Novel synthesis of industrial and agro waste-derived non-autoclaved aerated geopolymer composites

Resource conservation in construction materials remains a critical challenge, with the valorisation of industrial by-products and agricultural residues offering a sustainable waste-to-resource pathway. In this study, aerated geopolymer composites synthesised from ground granulated blast furnace slag (GGBS) and rice husk ash (RHA) provide a low-carbon, non-autoclaved alternative to Portland cement, combining lightweight features with enhanced durability. Precursors combined with other constituent materials were mixed with aluminum powder as an aerating agent and activated using Na₂SiO₃/NaOH solutions of varying alkalinity (6–10 M). The mixture was then cured under ambient conditions, avoiding energy-intensive autoclaving. Results demonstrate that alkali concentration critically governs gel chemistry, pore refinement, and durability indices. The optimum mix (8 M) achieved balanced performance, with a compressive strength of 17.4 MPa, reduced density, refined porosity, low water absorption, and superior resistance against acid, sulphate, and seawater exposure. It also exhibited a thermal conductivity of 0.483 W/m.K, confirming the synergy of mechanical strength and thermal insulation. Microstructural and thermal analyses validated the formation of a dense C–A–S–H/N–A–S–H network with high thermal stability. Cost–carbon benchmarking further revealed substantial reductions in embodied CO₂ emissions (up to 80 %) and production costs (up to 50 %) compared to OPC, establishing ambient-cured aerated geopolymer composite mortars as a scalable and eco-efficient solution for sustainable infrastructure. • Valorisation of GGBS–RHA wastes into non-autoclaved aerated geopolymer composites. • Ambient-cured NASAA-GPC avoids energy-intensive autoclaving and lowers CO₂ footprint. • Optimum 8 M mix achieved 17.4 MPa strength with 0.483 W/m·K thermal conductivity. • Superior resistance to acid, sulphate, and seawater ensured long-term durability. • Up to 80 % CO₂ and 50 % cost reduction over Portland cement confirms eco-efficient scalability.