EXPERIMENTAL STUDY ON THE KINETICS OF GEOPOLYMER’S SOLIDIFICATION

Geopolymer material is formed through the reaction of silica and alumina oxides
with alkali activator and has appeared as a viable alternative to the Ordinary Portland
Cement (OPC) in the construction field due to good properties such as more
resistance to corrosion and fire, high compressive and tensile strength, low
permeability and good acid resistance. Furthermore, the production of geopolymer
concrete offers a solution to the environmental issue as it utilized the industrial waste
that consist of Si and Al such as fly ash and wastewater from chemical industry.
However, there are limited research were conducted to investigate the effect of
parameters before setting time especially at the solidification phase in
geopolymerization process and explained it through Avrami‟s Kinetic Theory‟s
perspective that closely related to the nucleation of new particles and growth rate of
particles into spherical shaped. This research is to study the solidification of fly ash
geopolymer by determining setting time by varying curing temperature, alkaline
activator and concentrations of alkaline. However, prior to the study of the effects,
the feasibility of equipment used between LFRA Texture Analyzer and Vicat Needle
was determined. Further characterization on the phase exists during the solidification
process of geopolymer was done using XRD analysis. Besides that, this research also
focuses on the transformation of crystal in geopolymerization through Avrami‟s
Kinetic Theory. From the experimental results, the alkaline activation with the
addition of sodium silicate (Na2O3Si) to sodium hydroxide (NaOH) produced
shortest time for solidification geopolymer followed by potassium hydroxide (KOH)
solution and sodium hydroxide (NaOH) solution. Moreover, the increase in
concentration of alkaline solution and curing temperature produce shorter setting
time for geopolymer‟s solidification. From the Avrami Kinetic Theory‟s perspective,
the growth form of crystal in the geopolymerization process exhibits two and three
dimensional structure while certain samples of geopolymer shows there are presence
of secondary nucleation in geopolymer‟s growth.