Experimental Investigation On Mechanical Performance Of Steel Fibre Reinforced Fly Ash Concrete

Abstract

The growing demand for sustainable and high-performance concrete has encouraged the combined use of supplementary cementitious materials and fibre reinforcement to enhance mechanical behavior while reducing environmental impact. In this study, the fresh and hardened properties of M20 and M30 grade concretes incorporating fly ash as a partial replacement of cement and steel fibres as discrete reinforcement were experimentally investigated. Fly ash was used in the range of 0–35%, while steel fibre content was varied from 0 to 2.0% by volume of concrete. The workability of fresh concrete was evaluated using the slump test in accordance with IS 1199 (Part 4):2018. The hardened mechanical performance was assessed through compressive strength, split tensile strength, and flexural strength tests conducted at 7 and 28 days of curing as per IS 516:1959. The results indicate that increasing fly ash content leads to a marginal reduction in early-age strength and workability due to delayed pozzolanic activity, with a more pronounced effect on tensile-related properties than on compressive strength. However, the incorporation of steel fibres significantly enhanced split tensile and flexural strength by improving crack resistance, stress redistribution, and post-cracking behavior. Compressive strength showed only moderate improvement with fibre addition, whereas substantial gains were observed in tensile and bending performance. For both M20 and M30 grades, mixes containing 1.5–2.0% steel fibres combined with 15–20% fly ash replacement exhibited the most balanced mechanical performance at 28 days. Higher fly ash contents resulted in strength reduction despite fibre addition due to cement dilution effects. the study demonstrates that the synergistic use of steel fibres and fly ash can produce concrete with enhanced tensile and flexural performance and improved sustainability, making it suitable for structural applications governed by bending and tensile stresses such as pavements, slabs, and beams.