Effect of Silica Fume on the Mechanical Properties of Concrete: A Study on Strength and Durability

Abstract

This study investigates the influence of silica fume, an ultrafine by-product of ferrosilicon alloy production, on the strength characteristics of concrete. Silica fume, due to its high pozzolanic activity and fineness, has become an important additive to improve concrete’s compressive and flexural strength. Concrete specimens were prepared with varying silica fume replacement levels (0%, 5%, 10%, 15%) and tested for compressive and flexural strength at 7 and 28 days using a Universal Testing Machine. The results indicate that silica fume significantly enhances the strength of concrete, with the highest compressive strength of 43.56 MPa and flexural strength of 6.72 MPa achieved at 15% replacement. This improvement is attributed to the microfiller effect and pozzolanic reaction with calcium hydroxide, forming additional calcium silicate hydrate (C-S-H) gel. The findings confirm that silica fume can serve as a sustainable partial replacement for cement, leading to higher performance concrete and contributing to environmental conservation by reducing CO₂ emissions and river sand usage.