimental work was illustrated. This chapter showed the applied method for
alkali activation; moreover, the approach as a step by step method that being used to
identify the required parameters in alkali activation of an aluminosilicate material. The
designed methodology is considered as a reference for studying the alkali activation
for any aluminosilicate precursor. Chapter four discussed the test results for the used
method in alkali activation of POFA and POFA blended with GGBS. This chapter
tended to introduce the most effective parameters in the activation process. The
behavior of POFA geopolymer mortar and POFA blended with GGBS geopolymer
mortar after exposure to elevated temperatures and sulfate attack was also discussed.
Chapter five illustrated the conclusions of the study and recommendations for further
research.
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