Engineering properties and durability of self compacting concrete with no cement eco binder made from ternary recycling industrial by products

Both mechanical properties and bonding strength of the no-cement SFC-SCCs were found to be lower than those of the plain ordinary Portland cement OPC concretes with similar water to bind

105

國立臺灣科技大學 營建工程系 Department of Civil and Construction Engineering National Taiwan University of Science and Technology

i

Engineering Properties and Durability of Self-Compacting Concrete with No-Cement

Eco-Binder Made from Ternary Recycling Industrial By-Products

指導教授 Advisor：張大鵬 博士 Prof Ta-Peng Chang, Ph.D

民國一五年十二月 December 2016

摘要

本研究探討由爐石粉(S)、F 級飛灰(F)及循環式流化床燃燒飛灰(C)等三種工業副產品混合物所組成無水泥 SFC 膠結材之高強度自充填混凝土(SCC)工程性質與耐久性，也以拉拔試驗進行探討埋入鋼筋由此種 SFC-SCC 混凝土圍束時之鍵結行為，以瞭解其應用為結構混凝土之可能性，在循環式流化床燃燒飛灰重量佔爐石粉與 F 級飛灰混合物重量固定為 15%之最佳比率以激發水合作用之情況下，利用 F 級飛灰佔 0-50%大範圍重量比率調整 SFC-SCC 混凝土之新拌與硬固性質。

試驗結果顯示此種 SFC-SCC 之 28 天抗壓強度可達 65.6 MPa.，F 級飛灰重量比

為 30%時為最佳值，可達成優良流動與通過能力、較合宜耐久性、工程及鍵結性質，無水泥 SFC-SCC 混凝土工程與鍵結性質低於同水膠比之波特蘭水泥(OPC)混凝土，另一方面，在等值 28 天抗壓強度下，SFC-SCC 鍵結強度與波特蘭水泥(OPC)混凝土相同，但所需混凝土保護層厚度較小，鍵結與抗壓強度關係分析顯示 SFC-SCC 混凝土鍵結品質與波特蘭水泥(OPC)混凝土相同優良，表示前者具有高度應用潛能，可作為實務基礎建設之另一種鋼筋混凝土。

由傅里葉轉換紅外光譜(FTIR)分析微觀結構結果明顯地顯示，SFC 膠結材水化物

主要由氫氧鈣石(portlandite, Ca(OH)2) and 無水硫酸鈣(anhydrite, CaSO4)所組成，造成SFC 粉具有水硬性質，硬固漿體水化物主要為鈣釩石(AFt)及矽鋁酸鈣(C-A-S-H)膠體，

增加 F 級飛灰用量造成由於增加活性鋁所引致之高度鈣釩石(AFt)沈澱稀出。

關鍵字：CFBC 飛灰、F 級飛灰、爐石粉、水化物、自充填混凝土、無水泥、鍵結、

耐久性

iii

Engineering Properties and Durability of Self-Compacting Concrete with No-Cement

Eco-Binder Made from Ternary Recycling Industrial By-Products

Dissertation adviser : Prof Ta-Peng Chang

Abstract

This study investigated the engineering properties and durability of the high-strength

self-compacting concrete (SCC) manufactured by an innovative no-cement SFC binder,

which was purely produced with a ternary mixture of three industrial by-products of

ground granulated blast furnace slag (S), low calcium Class F fly ash (F) and circulating

fluidized bed combustion (CFBC) fly ash (C) To explore the possibility of applying this

SFC-SCC to structural concrete, the bonding behaviors of the embedded steel bar confined

by the SFC-SCC using the pull-out test was also conducted With a fixed amount of

circulating fluidized bed combustion fly ash at 15 wt.% of mixture of slag and Class F fly ash

as the optimum value to activate the hydration, Class F fly ash in a wide range of 0-50 wt.%

was used to adjust the properties of the SFC-SCCs at both fresh and hardened states

Experimental results showed that the compressive strengths of the resulting

SFC-SCC at age of 28 days reached the value up to 65.6 MPa The added amount of Class

F fly ash up to 30 wt.% was found to be an optimal amount to produce the SCC with

excellent flowing and passing capability, preferable durability and mechanical and bonding

properties Both mechanical properties and bonding strength of the no-cement SFC-SCCs

were found to be lower than those of the plain ordinary Portland cement (OPC) concretes

with similar water to binder ratio (W/B) On the other hand, at the equivalent 28-day

compressive strength, similar bonding strength of SFC-SCCs to that of the plain OPC

concretes was observed, but the required covering thickness of SFC-SCCs was lower than

that of OPC concretes The analysis on relationship between bonding and compressive

strengths showed that the bonding quality of the SFC-SCCs was as good as that of plain OPC

concretes implying that the former also could has a high potential of application as an

alternative reinforced concrete for practical infrastructural construction

The results of microstructural analysis of the hydration products of SFC binder using

Fourier Transform Infrared (FTIR) spectroscopy obviously showed that they mainly

consisted of portlandite (Ca(OH)2) and anhydrite (CaSO4) which attributed to the hydraulic

property of SFC powder The main hydration products of the hardened paste are ettringite

