Effect of Partial Replacement of GGBFS with Wheat Husk Ash (10–30%) on the Compressive Strength of Low-Alkali Geopolymer Concrete under Ambient Curing

Geopolymer Concrete (GPC) has gained acceptance as a solution for concrete applications, particularly those activated at low-alkali conditions and containing industrial or agricultural wastes, due to the increasing demand for more sustainable alternatives to Ordinary Portland Cement (OPC). This study investigates the effect of partial replacement of ground granulated blast furnace slag (GGBFS) with wheat husk ash (WHA) at 10%, 20%, and 30% on the compressive strength of geopolymer concrete. A combination of sodium hydroxide (6M) and sodium silicate solution at a concentration of 6M and 10% by weight silica fume to enhance active ability. At 7, 28 and 90 days compressive strength was determined. The improvement of long-term strength (90 days) was observed, with a 10% replacement of GGBFS by WHA showing almost complete retention of the control performance (up to 20% replacement of GGBFS by WHA). X-ray fluorescence (XRF) analysis indicated that the incremental increase of WHA raised SiO₂ concentration and decreased CaO concentration which impacted the gel composition and led to the increase in strength. WHA was found to be an attractive and a sustainable pozzolanic material in low-alkali geopolymer systems, owing to its mechanical and green benefits, which the study concludes.