Enhancing Mechanical Properties of High-Performance Concrete Using Steel Waste

In this study, steel waste is used as a sustainable replacement for quartz sand in high-performance concrete (HPC). Fifteen concrete mixes were prepared with 0%, 25%, 50%, 75%, and 100% as volume replacement of steel waste, with steel fibres added at 1%, 2%, and 3%. The experimental program included workability, compressive strength, splitting tensile strength, direct tensile strength, flexural strength, and density tests, in addition to microstructure analysis using scanning electron microscopy. The results showed that optimal performance was achieved when 50% of the steel waste was replaced with 3% steel fibres. The compressive strength of this mix was 118.6 MPa, the direct tensile strength was 16.62 MPa, the splitting tensile strength was 16.61 MPa, and the flexural strength was 20.16 MPa. Compared to the reference mix, compressive strength, direct tensile strength, and splitting tensile strength increased by 22.6%, 25.9%, and 36.7%, respectively. Higher replacement levels (75–100%) led to strength reductions due to weaker interfacial bonding and increased mix heterogeneity. In addition, steel waste increased concrete density, reaching heavyweight concrete at high replacement ratios. Overall, the findings indicate that a 50% replacement of quartz sand with steel waste provides the best balance between sustainability and mechanical performance in HPC.