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Abstract
This study investigated the effect of nanosilica (NS) as a partial replacement for ordinary Portland cement (OPC) on the mechanical and durability properties of concrete. The aim was to assess the suitability of nanosilica in improving concrete performance and to determine its optimum replacement level for sustainable construction applications in Nigeria.Concrete was produced using a nominal mix ratio of 1:2:4 and a constant water–cement ratio of 0.5. Nanosilica was used to replace cement at levels of 0%, 1%, 2%, and 3% by weight. Tests carried out included slump test, setting time determination, compressive strength test, flexural strength test, and water absorption test. Statistical analysis of the results was performed using oneway analysis of variance (ANOVA).Results showed that workability increased with increasing nanosilica content, while both initial and final setting times decreased. Compressive and flexural strengths increased up to an optimum nanosilica content of 2%, where 28-day values of 24.4 N/mm² and 5.25 N/mm² were recorded, compared to 22.5 N/mm² and 4.67 N/mm² for the control mix. Water absorption reduced to 7.3% at 2% nanosilica replacement compared to 9.7% for the control, indicating improved durability. ANOVA results showed no significant differences in compressive strength, flexural strength, and workability (p > 0.05), while setting time showed significant variation (p < 0.05). The study concluded that 2% nanosilica replacement provided the best overall performance and is recommended for producing stronger and more durable concrete
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