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Materials and Structures ISSN 1359-5997 Mater StructDOI 10.1617/s11527-014-0404-6
Performance of fly ash based geopolymerconcrete made using non-pelletized flyash aggregates after exposure to hightemperatures
M. Talha Junaid, Amar Khennane &Obada Kayali
1 23
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ORIGINAL ARTICLE
Performance of fly ash based geopolymer concrete madeusing non-pelletized fly ash aggregates after exposureto high temperatures
M. Talha Junaid • Amar Khennane •
Obada Kayali
Received: 22 May 2014 / Accepted: 19 August 2014
� RILEM 2014
Abstract The superior performance of geopolymer
paste, mortar and concrete (GPC) when exposed to
high temperatures has been well documented. Limi-
tations still exist however due to the use of similar
aggregates, coarse and fine, in both ordinary portland
cement concrete (OPC) and GPC. The behavior of
geopolymer concrete at elevated temperatures can be
further improved by using a recently developed
lightweight non-pelletized aggregates made entirely
from fly ash (named Flashag) as replacement for
conventional natural aggregates. Tests for the ambient
and residual properties of GPC made using these new
aggregates exposed to temperatures up to 1,000 �C
were carried out. The obtained results in terms of
compressive strength, splitting strength, and modulus
of elasticity are reported and compared with those
obtained for GPC produced using ordinary natural
aggregates as well as with those reported in the
literature for OPC concretes. The effects of heat
cycling, as well as, duration of heating on the strength
and deformational behavior of GPC are also investi-
gated. At ambient temperatures all the three concretes
displayed similar properties. At elevated tempera-
tures, however, the performance of GPC made from
Flashag was found to be far superior to that of both
OPC, and GPC made from ordinary aggregates.
Additionally, for up to 4 heating cycles, GPC made
with Flashag better retained its strength and stiffness
properties as compared to GPC made with ordinary
natural aggregates. The study also found that most
changes to the strength and microstructure of GPC
occur in the first few hours of exposure after which, the
duration of heating has no significant effect.
Keywords Geopolymer concrete stress–strain
curves � Modulus of elasticity � Lightweight GPC �Cyclic heating � High temperature performance
1 Introduction
Alkali liquids (usually a soluble metal hydro-oxide
and/or alkali silicate) can be used to react with silica
(SiO2) and alumina (Al2O3) rich natural source, like
metakaolin or with industrial by-products, like fly ash
(FA), silica fume (SF), rice husk ash (RHA) or Slag to
produce binders [5, 6, 25]. Such binders mixed with
typical coarse and fine aggregates can form concrete,
usually known as alkali activated concrete or geo-
polymer concrete. Currently there is sufficient evi-
dence to suggest that geopolymer concrete has a better
resistance to fire than OPC concrete [7, 8, 10, 11, 31].
Yet the intrinsic good fire behaviour of geopolymer
paste, and to some extent mortars, tends to be reduced
by the addition of conventional aggregates. Therefore,
M. T. Junaid (&) � A. Khennane � O. Kayali
School of Engineering and Information Technology,
UNSW Canberra, Northcott Drive, Canberra, ACT 2600,
Australia
e-mail: [email protected]
Materials and Structures
DOI 10.1617/s11527-014-0404-6
Author's personal copy
to fully utilize the superior fire resistance of GPC,
aggregates more compatible with the GPC matrix are
needed. Such aggregates are available, and were
developed by Kayali [16]. They are lightweight and
entirely manufactured from fly ash and referred to as
Flashag. They are expected to perform in synergy with
the geopolymer binder, which itself contains a large
amount of fly ash.
The focus of this research therefore is to investigate
whether the use of Flashag improves the thermal
performance of GPC. Additionally the environmental
benefits of geopolymer concrete made entirely from
fly ash (binder, fine and coarse aggregates) are
enormous.
