Importance of reactive SiO2, AI2O3 and Na2O in

th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
IMPORTANCE OF REACTIVE SIO 2 , AL 2 O 3 AND NA2 O IN
GEOPOLYMER FORMATION
Chandani Tennakoon, Swinburne University of Technology,
Australia
Ahmad Shayan, ARRB Group, Australia
Kwesi Sagoe-Crentsil, CSIRO, Australia
Jay G Sanjayan, Swinburne University of Technology, Australia
ABSTRACT
Geopolymer is an alternative for Portland cement based binder. It has shown better or similar
engineering and durability properties compared to Portland cement based binders. The
properties of geopolymer depend on the characteristics of the aluminosilicate source material
used. Hence, it is important to identify the characteristics of the source material that results in a
binder with good mechanical properties.
This paper investigates the levels of reactive (amorphous) SiO 2 and Al 2 O 3 contents of source
materials and alkali oxides content of Si-rich geopolymer binders required to achieve enhanced
mechanical properties. The study also evaluates the roles of Na 2 O and particle size in the
development of geopolymer micro-structures.
We have used six different Australian Class F fly ashes as aluminosilicate source materials in
geopolymer binders. These materials were characterised using XRF, XRD and particle size
analyser in order to determine the bulk chemical composition, mineralogy (including content of
amorphous phases) and particle size distribution. Geopolymer pastes were subsequently
prepared by activating the selected fly ashes with liquid alkaline activators and the samples
where cured at 60 ᴼC for 24 hrs. A constant flow was maintained for all mixtures, the
contributions of Na 2 O, SiO 2 and H 2 O content from the alkaline activator are different for each fly
ash source.
The compressive strength results showed that high strengths are given for mixtures in which the
molar ratio of reactive constituents lie within the ranges SiO 2 /Al 2 O 3 < 5 and Na 2 O/ reactive
(SiO 2 + Al 2 O 3 ) 0.09-0.12.
INTRODUCTION
Geopolymer binders are produced reacting aluminosilicate source materials with highly alkaline
liquids. The term “geopolymer” was first introduced by Joseph Davidovits. The reaction creates
three dimensional Si-O-Al-O bonds form monomers resulting in a poly (sialates) structure which
contains SiO 4 and AlO 4 tetrahedral interconnect by sharing oxygen atoms. Furthermore, cations
+ +
+2
(Na ,K ,Ca ) are required to balance the negative charge due to coordination of aluminium or
any broken bonds in the framework structure (Xu, 2002).
The reaction mechanism of geopolymerisation involves a series of dissolution and
precipitation/condensation reactions (Davidovits, 2008).
© ARRB Group Ltd and Authors 2014
1
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
1. Dissolution of SiO 2 and Al 2 O 3 sources:
-1
Al 2 O 3 + 3H 2 O + 2OH
→
2Al(OH) 4
→
SiO(OH) 3
→
SiO 2 (OH) 2
SiO 2 + H 2 O + OH
SiO 2 + 2OH
-1
-1
-1
-1
2-
2. Condensation of silicate and aluminate species:
2-1
-1
+
Na + SiO 2 (OH) 2 or SiO(OH) 3 + Al(OH) 4 →Na 2 O-Al 2 O 3 -SiO 2 -H 2 O gel
A number of factors control the chemistry of the above process. They are the amorphous
content of oxides (SiO 2 , Al 2 O 3 , CaO), physical properties (particle size and shape) alkali
activator content of the synthesis, mixing procedures and curing regime. The properties of
geopolymer binders, however, depend on the aluminosilicate material properties, alkaline
solution chemistry, mixing and curing regime (Duxson et al., 2007b, Khale and Chaudhary,
2007, Bakharev, 2005, Chancey, 2008, Bakri et al., 2011).
Fly ash, slag, red mud and rice husk ash or geological resources like metakaoline and kaolin
are used as aluminosilicate source materials in geopolymer. Chemical and physical properties
of these materials vary widely because of source origin or geological history, thermal process,
etc. These properties include SiO 2 , Al 2 O 3 and SiO 2 /Al 2 O 3 , ratio, particle size, amorphous
content and calcium content in the raw material. It is difficult to change alumino silicate material
characteristics significantly particularly in by-products like fly ash. Hence, the properties of the
final geopolymer binder are unpredictable.
