Properties of lightweight one-part geopolymer mortars containing pumice aggregates: mechanical, microstructure, and life cycle assessment

This study examines the mechanical, microstructural, and environmental properties of lightweight geopolymer mortars incorporating fly ash, ground granulated blast furnace slag, and pumice aggregate. The mortars were prepared with sodium contents of 8% and 10% and subjected to heat curing at 75 °C for 24, 48, and 72 h. Experimental results indicate that higher slag content enhances early-age strength but reduces workability. Compressive strength and ultrasonic pulse velocity (UPV) decreased at elevated temperatures, yet at 900 °C, strength increased due to glassy phase formation. FESEM and EDX analyses revealed increased porosity and micro-cracking at high temperatures, with a denser structure forming at 900 °C. Life Cycle Assessment (LCA) results demonstrate that geopolymer mortars have up to 58% lower global warming potential (GWP) than cement-based mortars. Raw material transportation and alkali activator usage significantly contribute to environmental impacts. Implementing local material sourcing reduced GWP by 46%, highlighting its potential for sustainability improvements. In conclusion, lightweight geopolymer mortars present a sustainable alternative to conventional cementitious materials, offering reduced carbon emissions and lower environmental impact while maintaining structural integrity under elevated temperatures.