Utilisation of waste material in geo-polymeric concrete
&1 Muhammad Fadhil Nuruddin PhDAssociate Professor, University Tecknology PETRONAS, Tronoh, Perak,Malaysia
&2 Sobia Anwar Qazi MSc<University Teknology PETRONAS, Tronoh, Perak, Malaysia
&3 Andri KusbiantoroPhD student, University Teknology PETRONAS, Tronoh, Perak, Malaysia
&4 Nasir Shafiq PhDAssociate Professor, University Teknology PETRONAS, Tronoh, Perak,Malaysia
Fly ash (FA), silica fume (SF) and rice husks are hazardous waste materials that have no use and in the past have been
landfilled. However, landfilling is becoming expensive and causes contamination to soil and ground water. Utilisation of
waste material in concrete is also very effective in overcoming the problems caused by the production of cement; namely
the emission of carbon dioxide and degradation of the environment due to the quarrying of rawmaterials (limestone and
clay) for the production of cement. This research studywas based on the complete elimination of ordinary Portland cement
(OPC) from concrete that can achieve 28 days target cube strength in the range of 40--50 MPa with the emphasis on the
curing techniques applicable for in situ construction; namely ambient and external exposure curing. Fly ashwas utilised as
a base sourcematerial and silica fume andmicrowave-incinerated rice husk ash (MIRHA)were used as replacements for the
fly ash by 3, 5 and 7%. Alkaline activators, namely sodium hydroxide and sodium silicate solution were used as activators
of silica and aluminium in the source material and sugar was incorporated in themix to increase the hardening time of the
concrete. Compressive strength, flexural strength and scanning electron microscopy (SEM) tests were conducted on the
specimens and the results showed that at 3, 7, 28, 56 and 90 days the fly ash along with silica fume, MIRHA and alkaline
activators could be a good replacement of cement. The compressive strength of external exposure curing for the
geopolymeric concrete reached up to 48.7 MPa at 28 days and this concrete had awell developedmicrostructure shown by
SEM analysis. The flexural strength showed values which were comparable with OPC concrete.=
1. IntroductionMaterial by-products such as fly ash (FA) and silica fume (SF)
which are derived from ever-expanding industrial processes or
waste such as rice husks from agricultural activities are
undesirable materials for the environment if they are not
properly disposed of. These materials may eventually find their
way to landfills, but landfills are becoming scarce and
expensive to maintain (Fytianos et al., 1998). Over time this
may lead to a waste disposal crisis. Fly ash is composed of
smaller particle sizes that contain some toxic elements such as
arsenic, chromium, boron, vanadium and antimony ( Sushil
and Batra, 2006). The toxic elements contained within the fly
ash may be leached from them after being placed in landfills.
Unfortunately, power plants produce millions of tonnes of fly
ash annually, the greater portion of which is mostly wasted in
landfills at a cost of around US$ 1 billion. The global
production of fly ash is expected to rise by 800 million tons
annually in 2010 (Izquierdo et al., 2009). The disposal costs of
fly ash can be saved if, for example, fly ash is used in the
manufacture of concrete; the actual cost of this fly ash is 11--22
cents/kg (Rohatgi et al., 2006).
On the other hand, disposal of rice husk is difficult because of
its low nutritional value; a long time period is required for it to
decompose sufficiently to be used in manure (Zemke and
Woods, 2009). Almost 2.2 million tons of rice husks are
produced per year from agricultural activity in Malaysia,
contributing to an annual production rice of husks of 500--
600 million metric tons worldwide (Bouman et al., 2007).
The utilisation of waste material in concrete as a replacement for
cement can also be useful in overcoming problems caused by the
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:55:31
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro and Shafiq
Proceedings of the Institution of Civil EngineersConstruction Materials 000 Month 2011 Issue CM000
Pages 1–13 doi:
Paper 1000045Received 30/06/2010 Accepted 02/11/2010
Keywords: ???/???/??? ;
ice | proceedings ICE Publishing: All rights reserved
1
production of cement, namely the emission of carbon dioxide
and degradation of the environment due to quarrying of raw
materials (limestone and clay) for the production of cement.