Previous research has been carried out to discover a correlation between geopolymer and
aluminosilicate material properties. Duxson and Provis (2008) correlated on the basis of total
aluminium content, silica content and network modifier cations of source materials to the
strength of respective binder systems in a ternary diagram. They designed this ternary diagram
using bulk chemical compositions of the alumino silica source materials and blast furnace slag.
They concluded that alumino silica sources with less network modifier (i.e. Ca, Mg) content tend
to produce low strength geopolymer binders. However, it was apparent that certain aluminasilicate source materials did not necessarily conform to the proposed trend. While the study
showed broad trends it did not reveal any clear boundary demarcating inter-relationships
between bulk chemical compositions of alumino-silicate source materials. For fully amorphous
and reactive metakaolin feedstock material, De Silva et al. (2007) reported characteristic higher
strength for systems with SiO 2 /Al 2 O 3 molar ratio in the range of 3.4 - 3.8. Parallel studies by
Duxson et al. (2007a) also disclosed that maximum strength results were achievable for similar
ratios in metakaolin systems.
More recently, Autef et al. (2012) demonstrated that the geopolymerisation reaction rate
increases with the decline of quartz SiO 2 in the system. Despite the finding, they observed
complete participation of amorphous silica in the reaction to fully develop the geopolymer
network. In addition, they found the optimal SiO 2 /Al 2 O 3 ratios for metakaolin based geopolymer
in the region of 3 and 3.6. Duxson and Provis (2008) categorized the source materials in a
ternary diagram according to the total aluminium content, silica content and network modifier
2+
2+
cations (Ca , Mg etc.) with the strength of the binder. There was no clear boundary between
strength ranges in there diagram corresponded to chemical composition.
Van Jaarsveld et al. (2003) observed that high amorphous content fly ashes result in better
mechanical properties in binders whereas Brouwers and Van Eijk (2002) confirmed the
dissolution rate of SiO 2 and Al 2 O 3 in the aluminosilicate material to be proportional to glass
content of the fly ash. Pietersen et al. (1989) researched fly ash reactivity during cement
hydration and reported that the ratio between network forming oxides (SiO 2 + Al 2 O 3 + Fe 2 O 3 )
and network modifier oxides (Na 2 O + K 2 O + CaO + MgO) in the glass structure of fly ash range
should be between 4 and 9 to obtain better reactivity.
© ARRB Group Ltd and Authors 2014
2
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
This paper discusses the best selection criteria of aluminosilicate source material to get high
compressive strength. In addition, contributions from alkaline oxides, particle size, water content
and reactive oxide components towards compressive strength development are evaluated.
EXPERIMENT PROCEDURE
Materials
Six types of Class F fly ashes obtained from six different Australian power stations; Gladstone,
Collie, Mt Piper, Eraring, Tarong and Bayswater were used as the main alumina-silica source
materials in this study. D-Grade sodium silicate solution (29.4 SiO 2 and 14.7 % Na 2 O by weight)
from PQ Australia and analytical grade NaOH solid from Sigma Aldrich were used as alkaline
activators.
Characterisation of fly ashes
The overall chemistry and mineralogy of fly ashes were analysed by XRD and XRF techniques.
Particle size of the materials was obtained using a Cilas laser diffraction particle analyser. The
chemical compositions of the fly ashes are given in Table 1 while Table 2 shows the
mineralogical phases percentage of fly ashes. Using the formula of the mineral, the amount of
crystalline Al 2 O 3 and SiO 2 present in the mineral phases can be calculated. By subtracting this
value from the total values given in chemical composition, the amorphous content or reactive
components of Al 2 O 3 and SiO 2 present in each fly ash can be obtained. Figure 1 shows the
particle size distribution variation for Australian Class F fly ashes and Table 3 summarises
particle size distribution in percentage values.
