Effect of Water-Solids Ratio on the Compressive Strength, Degree of Reaction and Microstructural Characterization of Fly Ash-Waste Glass-Based Geopolymers

Abstract

On a global scale, the production of portland cement is responsible for approximately 5% of carbon emissions. In an effort to reduce carbon emissions, alternative binders are being implemented into the cement industry. Geopolymer technology combines aluminosilicate sources with an alkali solution to create a binder that has the potential to completely eliminate the need for portland cement in concrete. There has been limited research regarding the effect that the water-solids ratio (similar to water-cement ratio) has on geopolymer performance. For that reason, this research focused on the effect of the water-solids ratio on compressive strength, degree of reaction, and microstructure of fly ash – waste glass-based geopolymer mortars. Geopolymer mortars made of varying levels of fly ash and waste glass were produced. Three water-solids ratios were examined for each mixture, and compressive strength, degree of reaction, and microstructure characteristics were investigated in an effort to discover trends. Results showed that the water-solids ratio had an effect on compressive strength, but not a significant effect on degree of reaction. When comparing mixture compositions, mixtures containing fly ash seemed to be more sensitive to the water-solids ratio. Unreacted particles and different types of zeolites, depending on the mixture composition, were observed during microstructural analysis. Locations where particles seemed to have been “pulled-out” of the geopolymer paste were also observed in mixtures with higher water-solids ratios. However, more research is required to confirm these conclusions.