Global concrete production in the world is expected to rise from
about 10 billion tons in 1995 to almost 16 billion tons in 2010
(Odd and Koji, 2000). Cement production also reached a new
record amount of 2?31 billion metric tons with an annual
increase of 5?5%, and that is expected to rise by 4?1% globally to
3?5 billion metric tons in 2013 (World Cement Industry, 2010).
The contribution of the global cement industry to greenhouse
gas emissions that give rise to global warming, is around
1?35 billion tons annually, which is 7% of the total man-made
greenhouse gas emissions in the Earth’s atmosphere (Malhotra,
2002). Apart the issue of carbon dioxide emissions derived
from the production of cement, the quarrying of raw materials
(limestone and clay) for the production of cement is increas-
ingly becoming a source of environmental degradation (Naik
et al., 2005). For example, to produce 1 ton of ordinary
Portland cement (OPC), 1?6 tons of raw materials are needed
and the rate of extraction of raw materials from the Earth is
20% greater than the capacity of the Eearth to replenish itself.
Hence, raw materials consumed in 12 months would take 14?4
months to be replenished (Naik et al., 2005).
In 1979, Davidovits created and applied the term geopolymer
because the process of polymerisation takes place, in which
silica and aluminium, present in the source material [i.e. fly ash
(FA)/ silica fume (SF)/rice husk), reacts with the alkaline liquid
to produce binders. Geopolymeric cements produced in this
manner produce 80 to 90% less carbon dioxide emissions in
comparison with that produced in OPC (Davidovits, 2008).
Such reductions in carbon dioxide emissions ultimately
support decreases in global warming and the depletion of
ozone layer.
For a geopolymer concrete, the polymerisation occurs through
a condensation process in which water and heat is released
during the endothermic chemical reaction. Within the geopo-
lymerisation process, the polycondensation of alumino-silicate
oxides (Si2O5, Al2O2) with alkali polysilicates (sodium or
potassium silicate) takes place producing silica (Si)—oxygen
(O)—aluminium (Al) bonds (Hardjito and Rangan, 2005).
The chemical reaction comprises the following steps (Xu and
Van Deventer, 2000)
(a) Dissolution of silica and aluminium atoms from the
source material through the action of hydroxide ions.
(b) Transport, orientation or condensation of precursor ions
into monomers.
(c) Polymerisation (through the polycondensation process)
and set of monomers into geopolymeric structures.
The hardening of concrete depends upon curing temperature
and curing time. For FA-based concrete, the setting time was
decreased by a factor of six when the temperature was increased
from 6 to 80 C (Brooks, 2002) and according to Wang et al.
(2004), the increased temperature during cure gives rise to
pozzolanic reactions. The reaction of FA is very slow at ambient
temperatures (Puertas et al., 2000) and this delays the initiation
of the setting of concrete (Kirschner and Harmuth, 2004).
Previously, research has been completed on the development of
mixture proportions for FA-based geopolymer concrete
(Hardjito et al., 2004) and for which were determined the
short-term and long-term performance properties of mixes
having low calcium content (Wallah and Rangan, 2006).
Researchers have up to now only found solutions appropriate
for the precast concrete industry such as adapting oven curing
for the production of geopolymeric concrete (Fernandez-
Jimenez et al., 2005; Rangan, 2008) ?. Nonetheless, given the
inherent strength and durability properties of polymer
concrete, there is a dire need to further develop its use for in
situ construction. This is an obvious gap in the previous
research and the information obtained in the present study
may help to provide a useful contribution.
2. Methodology
2.1 Material selection
The materials used in this research study were chosen according
to specifications that met the requirements of the appropriate
British Standards as well as the objectives of this research.
The FA was obtained from Manjung power station, Lumut,
Perak, Malaysia. The densified SF was obtained from Elkem
Materials (Malaysia) having a bulk density of 500—700 kg/m3,
whereas the microwave-incinerated rice husk (MIHRA) was
obtained from the Bernas rice milling plant, Kuala Selangor,
Malaysia. The chemical compositions of FA, SF and MIRHA
are shown in Table 1.