2 Nature and characteristics of geopolymer
concrete
The basic reaction mechanism for formation of the
geopolymer binder consists of three stages; namely:
dissolution of Si and Al from the source material (in
this case FA), hydrolysis or gelation, and condensation
forming a 3D network of silico-aluminates also termed
as the ‘geopolymer backbone’ [5–8, 10, 11, 31].
Davidovits describes geopolymerization as an exo-
thermic reaction, and has schematised it as shown
below [6].
GPC does not require any hydraulic binder. The
role of FA in GPC is entirely different from that it
plays when used as a cement replacement material in
OPC concrete to enhance certain properties such as
workability or to reduce the heat of hydration. In such
cases FA has no pronounced effect on the strength of
concrete [27] especially early strength. However, in
GPC, Fly Ash is the sole source of aluminosilicates for
reaction with the alkaline solution to form the binder,
and is thus a critical factor in strength development.
3 OPC and GPC concrete behaviour at high
temperatures
Owing to its very different chemistry as compared to
OPC, GPC behaves very differently when exposed to
high temperatures. When OPC concrete is taken to high
temperatures, the changes in its properties are highly
irreversible [32]. It is widely accepted that OPC loses
over 80 % of strength when the temperature exceeds
800 �C. This is due to inherent physical stresses caused
by the introduction of heat energy and the chemical
breakdown of the hydrated phases in the cement paste
[12]. There have been a number of general findings
published in the literature that cover the effects of high
temperature on OPC concrete, though the extent may
depend on several factors like water-cement ratio,
curing condition, aggregate type and size, type of
admixture, and so on. These are summarised as:
1. The loss of free water and chemically bound water
in the Ca(OH)2 through dehydroxylation leads to
significant dehydration of the concrete and loss of
chemical bonding and induces spalling [12].
2. The disparity in the amount of thermal expan-
sion in the aggregate in comparison to the
shrinkage of the OPC cement means that micro
stresses are induced and lead to cracking in the
concrete.
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3. Different types of aggregate have a significant
effect on the strength-temperature relationship of
concrete. For instance limestone aggregates
undergo a decarbonation at temperatures above
800 �C. This can be avoided by using siliceous
aggregates [32]. Yet quartz also undergoes a
phase change at around 570 �C (configuration a to
b), which results in very high thermal expansion.
4. The rate of heating has little effect on the sample
so long as the temperature gradient is below 10�per centimetre towards the core [32].
In previous research focusing on the residual
properties of geopolymer paste and mortar, it has
been found that fly ash based geopolymers retain most
of their residual strength after being exposed to
elevated temperatures [8, 9, 12, 13, 21–23, 29, 31].
However, the degree of strength retention is dependent
on the composition of fly ash used [8, 31]. The
relatively high degree of residual strength retention is
attributed to the fly ash based geopolymer having a
large number of small pores that act as a conduit for
water as it escapes the structure. More importantly, as
geopolymer concrete is not a hydraulic binder, it is
therefore hypothesised that moisture will have a less
pronounced effect on its thermal and mechanical
properties than it does on the properties of OPC
concrete. This means that there is minimal damage to
the geopolymer structure. It has been reported
however, that thermal testing of geopolymer using
standard fire testing profiles shows that the presence of
water plays an important role in its behaviour [30].
The high strength retention can also be due to the
gradual sintering of the un-reacted fly ash that is
present within the concrete [21–23]. Sintering occurs
when very fine powders (such as fly ash) are subject to
very high temperatures causing the molecules to
diffuse to the boundaries of the particles, which results
in their partial fusion. This means that the unused fly
ash powder, which is responsible for local weaknesses
before exposure, sinters into a strong solid material
within the concrete after exposure (Fig. 1).
4 Materials and methods
Since extensive research is available on the perfor-
mance of OPC at elevated temperatures [4, 17–20, 24,
27, 28, 32], the current research focuses on comparing
the residual properties of GPC with normal and
Flashag aggregates. Grade D sodium silicate and
12 M sodium hydroxide prepared from 98 % pure
flakes were used as alkaline solutions while ASTM
Class F Fly Ash was used as the main aluminium and
silicate source. The chemical composition of the FA
used as found out by XRF is given in Table 1, while
the particle size distribution for natural and Flashag
aggregates is given in Fig. 2.