Table 1: Bulk chemical composition of fly ashes
SiO 2
Al 2 O 3
CaO
MgO
Fe 2 O 3
Na 2 O
P2O5
Cr 2 O 3
K2O5
MnO
SO 3
LOI
TiO 2
Total
Gladstone
51.11
25.56
4.3
1.45
12.48
0.77
0.885
0.7
0.15
0.24
0.57
1.32
99.62
Collie
60.02
24.61
0.15
0.99
8.56
0.36
0.217
0.04
0.36
0.04
0.18
1.49
1.53
99.43
Mt Piper
65.77
26.72
0.05
0.25
1.32
0.32
0.139
2.69
0.02
0.11
1.44
1.11
100.28
Eraring
63.18
25.22
0.07
0.57
3.36
0.72
0.251
1.81
0.07
0.18
1.31
0.99
100.26
Tarong
73.05
23.22
0.07
0.14
0.89
0.06
0.046
0.52
0.02
0.06
0.75
1.31
100.36
Bayswater
80.43
14.02
0.04
0.31
3.57
0.1
0.087
0.85
0.04
0.08
0.54
0.49
100.36
Table 2: Mineralogical phases of fly ashes
Gladstone
Collie
Mt Piper
Eraring
Tarong
Bayswater
Quartz
Mullite
12.95
14.57
8.42
7.76
5.58
9.15
8.12
13.08
5.88
7.11
8.75
8.56
Hematite
Magnetite
4.17
1.88
1.87
1.71
1.88
-
-
-
2.21
6.52
80.22
8158
78.78
87.01
73.94
Amorphous 66.38
© ARRB Group Ltd and Authors 2014
3
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Figure 1: Particle size distribution of Class F fly ashes
Table 3: Particle size distribution (passing percentage)
Gladstone
Collie
Mt Piper
Eraring
Tarong
Bayswater
90%(µm)
24.44
43.33
41.83
55.85
40.09
35.25
50%(µm)
5.54
11.58
12.94
18.21
12.34
12.76
10%(µm)
1.1
1.61
2.23
3.02
2.71
2.54
Mean(µm)
9.32
17.38
17.96
24.64
17.25
16.22
Preparation of geopolymer samples
All geopolymer paste mixes were prepared by mixing each fly ash with alkaline activators. In
preparing the mixtures, solid NaOH was first dissolved in water to obtain 8M sodium hydroxide
solution. The solution was cooled to room temperature before mixing with the fly ash. Sodium
hydroxide and sodium silicate solution (1:1 ratio) were added to fly ash in the required amounts
in order to achieve equal flow for mixtures. The ratio between two alkaline activators is kept as
unity. The alkali activated mixtures were cast in 50 mm cubes that were sealed to prevent
o
moisture loss. The cubes were subsequently cured at 60 C and 100% RH for 24 hrs, after
which samples were removed from the moulds and placed in sealed polythene bags for storage
till testing. Table 4 shows geopolymer mix formulations for different fly ashes. Mix7, Mix8 and
Mix9 were obtained by blending 50% Gladstone and 50% Tarong, 50% Gladstone and 50%
Bayswater, 30% Gladstone and 70% Tarong fly ashes respectively. Important oxide ratios are
tabulated in Table 5 and calculations for the ratios are described as follows:
•
Reactive SiO 2 = SiO 2 from fly ash amorphous phases + SiO 2 from sodium silicate
activator
•
Reactive Al 2 O 3 = Al 2 O 3 from fly ash amorphous phases
•
Reactive SiO 2 /Al 2 O 3 of source material = SiO 2 from fly ash amorphous phases/Al 2 O 3
from fly ash amorphous phases
•
Total Reactive SiO 2 / Al 2 O 3 = Reactive SiO 2 /Al 2 O 3
© ARRB Group Ltd and Authors 2014
4
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Table 4: Class F fly ash geopolymer binder mix designs for equal flow
Mix no
Mix formulation
Fly
ash(g)
NaOH+
Na 2 SiO 3 (g)
Mix1
Mix2
Mix3
Mix4
Mix5
Mix6
Mix 7
Mix 8
Mix 9
Gladstone
Collie
Mt Piper
Eraring
Tarong
Bayswater
50%Gladstone/50%Tarong
50%Gladstone/50%Bayswater
30%Gladstone/70%Tarong
3000
3000
3000
3000
3000
3000
3000
3000
3000
800
1200
1300
1650
1900
1850
1272
1200
1440
Liquid/
Solid mass
ratio
0.267
0.400
0.433
0.550
0.630
0.617
0.424
0.400
0.480
Table 5: Important oxide ratios and 28 day compressive strength
Mix no
