Utilization of GGBS, Fly Ash, and Recycled Aggregates for Sustainable Geopolymer Concrete: A Carbon Reduction Approach

Cement production contributes significantly to greenhouse gas emissions, highlighting the need for sustainable alternatives. Geopolymer concrete (GPC) offers a lower carbon footprint and serves as a promising substitute for traditional cement-based concrete. This study investigated the use of fly ash, ground granulated blast furnace slag (GGBS), recycled coarse aggregate, alkaline solutions (sodium silicate and sodium hydroxide), and fine aggregate to make GPC. Varying percentages (each ranging from 10 to 100%) of fly ash and GGBS, different molarities (6, 10, and 14 M) of sodium hydroxide, and different ratios (1.5, 2.0, 2.5, and 3.0) of sodium silicate to sodium hydroxide were examined to determine the optimal combination for strength and durability of GPC. Two curing methods, ambient curing and membrane curing, were employed. The results showed that increasing the percentage (from 0 to 100%) of GGBS in the mix led to a higher compressive strength of 4122 psi and a lower water absorption of 4.83% at day 28. GGBS as the sole binder exhibited the highest strength and durability, and GPC with a 50% GGBS–50% fly ash composition outperformed conventional cement concrete. Membrane curing consistently yielded higher compressive strength compared to ambient curing. The study concluded that GGBS-fly ash-based recycled aggregate GPC could significantly reduce waste and the carbon footprint in the construction industry.