(AFt) and calcium aluminum silicate hydrate (C–A–S–H) gel An increase in Type F fly ash

addition led to the higher degree of AFt precipitation induced by an increase of active

alumina

Key words: CFBC fly ash; Class F Fly ash; Slag; Hydration products; Self-compacting

concrete; No-cement; Bonding behaviors; Durability

v

Acknowledgements

First of all, I would like to express thanks to the National Taiwan University of Science and Technology (NTUST) (Taiwan Tech) which gives me an opportunity to study

in a modern studying environment

Special mention comes to my enthusiastic supervisor, Prof Ta-Peng Chang During the time working under the big support of Prof Ta-Peng Chang, I figured out that not only

my knowledge but also my living behavior have improved It is always my honor to work as

a student of Prof Ta-Peng Chang

I would like to greatly appreciate strong support from Prof Chun-Tao Chen who has provided his precious experimental experience to refine my experiment and polish my scientific paper so that the role of Prof Chun-Tao Chen as my secondary supervisor is true

I also greatly appreciate the precious comments and suggestions from all committee members; consisting of Prof Jenn-Chuan Chern (陳振川 教授), Prof Ran Huang (黃 然

教 授), Prof Wen-Chen Jau (趙文成 教授), Prof Jong-Shin Huang (黃忠信 教授), Prof Chao-Lung Hwang (黃兆龍 教授), and Prof Chun-Tao Chen (陳君弢 教授); contributing to make the dissertation with improved quality

Special mention goes to all my colleagues including Mr Herry, Mr 李炳輝, Mr 陳

冠銘, Mr 郭祐豪, Ms 郭侑臻, Mr 翁子軒, Mr 羅佳豪, Ms 楊巧薇, Ms Anna, Ms Vina, and Mr Harry and the laboratory technicians including Mr 展維賢, Ms 蔡季玲, and Mr 呂冠群 for sharing me the precious experiences in inducting the experimental works

I greatly appreciate the supports on both materials and principles from my close friends consisting of Mr Duc-Thang Vo and Ms Duong-Ai-Nhan Au for inducting the test

on Fourier Transform Infrared (FTIR) spectroscopy which contributes to enrich the

microstructural evidences and thus improves the quality of the dissertation

Finally, but by means not least, thanks go to my family for spiritual encouragement

This thesis is a truly valuable gift I would like to give my grandparents, my parents, my wife,

and my daughter who are always the most important people in my life

Hoang-Anh Nguyen Taiwan Tech

Taipei, Taiwan December 2016

vii

Contents

摘要 i

Abstract iii

Acknowledgements v

Contents vii

List of symbols and abbreviations ix

List of tables xi

List of figures xii

Chapter 1 Introduction 1

Chapter 2 Literature Review 7

2.1 Environmental impact of cement manufacture 7

2.2 Environmental impacts related to increase in energy demand 9

2.3 Sustainable development of construction materials 13

2.3.1 Utilization of supplementary cementitious material (SCM) 13

2.3.2 The utilization of alkali activated material (AAM) as free cement binder 18

2.3.3 The utilization of sulfate activated material (SAM) as low alkaline no-cement binder 22

2.3.4 The utilization of cementing binder using 100% industrial solid wastes 23

2.4 Objective and significance 25

2.5 Outline 27

Chapter 3 Experimental Program 29

3.1 Materials and mix proportions 29

3.1.1 Materials 29

3.1.2 Mix proportions 30

3.2 Test methods 32

3.2.1 Workability 32

3.2.2 Compressive strength and strength efficiency of concrete 33

3.2.3 Drying shrinkage 35

3.2.4 Dynamic and shear moduli 36

3.2.5 Ultrasonic pulse velocity (UPV) 38

3.2.6 Bonding behavior 39

3.2.7 Rapid chloride penetration test (RCPT) 41

3.2.8 Fourier transform infrared (FTIR) spectroscopy 42

3.2.9 SEM/EDS and XRD 44

Chapter 4 Results and discussion 53

4.1 Examination on mineralization of SFC powder and microstructures of SFC

based hardened pastes 53

4.1.1 Analysis on FTIR spectra of raw materials 53

4.1.2 Analysis on FTIR spectra hardened SFC paste 54

4.1.3 Analysis on XRD patterns 57

4.1.4 Analysis on SEM/EDS observation 58

4.1.5 Proposed hydration mechanism 59

4.2 Workability 62

4.3 Compressive strength 63

4.4 Strength efficiency (SE) of slag 65

4.5 Bonding behavior 67

4.5.1 Bonding strength 67

4.5.2 Load-slip relationship 70

4.5.3 Analysis on bonding quality 73

4.6 Dynamic elastic and shear moduli 73

4.7 Ultrasonic pulse velocity (UPV) 74

4.8 Drying Shrinkage 75

4.9 Chloride penetration resistance 76

Chapter 5 Conclusions 95

Chapter 6 Future application potentials, drawbacks, and further research 98

References 100

ix

List of symbols and abbreviations

'

c

HVFA High volume low calcium Class F fly ash

xi

List of tables

Table 3-1 Physical and chemical compositions of materials 45 Table 3-2 Mix proportions for high strength self-compacting concrete (SFC-SCC) (kg/m3) 46 Table 3-3 Mix proportions for normal strength self-compacting concrete (SFC-SCC) (kg/m3) 47 Table 4-1 Setting times of the no-cement SFC binder pastes [149] 79 Table 4-2 Fresh properties of high strength SFC-SCC concretes and OPC references 80 Table 4-3 Fresh Properties of normal strength SFC Concretes and OPC references 80

