Laterite-GGBS geopolymer composites: Synthesis and thermal performance under static and cyclic loadings

As the construction industry seeks sustainable alternatives to conventional cement, geopolymers have emerged as promising low-carbon binders. Among the various potential precursors, laterite soil—abundant in tropical regions and rich in aluminosilicates—offers an underexplored yet viable source for geopolymer synthesis, especially when enhanced with industrial by-products like Ground Granulated Blast Furnace Slag (GGBS). This study focuses on evaluating the thermal performance of laterite-based geopolymer composites by varying NaOH molarity (10M and 12M) and calcination temperatures (600°C, 700°C, and 800°C) of laterite. Six mix combinations were designed and tested for flowability, setting time, density, water absorption, and compressive strength under both static and cyclic thermal exposure up to 800°C. Advanced characterization using XRD, TG-DTA, and FESEM-EDS provided insight into the phase transformations and microstructural changes. The investigation reveals that the composite with 12M NaOH and laterite calcined at 700°C offered the best balance of workability, strength retention, and thermal resistance. The compressive strength initially increased at 200°C due to densification but degraded beyond 400°C owing to microcracking and gel decomposition. XRD confirmed geopolymerization with the formation of amorphous gels and new crystalline phases, while TG-DTA and FESEM highlighted multi-stage weight loss and matrix disruption at high temperatures.