Optimization of compressive strength and short-term chemical resistance of agro-wastes-based-geopolymer concrete

Interest in geopolymer concrete (GPC) made from agricultural wastes has increased due to the growing demand for environmentally friendly building materials; however, few studies have compared the short-term chemical resistance performance and optimisation of multi-source ash-based systems in harsh environments. The compressive strength, short-term chemical resistance, and optimisation of GPC made from sawdust ash (SDA), cassava peel ash (CPA), and rice husk ash (RHA), all of which have combined SiO₂ and Al2O₃ values greater than 70%, guaranteeing acceptability as aluminosilicate precursors are examined in this work. Response Surface Methodology (RSM) was used to systematically optimise important processing factors such as activator-to-source ratio, curing temperature, curing duration, and NaOH molarity. An alkaline activator consisting of sodium silicate and sodium hydroxide (1:2.5) was utilised. The robustness of the optimisation framework was confirmed by the development and validation of statistically significant predictive models using ANOVA (Adjusted and Predicted R2 > 0.82). For RHA, SDA, and CPA-based GPC, the optimised mixes attained compressive strengths of 25.32 MPa, 24.10 MPa, and 20.44 MPa, respectively. In all harsh settings, the short-term chemical resistance order of RHA > SDA > CPA was verified, with CPA-based systems exhibiting the highest susceptibility (up to 11.9%) and RHA-based geopolymer concrete exhibiting the best short-term chemical resistancewith the lowest strength loss (≈5.9–7.5%). Overall, this study shows that silica-rich RHA-based GPC is a viable and sustainable substitute for structural applications in challenging service conditions by bridging the knowledge gap regarding the combined effects of agro-waste precursors and processing variables on both strength optimisation and short-term chemical resistance performance.