Mix1
Mix2
Mix3
Mix4
Mix5
Mix6
Mix7
Mix8
Mix9
Total reactive
SiO₂/Al₂O₃
Molar ratio
3.7
4.6
5.0
5.7
6.6
14.8
5.1
7.4
5.7
Reactive
SiO₂/Al₂O₃
Molar ratio
of fly ash
3.28
4.13
4.53
4.87
5.78
13.1
4.60
6.65
5.10
Water to
total solid
mass ratio
0.16
0.23
0.24
0.30
0.33
0.34
0.24
0.23
0.27
28 days
Na 2 O/(reactive
average
SiO 2 +Al 2 O 3 )
compressive
molar ratio
strength (MPa)
0.098
48
0.102
37
0.097
18
0.136
15
0.123
21
0.129
20
0.110
35
0.106
37
0.112
32
RESULTS AND DISCUSSION
According to the particle size distributions (Figure 1 and Table 3), Gladstone fly ash has the
smallest particle size compared to the other Australian fly ashes. Other fly ash types also have
90% of particles less than 55 µm. Diaz and Allouche (2010) investigated 25 different Class F
and class C fly ash, according to their conclusion when fly ash has very small particles(<90µm)
has high strength ( higher than 50 MPa). Geopolymertic leaching occurs (Si and Al ion leaching)
on the surface of the fly ash particle, therefore it is important to have fine particles and a large
surface area (Diaz and Allouche, 2010, Palomo et al., 1999).
Figure 2 shows the compressive strength variation for the geopolymer pastes. Gladstone and
Collie fly ashes based geopolymers(Mix1 and Mix2) showed one day strength 40 and 20 MPa
respectively. On the other hand, Tarong and Bayswater fly ash based geopolymer (Mix5 and
Mix6) had very poor compressive strength performance (5 and 6 MPa respectively).
Nevertheless, blending Gladstone fly ash with Tarong and Bayswater increased the strength
values (Mix7, Mix8, and Mix9). This is discussed thoroughly in the next paragraph.
© ARRB Group Ltd and Authors 2014
5
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Figure 2: Compressive strength variation of Class F fly ash based
geopolymer pastes
Figure 3 shows the compressive strength variation Gladstone and Tarong blended
geopolymers. 100% Gladstone fly ash based geopolymer (Mix1) has 48 MPa in 28 days.
Moreover, 100% Tarong fly ash based geopolymer has 21 MPa (Mix5). When Gladstone fly ash
is blended with Tarong geopolymer, the strength value is higher (> 30 MPa). Possible reasons
could be the initial 100% Tarong and Bayswater fly ash based synthesis had high SiO 2 contents
and consumed high alkaline liquid to get consistent workability. It may be noted that those
geopolymer systems have higher water content and higher Na 2 O content. However, Gladstone
fly ash appears to adjust the chemistry of the Tarong and Bayswater fly ashes thereby
improving mix workability. Fletcher et al. (2005) concluded that aluminosilicate systems with
high silica, consume higher water content than other systems.
Figure 3: Average 28 days compressive strength variation in Tarong and
Gladstone blended geopolymer systems
Figure 4 illustrates the compressive strength variation with total reactive SiO 2 /Al 2 O 3 ratio. Mix1
and Mix2 geopolymers have reactive SiO 2 /Al 2 O 3 ratio in between 3.5 and 4.6 and achieved a
compressive strength value over 30 MPa in 28 days. Mix3 to Mix6 geopolymer had a higher
reactive SiO 2 /Al 2 O 3 (> 5) and lower 28 days compressive strength value (< 25 MPa). Mix7 to
© ARRB Group Ltd and Authors 2014
6
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Mix9 geopolymer pastes do not follow the same co-relationship between reactive SiO 2 /Al 2 O 3
and compressive strength as other mixtures.