List of figures

Figure 1-1 Global cement production ([9]) 6

Figure 1-2 Cement types produced by Holcim 1995–2009 ([1]) 6

Figure 1-3 Factors affecting the specific fuel energy requirement of cement clinker kilns ([2]) 6

Figure 3-1 SEM images of (a) GGBFS, (b) Type F fly ash (FFA) and (c) CFBC fly ash (CFA) 48

Figure 3-2 Particle size distributions of powders of three industrial by-products 49

Figure 3-3 XRD patterns of three solid wastes 49

Figure 3-4 Procedure of compressive strength test for concretes 50

Figure 3-5 Procedure of drying shrinkage test for concrete 50

Figure 3-6 Apparatus of dynamic moduli tests for concrete 51

Figure 3-7 Apparatus of UPV test for concretes 51

Figure 3-8 Schematic diagram of specimen for pull-out test 52

Figure 3-9 Experimental set for pullout test 52

Figure 4-1 FTIR spectra of three solid waste materials 81

Figure 4-2 Effect of age of curing on FTIR spectra of SFC binders 82

Figure 4-3 Effect of FFA amount on FTIR spectra of SFC binders 83

Figure 4-4 XRD patterns of hydrated SFC paste with different FFA/slag ratio and ages of curing [149] 84

Figure 4-5 SEM images with different magnification and area and EDS analysis of SFC paste with FFA/slag ratio at 50/50 (F50 mix) at age of 28 days 85

Figure 4-6 Heat evolution of SFC pastes with (a) 15 wt.% CFBC fly ash and (b) FA/GGBFS = 0/100 [149] 86

Figure 4-7 Workability of the SFC-SCCs with (a) no FFA additive and (b) with FFA 87

Figure 4-8 Passing and filling abilities of the SFC-SCCs with optimized amounts of FFA 87

Figure 4-9 Sections of hardened SFC-SCC concretes with (a) no addition of FFA and (b) addition of FFA replacing for slag 88

xiii

Figure 4-10 Compressive strengths of high strength SFC-SCCs 89

Figure 4-11 Strength efficiencies (SE) of slag in the high strength SFC-SCCs 89

Figure 4-12 Bonding strength of normal strength SFC-SCCs at age of 28 days 90

Figure 4-13 Effect of diameter and type of steel bars on bonding strength of normal strength concretes at age of 28 days 90

Figure 4-14 Load-slip relationship of normal strength SFC-SCCs and OPC concretes with (a) deformed steel bars with diameter of 16 mm, (b) deformed steel bars with diameter of 13 mm, and (c) smooth steel bars with diameter of 16 mm at age of 28 days 91

Figure 4-15 Relationship between compressive strength and bonding strength (with deformed steel bar) of normal strength concretes at age of 28 days 92

Figure 4-16 Dynamic Young modulus of high strength SFC-SCCs 92

Figure 4-17 Dynamic shear modulus of high strength SFC-SCCs 93

Figure 4-18 UPV of high strength SFC-SCCs 93

Figure 4-19 Drying shrinkage of high strength SFC-SCCs 94

Figure 4-20 Charge passed of high strength SFC-SCC concrete at age of 28 days 94

Chapter 1 Introduction

During the past decades, the rapid increase in demands of global housing and modern

infrastructure needs significantly motivate the proportional growth of construction

materials such as steel, aluminum, etc However, the high consistency in prediction agrees

that cement will remain the key material due to its lower applied energy consumption when

compared with the other materials Appearing as the first industrial production in the

middle of the 19th century, the annual global cement production has been reported to reach

2.8 billion tonnes, and has been expected to increase to some 4 billion tonnes per year The

historical development of cement production showed that the area with high concentrated

population such as China and India as well as in regions like the Middle East and Northern

Africa has the high demand in housing needs and thus obviously becomes major place for

cement consumption (as can be shown in Fig 1-1) [1]

Energy consumption by clinker production has been always a crucial consideration

and has been annually minimized over the last few decades because of a high pressure of

sustainable development of construction materials Normally, the factors involved to

further reduce such demand are associated with plant-specific, the fed raw materials’

condition (particularly, moisture content) or given by-pass rates (Fig 1-3) [1-3] As such,

the primary strategy driving to reducing energy consumption applied through clinker

2

creation is the size of kiln, which is mostly inapplicable for existing installations [1]

Recently, the manufacturing capacities of cement plant will remain in the typical range of

1.5-2.5 million t/d, which is associated with a typical single clinker production falling in

range of 4000-7000 t/d Such large amount of cement and clinker (10,000 or even 12,000

t/d) will significantly occupy very large areas associated with rivers for domestic

distribution or related with the coast for international distribution [1, 4]

To overcome the problem of high energy applied during clinker manufacture, the

utilization of recycled waste fuels and/or alternate fuel and raw materials (AFR) for cement

clinker production has become one of the most effective strategies due to the dual benefits

of cement manufacturer with lowered applied energy and society resulted from the

reduction on environmental pollution In the middle of 1980s, alternative fuel utilization

began with replaced calciner lines up to almost 100% alternative fuel firing at the

precalciner stage was very quickly achieved During the time, the alternative fuels mostly

consisting of tires, waste oil, sewage sludges, animal residues, and lumpy materials have

still been utilized in the cement kilns with an annual increase up to 100% substitution rates

in some clinker kilns However, in others, the local waste markets and permitting

conditions do not accept such higher rates of AFR Although the valuable contribution of