Table 1 Chemical composition of fly ash using XRF
Compound SiO2 Al2O3 Fe2O3 CaO K2O TiO2 MgO Na2O SO3 L.O.I SiO2/Al2O3
% Composition by weight 62.19 27.15 3.23 1.97 0.89 1.06 0.4 0.3 0.07 1.75 2.29
Fig. 1 SEM images of GPC a before exposure and b after temperature exposure to 1000 �C
Materials and Structures
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Cylinders with nominal diameter and height of 75
and 150 mm respectively, were mixed and cast using the
procedure described in [14]. After an initial rest period
of 24 h, the samples were cured for 72 h at 80 �C. Then,
they were placed in an environmental chamber with a
relative humidity of 50 % and a temperature of 23 �C
till the time of testing. Samples containing Flashag are
identified as M4Sp, while M1 and M13 contain ordinary
natural aggregates. The composition of the mixes and
the mean compressive strength (f0
c) at ambient temper-
ature are given in Table 2.
The samples marked M13 and M4Sp were heated at
4.5 �C/min until they reached the target temperatures
(200, 400, and 1,000 �C). The target temperature was
then maintained to ensure that thermal equilibrium
was achieved. The time required for thermal equilib-
rium was determined by placing samples with embed-
ded K-type thermo-couples at the core of selected
samples. The time required to achieve consistent and
uniform core temperature was determined to be 2 h.
The furnace was then turned off and the samples were
left in the chamber to cool down to ambient temper-
ature. The samples were then removed from the
chamber, and tested for compressive strength (f0c),
modulus of elasticity (Ec) and splitting tensile strength
(fct). Strain measurements for the compressive
strength and modulus tests were done using a laser
extensometer and reflective strips stuck on the sam-
ples. Data were acquired using a data logging system.
Figure 3 shows the illustrative test setup for compres-
sive strength and elastic modulus tests while no strains
were measured during the indirect tensile tests. For
cyclic heating tests, samples were heated to 1,000 �C,
which was maintained for 2 h. The furnace was then
turned off and the samples allowed to cool within the
furnace. This was repeated to achieve the required
number of cycles, after which the samples were tested
in the test setup shown in Fig. 3.
0
10
20
30
40
50
60
70
80
90
100
1001010.10.01
Cu
m %
Pas
sin
g
Sieve Size (mm)
FlashAg Fines
Natural Fines
FlashAg 7mm
Natural 7mm
FlashAg 14mm
Natural 14mm
Fig. 2 Particle size
distribution of natural and
Flashag aggregates
Table 2 Composition and mean compressive strength (f0
c) of the GPC samples
FA
(kg/m3)
NaOH
(kg/m3)
Na2SiO3
(kg/m3)
Coarse
(kg/m3)
Fine
(kg/m3)
Water
(kg/m3)
VM and SPa
(kg/m3)f0c
(MPa)
M1 420 44 110 1,120 650 28.5 7.2 44
M13 420 44 110 1,130 570 56.2 8 38
M4Sp 440 65 162.5 660b 340b 11 8 40
a Viscosity modifier and superplasticizerb FLASHAG aggregates were used
Materials and Structures
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Samples marked M1 were heated for the same
duration and at the same rate as the other samples.
They were however tested for exposure duration of 2,
4 and 6 h at temperatures of 100, 350, 600, 800 and
1,000 �C. M1 samples were not monitored for defor-
mational behaviour during loading. Methods and
loading rates for all tests comply with the AS3600
standards [1–3].
