Role of alkali concentration on reaction kinetics of fly ash geopolymerization

Abstract

This paper assesses the effect of alkali concentration on the reaction kinetics and mechanism of fly ash geopolymerization. The kinetic parameters of fly ash with different alkali (6–10 M NaOH) solution have been determined by using heat of reaction data measured at isothermal conduction calorimeter at different reaction temperatures, 34–60 °C. With increasing alkali concentration the peak gets intensify and position shifts towards higher time and total heat of reaction enhances. At higher alkali concentration amount of Al and Si dissolute increases, thus, higher energy is required to initiate and forward the reaction. However, the kinetic parameters are varying with alkali, but no alternation is determined in the involved reaction mechanism, nucleation and growth. The apparent activation energy has been evaluated by rate method, suggests three main steps such as dissolution, gel formation and restructuring process of geopolymer reaction. Fly ash geopolymerization is kinetically favored in between 39 and 45 °C temperature with all alkali concentration in experimented condition.