Synthesis of ambient-cured geopolymer with recycled glass as binder and fine aggregate: Enhancing mechanical and durability performance

Geopolymers synthesized from industrial by-products provide a sustainable, low-carbon substitute for traditional cement. This study explores a novel approach involving the combined use of waste glass powder (GP) as a binder and glass sand (GS) as fine aggregate in geopolymer mortar under ambient curing conditions. Mortars containing 50 % GP, 25 % fly ash (FA), and 25 % ground granulated blast furnace slag (GGBS) were developed, with natural sand replaced by GS at varying levels (25–100 %). The effects of GS on mechanical, durability, and microstructural characteristics of the mortars were systematically evaluated. The results demonstrate that 50 % GS replacement develops an optimal performance, with improvements of 9 % in flowability, 13 % in compressive strength, and 14 % in splitting tensile strength, as well as reductions of 71 % in drying shrinkage and 2 % in water absorption compared to the control mix without GS. Microstructural analyses revealed that reactive silica from GS enhances geopolymerization, contributing to increased amorphous gel formation, reduced porosity, and a denser matrix. The outcomes demonstrate that the dual incorporation of GP and GS under ambient curing presents an effective pathway for valorizing glass waste while improving the performance and sustainability of geopolymer mortars. • Ambient-cured geopolymer formulated with recycled glass powder and sand. • 50 % glass sand replacement optimizes strength and durability performance. • SEM and EDS confirm dense matrix and active gel formation with glass sand. • XRD analysis reveals formation of N-A-S-H and C-A-S-H gels in matrix by glass sand. • Porosity tests show improved microstructure.