5 Results and discussion
The residual stress–strain curves for geopolymer
concrete with Flashag and natural aggregates for
different temperatures are given in Fig. 4. It is worth
noting that specimens from both mixes at all temper-
atures failed soon after reaching their peak strength,
displaying the brittle nature of GPC. However, the mix
containing Flashag (M4-SP) developed higher failure
strains at ambient temperatures when compared to
GPC containing normal aggregates. The modulus of
elasticity for M4Sp and M13 were 25 and 27 GPa
respectively at ambient temperatures, which is slightly
lower than OPC values for corresponding strengths.
No significant reduction in stiffness is observed for
M13 samples when heated to 200 �C, although there is
a marked reduction in the stiffness for temperatures of
400 �C and over. In fact the modulus of elasticity is
reduced by 60 % at 800 �C and by over 80 % when the
exposure temperature is 1,000 �C. A similar pattern is
observed for the M13 samples in compression and
tensile splitting as shown in Fig. 5a–c. After a slight
increase in both compression and splitting tensile
strength values at 200 �C, which may be attributed to
further geopolymerization at this temperature, there is
a steep decline in both properties as the temperature is
raised further.
One possible explanation for this change in behav-
iour may be the ‘glass transition’ of GP matrix, which
is characterised by abrupt loss of stiffness and
strength. Although this occurs between 520 and
680 �C in GP pastes [29], the presence of aggregates
and use of varying source material may affect the
exact value of this temperature. It is also observed that
normal GPC retains almost 50 % of splitting tensile
and compressive strength values after 1,000 �C expo-
sure. This is much higher than OPC, which retains
only about 5 % of its compressive strength and less
than 20 % of its splitting tensile strength at 800 �C.
The loss of stiffness in OPC is more accentuated as the
temperature is increased over 200 �C [26, 33, 34].
A rather unique behaviour is observed for the
Flashag (M4-SP) samples. At temperatures of 400 �C
and below, the samples steadily lose their stiffness and
strength. This may be attributed to the fact that Flashag
are lightweight aggregates with numerous voids, and
carry a significant amount of water to attain saturated
surface dry (SSD) condition. During heating this free
water escapes leaving behind voids in the matrix.
These voids contribute to the loss of stiffness and
strength at relatively low temperatures. Nevertheless
at higher temperatures M4-SP samples exhibit far
superior strength and stiffness properties. At 800 �C
the samples regain all but 20 % of their compressive
strength and modulus of elasticity, while the splitting
tensile strength is also increased from 50 % at 400 �C
to over 60 % at 800 �C of ambient values. This trend
continues as the temperate reaches 1,000 �C. The
residual values of compressive strength, modulus of
elasticity and splitting tensile strength after exposure
to 1,000 �C was recorded as 85, 95 and 62 % of
ambient, respectively. The initial loss of strength and
stiffness, attributed to the voids left behind by
escaping free water, is offset by the gain in these
properties due to accelerated geopolymerization and
changes in the material at higher temperatures [15]. A
more significant factor explaining why the strength of
Flashag-GPC concrete surpassed normal aggregate-
GPC concrete is the tight aggregate-matrix bond
accomplished with Flashag [16], where the matrix is
essentially thermally compatible with the aggregates.
A plausible consequence of this observation may be
that after cooling down from high temperatures, GPC
Fig. 3 Test setup
Materials and Structures
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with Flashag aggregates does not develop cracking at
the aggregate-matrix interface, while GPC with nor-
mal aggregates develops cracks at the aggregate-
matrix interface (Fig. 6a). The latter is attributed to
incompatibility between the expansion and contrac-
tion of aggregates and matrix, and hence results in loss
of strength and stiffness. On the other hand, GPC with
Flashag is far more thermally compatible internally
resulting in fewer cracks and near perfect matrix-
aggregate interface, contributing to higher strength
and stiffness (Fig. 6b). Also Flashag, contains numer-
ous voids which act more or less like tiny springs
distributed throughout the samples, reducing the
stresses developed due to the cooling period, hence
resulting in reduced cracking. Moreover, as the
temperature is increased over and above 400 �C, the
fly ash particles present in both the matrix and the
aggregates fuse together to form a near-monolithic
phase, which may contribute towards the increase in
strength and stiffness of M4-SP samples after 400 �C.