The coarse aggregate used in this experiment was crushed
granite stone having a maximum size of 20 mm (BSI, 1989)
whereas the fine aggregate was a natural Malaysian sand with
a fineness modulus of 2?7, classified in zone 3. Fine aggregate
was also sieved to exclude sizes of less than 5 mm.
Sodium silicate (Na2SiO3; Grade A53) was used in solution and
mixed with 56?31% (wt.) of water, 29?43% (wt.) of silica oxide
(SiO2) and 14?26% (wt.) of sodium oxide (Na2O). Sodium
hydroxide (NaOH) used was in the form of pellets.
The concentration of the sodium hydroxide solution was
8 mol/l and 29?4% (wt.) of pellets were added to the water to
make 1 kg of solution.
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:03
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
2
Sugar was used to increase the setting time of concrete. The
intention in adding refined white sugar to the concrete mix was
to prevent the cement from fully combining with the water and
thus retard the hardening process (McDonnell, 2006? ; Nuruddin
et al., 2009). Sugar is an organic compound which is chemically
named as sucrose or saccharose. Themolecular formula of sugar
used in this study is C12H22O11. Water used in the mix was tap
water in accordance with B.S. 3148:1980 (BSI, 1980).
2.2 Design of mix proportions
The proportions of the different materials used in the mix design
are given in Table 2. The base binder for all mixes was FA (bulk
density of 350 kg/m3). The FA used in the control mix was
replaced by 3, 5 and 7% of 350 kg/m3 of FA by SF andMIRHA.
All other material quantities were kept constant such that the
effects of replacement of FA with SF and MIRHA on the
strength, both in compression and flexure, and the workability
properties of the concrete could be determined. The sodium
silicate to sodium hydroxide weight ratio was 2?5 and coarse to
fine aggregate weight ratio was approximately 1?86.
Sugar was incorporated into the mix in proportions of 3% by
weight of the total binder. Extra water (other than the water
present in the alkaline solutions) was added to the mixture
equal to 10% by weight of the total binder to ensure the
required workability (Table 2).
2.3 Casting and curingCubes of concrete of dimension 100 mm were cast and after 24 h
of casting, the moulds were opened according to EN 12390-1
(CEN, 1996) ?. Specimens were cured under two types of conditions:
ambient and external exposure conditions. For ambient curing
conditions, samples were placed in the shade outside the
laboratory whereas for the curing of samples in external exposure
conditions, samples were placed in a stand covered by a
transparent white plastic sheet and exposed to direct sunlight.
2.4 Test procedureCompressive strength tests were performed on concrete
samples in accordance with BS EN 12390-3:2002 (BSI, 2002)
using a digital compressive testing machine. Three concrete
cubes at ages of 3, 7, 28, 56 and 90 days were tested. During the
test, the concrete cubes were loaded at a constant rate of
6?8 kN/s without any suddenly applied loads.
Flexural strength tests were completed according to BS EN 12390-
5 (BSI, 2000) using a 2000 kN digital compressive and flexural
testing machine. Beams of dimension 100 mm 6 100 mm 6500 mm were cast, cured and tested for each mix after 28 days of
curing.
Scanning electron microscopy (SEM) was performed with a
LEO 1430 VP scanning electron microscope using Inca X-Sight
Oxford Instruments software. Specimens of 0?5 mm diameter
were cored from sample cubes of concrete that had been cured
for 28 days.
3. Results and discussion
3.1 Properties of fresh geopolymeric concreteIn order to find out the fresh properties of geopolymeric
concrete, its workability was measured through a slump test.
