Enhancing geopolymer synthesis through calcination: Increasing the potential of natural material utilization

In this study, two types of calcined pozzolan were used as raw materials for geopolymer synthesis. The mechanical and microstructural properties of the geopolymers were investigated through compressive strength, XRD, FTIR and SEM/EDX analyses. Results indicated that the clinoptilolite-based geopolymer developed sufficient strength at room temperature, eliminating the need for thermal curing, a key limitation of natural material-based geopolymers. In contrast, despite calcination, the feldspar-based geopolymer exhibited inadequate activation and failed to achieve significant strength gains under both ambient and 50 °C curing conditions. This finding emphasizes the critical role of calcination in material activation while highlighting the significant impact of raw material composition on the overall performance of geopolymers. XRD and FTIR analyses revealed reduced clinoptilolite peak intensities, indicating its active involvement in geopolymer formation, while the presence of an amorphous hump suggested a well-developed geopolymeric gel network. SEM/EDX confirmed a stable Si/Al ratio in the clinoptilolite-based geopolymer, further supporting its enhanced mechanical performance. These findings highlight the significance of mineralogical characterization in predicting geopolymer reactivity and optimizing synthesis conditions.