The effect of time of exposure to high temperatures
on the residual strength of M1 samples was studied
and it was found that changes to GPC occur in the first
2 h of exposure (Fig. 7) after which the duration of
exposure has an insignificant effect on the residual
compressive strength of GPC. All samples experi-
enced a loss in strength when tested after cooling.
Depending on the exposure temperature, the percent-
age of strength lost varies between 25 and 50 %. At
higher temperatures of 600, 800 and 1,000 �C the
strength loss is between 40-50 % while at lower
temperatures the strength loss is 25–30 %. Although
M1 mix is different from M13 mix, their loss of
strength percentage values are comparable at these
temperatures, advocating the hypothesis that the loss
in strength may not be a result of changes to the
material itself but a result of the incompatibilities
between the aggregates and the matrix.
Stress–strain relationship of GPC with normal and
lightweight fly ash aggregates (Flashag) after 1, 2 and
4 cycles of heating from ambient to 1,000 �C are
presented in Fig. 8. As with the duration of heating,
the number of exposure cycles has an insignificant
effect on the stiffness and strength properties of GPC
irrespective of the type of aggregates used. This
further strengthens the argument that all changes
within the GPC occur within the first few hours of
exposure after which the system becomes very stable.
0
5
10
15
20
25
30
35
40
45
Str
ess
(MP
a)
Strain ( µµm/µm)
M13 M4-SP
0
5
10
15
20
25
30
35
40
45
Str
ess
(MP
a)
Strain ( µm/µm)
M13 M4-SP
0
5
10
15
20
25
30
35
40
45
Str
ess
(MP
a)
Strain (µm/µm)
M13 M4-SP0
5
10
15
20
25
30
35
40
45
0 0.002 0.004 0.006 0 0.002 0.004 0.006
0 0.002 0.004 0.006 0 0.002 0.004 0.006 0.008
Str
ess
(MP
a)Strain (µm/µm)
M13 M4-SP
(a) (b)
(c) (d)
Fig. 4 Residual stress–
strain curves for GPC with
Flashag (M4-SP) and
ordinary natural aggregates
(M13) after exposure to
different temperatures. a at
23 �C, b at 200 �C, c at
400 �C and d at 1,000 �C
Materials and Structures
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Nevertheless, the residual compressive strength after
the first cycle for both sample types returned margin-
ally higher values. GPC with Flashag also retained
higher strength and elastic modulus values when
compared to GPC with normal aggregates. However,
GPC with normal aggregates exhibited an increase in
post-peak ductile behaviour, while GPC with Flashag
still failed in a brittle mode after peak strength (Fig. 8).
6 Conclusions
A detailed study was conducted to investigate the
behaviour of GPC with normal and lightweight non-
pelletized fly ash aggregates after exposure to extreme
temperatures, and to compare the results with those for
OPC. It was found that when exposed to extreme
temperatures:
0
20
40
60
80
100
120
f cT/f c
' (%
)
Temp (oC)
M13M4SPOPC after [26]
0
20
40
60
80
100
120
EcT
/Ec(%
)
Temp (oC)
M13M4SPOPC after [27]
0
20
40
60
80
100
120
0 500 1000 0 500 1000
0 500 1000
f ct
T/f c
t(%
)
Temp (oC)
M13
M4SP
OPC after [28]
(b)(a)
(c)
Fig. 5 Variation in GPC
properties as a function of
temperature. a compressive
strength as function of temp,
b modulus of elasticity as
function of temp and
c splitting strength as
function of temp
(a) (b)
Matrix
Matrix
FlashAgg
Matrix-Agg Interface
Fig. 6 SEM Images of GPC with a view of GPC matrix containing normal aggregates (1000 �C) and b view of GPC matrix containing
flashag aggregates (1000 �C)
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1. GPC, both with normal or non-pelletized fly ash
aggregates, outperforms OPC. Reported data
indicate that OPC loses substantial structural
integrity at temperatures over 400 �C. GPC on
the other hand, retains over 60 % of its strength
and stiffness at similar temperatures.