Extra water (10%) was added to all the mixes, decided as an
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:03
> Compounds FA: % SF: % MIRHA: %
SO2 51?19 96?36 86?10
Al2O3 24?00 0?20 0?17
Fe2O3 6?60 0?77 2?87
CaO 5?57 0?23 1?03
MgO 2?40 0?52 0?84
SO3 0?88 0?55 0?41
K2O 1?14 1?02 4?65
Na2O 2?12 0?1
Table 1. Chemical composition of FA MIRHA and SF
Type of
curing
Fly ash:
kg/m3
MIRHA/ silica
fume: %
MIRHA/ silica
fume: kg/m3
Coarse agg.:
kg/m3
Fine agg.:
kg/m3
NaOH:
kh/m3
Na2SiO3:
kg/m3
Extra water/
10%: kg/m3
Sugar/3%:
kg/m3
Ambient
curing
350 0 0 1200 645 41 103 35 10?5
339?5 3 10?5
332?5 5 17?5
325?5 7 24?5
External
exposure
curing
350 0 0 1200 645 41 103 35 10?5
339?5 3 10?5
332?5 5 17?5
325?5 7 24?5
Table 2. Mix design proportions
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Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
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appropriate amount after several trial mixes. Slump test results
are shown in Table 3. To improve the workability of
geopolymeric concrete naphthalene-based superplasticiser had
also being investigated (i.e. used by Rangan (2008)) but the
concrete hardened in a short span of time due to the fast setting
time of geopolymeric concrete which made the preparation of
samples harder with prolonged vibrations for compaction. In
the present study, sugar was added to delay the setting time of
the concrete making it easier to produce the samples.
Fly ash particles are spherical in shape with smooth surfaces
(Figure 1) which reduced the water demand in concrete but the
addition of MIRHA to FA-based geopolymeric concrete
increased the water demand in the concrete by reducing the
value of the slump by 5 and 7%, approximately in comparison
with the SF mix and control mix, respectively. With the
increase in percentage of MIRHA, slump was decreased which
showed that as the MIRHA content increased the water
quantity should also be increased in order to maintain the
required consistency of the mix. The decrease in workability
was due to the cellular particles (Figure 2) of MIRHA that
were absorptive in nature. MIRHA is a hygroscopic material
having a specific surface area that is greater than that of
cement due to which it absorbed more water.
On the other hand, in the case of SF addition to the fly ash-
based geopolymeric concrete, there was no change in the slump
value for 3 and 5% replacement but a 5% decrease could be
seen in the 7% replacement of SF. This shows that for the 7%
increment (or more) of SF, the water requirement in the
concrete increased which was due to the increased amount of
silica in the mix. Because of larger surface area and smaller
particle size (Figure 3), SF requires more water when increased
after a certain amount. In comparison with the control mix the
slump value of the SF mix decreased by 1?8%.
3.2 Suitable curing regime for FA-MIRHAgeopolymeric concrete
Figure 4 shows that a 5% (wt.) addition of MIRHA to the
concrete mix provided the highest compressive strength of the
concrete samples cured in ambient conditions, specifically,
28?3 MPa at 90 days. This value was 38?6% greater than that
obtained for the mix having 3% addition, 50?7% greater than
that of the mix with a 7% addition and 19% greater than the
control mix. With respect to the mix having 5% addition of
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:03
Type of mix Slump: mm
FA 230
FA-MIRHA 3% 220
FA-MIRHA 5% 210
FA-MIRHA 7% 200
FA-SF 3% 230
FA-SF 5% 230
FA-SF 7% 230
Table 3. Slump test results for each mix
10 mm EHT = 5.00 kVWD = 7.2 mm
Signal A = SE2Mag = 1.00 KX
Date: 1 Apr 2010Universiti Teknologi
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Figure 1. FESEM of fly ash
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
4
MIRHA, this quantity was found to be the optimum amount
for FA-based geopolymeric concrete.
External exposure curing conditions (Figure 5) resulted in the
highest compressive strength in comparison with concrete
cured under ambient conditions. Among mixes having
replacements of FA, the 7% replacement by MIRHA gave
the highest compressive strength at 90 days (46 MPa), which
was 48?4% greater than the 5% MIRHA mix and 11?7% less
than the control mix. In the control mix 67% of the 90 day
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:07
10 mm EHT = 1.00 kVWD = 4.9 mm
Signal A = SE2Mag = 1.00 KX
Date: 1 Apr 2010Universiti Teknologi
Time: 13: 20: 49PETRONAS
Figure 2. FESEM image of MIRHA
100 mm EHT = 5.00 kVWD = 7.2 mm
Signal A = SE2Mag = 100 X
Date: 1 Apr 2010Universiti Teknologi
Time: 13: 16:44PETRONAS
Figure 3. FESEM image of silica fume
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
5
strength was developed in the first 3 days which then led to
51?36 MPa at 90 days, the highest strength value of all the
mixes. Whereas between 7 and 28 days, the highest increase in
strength was for the 3%MIRHAmix, for which a 30% strength
increase was obtained in comparison with the control mix. All
results are given in Table 4.
