Performance evaluation of self-compacting concrete with steel slag and hybrid fibers: enhancing fresh, mechanical, durability, and microstructural characteristics

Abstract

Building on our previous research (Singh and Anand 2024), which identified 50% steel slag replacement as optimal for SCC performance, this study explores the addition of hybrid fibers (50% steel and 50% polypropylene) at varying proportions (0.25–2%). The main objective of this paper is to optimize SCC using 50% steel slag as a fine aggregate replacement and hybrid fibers to enhance its fresh, mechanical, durability, and microstructural properties. The mix design adheres to IS 10262:2019 and EFNARC guidelines to ensure compliance with international standards for flowability, passing ability, and viscosity. The findings reveal that hybrid fibers significantly enhance the fresh and hardened properties of SCC. An optimal fiber addition (1% total content) achieved compressive strength of 85.2 MPa at 56 days, tensile strength of 6.71 MPa, and flexural strength of 8.57 MPa, while maintaining superior flowability (slump flow: 710.3 mm). Enhanced durability was evidenced by reduced water absorption, improved sulfate resistance, and freeze–thaw durability. Microstructural analysis (SEM, TGA, XRD) confirmed denser interfacial transition zones and improved hydration product formation. This research highlights the synergistic benefits of hybrid fibers in SCC with steel slag, offering a sustainable and high-performance material solution for modern construction applications.