However, the final reaction product (Na 2 O-Al 2 O 3 -SiO 2 -H 2 O gel) may evolve concurrently either
into a crystalline zeolitic phase or to an amorphous geopolymer phase depending on the
concentration of available aluminate and silicate species in solution. The formation of zeolitic
phases is a common feature in geopolymer systems and the type of zeolite formed usually
depend on the SiO 2 /Al 2 O 3 ratio of the system (De Silva and Sagoe-Crentsil, 2008, Oh et al.,
2011, Hajimohammadi et al., 2010, Buchwald et al., 2011, Kovalchuk et al., 2008). Na 2 OAl 2 O 3 -SiO 2 -H 2 O gel compositions with higher or lower than SiO 2 /Al 2 O 3 ≈ 4 usually develop into
zeolitic phases (De Silva and Sagoe-Crentsil, 2008). This possibly accounts for the presence of
Si rich zeolitic phases such as faujasite. Zeolitic crystalline phases in alkali activated binders are
unstable than 3 dimensional geopolymer network. Fletcher et al. (2005) analysed for
metakaoline based geopolymer systems with different SiO 2 /Al 2 O 3 ratios ranging from 0.5 to
300. They found that when SiO 2 /Al 2 O 3 ratio is greater than 24 geopolymer binder becomes
more rubbery than brittle behaviour. Moreover, geopolymer binder with lower SiO 2 /Al 2 O 3 (< 2)
ratio or high aluminium content shows weak structure with several discrete compounds.
Chindaprasirt P et al. (2012) reported that most favourable SiO 2 /Al 2 O 3 ratio for mechanical
properties of the geopolymer in the range of 3.2 - 3.7. They observed that when the SiO 2 /Al 2 O 3
ratio is increased more than 4, high calcium fly ash based geopolymer systems, the mechanical
properties decrease. De Silva et al. (2007) reported that metakaoline based geopolymer
systems with the SiO 2 /Al 2 O 3 ratio in the range of 3.4 - 3.8 showed the highest strength. . This
is in line with Thakur and Ghosh (2009). Fernández-Jiménez et al. (2006) stated that fly ashes
with the highest reactive SiO 2 /Al 2 O 3 ratio (4.76) exhibit the lowest mechanical strength (below
25 MPa within 7 days) compared to other ash types with lower SiO 2 /Al 2 O 3 ratios. However,
they did not take reactive SiO 2 /Al 2 O 3 molar ratios into account.
Figure 4: Average 28 days compressive strength variation with total reactive
SiO 2 /Al 2 O 3 ratio for geopolymer
Figure 5 illustrates the average 28 days compressive strength variation with water to total solid
ratio. Mix3 has a significantly low level of water to solid ratio (0.24) in the geopolymer system
but the strength value is lower than 20 MPa. Panias et al. (2007) showed that when water
content in the geopolymer mixture decreases compressive strength increases exponentially. It is
obvious that, excessive water in the geopolymer evaporates creating voids in the binder. It can
affect the mechanical properties of the binder (Diaz and Allouche, 2010). Diaz and Allouche
(2010) provide evidence to prove that high alkaline liquid weakens the geopolymer binders. In
their work, some geopolymer binders with lower liquid to fly ash ratio (0.4) had lower
compressive strength (< 45 MPa). But some geopolymers with a higher liquid to fly ash ratio
© ARRB Group Ltd and Authors 2014
7
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
(0.66) had a higher compressive strength (> 45 MPa). There is no direct co-relationship with
water content in the binder and the geopolymer compressive strength.
Figure 5: Average 28 days compressive strength variation with water to total solid mass
ratio
Figure 6 shows the variation in 28 days compressive strength with the molar ratio of available
Na 2 O to reactive (SiO 2 + Al 2 O 3 ) in the geopolymer systems. Dissolution of SiO 2 and Al 2 O 3 is
mainly based on amorphous content and as well as alkalinity of the system. As seen in Figure 6,
geopolymer systems with different mix designs are correlated well with the alkalinity as well as
total reactive alumina silica components (amorphous SiO 2 and Al 2 O 3 ). Chen-Tan et al. (2009)
observed that amorphous content of the alumina-silicate material decreases quickly and
crystalline phase dissolves comparatively slowly in the alkaline liquid. This results are in line
with those of (Fernández-Jiménez and Palomo, 2003). Álvarez-Ayuso et al. (2008) stated that
higher amorphous content led to geopolymer binder becoming more stable and strong. If high
content of mullite or quartz are present in the fly ash, the reactivity of Al-Si bearing fraction
decreases drastically (Álvarez-Ayuso et al., 2008). Even though Mix1 and Mix3 have the almost
equal alkalinity to amorphous (SiO 2 + Al 2 O 3 ) molar ratio (i.e. 0.98), the strength value is different
significantly 48 MPa and 18 MPa. Mix3 has higher reactive SiO 2 /Al 2 O 3 ratio compared to Mix1.