2. At even higher temperatures, GPC containing
aggregates which were manufactured from fly ash
as their basic component, has outmatched the
performance of normal aggregate GPC with
properties almost equivalent to those at ambient
temperatures.
3. Most changes in strength and microstructure of
GPC samples occur in the first 2 h of exposure to
high temperatures after thermal equilibrium is
reached. After the initial changes have taken
place, the duration of exposure has an insignifi-
cant effect on the strength of GPC samples.
4. At high temperatures of over 600 �C, GPC under-
goes material changes and the fly ash particles start
to collapse and fuse to form a homogeneous melt,
which contributes to higher residual strength
compared to OPC. However, cracking is observed
in these homogeneous regions in samples contain-
ing normal aggregates. Samples containing Fla-
shag experience far less cracking and retain higher
residual strength and stiffness values.
5. Cyclic exposure to 1,000 �C has an insignificant
effect on the strength and stiffness properties of
both GPC samples with normal and Flashag
aggregates. This further strengthens the argument
that all changes within the GPC occur within the
first few hours of exposure after which the system
becomes very stable.
References
1. Australian S (1997) AS1012.17-1997: determination of
static chord modulus of elasticity and Poissons ratio of
concrete specimens
2. Australian S (1999) AS 1010.9-1999: Determination of the
Compressive Strength of Concrete Specimens
3. Australian S (2000) AS1012.10-2000: determination of
indirect tensile strength of concrete cylinders
4. Bazant ZP, Kaplan MF (1996) Concrete at high tempera-
tures. Material properties and mathematical models. Long-
man House, Burnt Mill, Essex
5. Davidovits J (1988) Soft mineralogy and geopolymers. In:
Technologie Ud (ed) Proceedings of the geopolymer 88
international conference
6. Davidovits J (1991) Geopolymers Inorganic polymerie new
materials. J Therm Anal 37:1633–1656
7. Diaz-Loya EI, Allouche E, Eklund S (2010) Factors
Affecting the suitability of fly ash as source material for
geopolymers. Fuel 89:992–996
8. Diaz-Loya EI, Allouche E, Vaidya S (2011) Mechanical
Properties of fly-ash-based geopolymer concrete. ACI
Mater J 108:300–308
9. Elimbi A, Tchakoute HK, Njopwouo D (2011) Effects of
calcination temperature of kaolinite clays on the properties
of geopolymer cements. Constr Build Mater 25:2805–2812
10. Fernandez-Jimenez A, Palomo A (2004) Alkaline activation
of fly ashes. Manufacture of concrete not containing port-
land cement. Paper presented at the International RILEM
Conference on the Use of Recycled Materials in Buildings
and Structures
11. Gourley TJ, Johnson GB (2005) Development in geopoly-
mer precast concrete. In: International workshop on geo-
polymers and geoplymer concrete, Perth
12. Guerrieri M, Sanjayan J, Collins F (2010) Residual strength
properties of sodium silicate alkali activated slag paste
exposed to elevated temperatures. Mater Struct 43:765–773
0
20
40
60
80
100
120
0 1 2 3 4 5 6 7
No
rmal
ized
Str
eng
th (
%)
Time (hr)
Resi 100C Resi 350C Resi 600C
Resi 800C Resi 1000C
Fig. 7 Normalized residual compressive strength of M1 GPC
samples
0
5
10
15
20
25
30
35
40
0 0.002 0.004 0.006 0.008 0.01
Str
ess
(MP
a)
Strain (um/um)
1 Cycle M4-Sp2 Cycle M4-Sp4 Cycle M4-Sp1 Cycle M-132 Cycle M-134 Cycle M-13
Fig. 8 Stress–strain curves for GPC after cyclic heating to
1,000 �C
Materials and Structures
Author's personal copy
13. JV Jaarsveld, JV Deventer, Lukey G (2002) The effect of
composition and temperature on the properties of fly ash-
and kaolinite-based geopolymers. Chem Eng J 89:63–73
14. Junaid MT, Kayali O, Khennane A (2012) Mix design
procedure for alkali activated fly ash-based geopolymer
concretes. In: International conference on engineering and
applied science, Beijing. Oxford University Press, Oxford,
pp 139–152
15. Junaid MT, Khennane A, Kayali O (2014) Investigation into
the effect of the duration of exposure on the behavior of
geopolymer concrete at elevated temperatures international
congress on materials and structural stability 11. doi:10.
