EFFECT OF NANO-SILICA ON GEOPOLYMER CONCRETE STRENGTH

Abstract

Portland cement concrete contributes significantly to carbon emissions, highlighting the need for sustainable alternatives like geopolymer concrete (GPC). However, GPC often shows inconsistent mechanical strength, especially at early ages. This study investigates the effect of nano-silica (0–4% by fly ash weight) on the mechanical and microstructural properties of GPC. Compressive, tensile, and flexural strength tests, along with SEM and XRD analyses, were conducted. Statistical tools (ANOVA, Tukey HSD, regression) revealed that 3% nano-silica yielded the highest compressive strength (39.66 ± 0.91 MPa), with notable improvements in tensile (32.4%) and flexural (24.2%) strengths. Microstructural analysis showed reduced porosity (8.5% vs. 12.5% in control). However, workability decreased with higher dosages. Optimal performance was observed at 2–3% dosage, balancing strength and handling. These findings demonstrate nano-silica's potential to enhance GPC performance and contribute to low-carbon, sustainable construction.