Mechanical properties and elevated temperature performance of structural lightweight geopolymer concrete

Ambient-cured structural lightweight geopolymer concrete (LWGPC) with reliable high-temperature performance remains insufficiently documented, as most existing studies rely on thermal or steam curing, which limits field applicability. This study (i) optimized production parameters to develop LWGPC that hardens under laboratory conditions and (ii) evaluated its behavior at elevated temperatures (150-750 °C) relative to a normal-weight geopolymer concrete (NWGPC) reference. Investigated parameters included precursor dosage, NaOH molarity, alkali-to-binder (a/b) ratio, aggregate gradation, silica fume content, and superplasticizer demand. Based on fresh and hardened properties, two optimized LWGPC mixtures were selected for thermal testing. Life Cycle Assessment (LCA) was also conducted to evaluate CO₂-equivalent emissions and energy consumption. Results demonstrated that LWGPCs incorporating pumice aggregate exhibited superior property retention and structural integrity compared to NWGPC across all temperatures. Overall, the findings indicate that pumice-based, ambient-cured geopolymer concretes achieve enhanced thermal resilience with lower embodied impacts than Portland cement-based mixes, making them promising for field implementation.