1051/matecconf/20141101003
16. Kayali O (2008) Fly ash lightweight aggregates in high
performance concrete. Constr Build Mater 22:2393–2399
17. Khaliq W, Kodur V (2011) Thermal and mechanical prop-
erties of fiber reinforced high performance self-consolidat-
ing concrete at elevated temperatures. Cem Concr Res
41:1112–1122
18. Khennane A (1992) Mechanical modelling of the behaviour
of concrete at elevated temperatures. The University of
Queensland, St Lucia
19. Khennane A, Baker G (1993) Uniaxial model for concrete
under variable temperature and stress. J Eng Mech ASCE
119:1507–1525
20. Khoury GA, Grainger BN, Sullivian PE (1985) Transient
thermal Strain of concrete: literature review, conditions
within specimen and behaviour of individual constituents.
Mag Concr Res 37:131–144
21. Kong D, Sanjayan JG (2008) Damage behavior of geo-
polymer composites exposed to elevated temperatures. Cem
Concr Compos 30:986–991
22. Kong D, Sanjayan JG (2009) Effect of elevated tempera-
tures on geopolymer paste, mortar and concrete. Cem Concr
Res 40:334–339
23. Kong D, Sanjayan JG, Sagoe-Crentsil K (2007) Compara-
tive performance of geopolymers made with metakaolin and
fly ash after exposure to elevated temperatures. Cem Concr
Res 37:1583–1589
24. Li LY, Purkiss J (2005) Stress–strain constitutive equations
of concrete material at elevated temperatures. Fire Saf J
40:669–686
25. Lloyd NA, Rangan BV (2010) Geopolymer concrete with
fly ash. Paper presented at the Second International Con-
ference on Sustainable Construction Materials and
Technologies
26. Lu Z (1989) A research on fire response of reinforced
concrete beams. Tongji University, Shanghai
27. Neville A (1995) Properties of concrete, 4th edn. Longman
Group Limited, Essex
28. Noumowe AN, Clastres P, Debicki G, Costaz JL (1996)
Thermal stresses and water vapour pressure of high per-
formance concrete at high temperature. In: Fourth interna-
tional symposium on the utilisation of high strength/high
performance concrete, Paris, pp 561–570
29. Pan Z, Sanjayan JG (2010) Stress–strain behaviour and
abrupt loss of stiffness of geopolymer at elevated temper-
atures. Cem Concr Compos 32:657–664
30. Rickard WDA, Temuujin J, Av Riessen (2012) Thermal
analysis of geopolymer pastes synthesised from five fly
ashes of variable composition. J Non-Cryst Solids
358:1830–1839
31. Rickard WDA, Williams R, Temuujin J, Riessen AV (2011)
Assessing the suitability of three Australian fly ashes as an
aluminosilicate source for geopolymers in high temperature
applications. Mater Sci Eng A 528:3390–3397
32. Schneider U (1988) Concrete at high temperatures—a
general review. Fire Saf J 13:55–68
33. Tan W (1990) A research on reinforced concrete beams
subjected to high temperatures and expert system. Tongji
University, Shanghai
34. Xie G, Qian Z (1998) Research on bond and tension
behaviour of concrete after high temperature. J Zhejiang
Univ 32:597–602
Materials and Structures
Author's personal copy
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