The strength value depend on the reactive SiO 2 /Al 2 O 3 ratio and the Na 2 O/(SiO 2 +Al 2 O 3 ).
Na 2 O controls the fly ash dissolution process. Therefore it is important to have appropriate
alkaline environment in geopolymer synthesis. Pietersen et al. (1989) explained that fly ash
digestion starts with ion exchange and finally bulk glass phase dissolution. Moreover, fly ash
with high alkaline increased the pH of the pore solution and thereby improved the reactivity. Van
Jaarsveld and Van Deventer (1999) concluded that alkalinity of the geopolymer influences in
every stage of the geopolymer even after setting. In Figure 2, Mix5 and Mix6 showed better
compressive strength (> 20 MPa) in 28 days while their 7 day compressive strength was very
low (< 10 MPa). High alkaline content in pore solution particularly in Mix5 and Mix6 geopolymer
can participate for further dissolution process of unreacted fly ash. Further investigations need
for clarification.
© ARRB Group Ltd and Authors 2014
8
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Figure 6: Average 28 days compressive strength variation with
Na 2 O/ (reactive SiO 2 +Al 2 O 3 ) molar ratio
There is a combination effect for the geopolymer reaction from factors: SiO 2 and Al 2 O 3 , particle
size distribution, liquid to solid ratio and alkalinity of the system. However, considering the
above results obtained most critical factors for strong geopolymer network are the reactive
SiO 2 /Al 2 O 3 and Na 2 O/reactive (SiO 2 +Al 2 O 3 ).
CONCLUSIONS
Based on the outcome of this work the following conclusions can be drawn.
•
Aluminosilicate material with high reactive SiO 2 / Al 2 O 3 molar ratio (>5) tends to absorb
high alkaline liquid contents.
•
Blending Gladstone fly ash with other fly ashes significantly increase the compressive
strength of the resulting geopolymer.
•
The most suitable Na 2 O to reactive (SiO 2 + Al 2 O 3 ) molar ratio is in the range between
0.09-0.12.
•
The combination of the molar ratios ranges of reactive SiO 2 /Al 2 O 3 < 5 and Na 2 O/
reactive (SiO 2 + Al 2 O 3 ) 0.09-0.12 gives higher compressive strength values.
ACKNOWLEDGEMENT
The research was supported by Austroads project (TS1835) awarded to the ARRB Group,.
Authors would also like to acknowledge Bill Sioulas from Fly Ash Australia for providing fly ash
samples.
REFERENCES
Álvarez-Ayuso, E., Querol, X., Plana, F., Alastuey, A., Moreno, N., Izquierdo, M., Font, O.,
Moreno, T., Diez, S., Vázquez, E. & Barra, M. (2008), Environmental, physical and structural
characterisation of geopolymer matrixes synthesised from coal (co-)combustion fly ashes.
Journal of Hazardous Materials, 154, 175-183.
Autef, A., Joussein, E., Gasgnier, G. & Rossignol, S. (2012), Role of the silica source on the
geopolymerization rate. Journal of Non-Crystalline Solids, 358, 2886-2893.
© ARRB Group Ltd and Authors 2014
9
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Bakharev, T. (2005), Geopolymeric materials prepared using Class F fly ash and elevated
temperature curing. Cement and Concrete Research, 35, 1224-1232.
Bakri, A. M. M. A., ,Kamarudin, H., Bnhussain M., Nizar, I. K., Rafiza , A. R., & Zarina, Y.
(2011), Microstructure of different NaOH molarity of fly ashbased green polymeric cement.
