Kaolin and alkali activator were mixed with the solids-to-liquid ratios in range of 0.60–1.20 (Al... more Kaolin and alkali activator were mixed with the solids-to-liquid ratios in range of 0.60–1.20 (Al2O3/Na2O
molar ratio of 0.63–1.27). Sodium silicate and sodium hydroxide ranged between 0.16 and 0.36 (SiO2/
Na2O molar ratio of 3.19–3.67) were mixed together to prepare alkali activator. The results concluded
that compressive strength was affected by both S/L and Na2SiO3/NaOH ratios and strength increased with
ageing day. Both these ratio also influenced the workability of the mixes. Besides, the kaolin geopolymers
showed good volume stability in water. Compressive strength was highest at S/L and Na2SiO3/NaOH
ratios of 1.00 and 0.32, respectively. In term of molar ratios, optimum was achieved at Al2O3/Na2O of
1.09 and SiO2/Na2O molar ratios of 3.58. Microstructures showed that kaolin particles were slightly activated
with large part of unreacted raw materials remained in the system. Geopolymer sample reduced in
peak intensities over time as presented by XRD analysis and the presence of crystalline peaks in the kaolin
geopolymers was Zeolite X. FTIR analysis showed the presence of geopolymer bonding increased over
age. In overall, kaolin geopolymers does not undergo complete geopolymerization and showed slow
strength development. Vast research works have to be carried out to further improve the properties of
kaolin geopolymers.
This paper aimed at investigating the possibility of calcined kaolin to produce cement powder tha... more This paper aimed at investigating the possibility of calcined kaolin to produce cement powder that could
be an alternative to Portland cement by applying geopolymerization process. Cement paste was firstly
made by alkaline activation of calcined kaolin with alkali activator (mixture of 6–10 MNaOH and Na2SiO3
solution), heated in oven at temperature of 80 C forming a solidified product, followed by pulverization
to fixed particle size powder. The parameters involved in this processing route (alkali concentration, calcined
kaolin to activator ratio, alkali activator ratio and heating conditions) were investigated. For compressive
testing, cement powder was added with water and then cured to produce cubes. Compressive
strength, microstructure, XRD and FTIR analysis were studied. Result showed that the processing route
has the potential to produce cement powder where SEM micrographs have proved that the geopolymerization
process continued after addition of water forming a homogeneous structure and geopolymers
bonding increased in intensity which was observed through IR analysis. It was believed that presences
of crystalline phase as seen in XRD diffractogram were good for mechanical properties.
This paper investigates the effect of S/L and alkali activator ratios on the synthesis of geopoly... more This paper investigates the effect of S/L and alkali activator ratios on the synthesis of geopolymeric powder.
Geopolymeric powder was synthesized by applying geopolymerization process. By adopting the concept
of ‘‘just adding water’’, resulted geopolymer paste was produced from geopolymeric powder.
Compressive testing, bulk density measurement SEM, EDX, XRD and IR analyses were performed. The
results concluded that solids-to-liquid and waterglass-to-NaOH solution ratios affected the strength significantly
and these ratios were optimized at 0.80 and 0.20, respectively. The densification of microstructure,
presence of amorphous gels and crystalline zeolite phases as well as the increase in the geopolymer
bonding could be revealed in this study.
Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a... more Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a mixture
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a... more Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a mixture
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
The effect of mechanical activation of kaolin on properties of geopolymers was investigated.
The... more The effect of mechanical activation of kaolin on properties of geopolymers was investigated.
The analysis on mechanical-activated kaolin showed that kaolin’s particle size decreased accompanied
with increase in surface area along with activation time. XRD diffraction peaks of kaolinite decreased
as well. FTIR analysis demonstrated the distortion of the tetrahedral and octahedral layers after the
activation process. The compressive strength of geopolymers produced using mechanical-activated
kaolin rose with activation time from 1 to 28 days. Thus, mechanical activation was deduced to have
altered the particle size and surface area as well as the reactivity of kaolin towards geopolymerization
reaction.
This paper discussed the relation between composition design and properties of calcined kaolin ge... more This paper discussed the relation between composition design and properties of calcined kaolin geopolymeric powder. Geopolymeric powder was produced by applying the geopolymerization process. The solids-to-liquid ratios were varied while the NaOH concentration and waterglass-to-NaOH ratios were kept constant. The oxide molar ratios (SiO2/Al2O3, Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O) were calculated from the mixture proportion. Compressive strength and SEM analysis were conducted. The results showed solids-to-liquid ratio affected the compressive strength significantly. For a geopolymer system, there was an optimum value of S/L ratios and hence optimum oxide molar ratios that leads to materials with better compressive strength. The compressive strength of samples maximized at an optimum and then decreased gradually for subsequent increases. The optimum SiO2/Al2O3, SiO2/Na2O, Al2O3/Na2O and H2O/Na2O molar ratios were 3.16, 2.78, 0.88 and 14.36, respectively. SEM showed growth of microstructure towards a more homogeneous structure after addition of water and S/L ratios influenced the level of porosity in the resulted geopolymer pastes.