These results explained the importance of heat in the curing of
geopolymeric concrete which was insufficient in ambient curing
conditions to produce the strength increases that were evident
for the concrete cured under external exposure conditions. The
increase in temperature during cure gave rise to a pozzolanic
reaction. When cured in the external exposure conditions the
geopolymeric reaction was enhanced by the heat from sunlight
which helped develop early age strength. It was supposed that
the additional heat helped promote the dissolution of silica and
aluminium atoms from the amorphous portion of the source
material by the action of hydroxide ions and concurrently these
precursor ions converted to monomers that further advanced
the polycondensation process (hardening process) to ultimately
form a geopolymeric structure as described by Davidovits
(2008).
The performance of geopolymeric concrete incorporating
MIRHA depended upon the proper utilisation of its particles
from which the Al and Si content could easily dissolve to form
a supersaturated aluminosilicate solution that further trans-
formed into a gel. This gel consisted of a network of oligomers
which continued to develop g until the maximum volume of
alkaline liquids was used. Following this, the gel started to
harden and the hardening process was enhanced if samples
were cured under the external exposure conditions given the
heat generated from exposure to sunlight.
Figure 6 shows that a 7% (wt.) addition of MIRHA in the mix
provided the highest values for flexural strength for concrete
cured under ambient and external exposure conditions,
attaining 8?38 and 6?52 MPa, respectively. Ambient curing
provided the best in MIRHA geopolymeric concrete.
According to the commentary given in ACI (Neville, 1990)
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:15
Com
pres
sive
stre
ss: M
pa
Age: daysControl mix 3%MIRHA 5%MIRHA 7%MIRHA
1 10 100
60
50
40
30
20
10
0
Figure 4. Compressive strength of FA--MIRHA-based polymeric
concrete with ambient curing
Com
pres
sive
stre
ss: M
pa
Age: daysControl mix 3%MIRHA 5%MIRHA 7%MIRHA
1 10 100
60
50
40
30
20
10
0
Figure 5. Compressive strength of FA--MIRHA-based polymeric
concrete with external exposure curing
Curing type MIRHA: % Compressive strength: MPa
3 days 7 days 28 days 56 days 90 days
Ambient
curing
0 9?50 14?11 19?73 21?92 23?77
3 9?00 11?90 17?92 19?19 20?42
5 9?77 15?89 24?08 27?00 28?30
7 8?55 11?00 16?75 17?03 18?78
External
exposure
curing
0 34?50 42?30 48?70 50?60 51?36
3 18?50 25?98 33?80 37?30 38?50
5 14?98 22?13 27?58 29?80 31?00
7 23?80 31?90 40?70 44?50 46?00
Table 4. Compressive strength of FA-based polymeric concrete
replaced by MIRHA
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
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the tensile strength in flexure should be 10--15% of the
compressive strength which was slightly better for geopoly-
meric concrete. The ratio of flexural to compressive strength
was found to be more than 10--15%, which is perhaps an
indication of good flexural strength for the geopolymeric
concrete as compared with OPC concrete.
3.3 Suitable curing regime for FA--SF geopolymericconcrete strength
Figure 7 shows that 3% (wt.) addition of SF in the FA-based
geopolymeric concrete yielded the highest compressive strength
(32?55 MPa) as compared to the control and othermixes. This value
was 37% greater than the control mix and 5% greater than the SF
sample having a 5% (wt.) addition to the FA-based geopolymeric
concrete which showed the lowest strength amongst all mixes.
This sample gained the most strength within 28 days, after
which no marked difference in strength is evident. Whereas
over a 3 to 7 day period a gain of 106% in strength was
observed for the 5% SF mix.
