VARIABLE FACTORS CONTROLLING AMORPHOUS-ZEOLITE PHASE TRANSFORMATION IN METAKAOLIN BASED GEOPOLYMER

Abstract

Metakaolin based geopolymer binder was synthesized using variable factors such as Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O molar ratios as well as curing time. Metakaolin was used as an alumino silicate source incorporating with strong alkali activators; sodium hydroxide solution to undergo polycondenation and hence a formation of hardened geopolymeric binder. This work was aimed to investigate the effect of Na2O/SiO2, Na2O/Al2O3 and H2O/Na2O ratios, as well as curing time on phase transformation. The chemical composition, phase development and microstructure of reaction products were examined by X-ray fluorescence, X-ray diffraction analysis and scanning electron microscopy with respect to their final compressive strength. Increasing the molar ratios of Na2O/Al2O3 and H2O/Na2O tended to favour the transformation of amorphous gel to various types of crystalline zeolite. Sodalite (pseudo-phase zeolite) and zeolite belonging to the Faujasite group, as well as zeolite X and A were identified in these mixtures. Based on this study, systems that favoured the formation of zeolitic products tended to possess lower strengths.