Performance evaluation of ternary blended GGBFS based geopolymer concrete with silica fume and fly ash

Due to its relatively lower carbon footprint and higher durability, geopolymer concrete (GPC) is gaining popularity as an eco-friendly alternative to ordinary Portland cement (OPC). This study evaluates ternary mixes of ground granulated blast furnace slag (GGBFS), fly ash (FA), and silica fume (SF) under a constant alkaline activator (silicate-to-hydroxide ratio 2.5, 12 M NaOH). Four mixes were analyzed: M1 (G100), M2 (G70F25S5), M3 (G95S5), and M4 (G50F45S5). The mechanical durability properties and microstructural analysis under ambient conditions, sulphate exposure and varied fire exposure were studied. The findings reflected that M3 achieved the optimal overall performance, with compressive strength about 13–14% higher than M1, 20–24% higher than M2, and 30–32% higher than M4 at 56 days. M3 indicated the least amount of strength loss (2–3%) and weight loss (1–2%) after sulphate exposure (120 days), whereas M4 showed the most deterioration (8–10% strength loss & 6–7% weight loss). M3 exhibits some amount of strength loss during exposure to high temperatures while maintaining an increased residual strength. M3 showed better results in all the areas of testing among the 4 mixes that were evaluated. The findings show that optimizing the precursor composition enhances the mechanical properties, sulphate resistance, and thermal stability of GPC, with the greatest improvements occurring when adding SF to high GGBFS blends.