Figure 8 shows that the control mix provided the highest
compressive strength results, specifically, 32?4% higher than
the 3% SF mix, 56% higher than the 5% SF mix and 10?5%
higher than the 7% SF mix. Among all replacement quantities,
the 7% SF replacement amount provided the highest compres-
sive strength which was comparable with the MIRHA mix
having the same replacement value. The results obtained for
SF as replacement were slightly better than those for MIRHA
because MIRHA absorbed more liquid due to its hygroscopic
characteristic whereas SF needed water after exceeding a
certain amount. This made it possible for the precursor ions to
fully mobilise and thereafter orient themselves into monomers
within the liquid provided. These monomers were then
transformed into oligomers and within the gelation process
were reorganised to form a three-dimensional aluminosilicate
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:16
Fle
xura
l stre
ngth
at 2
8 da
ys: M
pa
Percentage replacement of fly ash with MIRHA3 50 7
9
8
7
6
5
4
3
1
2
0
Figure 6. The 28 day flexural strength of FA--MIRHA-based
polymeric concrete: vertical lines shading, ambient curing;
horizontal lines shading, external exposure curing
Com
pres
sive
stre
ss: M
pa
Age: daysControl mix 3%SF 5%SF 7%SF
1 10 100
60
50
40
30
20
10
0
Figure 7. Compressive strength of FA--SF-based polymeric
concrete with ambient curing
Com
pres
sive
stre
ss: M
pa
Age: daysControl mix 3%SF 5%SF 7%SF
1 10 100
60
50
40
30
20
10
0
Figure 8. Compressive strength of FA--SF-based polymeric
concrete with external exposure curing F
lexu
ral s
treng
th a
t 28
days
: Mpa
Percentage replacement of fly ash with MIRHA3 50 7
9
8
7
6
5
4
3
1
2
0
Figure 9. The 28 day flexural strength of FA--SF-based polymeric
concrete: vertical lines shading, ambient curing; horizontal lines
shading, external exposure curing
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
7
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:17
Curing type SF: % Compressive strength: MPa
3 days 7 days 28 days 56 days 90 days
Ambient
curing
0 7?46 14?11 19?73 21?92 23?77
3 12?07 24?04 30?27 31?75 32?55
5 5?35 11?04 12?97 15?10 16?54
7 11?90 18?39 26?50 28?82 29?98
External
exposure
curing
0 34?50 42?30 48?70 50?60 51?36
3 22?00 28?30 35?00 37?50 38?80
5 19?10 25?10 30?50 32?00 32?90
7 31?90 37?00 42?30 45?10 46?50
Table 5. Compressive strength of FA-based geopolymeric concrete
replaced by SF
1 mm EHT = 15.00 kVWD = 10.4 mm
Signal A = VPSEMag = 5.00 X
Date: 29 Jul 2009Universiti Teknologi
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a
2 mm EHT = 15.00 kVWD = 11.4 mm
Signal A = VPSEMag = 2.00 X
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b
10 mm EHT = 15.00 kVWD = 9.7 mm
Signal A = VPSEMag = 1.00 X
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c
2 mm EHT = 15.00 kVWD = 10.8 mm
Signal A = VPSEMag = 2.00 X
Date: 29 Jul 2009Universiti Teknologi
Time: 12: 12: 00PETRONAS
d
Figure 10. SEM images of ambient-cured FA-based polymeric
concrete with MIRHA: (a) control mix; (b) 3% MIRHA; (c) 5%
MIRHA; (d) 7% MIRHA
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
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network. Once the polymerisation process was initiated, it
enhanced the aluminosilicate network that, with the additional
heat from exposure to sunlight, produced a more hardened
matrix which ultimately resulted in higher compressive
strengths. All results are given in Table 5.
Figure 9 shows that in external exposure curing conditions, 7%
inclusion of SF showed the highest values for flexural strength
(7?91 MPa), whereas for ambient curing conditions the best
flexural strength (6?58 MPa) was achieved by the 5% inclusion
of SF.
