Effects of relative humidity on the properties of fly ash-based geopolymers

The investigation into geopolymers (GPs) is developing rapidly due to the properties they offer. In spite of this, few researchers have reported on the relative humidity (RH) during the curing process and its impacts on alkali-activated fly ash-based geopolymers. This study investigates the mechanical and microstructural properties of alkali-activated fly ash (FA) based geopolymers cured at various RH ratios at 75 °C. Compressive and flexural strength tests were conducted to determine the mechanical properties, and X-ray diffraction (XRD), as well as scanning electron microscopy (SEM) tests were carried out to study the microstructural properties of the mixtures. The study revealed that both compressive and flexural strengths improved when RH was set at 70%. The microstructural analysis indicated a mixture of unreacted fly ash particles, some crystals, and a reacted gel phases as the geopolymerization products.