ARCHIVES

This study investigates the mechanical strength and acid resistance of geopolymer concrete (GPC) produced by partially replacing fly ash with Rice Husk Ash (RHA) and Pumicite. Geopolymer concrete, which eliminates Ordinary Portland Cement (OPC) entirely, offers a sustainable alternative with significantly lower CO₂ emissions. Low-calcium fly ash (Class F) was used as the primary binder activated by a combination of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃). RHA and Pumicite were incorporated at replacement levels of 0%, 2.5%, 5%, 7.5%, and 10% by weight of fly ash. Compressive strength was evaluated at 28 and 90 days, while acid resistance was assessed by immersing specimens in 5% H₂SO₄ solution for 30, 60, and 90 days, monitoring weight loss and residual compressive strength. Results show that 10% RHA replacement yielded the highest compressive strength (53 N/mm² at 28 days; 56 N/mm² at 90 days), whereas 7.5% Pumicite replacement was optimal for Pumicite blends (49 N/mm² at 28 days). In acid resistance tests, 7.5% RHA and 5% Pumicite blended mixes exhibited the best residual compressive strength. The study demonstrates that partial replacement of fly ash with RHA and Pumicite enhances both the mechanical and durability properties of geopolymer concrete.