Journal of Engineering and Technology Research, 3, 44-49.
Brouwers, H. J. H. & Van Eijk, R. J. (2002), Fly ash reactivity: Extension and application of a
shrinking core model and thermodynamic approach. Journal of Materials Science, 37, 21292141.
Buchwald, A., Zellmann, H. D. & Kaps, C. (2011) Condensation of aluminosilicate gels—model
system for geopolymer binders. Journal of Non-Crystalline Solids, 357, 1376-1382.
Chancey, R. T. (2008), Characterization of Crystalline and Amorphous Phases and Respective
Reactivities in a Class F Fly Ash. PhD, The University of Texas at Austin.
Chen-Tan, N. W., Van Riessen, A., Ly, C. V. & Southam, D. C. (2009), Determining the
Reactivity of a Fly Ash for Production of Geopolymer. Journal of the American Ceramic Society,
92, 881-887.
Chindaprasirt, P., De Silva, P., Sagoe-Crentsil, K. & Hanjitsuwan S.(2012) Effect of SiO 2 and
Al 2 O 3 on the setting and hardening of high calcium fly ash-based geopolymer systems. Journal
of Materials Science, 47, 4876-4883.
Davidovits, J. 2008. Geopolymer chemistry and Applications, France, Institut Géopolymère.
De Silva, P. & Sagoe-Crentsil, K.(2008) Medium-term phase stability of Na 2 O–Al 2 O 3 –SiO 2 –
H 2 O geopolymer systems. Cement and Concrete Research, 38, 870-876.
De Silva, P., Sagoe-Crentsil, K. & Sirivivatnanon, V. (2007), Kinetics of geopolymerization: Role
of Al 2 O 3 and SiO 2 . Cement and Concrete Research, 37, 512-518.
Diaz, E. I. & Allouche, E. N. (2010) Recycling of fly ash into geopolymer concrete: creation of a
database. Green Technologies Conference, IEEE,1-7.
Duxson, P., Mallicoat, S. W., Lukey, G. C., Kriven, W. M. & Van Deventer, J. S. J. (2007a), The
effect of alkali and Si/Al ratio on the development of mechanical properties of metakaolin-based
geopolymers. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 292, 8-20.
Duxson, P. & Provis, J. L. (2008), Designing precursors for geopolymer cements. Journal of the
American Ceramic Society, 91, 3864-3869.
Duxson, P., Provis, J. L., Lukey, G. C. & Van Deventer, J. S. J. (2007b), The role of inorganic
polymer technology in the development of ‘green concrete’. Cement and Concrete Research,
37, 1590-1597.
Fernández-Jiménez, A. & Palomo, A. (2003) Characterisation of fly ashes. Potential reactivity
as alkaline cements. Fuel, 82, 2259-2265.
Fernández-JiméneZ, A., Palomo, A., SobradoS, I. & Sanz, J. (2006), The role played by the
reactive alumina content in the alkaline activation of fly ashes. Microporous and Mesoporous
Materials, 91, 111-119.
Fletcher, R. A., Mackenzie, K. J. D., Nicholson, C. L. & Shimada, S. (2005), The composition
range of aluminosilicate geopolymers. Journal of the European Ceramic Society, 25, 14711477.
Hajimohammadi, A., Provis, J. L. & Van Deventer, J. S. J. (2010), Effect of alumina release rate
on the mechanism of geopolymer gel formation. Chemistry of Materials, 22, 5199-5208.
Khale, D. & Chaudhary, R. (2007), Mechanism of geopolymerization and factors influencing its
development: a review. Journal of Materials Science, 42, 729-746.
Kovalchuk, G., Fernández-Jiménez, A. & Palomo, A. (2008), Alkali-activated fly ash.
Relationship between mechanical strength gains and initial ash chemistry. Materiales de
construccion, 58, 35-52.
Oh, J. E., Moon, J., Mancio, M., Clark, S. M. & Monteiro, P. J. M. (2011), Bulk modulus of basic
sodalite, Na 8 [AlSiO 4 ] 6 (OH) 2 ·2H 2 O, a possible zeolitic precursor in coal-fly-ash-based
geopolymers. Cement and Concrete Research, 41, 107-112.
