Ambient and Elevated Temperature Geopolymerization Behaviour of Class F Fly Ash

Abstract

Geopolymerization is the process, where synthetic alkali activated alumino-silicate material is produced by reaction of a solid alumino-silicate with a highly concentrated aqueous alkali hydroxide or silicate solution. Depending on the raw material selection and processing conditions, geopolymers can exhibit a wide variety of properties and characteristics, including high compressive strength, fast or slow setting, acid resistance, and fire resistance. Fly ash, a by-product of coal fired power plant, is produced during combustion of coal. Fly ash is a powdery, aluminosilicate material along with minor impurities which is suitable for geopolymer reaction. The geopolymerization behaviour of class F fly ash has been studied in a temperature range of 27°-55°C using isothermal conduction calorimeter with different alkali concentrations. It was observed that the rate of reaction got intensified and increased with temperature. Compressive strength of the resulting geopolymer was also found to increase with temperature more significantly during early days. Attempt has been made to correlate the reaction with structure and properties.