Synergistic effects of GGBFS addition and oven drying on the physical and mechanical properties of fly ash-based geopolymer aggregates

Abstract

Conventional coarse aggregates, extracted from natural sources, pose environmental challenges such as habitat destruction, resource depletion, and high energy consumption. To mitigate these effects, this study prepared geopolymer aggregates (G.A.) using fly ash–GGBFS and an alkali ac- tivator solution through pelletization. Furthermore, two aggregate drying methods, oven drying, and ambient air drying, are adopted to evaluate their optimal performance through physical and mechanical tests. The results Indicated that oven-dried geopolymer aggregates exhibited optimal behavior in all experimental aspects compared to ambient air-dried aggregates. Specifically, the 80% fly ash–20% GGBFS mixed aggregates demonstrated lower crushing value (20.80%), impact value (24.7%), water absorption (13.67%), and abrasion values (7.01%) than other mixes. No considerable difference was observed in the density and specific gravity of aggregates between the two drying methods. Subsequently, these aggregates were used as a 100% replacement for conventional coarse aggregates in concrete, and the concrete's mechanical properties, such as compressive, split tensile, and flexural strengths, were investigated. Please update the following sentence in place of the highlighted sentence. The mix M3 (i.e., 80% fly ash–20% GGBFS mixed aggregates incorporated concrete) showed superior performance and are considered the opti- mum mix. Specifically, in the compressive strength results, the mix M3 showed a 26.31% and 14.28% strength increase compared to the 100% fly ash aggregates incorporated concrete mix in oven-dried aggregates and ambient-dried aggregates incorporated concrete, respectively. The lin- ear regression equation derived from the experimental results was used to predict the split tensile and flexural strength, showing a good correlation between the experimental and expected results.