Experimental Investigation on the Use of Steel Scrap as a Replacement for Coarse Aggregate in Concrete

Concrete is one of the most widely used construction materials, but the continuous extraction of natural aggregates poses serious environmental and sustainability challenges. At the same time, industrial waste such as steel scrap is generated in large quantities and often remains underutilized. This study explores the feasibility of using steel scrap as a partial replacement for coarse aggregate in concrete. Steel scrap, cut into small cylindrical pieces of varying sizes (10 mm, 15 mm, 20 mm, etc.), was introduced in place of coarse aggregate at replacement levels of 5%, 10%, 15%, 20%, 25%, 30%, and 35% by weight. Standard concrete specimens were cast, including 150 mm cubes for compressive strength, 150 × 300 mm cylinders for split tensile strength, and 150 × 150 × 700 mm beams for flexural strength. All specimens were cured under normal conditions and tested at 7 days and 28 days. The results demonstrated that the inclusion of steel scrap consistently enhanced the mechanical properties of concrete. Compressive strength increased from 15.11 MPa at 5% replacement to 21.63 MPa at 35% replacement after 28 days, showing an improvement of about 43%. Split tensile strength rose from 2.17 MPa (5%) to 2.97 MPa (30–35%), representing a 37% gain. Flexural strength also improved from 133.93 MPa at 5% to 168.00 MPa at 35% replacement, marking a 24% enhancement. The improvements are attributed to the crack-bridging effect and better stress distribution provided by steel scrap within the concrete matrix. From the study, it can be concluded that steel scrap can effectively replace coarse aggregate up to 30–35% without compromising strength. The findings highlight the dual benefit of improving concrete performance while promoting sustainable waste utilization, making this approach suitable for future construction practices.