Effect of natural zeolite replacement with waste marble powder on the physical, mechanical, and microstructural properties of geopolymers at different curing temperatures

Abstract Geopolymer technology offers a sustainable pathway for reducing the environmental impact of construction materials through the valorization of industrial wastes. Given this, waste marble powder (WMP), generated in large quantities worldwide, represents a promising alternative precursor to conventional aluminosilicate sources. The primary aim of this study is to evaluate the feasibility and performance of natural zeolite (NZ)–based geopolymers incorporating WMP, with particular emphasis on the effects of precursor replacement level, silicate modulus (MS), and curing temperature. Geopolymer composites were produced by partially replacing NZ with WMP at levels of 0–30 %, using binary alkali activation with MS values of 0, 0.05, and 0.1, and curing at temperatures of 95 ºC, 105 ºC, and 115 ºC. Physical, mechanical, and microstructural properties were evaluated, alongside cost, embodied energy analyses, and mix design optimization. The results demonstrate that WMP incorporation significantly improves the physical and mechanical properties of NZ-based geopolymers, with an optimal replacement level of 30 %. Material costs were reduced by 6.0–10.8 % while maintaining comparable embodied energy emissions. Geopolymers with MS = 0 achieved maximum compressive strength (25.2 MPa) at 115 ºC, whereas systems with higher MS values exhibited optimal performance at 105 ºC, indicating that lower MS formulations require higher curing temperatures but yield superior mechanical performance. Increasing MS increased both production cost and embodied energy due to higher sodium silicate demand. Mix design optimization confirmed that high WMP content combined with low MS values produces geopolymers with enhanced compressive and flexural strength. Overall, the findings highlight the potential of WMP as a sustainable geopolymer precursor and support its application in medium-grade structural components, contributing to waste reduction and resource-efficient construction practices.