AFR utilization to minimizing applicable energy for cement industry is obviously observed,

in any case, the AFR utilization requires the adaptation of suitable combustion process

Indeed, the established ideal burner position results in a significant benefit for the burning

process and clinker quality The oxygen enrichment of primary or secondary air is proving

to be promising for the advanced alternative fuel combustion However, the cost for

research and technology transferring adapted to burning process possibly causes an

increased cost In addition, the future requirements of adapting a great deal of sources of

raw materials for AFR also challenge the clinker/cement manufacture to develop the

reasonable burning technique

Nowadays, producing new types of binders with low energy consumption as the

alternatives to the ordinary cement clinker has become a research interest which

significantly contributes to globally available in sufficient cement amounts Typically, the

basic principle for cement manufacture prioritizes the consideration on the compounds of

CaO, SiO2 as well as Fe2O3 and Al2O3 as the crucial key Accordingly, some new cements

starting from mostly plain Portland cement based binder to pure aluminosilicates based

cements with totally free in lime have been achieved Such new binding cement or their

basic concepts have been standardized for decades and have gained more attention recently,

while others are in accordance with some new concepts Indeed, the alkali-activated

pozzolanic materials typically represented by geopolymer were used to indicate a large

group of new binders in which the mechanism of solidification takes place after the

activating process of the reactive ingredients of raw materials in a highly alkaline

4

environment The setting and strength development are followed by the polycondensation

process after the amorphous inorganic aluminosilicates being formed under three

dimensional networks Generally, geopolymers can be fabricated by activating natural

sources of aluminosilicates including such materials like kaolin/metakaolin or low calcium

fly ash The differences in the source of material and the activation conditions used result

in the geopolymer binders with certainly distinguished characteristics During the existing

period, the geopolymer has been known as the binder with the advantages of high early

strength and superior durability in terms of high resistance to severely chemical attack

However, the prices of activators, the safe requirement in jobsite application, and some

remained open questions associated with the durability issues certainly narrows the wide

application of such innovative binder when compared with that of Portland cement

On the other hand, the basic ideal of making cementing binder based on the principle

of sulfate activate pozzolanic materials seems to be a preferred choice with regarding of

establishing sustainable development for cement industry The cement manufacture based

on such principle has been preferred in Europe and India [5-7] By adopting this principle

for cement manufacture, a majority of benefits has been reported to be more simple

manufacture process, depression on waste management procedure, and reduced

deteriorations of natural raw material and global environment when compared with the

manufacture of Portland [8] Typically, the setting property and strength gaining of such

cement are associated with the hydration ingredients rich in the sulfate under ettringite

(AFt) and/or mono sulfate crystals blending with the calcium aluminum/silicate hydrate

(C−S−H/C−A−S−H) amorphous gels When compared with the geopolymer binder, the

binding systems based rich amount of sulfate performs the early compressive strength and

high resistance to chemical aggressive environment similar to those illustrated by

geopolymer However, the manufacture process of such binder is safer, simpler, and

lowered consumption of energy applied As such it has been one of the most promising

cementing binders which is encouraged to be used as the representative candidate adapting

the serious requirement for modern sustainable development of construction materials

Therefore, the possibility of application of such innovative cementing binder for widely

infrastructural construction, particularly for structural concrete, will be the aim of the

current research

6

Figure 1-1 Global cement production ([9])

Figure 1-2 Cement types produced by Holcim 1995–2009 ([1])

Figure 1-3 Factors affecting the specific fuel energy requirement of cement clinker

kilns ([2])

Chapter 2 Literature Review

2.1 Environmental impact of cement manufacture

The ordinary Portland cement (OPC) has become one of the primary construction

materials during the past decade because of its lower energy consumption than those of

others such as aluminum and steel However, the cement industry has been remarked as an

intensive consumer of natural raw materials, fossil fuels, energy, and a major source of

multiple pollutants Indeed, during the manufacturing process of OPC cement, a great deal

of amounts of lime stone, quartz, and clay are fed as the raw materials As such, the OPC

manufacture significantly causes the serious damage of natural resources, particularly the

surface of the earth

When the ingredients (i.e., raw materials) of cement products are mostly optimized,

the heating process is applied for making the clinker Normally, the temperature adopted in

this step is really high up to approximate 2000 oC being obviously associated with the high

energy applied Actually, the burning coal has been widely used to generate energy

supplying for making clinker for many decades Therefore, an extra consumption of natural

resource, i.e., natural coal, is apparently observed through the process of making clinker of

OPC manufacture In addition, during the coal burning process, a great deal of flue gases

and solid waste has been released throughout the environment Such residual by-products

8

have become the primary factors inducing the environmental pollution by solid waste

footprint and climate change due to the disposal of flue gases Therefore, it is not an

exaggeration to say that the cement plants are characterized as an intensive consumer of

natural raw materials and fossil fuels, and has been remarked as emitters of pollutants

