Performance and microstructural optimization of sustainable geopolymer mortars using fly ash, ground granulated blast furnace slag, and rice husk ash

Abstract The environmental consequences of conventional Portland cement production necessitate sustainable alternatives that reduce carbon emissions. This paper presents the development and optimization of geopolymer mortars using fly ash (FA), ground granulated blast‐furnace slag (GGBFS), and rice husk ash (RHA) as binding materials. The effects of the RHA content (5%–25%), NaOH molarity (8, 12, 16 M), and water glass moduli (1.99, 2.92) on the mechanical and rheological properties were systematically investigated under ambient and oven curing conditions. Compressive strengths exceeding 73 MPa were achieved with an optimal mix containing 50% FA, 45% GGBFS, and 5% RHA, and cured under controlled conditions. Additionally, microstructural analysis using scanning electron microscopy (SEM) and energy‐dispersive x‐ray spectroscopy (EDAX) revealed dense geopolymer matrices with Si/Al ratios of ~2.0, contributing to superior mechanical strength and durability. Key findings showed that replacing GGBFS with RHA enhanced standard consistency and reduced permeability, whereas higher NaOH molarity significantly accelerated setting and strength development. This research highlights the transformative potential of geopolymer technology in valorizing industrial and agricultural by‐products, achieving an 80% reduction in the carbon footprint compared to ordinary Portland cement, and promoting sustainable construction practices.