Effect of Varying Fine and Coarse Steel Slag Contents on Strength, Sorptivity and Freeze-Thaw Resistance of Micro Silica-Modified Concrete

The sustainable utilization of industrial by-products in concrete production has recently become a priority in modern construction engineering due to its global availability, environmental benefits, and potential engineering properties. The use of steel slag (SS) in fine and coarse sizes with mineral admixtures, including micro silica (MS), in concrete design must be thoroughly examined for durability and efficiency, considering several variables, including their types and contents. The combined impacts of MS and SS must also be well investigated. This article examined the mechanical and durability properties of concrete after adding SS and MS separately and in combination. In an experimentally based investigation, fine steel slag (FSS) and coarse steel slag (CSS) was substituted for natural fine and coarse aggregate, respectively in varying ratios (20% - 70%) in the same mixture with and without MS (10%) as partial cement replacement. The concrete mixtures' workability, density, compressive strength, flexural strength, splitting tensile strength, capillary water absorption rate (sorptivity), and freeze-thaw resistance were assessed. Results indicate that compressive strength increased progressively up to 40% SS replacement, achieving 42.1 MPa compared with 36.4 MPa for plain concrete. Beyond 50% replacement, strength declined despite continuous increases in density. According to the mechanical properties and durability investigated in the present study, the optimum performance was observed in the replacement of 30–40% SS along with 10% MS, which confirmed its modification. The findings provide engineers, researchers, and decision-makers in the construction industry with valuable guidance on the practical benefits and elements to consider when including SS and MS into concrete mixtures. This application maximizes resource efficiency and reduces environmental impact while enhancing the mechanical and durability properties of concrete.