Hope or hype? Evaluating the environmental footprint of reclaimed fly ash in geopolymer production

This study explores the suitability of reclaimed fly ash (RFA) as an alternative aluminosilicate material for geopolymer production based on strength and sustainable potential compared to ground granulated blast furnace slag (GGBFS). A cradle-to-gate life cycle assessment was conducted to examine the environmental impact of experimentally developed geopolymer mixtures that incorporate varying quantities of RFA and GGBFS compared to cement mortar (CM). Moreover, a multi-criteria decision-making analysis was performed, incorporating different weightage scenarios, aimed to conduct sensitivity analysis and determine optimal mix design based on quality and environmental burden. The results revealed that RFA/GGBFS-based geopolymers can reduce global warming potential (GWP) by 29.6–35.4 % compared to CM. Furthermore, 20–80 % RFA-based geopolymers reduce GWP, acidification potential, and energy consumption by 1.6–8.2, 3.8–28.9, and 3.1–17.7 % compared to 100 % GGBFS-based geopolymer, respectively. This research's promising findings may promote sustainable development in the construction industry by replacing cement with geopolymers and reclaiming landfilled fly ash.