Optimizing self-compacting concrete with steel slag and fiber additions: enhancing fresh, mechanical, durability, and microstructural properties

Abstract

Building on previous research, which demonstrated that 50% steel slag replacement for fine aggregates optimally enhanced the fresh, mechanical, and durability properties of self-compacting concrete (SCC) (Singh & Anand, 2024), this study further investigates the effects of incorporating steel and polypropylene fibers to improve performance. Steel fibers were added in proportions ranging from 0.5 to 2%, while polypropylene fibers were varied within the same range. The concrete mix design was based on IS 10262:2019, and EFNARC guidelines were followed to ensure the concrete mix met international standards for fresh properties such as flowability, passing ability, and viscosity. The results show that steel fiber significantly outperformed polypropylene fiber in terms of strength, with the optimal addition of 2% steel fiber resulting in compressive strengths of 51.5 MPa at 7 days, 71.8 MPa at 28 days, and 78.1 MPa at 56 days, along with notable improvements in tensile and flexural strengths. In contrast, the addition of 0.5% polypropylene fiber demonstrated optimal fresh properties but provided relatively lower strength. Durability tests, including water absorption and sulfate attack resistance, indicated superior performance with steel fiber, exhibiting lower water absorption and reduced weight loss under aggressive conditions. Microstructural analysis via SEM and XRD confirmed a denser interfacial transition zone (ITZ) and better bonding with steel fiber compared to polypropylene fiber. Overall, the incorporation of steel fiber in SCC with steel slag replacement leads to superior strength and durability, making it a promising solution for high-performance concrete applications.