3.4 Microstructure analysis of geopolymericconcrete
In 3% MIRHA (Figure 10(b)) mix the microstructure was
better hardened in comparison with the control mix
(Figure 10(a)), which was due to the greater amount of silica
oxide present in MIRHA therefore more silica atoms were
expected to dissolve from the source material and participate in
the geopolymeric reaction to produce aluminosilicate gel,
which has a tube-like structure (Figure 11) unlike that of
calcium—silicate--hydrate (C--S--H) gel as found in OPC
concrete (Famy et al., 2003). The composition of aluminosi-
licate gel was examined by energy dispersive X-ray (EDX)
analysis (Figure 12). Fewer micropores were present in the
matrix; this was due to the inclusion of fine MIRHA particles
that filled these pore spaces.
The microstructure of the sample with the addition of 5% (wt.)
MIRHA (Figure 10(c)) was even better than the sample mix
having 3% addition of MIRHA in terms of the extent of
hardening of the gel because the amount of dissolved silica
increased with the increase in the amount of MIRHA.
Although some precipitated particles were present in the
matrix, these were not converted to aluminosilicate gel because
of the reduced temperature during the ambient curing period.
The average temperature was 20--25 C in ambient curing. For
the 7% MIRHA mix (Figure 10(d)) the amount of undissolved
particles were greater in comparison with those evident for the
3 and 5% MIRHA mixes and this showed that additions of
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:25
200 nm EHT = 2000 kVWD = 9.5 mm
Signal A = VPSEMag = 30.00 KX
Date: 31 Mar 2010Universiti Teknologi
Time: 12: 40: 50PETRONAS
Figure 11. FESEM image of polymeric paste showing
aluminosilicate gel
Full Scale 2514 cts Cursor: 0.0001
Ca
Ca
CaK
KK
Fe
Fe Fe
O
AlMg
Si
CaK
Fe
Total
AlMg
Si
Element
O 48.56 64.153.25 2.994.26 3.703.35 2.6224.84 18.701.00 0.5411.583.17
6.11
100.00
1.20
Weight% Atomic%
Na
Na
2 3 4 5 6 7 8 9 10keV
Figure 12. EDX analysis of aluminosilicate gel after 7 days
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
9
more than 5% of MIRHA increased the amount of silica in the
mix which was not able to fully react with alkaline liquids. Due
to low heat the polymeric reaction was slow and the time taken
for the alkaline liquids to leach out of the mix before properly
coming into contact with the reactive solid material increased.
As a result, a greater number of unreacted particles were
present in the matrix in comparison with the reactive ones
which consequently provided for a reduction in the compres-
sive strength.
The addition of 3% (wt.) of SF to the geopolymeric concrete
mix (Figure 13(b)) was found to produce a better yield in
comparison with the 5% (Figure 13(c)) and 7% inclusion
(Figure 13(d)) unlike MIRHA because SF contained more
silica content in comparison with MIRHA. This showed that
beyond an addition of 3% of SF, the alkaline liquids were not
sufficient for the mix to dissolve silica from the source material.
Un-reacted particles were still present, given that there was
insufficient heat from the surroundings which in turn
prevented the precipitated particles from converting into a
gel. For those mixtures to which 5 and 7% of SF was added,
un-reacted particles were abundantly present in the matrix
which was also porous because sufficient gel had not formed to
fill these pores.