This paper investigates the physical and mechanical properties as well as the morphology study of... more This paper investigates the physical and mechanical properties as well as the morphology study of the MK geopolymeric binder. Mixture of waterglass liquid and NaOH solution were used as the activator solution for the activation of MK. The slurry was oven-heated to obtain solidified paste. It was then pulverized to obtain the geopolymeric binder. For testing, this geopolymeric binder was mixed with water (≈22%) to form resulted geopolymer paste. The results indicated that the surface area of the MK geopolymeric binder was 9.76 m2/g. The resulted geopolymer paste set in 420 minutes at 60 °C. The bulk density of the resulted geopolymer paste was low (1000 kg/m3–1300 kg/m3). The compressive strength of resulted MK geopolymer paste increased over age and the strength at 28 days was 9.58 MPa. In addition, the microstructures of the resulted geopolymer pastes displayed the increase of the spherical aggregates of geopolymer gel and the densification of the structure, which complied with the increasing strength.
The properties of metakaolin geopolymer paste are affected by the alkali concentration,
the init... more The properties of metakaolin geopolymer paste are affected by the alkali concentration,
the initial raw materials, solidification process, and amount of mixing water as well as the curing
conditions. This study aimed to investigate the effect of curing temperature (room temperature,
40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer
pastes produced from geopolymer powder. The results showed that curing at room temperature was
unfeasible. Heat was required for the geopolymerization process, where strength increased as the
curing temperature was increased. Moderate elevated curing temperature favored the strength
development of geopolymer pastes in comparison with those treated with extreme elevated curing
temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter
curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was
recommended for moderate elevated curing temperature. The microstructure of geopolymer paste
cured at moderate curing temperature showed obvious densification of structure. In contrast, the
structure formed was weak and less compact at very high elevated curing temperature.
Oxide molar ratios are the main key parameter determining the performance of a kaolin geopolymers... more Oxide molar ratios are the main key parameter determining the performance of a kaolin geopolymers. The kaolin composition and various mixture proportions will lead to different oxide molar ratios in geopolymer system. In this experiment, NaOH solution prepared in 6–14 M was mixed with Na2SiO3/NaOH ratio ranged between 0.16–0.36 to prepare a alkali activator, 24 h prior to use. Kaolin powder and alkali activator were mixed at S/L ratio of 0.60–1.20, and stirred using mechanical mixer. Finally, the samples were cured at temperature of 80 °C for 24 h. From the important factors investigated in this study, various oxide molar ratios of each mixture proportions were calculated and the optimum molar ratios obtained were SiO2/Al2O3 = 3.28, SiO2/Na2O = 3.58, H2O/Na2O = 14.61 and Al2O3/Na2O = 1.09. Besides that, the conditions to synthesize kaolin geopolymers were 8 M alkali concentration with S/L ratio of 1.00 and Na2SiO3/NaOH ratio of 0.32 in order to produce kaolin geopolymers.
This paper reported the properties of kaolin geopolymers in term of the bulk density, compressive... more This paper reported the properties of kaolin geopolymers in term of the bulk density, compressive strength, qualitative observation and SEM analysis of the kaolin geopolymers. Kaolin geopolymers were synthesized through the activation of kaolin with mixture of 8 M NaOH solution and Na2SiO3 solution at kaolin/activator ratio of 1.00 and Na2SiO3/NaOH ratio of 0.32. The kaolin geopolymers were cured at 60 °C up to 3 days. Results showed kaolin geopolymers has bulk density in range of 1483 kg/m3–1605 kg/m3. The kaolin geopolymers have good volume stability in water. Compressive strength improved with increasing ageing. However, the strength development is very slow probably because of the limitation of the structure of kaolinite with low surface area and limited substitution of other element during reaction. Microstructures of kaolin geopolymers showed the formation of geopolymer gel and denser structure.
Kaolin geopolymers exhibit low strength properties due to its plate-like nature which contribute ... more Kaolin geopolymers exhibit low strength properties due to its plate-like nature which contribute to smaller surface area for geopolymerization reactions. Layered kaolin structure only allows very little, if any, substitution of other elements. Therefore, mechanical activation is an alternative way to break the kaolin structure to become finer to change the morphological features to smoother surface, and to cause edge distortion to the kaolin particles. Rounded particles also can be produced using this technique. These mechanical-activated kaolin were use to produce mechanical-activated kaolin geopolymers in this study. From the results, compressive strength increased as mechanical activation time increased and the compressive strength increased with the ageing day. The SEM micrograph showed that the mechanical-activated kaolin geopolymers have denser structure which complies with the compressive strength measured.
This paper aims at investigating the influence of solidification condition on the
processing of ... more This paper aims at investigating the influence of solidification condition on the
processing of calcined kaolin geopolymeric powder. This is a new process developed using the
geopolymerization process. Geopolymer slurry was prepared from calcined kaolin and activating
solution (mixture of NaOH and Na2SiO3). This slurry was allowed to solidify in oven and then
crushed and grounded to fixed particle size. Compressive testing and SEM analysis were performed
in this study. The results showed that the solidification condition at 80 ºC for 4 hours was the best to
synthesize the geopolymeric powder where this solidification condition results in geopolymeric
powder which can produce higher strength resulted geopolymer paste. The microstructure showed
more intervening gel phase which indicates that the geopolymerization process continued to react
after the addition of water to the calcined kaolin geopolymeric powder.