Nowadays, the modern cement factories have been under intense pressure to reduce

the environmental impacts of their products and operations In cement industry, thus, it is

important to implement sustainable manufacturing process The sustainable development

has become the mostly critical issue in the cement industry It has been obvious to agree

that the sustainable manufacturing has been currently a very important issue for not only

cement industries but also governments because the solution for environmental pollution

and climate change is the urgently worldwide issue In general, the sustainable

manufacture of cement has been defied as the creating process of manufactured products

during which the negative effects on environmental impacts and the consumptions of

applied energy, human labor, and natural resources are minimized According to the

definitions, sustainable manufacturing must address the integration of all the three

indicators of environmental, social, and economic, known as the triple bottom line of

sustainability

Sustainable achievement in accordance with economical challenge has been defined

as a development of manufacturing process producing the resulting products with high

potential of competitiveness through time In accordant to environmental challenge the

sustainable development has to be responsible for the consideration of minimizing the use

of non-renewable natural resources and reducing/eliminating the environmental impact

Also, the sustainable achievement in accordance with the social challenge has been related

to the promotion of both developed society and improved human life quality associated

with the renewed quality of wealth and jobs Currently, it has been apparently to accept

that sustainable development for cement manufacture has to be evaluated based on not

only the individual triple bottom lines of economic, environmental, and social performance

but also to consider their interdependencies

2.2 Environmental impacts related to increase in energy demand

During the past decades, the productions of electricity and metal industries have been

crucially depended on sources of heat energy from the combustion process of solid fuels In

most of the traditional power plants with the immature burning technique combustion of

fuel such as coal occurs at rather high temperatures in range of 1150 and 1750 °C, which is

associated with the low burning efficiency of raw materials As such, the out of date

burning process results in the generation of significant amounts of sulfur and carbon

dioxides, mainly contributes to the global environmental pollution and climate change [10]

Recently, the requirement for green power generation has been one of the primary

10

circulating fluidized bed combustion (CFBC); which contributes to the significant reduction

on the SO2 and NOx emission and widely adapts to a great deal of raw fuel with either high

moisture and/or internal sulfur amount in a comparison with the traditional coal combustion

techniques [11, 12] Therefore, the application of CFBC technique for renewal of burning

process apparently leads to the dual advantages associated with reduced polluting gas

during process of desulfurization and enhanced efficiency of fuel combustion

However, such CFBC technique also releases a lot of ash, the by-product of

combustion process In the circulating fluidized bed combustion (CFBC) boiler, SO2 is

absorbed by as the main absorbent normally consisted of limestone or dolomite which is

added during the burning process The mechanism of the captured SO2 process can be

briefly described as the following stoichiometric formula [13]:

2

3 CaO CO

4 2

2

2

1

CaSO O

SO

In general, the ratio of Ca to S in mole in high range of 2.0-2.5 has been adapted,

which results in the significant amounts of free lime (f-CaO) and desulphurization anhydrite

(CaSO4) remaining as the primary ingredients of residual product (i.e the CFBC ashes)

[14] Therefore, such ashes released from the CFBC method have the special

physicochemical properties putting it out of the classification of both Class C and Class F

coal fly ashes In accordance to the previous study conducted by Sheng, Li and Zhai [14]

investigating the comparison in term of hydraulic property between traditional coal fly ash

and CFBC fly ash, the CFBC fly ash consists of high content of f-CaO and SO3 and has the

novel characteristics of self-cementing through hydration process, obviously different from

the behavior of traditional coal fly ash as contacting with distilled water Also in such

investigation, the authors had made a confirmation on the crucial contribution of f-CaO to

the self-cementing property of CFBC powder The explanation for the mechanism of the

hydration process could be based on the stoichiometric formula suggested by Anthony, Jia

and Wu [13] as the following described:

2O Ca OH H

CaO 

(2-3)

O H CaSO O

H

Accordingly, it has been apparently to agree that the presence of free lime (f-CaO)

accompanying with the plenty of SO3 in CFBC ash restricts its utilization of wide

construction fields because of an serious issue related to the high potential of expansive

phenomenon induced by secondary gypsum and/or delayed ettringite precipitation[14]

Indeed, according to the previous study investigated by Li, Chen, Ma, Huang, Jian and Wu

[15], the binary cementing binder with the partial substitution of beyond 10% OPC by

physicochemical pretreated CFBC fly ash had the significantly decreased compressive

strength because of the reduced the cement content and excessive Ca(OH)2 generated from

the reaction of f-CaO with water which is unfavorable for the mechanical properties of

12

hardened cement [15] As such, the limited application of such CFBC fly ash for the

infrastructural construction due to the aforementioned impact on the integrity of

cement/concrete structures significantly causes serious problem of liable big ash footprint

which has challenged the proper solid waste management system

One of the promising strategies to overcome the problem of liable big ash footprint has

been the incorporation such CFBC ashes into other application such as manufacturing the

controlled low strength materials (CLSM) as suggested by Shon, Mukhopadhyay, Saylak,