In comparison with the ambient curing conditions, the curing
of concrete samples in external exposure conditions provided
better microstructural development, which was thought to be
due to the additional heat available during the external
exposure curing period in comparison with that of the ambient
cure. Greater heat helped in greater dissolution of silica from
the pozzolan (FA/MIRHA/SF) and the additional heat
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:29
1 mm EHT = 15.00 kVWD = 10.4 mm
Signal A = VPSEMag = 5.00 X
Date: 29 Jul 2009Universiti Teknologi
Time: 11: 10: 26PETRONAS
a
10 mm EHT = 15.00 kVWD = 7.8 mm
Signal A = VPSEMag = 1.00 KX
Date: 30 Jul 2009Universiti Teknologi
Time: 12: 00: 54PETRONAS
b
10 mm EHT = 15.00 kVWD = 9.8 mm
Signal A = VPSEMag = 1.00 KX
Date: 30 Jul 2009Universiti Teknologi
Time: 12: 36: 28PETRONAS
c
10 mm EHT = 15.00 kVWD = 10.9 mm
Signal A = VPSEMag = 1.00 X
Date: 30 Jul 2009Universiti Teknologi
Time: 12: 46: 37PETRONAS
d
Figure 13. SEM images of ambient-cured FA-based polymeric
concrete with SF: (a) control mix; (b) 3% SF; (c) 5% SF; (d) 7% SF
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
10
Proceedings of the Institution of Civil Engineers tcm1000045.3d 11/7/11 14:56:37
10 mm EHT = 15.00 kVWD = 6.6 mm
Signal A = VPSEMag = 500 X
Date: 30 Jul 2009Universiti Teknologi
Time: 16: 13: 06PETRONAS
Aggregate
Hardened paste
Figure 14. SEM images of external exposure-cured FA-based
polymeric concrete with MIRHA
10 mm EHT = 15.00 kVWD = 8.9 mm
Signal A = VPSEMag = 300 X
Date: 30 Jul 2009Universiti Teknologi
Time: 12: 56: 28PETRONAS
Aggregate
Hardened paste
Figure 15. SEM images of external exposure-cured FA-based
polymeric concrete with SF
Construction MaterialsVolume 000 Issue CM000
Utilisation of waste material ingeopolymeric concreteNuruddin, Qazi, Kusbiantoro andShafiq
11
apparently accelerated the geopolymeric reaction which, in
turn, resulted in the production of aluminosilicate gel that
filled voids at the interfacial transitional zone (ITZ) and within
the matrix.
Unlike the setting times obtained for concrete samples cured
under ambient conditions, the setting time of geopolymeric
concrete cured under external exposure conditions was not
delayed. This is thought to be due to the additional heat
provided by exposure to sunlight which readily promoted
contact of alkaline solutions with the reactive solid material
before being leached from the mix. The average temperature in
external exposure curing was 35—40 C All mixes replaced by
MIRHA (Figure 14) or SF (Figure 15) showed a compact
microstructure with a smaller number of un-reacted particles
which led to a better strength of concrete. The ITZ was
properly developed as no evident interface can be observed
between aggregates and the geopolymeric matrix. Such
microstructural properties were consistent with the 28 day
compressive strength of 48?7 MPa which was as good as OPC
concrete.
On the other hand, in the case of SF addition to the FA-based
geopolymeric concrete, there was no change in the slump value
for replacement values of 3 and 5% whereas a 5% decrease in
slump can be seen for a 7% replacement with SF. This shows
that for the 7% increment (or more) of SF, the water
requirement in the concrete increased which was due to the
increased amount of silica in the mix. It is apparent that given
the smaller particle size and large surface area of SF, SF
requires more water when added to an FA mix beyond
replacement values of 7% (wt.). In comparison with the control
mix, the slump value of the SF mix decreased by 1?8%.
4. Conclusions
(a) Geopolymeric concrete was developed that achieved a
target strength compressive strength at 28 days equal to
that of OPC concrete. The results of a microstructure
study helped verify the cementing potential of geopoly-
meric concrete to be used in the construction industry;
this study was able to show the dense microstructure of
the geopolymeric concrete and the well developed
interfacial transition zone (ITZ) between particles and
cement paste.
(b) External exposure curing conditions were found to be the
best curing regime for geopolymeric concrete given that it
showed the highest value of compressive strength in
comparison with similar concretes cured under ambient
curing in this study.
(c) The compressive strength of the geopolymeric concrete
under external exposure conditions developed up to 28
days however; there was no significant increase in
strength beyond this time.
(d) The flexural strength of geopolymeric concrete was
comparable to OPC concrete.
(e) The best performing geopolymeric concrete mix design,
based on the results of compressive strength tests and a
microstructure study, was the concrete mix cured under
external exposure conditions. This mix comprised
i. fly ash: 350 kg/m3
ii. sodium hydroxide (NaOH): 41 kg/m3
iii. sodium silicate (Na2SiO3): 103 kg/m3
iv. table sugar: 10?5 kg/m3 (3% of FA)
v. extra water: 35 kg/m3 (10% of FA)
vi. fine aggregate: 645 kg/m3
vii. coarse aggregate: 1200 kg/m3 @
AcknowledgementsThe authors would like to acknowledge the University
Technology PETRONAS for providing facilities to complete
this research study.
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