This paper describes the synthesis of calcined kaolin geopolymeric powder from the
alkaline acti... more This paper describes the synthesis of calcined kaolin geopolymeric powder from the
alkaline activation of calcined kaolin followed by solidification and pulverizing process. The
geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this
paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted
geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of waterto-
cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here
was based on geopolymerization process. The compressive strength, setting time and SEM analysis
of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-togeopolymer
powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120
minutes and reached final setting after about 4 hours of setting. Microstructure showed the
formation of geopolymeric gel after the addition of water to the geopolymeric powder.
Raw materials kaolin was subjected to mechanical modification; the effect of the
mechanical acti... more Raw materials kaolin was subjected to mechanical modification; the effect of the
mechanical activation of kaolin on the compressive strength and morphological properties of the
geopolymers has been studied. Mechanical activation of the kaolin results in particle size reduction
and morphology changes with increase in reactivity. Mechanical activated kaolin has overall higher
strength gain compared to raw kaolin. Wider particle size distribution and some spherical particles
produced, promote a higher packaging density in the sample resulting in higher strength obtained.
Mechanically activation of kaolin can be considered as an alternative method to achieve better
geopolymerization reaction for kaolin-based geopolymer.
This paper aims at investigating the influence of curing process on kaolin-based
geopolymers. Ka... more This paper aims at investigating the influence of curing process on kaolin-based
geopolymers. Kaolin-based geopolymers were prepared by the alkali-activation of kaolin with alkali
activating solution (mixture of NaOH and Na2SiO3 solutions). The compressive testing, XRD and
FTIR analysis were performed. The compressive strength results showed that curing at 60°C for 3
day achieves better strength. XRD analysis revealed that the entire geopolymer sample reduced in
intensities and became amorphous at longer age while FTIR analysis indicated the presence of
geopolymer bondings. Both analyses showed the presence of large amount of un-reacted remained
in the system were the reason of the low compressive strength obtained.
This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolyme... more This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolymer slurry was
produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground
to obtain cement powder. Ultilizing the concept of “just adding water”, hardened cement paste could be produced
from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have
a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium
silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing
route to produce cement powder by “just adding water” was possible, and the structure became denser and fewer
unreacted particles were observed.
Depending on the processing conditions, geopolymers can exhibit a wide variety of properties and ... more Depending on the processing conditions, geopolymers can exhibit a wide variety of properties and characteristics.
Curing profile serves as a crucial parameter in synthesis of geopolymers. In this paper, the influence of curing
temperature and curing time on the properties of kaolin-based geopolymer was studied. The samples were separated
into several curing conditions; including curing at ambient temperature, 40°C, 60°C, 80°C and 100°C for 1 day, and
up to 3 days. The compressive strength and SEM analysis of geopolymer products were evaluated. Results showed
that curing condition has a significant effect on the mechanical properties of kaolin-based geopolymer. Generally,
curing at ambient temperature was not feasible, while increase in temperature favored the strength development. In
addition, prolonged curing time improved the geopolymerization process, and led to higher strength gain. However,
curing at high temperature for a long period of time caused failure of the sample at a later age.
Kaolin and alkali activator were mixed with the solids-to-liquid ratios in range of 0.60–1.20 (Al... more Kaolin and alkali activator were mixed with the solids-to-liquid ratios in range of 0.60–1.20 (Al2O3/Na2O
molar ratio of 0.63–1.27). Sodium silicate and sodium hydroxide ranged between 0.16 and 0.36 (SiO2/
Na2O molar ratio of 3.19–3.67) were mixed together to prepare alkali activator. The results concluded
that compressive strength was affected by both S/L and Na2SiO3/NaOH ratios and strength increased with
ageing day. Both these ratio also influenced the workability of the mixes. Besides, the kaolin geopolymers
showed good volume stability in water. Compressive strength was highest at S/L and Na2SiO3/NaOH
ratios of 1.00 and 0.32, respectively. In term of molar ratios, optimum was achieved at Al2O3/Na2O of
1.09 and SiO2/Na2O molar ratios of 3.58. Microstructures showed that kaolin particles were slightly activated
with large part of unreacted raw materials remained in the system. Geopolymer sample reduced in
peak intensities over time as presented by XRD analysis and the presence of crystalline peaks in the kaolin
geopolymers was Zeolite X. FTIR analysis showed the presence of geopolymer bonding increased over
age. In overall, kaolin geopolymers does not undergo complete geopolymerization and showed slow
strength development. Vast research works have to be carried out to further improve the properties of
kaolin geopolymers.
This paper aimed at investigating the possibility of calcined kaolin to produce cement powder tha... more This paper aimed at investigating the possibility of calcined kaolin to produce cement powder that could
be an alternative to Portland cement by applying geopolymerization process. Cement paste was firstly
made by alkaline activation of calcined kaolin with alkali activator (mixture of 6–10 MNaOH and Na2SiO3
solution), heated in oven at temperature of 80 C forming a solidified product, followed by pulverization
to fixed particle size powder. The parameters involved in this processing route (alkali concentration, calcined
kaolin to activator ratio, alkali activator ratio and heating conditions) were investigated. For compressive
testing, cement powder was added with water and then cured to produce cubes. Compressive
strength, microstructure, XRD and FTIR analysis were studied. Result showed that the processing route
has the potential to produce cement powder where SEM micrographs have proved that the geopolymerization
process continued after addition of water forming a homogeneous structure and geopolymers
bonding increased in intensity which was observed through IR analysis. It was believed that presences
of crystalline phase as seen in XRD diffractogram were good for mechanical properties.