Zollinger and Mejeoumov [16] According to the experimental results, the authors

concluded that CFBC ash could be used as a either partial or full replacement for traditional

coal fly ash in standardized CLSM mixtures with permissible engineering properties

consisting of flowability, bleeding, setting time, bulk density, absorption, and strength

requirements Fortunately, the substitution of CFBC ash to the coal fly ash significantly

shortened setting time, enhanced the early strength, reduced permeable voids, and

minimized the expansion of the CLSM Another study from China [17] reported that the

physically treated CFBC fly ash could be introduced in preparing the non-autoclaved aerated

concrete production with the optimal proportion of cement and lime, which implies one

different interesting application field of CFBC fly ash Also from China, according to the

laboratory experimental results, Zhang, Qian, You and Hu [18] had drawn an achievement

that the CFBC fly ash could be suitably applied for manufacturing autoclaved brick without

serious impact on the resultant final products Actually, the autoclaved brick fabricated with

up to 77% CFBC fly ash, 20% CFBC slag, and 3% cement by weight illustrated mostly

acceptable performance on compressive strength (up to 14.3 MPa) and long-term volume

stability The microstructural examination obviously confirmed for the absence of

destructive expansion due to no secondary gypsum transformed from the anhydrite from the

ash and AFm formation in the final products of autoclaved brick[18] With the purpose of

extending the application of CFBC fly ash, some researchers [19, 20] utilized such fly ash

as the chemical addition in alkali activated aluminosilica-rich material, normally known as

geopolymer binder The innovative achievement showed that when CFBC fly ash was

blended with traditional coal fly ash for making raw activated material, the hardened

samples of geopolymer could reach a satisfactory 7-day compressive strength of up to 32.7

MPa However, the utilized amount of CFBC fly ash is not high enough to solve the

problem of ashes footprint induced by the rapid increase in energy demand for human life

2.3 Sustainable development of construction materials

The utilization of SCMs in which part of ordinary Portland cement (OPC) is

substituted by using pozzolanic materials such as traditional coal combustion fly ash in

cement/concrete industry has been significantly increased during the past decades due to the

14

improvements of engineering and durability at both fresh and hardened states of the final

products Such benefits of using SCMs have facilitated the artificial role of fly ash articles

acting as filler at early and chemical reactant through pozzolanic reactivity at later age

[21-26] Actually, the fly ash particles with various size and mostly spherical, when being

incorporated in SCMs as partial replacement for OPC, significantly increase the

workability of the fresh mixture due to the optimization of particle distribution and

reduction of friction between the particles [24, 27] Although the large percentage of fly ash

particles is proved to be inert due to insufficient alkali during the early hydration process of

cement, the annual increase in degree of hydration of OPC later leads to a significant

increase in pH value induced by the precipitation of variety of calcium hydroxide

(Ca(OH)2), leading to the dissolution of FA particles followed by the precipitation of

additional hydration products mainly consisting of calcium silicate hydrate/calcium

aluminate hydrate (C−S−H/C−A−H) gels As such, the hardened cement specimens using

optimized ingredients of SCMs, in most cases, illustrated the improvement on both

mechanical and durability properties because of the refinement of pores between cement

hydrates [25] Normally, the SCMs with lower than 20% fly ash were preferred to be used

for fabricating concrete with mostly expected mechanical and durability performances [21,

28] However, in according with Poon, Lam and Wong [22], such level of fly ash

replacement for OPC is insufficient to produce concrete reducing/eliminating cracking

effect induced by high-rise temperature released when low water to binder ratio (W/B) is

used

The revolution of applying large amount of fly ash for SCMs has started in the 1970s

Accordingly, the concretes with high substitution of OPC volume of 50% by low calcium

fly ash, defined as high volume low calcium fly ash (HVFA), was firstly proposed to be

applied for the roller-compacted dam and highway basement where there were no

requirements of high strength and workability [22, 23] Since 1985, the Canada Centre for

Mineral and Energy Technology (CANMET) has widened the application of such

innovative HVFA concrete for structural construction [22, 23, 29-32] The state-in-the-art

designing strategy was based on the principle of using the low W/B accompanying with

addition of high amount of superplasticizer (SP) Following the state-in-the-art strategy, the

first high performance concretes with high workability, satisfactory mechanical properties,

and superior durability (especially chemically aggressive and high temperature resistances)

have been successfully achieved [21, 33-35] and annually have been become preferred

choice for not only pavement but also building structure because it satisfied the

requirement for sustainable construction materials with low cost, high durability, low

energy consumption, and minimized emissions of CO2 flue gas and ashes footprint [29, 36]

However, the issues of using the HVFA cements are associated with the delayed initial

and final setting times and decreased early compressive strengths [21, 22, 26, 27] As such,

16

an adaption of physicochemical treatment on raw material such as mechanical grinding

and/or on fresh concrete mixture consisting of accelerated curing, and mineral or chemical

addition , have been widely considered [18, 26, 37-42] Normally, the application of

chemical activation for accelerating the hydration of SMC systems has been the most

preferred technique because of the simple manufacture and high possibility applied for job

site Indeed, the usages of alkali and sulfate as chemical activators to trigger the hydration

of SCMs’ ingredients resulted in the hardened concretes with mostly expected compressive

strengths at both early and later ages [43-47] In the applications where the requirements of

safety and low cost are required, the sulfate activation such as sodium sulfate (Na2SO4) and

particularly gypsum/anhydrite (CaSO4.2H2O/CaSO4), the CaSO4.2H2O/CaSO4 has been the

preferred choice for manufacturing sustainable cement due to the ability of reusing the

sulfate rich by-product to substitute the commercial activator [44]

Similar to the utilization of fly ash, the usage of ground granulated blast-furnace slag

(GGBFS), known as the by-product of steel and iron industry, in SCM manufacture leads

to an ecological benefit because of the significant reduction of CO2 emissions and energy

consumption applied for cement manufacture [48] In general, because the GGBFS itself

owns the inherent cementitious properties, the applied energy required for accelerating the

early hydration is lower when compared with that required for fly ash activation [49]

