Synergistic Effects of Silica Fume and Steel Slag and Steel Slag in Advanced Concrete Composites

Concrete is highly versatile, capable of withstanding harsh environments and achieving inspirational forms. Modern advancements focus on enhancing its performance through innovative chemical admixtures and supplementary cementitious materials (SCMs). SCMs, often industrial byproducts like fly ash, silica fume, ground granulated blast furnace slag, and steel slag, replace a portion of Portland cement, reducing costs and environmental impact while improving concrete properties. Silica fume, a particularly successful SCM, significantly enhances concrete’s strength and durability, especially in high-strength applications. Steel slag, a byproduct of steel manufacturing, shows potential as an aggregate in concrete, despite its tendency to expand due to free lime and magnesium oxides. Proper treatment and the use of pozzolanic materials like silica fume can mitigate this expansion. This study investigates the mechanical properties of concrete mixes using ACC brand slag cement, fly ash cement, and their blend (1:1), modified with 10% and 20% silica fume. Natural sand (zone II, IS 383-1982) serves as the fine aggregate, and steel slag (20 mm down) as the coarse aggregate, mixed in a 1:1.5:3 ratio. Tests on 7-day, 28-day, and 56-day compressive strengths, flexural strength, porosity, and capillary absorption were conducted. Key findings include an increased water requirement with higher silica fume content, higher early strength gain with fly ash cement, and better later strength with slag cement. Silica fume reduces capillary absorption and porosity, particularly with fly ash cement.