This paper investigates the effect of S/L and alkali activator ratios on the synthesis of geopoly... more This paper investigates the effect of S/L and alkali activator ratios on the synthesis of geopolymeric powder.
Geopolymeric powder was synthesized by applying geopolymerization process. By adopting the concept
of ‘‘just adding water’’, resulted geopolymer paste was produced from geopolymeric powder.
Compressive testing, bulk density measurement SEM, EDX, XRD and IR analyses were performed. The
results concluded that solids-to-liquid and waterglass-to-NaOH solution ratios affected the strength significantly
and these ratios were optimized at 0.80 and 0.20, respectively. The densification of microstructure,
presence of amorphous gels and crystalline zeolite phases as well as the increase in the geopolymer
bonding could be revealed in this study.
Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a... more Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a mixture
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a... more Kaolin geopolymers were produced by the alkali-activation of kaolin with an activator solution (a mixture
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
The effect of mechanical activation of kaolin on properties of geopolymers was investigated.
The... more The effect of mechanical activation of kaolin on properties of geopolymers was investigated.
The analysis on mechanical-activated kaolin showed that kaolin’s particle size decreased accompanied
with increase in surface area along with activation time. XRD diffraction peaks of kaolinite decreased
as well. FTIR analysis demonstrated the distortion of the tetrahedral and octahedral layers after the
activation process. The compressive strength of geopolymers produced using mechanical-activated
kaolin rose with activation time from 1 to 28 days. Thus, mechanical activation was deduced to have
altered the particle size and surface area as well as the reactivity of kaolin towards geopolymerization
reaction.
This paper discussed the relation between composition design and properties of calcined kaolin ge... more This paper discussed the relation between composition design and properties of calcined kaolin geopolymeric powder. Geopolymeric powder was produced by applying the geopolymerization process. The solids-to-liquid ratios were varied while the NaOH concentration and waterglass-to-NaOH ratios were kept constant. The oxide molar ratios (SiO2/Al2O3, Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O) were calculated from the mixture proportion. Compressive strength and SEM analysis were conducted. The results showed solids-to-liquid ratio affected the compressive strength significantly. For a geopolymer system, there was an optimum value of S/L ratios and hence optimum oxide molar ratios that leads to materials with better compressive strength. The compressive strength of samples maximized at an optimum and then decreased gradually for subsequent increases. The optimum SiO2/Al2O3, SiO2/Na2O, Al2O3/Na2O and H2O/Na2O molar ratios were 3.16, 2.78, 0.88 and 14.36, respectively. SEM showed growth of microstructure towards a more homogeneous structure after addition of water and S/L ratios influenced the level of porosity in the resulted geopolymer pastes.
This paper investigates the physical and mechanical properties as well as the morphology study of... more This paper investigates the physical and mechanical properties as well as the morphology study of the MK geopolymeric binder. Mixture of waterglass liquid and NaOH solution were used as the activator solution for the activation of MK. The slurry was oven-heated to obtain solidified paste. It was then pulverized to obtain the geopolymeric binder. For testing, this geopolymeric binder was mixed with water (≈22%) to form resulted geopolymer paste. The results indicated that the surface area of the MK geopolymeric binder was 9.76 m2/g. The resulted geopolymer paste set in 420 minutes at 60 °C. The bulk density of the resulted geopolymer paste was low (1000 kg/m3–1300 kg/m3). The compressive strength of resulted MK geopolymer paste increased over age and the strength at 28 days was 9.58 MPa. In addition, the microstructures of the resulted geopolymer pastes displayed the increase of the spherical aggregates of geopolymer gel and the densification of the structure, which complied with the increasing strength.
The properties of metakaolin geopolymer paste are affected by the alkali concentration,
the init... more The properties of metakaolin geopolymer paste are affected by the alkali concentration,
the initial raw materials, solidification process, and amount of mixing water as well as the curing
conditions. This study aimed to investigate the effect of curing temperature (room temperature,
40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer
pastes produced from geopolymer powder. The results showed that curing at room temperature was
unfeasible. Heat was required for the geopolymerization process, where strength increased as the
curing temperature was increased. Moderate elevated curing temperature favored the strength
development of geopolymer pastes in comparison with those treated with extreme elevated curing
temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter
curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was
recommended for moderate elevated curing temperature. The microstructure of geopolymer paste
cured at moderate curing temperature showed obvious densification of structure. In contrast, the
structure formed was weak and less compact at very high elevated curing temperature.
Oxide molar ratios are the main key parameter determining the performance of a kaolin geopolymers... more Oxide molar ratios are the main key parameter determining the performance of a kaolin geopolymers. The kaolin composition and various mixture proportions will lead to different oxide molar ratios in geopolymer system. In this experiment, NaOH solution prepared in 6–14 M was mixed with Na2SiO3/NaOH ratio ranged between 0.16–0.36 to prepare a alkali activator, 24 h prior to use. Kaolin powder and alkali activator were mixed at S/L ratio of 0.60–1.20, and stirred using mechanical mixer. Finally, the samples were cured at temperature of 80 °C for 24 h. From the important factors investigated in this study, various oxide molar ratios of each mixture proportions were calculated and the optimum molar ratios obtained were SiO2/Al2O3 = 3.28, SiO2/Na2O = 3.58, H2O/Na2O = 14.61 and Al2O3/Na2O = 1.09. Besides that, the conditions to synthesize kaolin geopolymers were 8 M alkali concentration with S/L ratio of 1.00 and Na2SiO3/NaOH ratio of 0.32 in order to produce kaolin geopolymers.