During the past decades, the GGBFS commonly used as partial replacement for OPC in

SCMs applied for producing concrete meeting the requirements of low cost, increased

workability, lowered heat evolution of hydration, improved mechanical and durability

properties According to the previous study of Hale, Freyne, Bush Jr and Russell [50], the

SCM with 25% OPC substituted by slag could be used to produce concrete with improved

long term engineering properties without considered sacrifice at early age The laboratory

experimental work conducted by Ortega, Sánchez and Climent [48] obviously shows that

the mortars produced with slag cement illustrated better durability than that of plain OPC

mortars irrespective to hardening age and curing condition Studying on SCM adapting

slag as OPC replacement, Chen, Huang, Tang, Malek and Ean [51] concluded that the

GGBFS could be used to replace for OPC with high volume to produce slag cement

concretes illustrating the considerable resistance to chlorides ion penetration better than

that of the OPC concretes In addition, Gruyaert, Van den Heede, Maes and De Belie [52]

studied the influence of GGBFS on the resistances of concrete with SCM to organic acid

and sulfate attack and explored that slag cement concrete had the superior capacity of

resistance to acid deterioration However, because the mechanical property of slag cement

concrete is sensitively affected by curing temperature, particularly under standard 20 oC, its

application has been restricted in some construction fields where the early high strengths

are required [53]

18

From the 1940’s, the alkali activated material (AAM) was studied for applications as

the construction material During the last decades, it has been one of the researching

interests making it becomes an alternative to the OPC in cement/concrete In most cases, the

AAM manufacture requires lower energy consumption as compared with that of the OPC

Another benefit of using the AAM is that the hardened specimens normally have high early

mechanical properties and superior properties (particularly, resistance to the chemical

attacks), implying the infrastructural construction with increase in serve life According to

the aforementioned advantages, the AAMs have been widely utilized in the precasting

concrete industry and pavement repair Recently, the alkali activated GGBFS and alkali

activated fly ash, known as geopolymer, have played the crucial roles in AAM manufacture

due to the large amount of raw materials

The alkaline activated slag (AAS) is manufactured by using alkali activator such as

NaOH and KOH to trigger the hydration of ground granulated blast furnace slag (GGBFS)

acting as the main raw material to precipitate the calcium silicate hydrate (C−S−H) gels as

the crucial hydration products inducing the engineering and durability properties of the

hardened products Empirical application of AAS obviously shows that the AAS challenges

the OPC by its high mechanical properties at early ages and superior long-term durability

while its manufacture consumes lower energy applied [54] In general, the physicochemical

properties of raw material, type and dosage of activator and curing condition are the most

crucial factors that sensitively influence the precipitated hydration products[55] In practice,

the sodium silicate (Na2SiO3) has been preferred for the final products with high

engineering properties [55, 56] Both laboratory and job site experiments suggested to use

the ambient temperature as the optimized curing condition to fabricate hardened AAS

without un-expected decrease of long-term mechanical and durability properties [55]

Whereas, the effect of fine particle size of the GGBFS has been not obviously described with

the varied activator used [55] Recently, the remaining issues associated with the utilization

of the AAS are the rapid set and the high drying shrinkage when compared with those of the

plain OPC [57, 58] Although in precast concrete manufacture and pavement repair, such

behaviors has been its advantage [58], but the cracking potential limited its application in

infrastructure construction such as structural construction According to the previous

studies [57, 59], the increased volume of mesopores between the hydrates of AAS

associated with the higher hydration degree of GGBFS significantly contributed to the

higher drying shrinkage of the hardened samples As such, the usage of chemical agents

such as air-entraining agent (AEA), shrinkage-reducing (SHR) admixtures, and gypsum (G)

has been the main keys for reducing the drying shrinkage of the AAS [56, 58, 60] Indeed,

experimental results [56, 60] apparently proved that the addition of SHR or AEA resulted in

significant reduction on drying shrinkage of the hardened AAS specimens On the other

20

hand, the incorporation of gypsum in the AASs not only reduced the drying shrinkage but

also improved compressive strengths of final products

On the other hand, the geopolymer had been firstly proposed as an innovative

no-cement binder in 1979 by Davidovits According to the findings, the geopolymer itself

owns the higher early strength and better durability (especially in acid and sulfate

resistances) when compared with those of plain OPC binder while the energy consumption

required for the manufacture was significantly reduced [61] Actually, geopolymer can be

synthesized based on the mechanism of alkali activation of materials rich in silicon oxide

and aluminum oxide known as aluminosilicate materials It has been unanimously agreed

that the mechanisms of polymerization process includes three main stages consisting of the

dissolution of raw materials in sufficient alkali medium, the orientation of dissolved species,

and the condensation of arranged species [62, 63] At the end of condensation process, the

amorphous three-dimensional network of silicon and aluminum atoms linked by oxygen

atom in a four-fold condition as a zeolite structure has been crucially precipitated The

positive ions of sodium, potassium and calcium from the activator solution contribute to

balancing the negative charge on Al3+ in four-fold coordination [63, 64] In general, there are

three types of structures of geopolymer including polysialate (–Si–O–Al–O–),

polysialate-siloxo (–Si–O–Al–O–Si–O–), and polysialate-disiloxo (–Si–O–Al–O–Si–O–Si–

