Development of sustainable green geopolymer concrete incorporating sugarcane bagasse ash

Sugarcane bagasse ash (SCBA) is increasingly being considered as an alternative aluminosilicate source for geopolymer binders. however, limited studies have comprehensively evaluated the combined effects of high SCBA replacement levels, alkaline activator molarity, thermal performance, microstructural characteristics, and economic feasibility. Therefore, this study investigates the use of SCBA as a partial and near-complete replacement of the total binder in geopolymer concrete. Fifteen mixtures were prepared with SCBA replacement levels of 0, 25, 50, 75, and 95% at NaOH molarities of 12, 14, and 16 M. Fresh, mechanical, durability, thermal, and microstructural properties, along with cost analysis, were comprehensively evaluated. The mixture containing 25% SCBA and activated with 14 M NaOH showed the best overall performance, with a compressive strength of 30.13 MPa, a splitting tensile strength of 3.02 MPa, and a sorptivity of 2.449 × 10⁻³ g/cm·s⁰·⁵ at 28 days. After exposure to 200 °C, its compressive strength increased by 39.30%, before declining at higher temperatures. Mixtures with higher SCBA contents showed slower strength loss, suggesting improved thermal stability. SEM-EDX observations were consistent with these results, as the optimum mixture showed a dense geopolymeric matrix, while higher SCBA contents and elevated temperatures led to increased porosity and microcracking. The cost analysis also showed that production cost decreased considerably as the SCBA content increased. Overall, the results indicate that moderate SCBA replacement can provide a practical balance between mechanical performance, durability, thermal resistance, and cost, supporting the use of SCBA as a sustainable binder component in geopolymer concrete.