This paper reported the properties of kaolin geopolymers in term of the bulk density, compressive... more This paper reported the properties of kaolin geopolymers in term of the bulk density, compressive strength, qualitative observation and SEM analysis of the kaolin geopolymers. Kaolin geopolymers were synthesized through the activation of kaolin with mixture of 8 M NaOH solution and Na2SiO3 solution at kaolin/activator ratio of 1.00 and Na2SiO3/NaOH ratio of 0.32. The kaolin geopolymers were cured at 60 °C up to 3 days. Results showed kaolin geopolymers has bulk density in range of 1483 kg/m3–1605 kg/m3. The kaolin geopolymers have good volume stability in water. Compressive strength improved with increasing ageing. However, the strength development is very slow probably because of the limitation of the structure of kaolinite with low surface area and limited substitution of other element during reaction. Microstructures of kaolin geopolymers showed the formation of geopolymer gel and denser structure.
Kaolin geopolymers exhibit low strength properties due to its plate-like nature which contribute ... more Kaolin geopolymers exhibit low strength properties due to its plate-like nature which contribute to smaller surface area for geopolymerization reactions. Layered kaolin structure only allows very little, if any, substitution of other elements. Therefore, mechanical activation is an alternative way to break the kaolin structure to become finer to change the morphological features to smoother surface, and to cause edge distortion to the kaolin particles. Rounded particles also can be produced using this technique. These mechanical-activated kaolin were use to produce mechanical-activated kaolin geopolymers in this study. From the results, compressive strength increased as mechanical activation time increased and the compressive strength increased with the ageing day. The SEM micrograph showed that the mechanical-activated kaolin geopolymers have denser structure which complies with the compressive strength measured.
This paper aims at investigating the influence of solidification condition on the
processing of ... more This paper aims at investigating the influence of solidification condition on the
processing of calcined kaolin geopolymeric powder. This is a new process developed using the
geopolymerization process. Geopolymer slurry was prepared from calcined kaolin and activating
solution (mixture of NaOH and Na2SiO3). This slurry was allowed to solidify in oven and then
crushed and grounded to fixed particle size. Compressive testing and SEM analysis were performed
in this study. The results showed that the solidification condition at 80 ºC for 4 hours was the best to
synthesize the geopolymeric powder where this solidification condition results in geopolymeric
powder which can produce higher strength resulted geopolymer paste. The microstructure showed
more intervening gel phase which indicates that the geopolymerization process continued to react
after the addition of water to the calcined kaolin geopolymeric powder.
This paper describes the synthesis of calcined kaolin geopolymeric powder from the
alkaline acti... more This paper describes the synthesis of calcined kaolin geopolymeric powder from the
alkaline activation of calcined kaolin followed by solidification and pulverizing process. The
geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this
paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted
geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of waterto-
cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here
was based on geopolymerization process. The compressive strength, setting time and SEM analysis
of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-togeopolymer
powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120
minutes and reached final setting after about 4 hours of setting. Microstructure showed the
formation of geopolymeric gel after the addition of water to the geopolymeric powder.
Raw materials kaolin was subjected to mechanical modification; the effect of the
mechanical acti... more Raw materials kaolin was subjected to mechanical modification; the effect of the
mechanical activation of kaolin on the compressive strength and morphological properties of the
geopolymers has been studied. Mechanical activation of the kaolin results in particle size reduction
and morphology changes with increase in reactivity. Mechanical activated kaolin has overall higher
strength gain compared to raw kaolin. Wider particle size distribution and some spherical particles
produced, promote a higher packaging density in the sample resulting in higher strength obtained.
Mechanically activation of kaolin can be considered as an alternative method to achieve better
geopolymerization reaction for kaolin-based geopolymer.
This paper aims at investigating the influence of curing process on kaolin-based
geopolymers. Ka... more This paper aims at investigating the influence of curing process on kaolin-based
geopolymers. Kaolin-based geopolymers were prepared by the alkali-activation of kaolin with alkali
activating solution (mixture of NaOH and Na2SiO3 solutions). The compressive testing, XRD and
FTIR analysis were performed. The compressive strength results showed that curing at 60°C for 3
day achieves better strength. XRD analysis revealed that the entire geopolymer sample reduced in
intensities and became amorphous at longer age while FTIR analysis indicated the presence of
geopolymer bondings. Both analyses showed the presence of large amount of un-reacted remained
in the system were the reason of the low compressive strength obtained.
This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolyme... more This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolymer slurry was
produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground
to obtain cement powder. Ultilizing the concept of “just adding water”, hardened cement paste could be produced
from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have
a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium
silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing
route to produce cement powder by “just adding water” was possible, and the structure became denser and fewer
unreacted particles were observed.
Depending on the processing conditions, geopolymers can exhibit a wide variety of properties and ... more Depending on the processing conditions, geopolymers can exhibit a wide variety of properties and characteristics.
