Comparative Evaluation of Fly Ash and GGBS-Based Geopolymer Concrete: Mechanical and Durability Performance

The urgent need for sustainable alternatives to Ordinary Portland Cement (OPC) has driven the exploration of geopolymer concrete (GPC) as a viable solution to reduce carbon emissions and utilize industrial by-products. This study presents a comparative evaluation of geopolymer concrete synthesized using two primary binders: Class F fly ash and ground granulated blast furnace slag (GGBS). The research investigates the influence of these materials on fresh properties, mechanical performance (compressive, split tensile, and flexural strengths), and durability under acidic and sulphate environments. Fly ash-based GPC required elevated curing temperatures for optimal strength gain, while GGBS-based GPC demonstrated rapid early-age strength under ambient conditions due to its higher calcium content. Experimental results revealed that GGBS-GPC exhibited superior early compressive and flexural strengths, whereas fly ash-GPC showed enhanced durability under aggressive chemical exposure. The findings highlight the potential of GPC, particularly hybrid blends, to replace OPC in structural applications, contributing to reduced environmental impact and enhanced construction sustainability. The study also emphasizes the necessity for further standardization of mix design and curing protocols to facilitate the practical adoption of geopolymer technologies in mainstream construction.