© ARRB Group Ltd and Authors 2014
10
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Palomo, A., Grutzeck, M. W. & Blanco, M. T. (1999), Alkali-activated fly ashes: A cement for the
future. Cement and Concrete Research, 29, 1323-1329.
Panias, D., Giannopoulou, I. P. & Perraki, T. (2007), Effect of synthesis parameters on the
mechanical properties of fly ash-based geopolymers. Colloids and Surfaces A: Physicochemical
and Engineering Aspects, 301, 246-254.
Pietersen, H. S., Fraay, A. L. A. & Bijen, J. M. (1989), Reactivity of fly ash. Fly ash and coal
coversion by-products VI, 178, 139 -157.
Thakur, R. N. & Ghosh, S. (2009), Effect of mix composition on compressive strength and
microstructure of fly ash based geopolymer composites. Journal of Engineering and Applied
Sciences, 4, 68-74.
Van Jaarsveld, J. G. S. & Van Deventer, J. S. J. (1999), Effect of the alkali metal activator on
the properties of fly ash-based geopolymers. Industrial & Engineering Chemistry Research, 38,
3932-3941.
Van Jaarsveld, J. G. S., Van Deventer, J. S. J. & Lukey, G. C. (2003), The characterisation of
source materials in fly ash-based geopolymers. Materials Letters, 57, 1272-1280.
Xu, H. (2002), Geopolymerisation of aluminasilicate minerals.PhD, The University of Melbourne.
AUTHOR BIOGRAPHIES
Chandani Tennakoon is currently pursuing A Ph.D. degree at the Faculty of Science,
Engineering and Technology, Swinburne University of Technology. She is working in
collaboration with the ARRB Group Melbourne, Australia to investigate the durability of fly ash
based geopolymer concrete for bridge constructions. Her current research interests include
geopolymer binders, sustainable construction materials and durability of geopolymer concrete.
Dr Ahmad Shayan is a Chief Research Scientist at ARRB. He was Chairman, Standards
Australia Committee CE/12 for 10 years, served on IOC of many AAR conferences, and was
Chairman, 10th IAARC, Melbourne, 1996. His research interests include AAR, DEF, waste
materials utilization in concrete, steam cured concrete, corrosion of steel reinforcement in
concrete, utilization of stainless steel in concrete under aggressive environments and use of
CFRP to confine AAR-induced expansion of concrete elements. He has written over 400 papers
and technical reports. He won the prestigious Clunies Ross Medal in 2003 for his work on
durability of concrete structures.
Professor Kwesi Sagoe-Crentsil received his PhD in 1987 from the University of British
Columbia, Vancouver, Canada and joined CSIRO in 1993. His career at CSIRO has focused on
technology development roles including leading multi-disciplinary teams in the development of
sustainable materials and process technologies. His contributions to the emerging field of
geopolymer technology have focused on the implications of varying oxide ratios and the
fundamental mechanisms governing silicate dissolution and condensation reactions.
Professor Jay G Sanjayan is the Director of the Centre of Sustainable Infrastructure at
Swinburne University of Technology. He joined Swinburne in 2010 following a 22 year academic
career at Monash University. He is the Chairman of the editorial board of the Concrete in
Australia journal, associate editor of materials and structures journal and editorial board
member of the journal of sustainable cement-based materials. His main research interests are
geopolymer concrete, fire resistance of concrete, and development of alternative cements for
geo-sequestration of carbon dioxide.
© ARRB Group Ltd and Authors 2014
11
th
9 Austroads Bridge Conference, Sydney, New South Wales 2014
Copyright Licence Agreement
th
The Author allows ARRB Group Ltd to publish the work/s submitted for the 9 Austroads Bridge
Conference, granting ARRB the non-exclusive right to:
• publish the work in printed format
• publish the work in electronic format
• publish the work online.
The Author retains the right to use their work, illustrations (line art, photographs, figures, plates) and
research data in their own future works
The Author warrants that they are entitled to deal with the Intellectual Property Rights in the works
submitted, including clearing all third party intellectual property rights and obtaining formal permission from
their respective institutions or employers before submission, where necessary.
© ARRB Group Ltd and Authors 2014
12

Download Report