Curing profile serves as a crucial parameter in synthesis of geopolymers. In this paper, the influence of curing
temperature and curing time on the properties of kaolin-based geopolymer was studied. The samples were separated
into several curing conditions; including curing at ambient temperature, 40°C, 60°C, 80°C and 100°C for 1 day, and
up to 3 days. The compressive strength and SEM analysis of geopolymer products were evaluated. Results showed
that curing condition has a significant effect on the mechanical properties of kaolin-based geopolymer. Generally,
curing at ambient temperature was not feasible, while increase in temperature favored the strength development. In
addition, prolonged curing time improved the geopolymerization process, and led to higher strength gain. However,
curing at high temperature for a long period of time caused failure of the sample at a later age.
Uploads
Papers by LIEW YUN MING
molar ratio of 0.63–1.27). Sodium silicate and sodium hydroxide ranged between 0.16 and 0.36 (SiO2/
Na2O molar ratio of 3.19–3.67) were mixed together to prepare alkali activator. The results concluded
that compressive strength was affected by both S/L and Na2SiO3/NaOH ratios and strength increased with
ageing day. Both these ratio also influenced the workability of the mixes. Besides, the kaolin geopolymers
showed good volume stability in water. Compressive strength was highest at S/L and Na2SiO3/NaOH
ratios of 1.00 and 0.32, respectively. In term of molar ratios, optimum was achieved at Al2O3/Na2O of
1.09 and SiO2/Na2O molar ratios of 3.58. Microstructures showed that kaolin particles were slightly activated
with large part of unreacted raw materials remained in the system. Geopolymer sample reduced in
peak intensities over time as presented by XRD analysis and the presence of crystalline peaks in the kaolin
geopolymers was Zeolite X. FTIR analysis showed the presence of geopolymer bonding increased over
age. In overall, kaolin geopolymers does not undergo complete geopolymerization and showed slow
strength development. Vast research works have to be carried out to further improve the properties of
kaolin geopolymers.
be an alternative to Portland cement by applying geopolymerization process. Cement paste was firstly
made by alkaline activation of calcined kaolin with alkali activator (mixture of 6–10 MNaOH and Na2SiO3
solution), heated in oven at temperature of 80 C forming a solidified product, followed by pulverization
to fixed particle size powder. The parameters involved in this processing route (alkali concentration, calcined
kaolin to activator ratio, alkali activator ratio and heating conditions) were investigated. For compressive
testing, cement powder was added with water and then cured to produce cubes. Compressive
strength, microstructure, XRD and FTIR analysis were studied. Result showed that the processing route
has the potential to produce cement powder where SEM micrographs have proved that the geopolymerization
process continued after addition of water forming a homogeneous structure and geopolymers
bonding increased in intensity which was observed through IR analysis. It was believed that presences
of crystalline phase as seen in XRD diffractogram were good for mechanical properties.
Geopolymeric powder was synthesized by applying geopolymerization process. By adopting the concept
of ‘‘just adding water’’, resulted geopolymer paste was produced from geopolymeric powder.
Compressive testing, bulk density measurement SEM, EDX, XRD and IR analyses were performed. The
results concluded that solids-to-liquid and waterglass-to-NaOH solution ratios affected the strength significantly
and these ratios were optimized at 0.80 and 0.20, respectively. The densification of microstructure,
presence of amorphous gels and crystalline zeolite phases as well as the increase in the geopolymer
bonding could be revealed in this study.
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
The analysis on mechanical-activated kaolin showed that kaolin’s particle size decreased accompanied
with increase in surface area along with activation time. XRD diffraction peaks of kaolinite decreased
as well. FTIR analysis demonstrated the distortion of the tetrahedral and octahedral layers after the
activation process. The compressive strength of geopolymers produced using mechanical-activated
kaolin rose with activation time from 1 to 28 days. Thus, mechanical activation was deduced to have
altered the particle size and surface area as well as the reactivity of kaolin towards geopolymerization
reaction.
the initial raw materials, solidification process, and amount of mixing water as well as the curing
conditions. This study aimed to investigate the effect of curing temperature (room temperature,
40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer
pastes produced from geopolymer powder. The results showed that curing at room temperature was
unfeasible. Heat was required for the geopolymerization process, where strength increased as the
curing temperature was increased. Moderate elevated curing temperature favored the strength
development of geopolymer pastes in comparison with those treated with extreme elevated curing
temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter
curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was
recommended for moderate elevated curing temperature. The microstructure of geopolymer paste
cured at moderate curing temperature showed obvious densification of structure. In contrast, the
structure formed was weak and less compact at very high elevated curing temperature.
processing of calcined kaolin geopolymeric powder. This is a new process developed using the
geopolymerization process. Geopolymer slurry was prepared from calcined kaolin and activating
solution (mixture of NaOH and Na2SiO3). This slurry was allowed to solidify in oven and then
crushed and grounded to fixed particle size. Compressive testing and SEM analysis were performed
in this study. The results showed that the solidification condition at 80 ºC for 4 hours was the best to
synthesize the geopolymeric powder where this solidification condition results in geopolymeric
powder which can produce higher strength resulted geopolymer paste. The microstructure showed
more intervening gel phase which indicates that the geopolymerization process continued to react
after the addition of water to the calcined kaolin geopolymeric powder.
alkaline activation of calcined kaolin followed by solidification and pulverizing process. The
geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this
paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted
geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of waterto-
cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here
was based on geopolymerization process. The compressive strength, setting time and SEM analysis
of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-togeopolymer
powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120
minutes and reached final setting after about 4 hours of setting. Microstructure showed the
formation of geopolymeric gel after the addition of water to the geopolymeric powder.
mechanical activation of kaolin on the compressive strength and morphological properties of the
geopolymers has been studied. Mechanical activation of the kaolin results in particle size reduction
and morphology changes with increase in reactivity. Mechanical activated kaolin has overall higher
strength gain compared to raw kaolin. Wider particle size distribution and some spherical particles
produced, promote a higher packaging density in the sample resulting in higher strength obtained.
