<![CDATA[The environmental consequence of ordinary Portland cement (OPC), which accounts for 7–8% of worldwide CO₂ emissions, demands the development of low-carbon alternative binders. This research develops and enhances geopolymer concrete (GPC) obtained from agro-waste, utilizing rice husk ash (RHA) and sugarcane bagasse ash (SCBA) as supplementary aluminosilicate precursors in combination with ground-granulated blast-furnace slag (GGBS). A Central Composite Design within Response Surface Methodology optimized three variables—RHA content (10–40%), SCBA content (10–30%), and NaOH molarity (8–12 M)—across twenty mix configurations. Compressive, split-tensile, and flexural strengths were assessed at 7 and 28 days, along with microstructural characterization using XRD, SEM-EDX, and FTIR techniques. The optimized formulation (10% RHA, 10% SCBA, 11.9 M NaOH) attained compressive strengths of 39.2 MPa and 47.1 MPa at 7 and 28 days, respectively, in addition to split-tensile and flexural strengths of 7.34 MPa and 7.54 MPa at 28 days. All models produced R² values greater than 0.97 and an Average Relative Deviation (ARD) below 5%. Microstructural investigation verified the development of dense N-A-S-H and C-A-S-H gels, with the optimized mixture achieving an approximate 60% reduction in embodied CO₂ compared to OPC. This study is the inaugural investigation to concurrently optimize the ternary RHA–SCBA–GGBS system utilizing RSM-CCD, illustrating that agricultural by-products can attain structural-grade performance while promoting circular economy principles in sustainable construction.]]>
