Influence of activator composition on the properties of calcined kaolin geopolymeric powder

Abstract

This paper studied the influence of activator composition on the properties of calcined kaolin geopolymeric powder. The alkaline activation of calcined kaolin was performed in mixture of waterglass liquid and NaOH solution at ratios ranged between 0.12 – 0.28. The activator modulus (SiO2/Na2O ratio) calculated from the mix composition were in range of 0.17 – 0.38. The results showed that the waterglass liquid/NaOH ratios peaked at 0.20 and dropped for any increase in this ratio. The bulk densities results were consistent with the compressive strength measured. Bulk densities values of resulted geopolymer paste were quite low, which were between 950 kg/m3 to 1050 kg/m3. The H2O/Na2O molar ratio has significant effect on the bulk density and thus affecting the compressive strength of the resulted geopolymer paste. The microstructure revealed the densification of the structure after the addition of water and more intervening structures were observed in microstructure of resulted geopolymer paste with waterglass/NaOH ratio of 0.20.