Mechanically activation of kaolin can be considered as an alternative method to achieve better
geopolymerization reaction for kaolin-based geopolymer.
geopolymers. Kaolin-based geopolymers were prepared by the alkali-activation of kaolin with alkali
activating solution (mixture of NaOH and Na2SiO3 solutions). The compressive testing, XRD and
FTIR analysis were performed. The compressive strength results showed that curing at 60°C for 3
day achieves better strength. XRD analysis revealed that the entire geopolymer sample reduced in
intensities and became amorphous at longer age while FTIR analysis indicated the presence of
geopolymer bondings. Both analyses showed the presence of large amount of un-reacted remained
in the system were the reason of the low compressive strength obtained.
produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground
to obtain cement powder. Ultilizing the concept of “just adding water”, hardened cement paste could be produced
from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have
a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium
silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing
route to produce cement powder by “just adding water” was possible, and the structure became denser and fewer
unreacted particles were observed.
Curing profile serves as a crucial parameter in synthesis of geopolymers. In this paper, the influence of curing
temperature and curing time on the properties of kaolin-based geopolymer was studied. The samples were separated
into several curing conditions; including curing at ambient temperature, 40°C, 60°C, 80°C and 100°C for 1 day, and
up to 3 days. The compressive strength and SEM analysis of geopolymer products were evaluated. Results showed
that curing condition has a significant effect on the mechanical properties of kaolin-based geopolymer. Generally,
curing at ambient temperature was not feasible, while increase in temperature favored the strength development. In
addition, prolonged curing time improved the geopolymerization process, and led to higher strength gain. However,
curing at high temperature for a long period of time caused failure of the sample at a later age.
molar ratio of 0.63–1.27). Sodium silicate and sodium hydroxide ranged between 0.16 and 0.36 (SiO2/
Na2O molar ratio of 3.19–3.67) were mixed together to prepare alkali activator. The results concluded
that compressive strength was affected by both S/L and Na2SiO3/NaOH ratios and strength increased with
ageing day. Both these ratio also influenced the workability of the mixes. Besides, the kaolin geopolymers
showed good volume stability in water. Compressive strength was highest at S/L and Na2SiO3/NaOH
ratios of 1.00 and 0.32, respectively. In term of molar ratios, optimum was achieved at Al2O3/Na2O of
1.09 and SiO2/Na2O molar ratios of 3.58. Microstructures showed that kaolin particles were slightly activated
with large part of unreacted raw materials remained in the system. Geopolymer sample reduced in
peak intensities over time as presented by XRD analysis and the presence of crystalline peaks in the kaolin
geopolymers was Zeolite X. FTIR analysis showed the presence of geopolymer bonding increased over
age. In overall, kaolin geopolymers does not undergo complete geopolymerization and showed slow
strength development. Vast research works have to be carried out to further improve the properties of
kaolin geopolymers.
be an alternative to Portland cement by applying geopolymerization process. Cement paste was firstly
made by alkaline activation of calcined kaolin with alkali activator (mixture of 6–10 MNaOH and Na2SiO3
solution), heated in oven at temperature of 80 C forming a solidified product, followed by pulverization
to fixed particle size powder. The parameters involved in this processing route (alkali concentration, calcined
kaolin to activator ratio, alkali activator ratio and heating conditions) were investigated. For compressive
testing, cement powder was added with water and then cured to produce cubes. Compressive
strength, microstructure, XRD and FTIR analysis were studied. Result showed that the processing route
has the potential to produce cement powder where SEM micrographs have proved that the geopolymerization
process continued after addition of water forming a homogeneous structure and geopolymers
bonding increased in intensity which was observed through IR analysis. It was believed that presences
of crystalline phase as seen in XRD diffractogram were good for mechanical properties.
Geopolymeric powder was synthesized by applying geopolymerization process. By adopting the concept
of ‘‘just adding water’’, resulted geopolymer paste was produced from geopolymeric powder.
Compressive testing, bulk density measurement SEM, EDX, XRD and IR analyses were performed. The
results concluded that solids-to-liquid and waterglass-to-NaOH solution ratios affected the strength significantly
and these ratios were optimized at 0.80 and 0.20, respectively. The densification of microstructure,
presence of amorphous gels and crystalline zeolite phases as well as the increase in the geopolymer
bonding could be revealed in this study.
