EFFECT OF CALCINATION TEMPERATURE OF THE KAOLIN AND MOLAR Na۲O/SiO۲ ACTIVATOR RATIO ON PHYSICAL AND MICROSTRUCTURAL PROPERTIES OF METAKAOLIN BASED GEOPOLYMERS

Metakaolinite-based geopolymer has been synthesized at about ۲۵ °C from metakaolin which has been calcined in different temperatures (۶۰۰-۹۰۰ °C) and different Na۲O/SiO۲ ratio activator (۰.۳-۱.۱). Compressive strength and microstructure of cement pastes after ۷-۲۸ days curing at ambient temperature were measured. Compressive strength tests on the samples showed that the sample made with calcined kaolin at ۷۰۰ °C and molar ratio of ۰.۶ has highest average compressive strength of ۳۲ MPa after ۲۸ days of curing. Evaluation of infrared spectroscopy (FTIR) and microstructure showed that geopolymer cement developed and new molecular structure established