Mix design of FA-GGBS based lightweight geopolymer concrete incorporating sintered fly ash aggregate as coarse aggregate

Geopolymer concrete (GPC) is emerging as a sustainable alternative to conventional Portland cement-based concrete due to its significantly reduced carbon footprint and enhanced durability. To mitigate the environmental hazard posed by the disposal of fly ash (FA) and ground granulated blast furnace slag (GGBS) waste and reduce cement consumption, effective promotion of the geopolymerization technique is necessary. Incorporating sintered fly ash coarse aggregate (SFA) in GPC makes the concrete light in weight. This study involves the synthesis of geopolymer technology using FA and GGBS, as the primary source material. Due to the lack of an appropriate mix design method for using SFA in GPC, their application as a structural concrete is scanty. By using FA and GGBS with 100% SFA, a novel mix design methodology that offers greater simplicity and consistency is established in the present study. The proposed method is further verified by developing different concretes with alkali content to binder (AC/B) ratios ranging from 0.3 to 0.8. Fresh densities range between 1860 and 1930 kg/m3 and maximum compressive strength of nearly 50 MPa was attained after 28 days of ambient curing. The binder penetration and internal curing in SFA indicate that GGBS and FA have a superior synergistic effect on the efficacy of lightweight GPC using SFA.