O–) Among them, the geopolymer precipitated with polysialate structure illustrated

unstable and weak properties when compared with either polysialate-sioxo or

polysialate-disioxo structure [63, 64] Actually, not only the ratios of species associated with

the raw materials used [65] but also the types and dosages of activator and curing condition

[66-68] primarily indicate the final structures of geopolymerisation mechanisms resulting in

the mechanical and durability of the final hardened products

Recently, various natural and/or industrial by-products such as fly ash, metakaoline,

and silica fume are available for manufacturing geopolymer binder [69, 70] However, the

low calcium Class F fly ash has been the preferred choice as the source of raw materials

because of its optimum contents of silica and alumina and low cost [71] To activate the

hydration process, the solution of sodium or potassium hydroxide and sodium silicate with

mostly concerned ratio of Na2O/SiO2 (modulus) have been mainly used [72] To trigger

the processes of dissolution and the polycondensation, a mild to high curing temperature

has to be applied In practice, 8-12 M NaOH and cured at 85 oC for 24 h could be applied

to fabricate geopolymer with compressive strengths in range of 35 and 40 MPa, whereas,

when the solution of water glass and NaOH (SiO2/Na2O = 1.23) was used, the compressive

strength of hardened geopolymer specimen could reach 90 MPa [73] With the fixed

modulus value of Na2SiO3/NaOH at 0.67, the increase in NaOH concentration in range of

8-18M led to the increased setting times and compressive strength due to a dense matrix of

microstructure [74] However, to make the raw powder with high activity and optimized

22

chemical composition, the mixtures of fly ash and some pozzolans such as GGBFS or

metakaolin have become the current research interest [75, 76]

no-cement binder

The requirement of producing a new kind of cement being possibly applied for marine

environment due to sufficient resistance to sulfate attack has strongly motivated the

established mechanism of sulfate activated material (SAM) Accordingly, the consideration

of adding different sources of sulfate as one of the reacting ingredients of cementing

powder becomes the state-of-the-art choice During the past decades, the super sulfated

cement (SSC) has been one of the most early cement inheriting such principle, and has

been preferred in Europe and India [5-7] because of the simplicity and low consumptions of

natural raw material and energy applied and significant reduction of flue gases released

during its manufacture when compared with the manufacture of ordinary Portland cement

(OPC) [8] In general, the ingredient of SSC includes a composition of 80-85% slag, 10-15%

anhydrite/gypsum, and 5% OPC [5, 7] Different from the OPC cement, the hydration

products of the SSC include tremendous amount of AFt crucially contributing to the setting

and early mechanical properties and C-S-H which relates to long-term engineering and

durability behaviors of the hardened samples The absence of calcium hydroxide (Ca(OH)2)

obviously clarifies the superior resistance of the SSC to sulfate due to the eliminated

secondary gypsum and/or delayed AFt formation

For the super sulfated cement, because the glassy phases included in blast furnace slag

are normally formed as monosilicates likely to those in Portland clinker, the GGBFS is

easily dissolved in sulfate activated solution and thus it plays a crucial role of the main

powder [25] As such, there are some issues associated with using the SSC Indeed, the

GGBFS with mostly irregular-shape articles and large surface area of have significantly

influenced on the increase of demanded water for certain workability Such un-reacted

water known as free water maintains in the structure of cement hydrates and thus possibly

causes the impact on mechanical properties and durability of hardened cement structure

The usage of blending mixture of slag and fly ash to replace the plain slag as the raw

powder seemed to be an expected solution for the aforementioned problem as proposed by

Zhao, Ni, Wang and Liu [77] Zhong, Ni and Li [78] has confirmed the benefit of using

combined mixture of fly ash and slag as the main powder for SSC Accordingly, the

blending mixture of FA and GGBFS as the main powder activated by uncalcined flue gas

desulfurization gypsum as sulfate activator could be applied to some civil engineering

construction fields where the high strength is not required, such as grouting mortars for tail

void grouting of shield tunnel, road sub-base, and other low strength concrete

24

leads to the high potential causing the severe air and surface water pollutions The strategy

of utilizing such alkali sulfur rich solid wastes in cement/concrete industry has been one of

the most efficient ways for mitigated such impacts Therefore, beside the rapid increase of

applying the by-product pozzolans for complementary cementitious materials or alkaline

activated binder [25, 79-83], the development of cementing powder with 100% by-product

pozzolans seems to be preferred in eco-binder manufacture because of its low cost and

environmentally friendly

Actually, the proposal of using binary or ternary mixture of solid waste to produce free

cement/strong commercial alkalis binder has paid a promising base for future researches on

no-cement binders with high competitive cost [77, 78, 84-86] Generally, the hydration

mechanism of such no-cement binders were in accordance with the literature principle of

sulfate-activated pozzolanic materials similar to the hydration process reported for SSC as

mentioned in the previous section [5-8, 87] However, the traditional activator such as

commercial gypsum and OPC clinker/lime was totally substituted by the by-product

materials rich in sulfur and alkali, such as CFBC fly ash and flue gas desulfurization (FGD)

gypsum [85] Similar to the traditional SSC, the powders of the cementing mixture were the

plain GGBFS [84, 86] with more reactive glassy phases Pretreated fly ash [85] with

reducing the particle sizes was also used as partial replace for slag for producing the raw

powder with expected sufficient activity As such, the high cost and the significant energy