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
of NaOH and sodium silicate solutions). The NaOH solution was prepared at a concentration of 6-14 mol/L and was
mixed with the sodium silicate solution at a Na2SiO3/NaOH mass ratio of 0.24 to prepare an activator solution. The
kaolin-to-activator solution mass ratio used was 0.80. This paper aimed to analyze the effect of NaOH concentration on
the compressive strength of kaolin geopolymers at 80
◦
C for 1, 2, and 3 d. Kaolin geopolymers were stable in water, and
strength results showed that the kaolin binder had adequate compressive strength with 12 mol/L of NaOH concentration.
When the NaOH concentration increased, the SiO2/Na2O decreased. The increased Na2O content enhanced the dissolution
of kaolin as shown in X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses. However,
excess in this content was not beneficial for the strength development of kaolin geopolymers. In addition, there was the
formation of more geopolymeric gel in 12 mol/L samples. The XRD pattern of the samples showed a higher amorphous
content and a more geopolymer bonding existed as proved by FTIR analysis.
The analysis on mechanical-activated kaolin showed that kaolin’s particle size decreased accompanied
with increase in surface area along with activation time. XRD diffraction peaks of kaolinite decreased
as well. FTIR analysis demonstrated the distortion of the tetrahedral and octahedral layers after the
activation process. The compressive strength of geopolymers produced using mechanical-activated
kaolin rose with activation time from 1 to 28 days. Thus, mechanical activation was deduced to have
altered the particle size and surface area as well as the reactivity of kaolin towards geopolymerization
reaction.
the initial raw materials, solidification process, and amount of mixing water as well as the curing
conditions. This study aimed to investigate the effect of curing temperature (room temperature,
40°C, 60°C, 80°C and 100°C) and curing time (6h, 12h, 24h, 48h and 72h) on the geopolymer
pastes produced from geopolymer powder. The results showed that curing at room temperature was
unfeasible. Heat was required for the geopolymerization process, where strength increased as the
curing temperature was increased. Moderate elevated curing temperature favored the strength
development of geopolymer pastes in comparison with those treated with extreme elevated curing
temperature. When geopolymer paste was subjected to extreme elevated curing temperature, shorter
curing time should be used to avoid deterioration in strength gain. Similarly, longer curing time was
recommended for moderate elevated curing temperature. The microstructure of geopolymer paste
cured at moderate curing temperature showed obvious densification of structure. In contrast, the
structure formed was weak and less compact at very high elevated curing temperature.
processing of calcined kaolin geopolymeric powder. This is a new process developed using the
geopolymerization process. Geopolymer slurry was prepared from calcined kaolin and activating
solution (mixture of NaOH and Na2SiO3). This slurry was allowed to solidify in oven and then
crushed and grounded to fixed particle size. Compressive testing and SEM analysis were performed
in this study. The results showed that the solidification condition at 80 ºC for 4 hours was the best to
synthesize the geopolymeric powder where this solidification condition results in geopolymeric
powder which can produce higher strength resulted geopolymer paste. The microstructure showed
more intervening gel phase which indicates that the geopolymerization process continued to react
after the addition of water to the calcined kaolin geopolymeric powder.
alkaline activation of calcined kaolin followed by solidification and pulverizing process. The
geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this
paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted
geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of waterto-
cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here
was based on geopolymerization process. The compressive strength, setting time and SEM analysis
of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-togeopolymer
powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120
minutes and reached final setting after about 4 hours of setting. Microstructure showed the
formation of geopolymeric gel after the addition of water to the geopolymeric powder.
mechanical activation of kaolin on the compressive strength and morphological properties of the
geopolymers has been studied. Mechanical activation of the kaolin results in particle size reduction
and morphology changes with increase in reactivity. Mechanical activated kaolin has overall higher
strength gain compared to raw kaolin. Wider particle size distribution and some spherical particles
produced, promote a higher packaging density in the sample resulting in higher strength obtained.
Mechanically activation of kaolin can be considered as an alternative method to achieve better
geopolymerization reaction for kaolin-based geopolymer.
geopolymers. Kaolin-based geopolymers were prepared by the alkali-activation of kaolin with alkali
activating solution (mixture of NaOH and Na2SiO3 solutions). The compressive testing, XRD and
FTIR analysis were performed. The compressive strength results showed that curing at 60°C for 3
day achieves better strength. XRD analysis revealed that the entire geopolymer sample reduced in
intensities and became amorphous at longer age while FTIR analysis indicated the presence of
geopolymer bondings. Both analyses showed the presence of large amount of un-reacted remained
in the system were the reason of the low compressive strength obtained.
produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground
to obtain cement powder. Ultilizing the concept of “just adding water”, hardened cement paste could be produced
from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have
a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium
silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing
route to produce cement powder by “just adding water” was possible, and the structure became denser and fewer
unreacted particles were observed.
Curing profile serves as a crucial parameter in synthesis of geopolymers. In this paper, the influence of curing
temperature and curing time on the properties of kaolin-based geopolymer was studied. The samples were separated
into several curing conditions; including curing at ambient temperature, 40°C, 60°C, 80°C and 100°C for 1 day, and
up to 3 days. The compressive strength and SEM analysis of geopolymer products were evaluated. Results showed
that curing condition has a significant effect on the mechanical properties of kaolin-based geopolymer. Generally,
curing at ambient temperature was not feasible, while increase in temperature favored the strength development. In
addition, prolonged curing time improved the geopolymerization process, and led to higher strength gain. However,
curing at high temperature for a long period of time caused failure of the sample at a later age.