Impact of curing parameters on the properties of geopolymers derived from different class F fly ashes

Abstract

This study investigates the effect of curing temperature and duration on the properties of Class F fly ash-based geopolymers (FGPs). FGP samples produced from three different fly ash sources were cured under various temperatures (ambient, 60 °C, 75 °C, and 90 °C) and durations (8, 24, 72, and 168 h). The compressive strength development, phase characterisation (FTIR and XRD) and microstructural evaluations (SEM and MIP) were performed. The major results reveal that although the chemical compositions of the fly ashes are quite similar, properties such as particle size distribution and particle morphology have a substantial impact on the properties of the FGPs. Fly ashes with a particle size distribution in a narrow range and mostly spherical morphology show higher reactivity, thereby minimising the requirement for extreme curing conditions. Therefore, FGPs produced with high-reactivity fly ash achieved high strength even at lower curing temperatures and shorter durations.