Effect of Hybrid Steel Fibre Geometry on the Performance of Fibre Reinforced Concrete

Abstract

The incorporation of steel fibres into concrete is an effective approach for improving its post-cracking behaviour, ductility, toughness, and energy absorption capacity. However, the geometry and aspect ratio of steel fibres significantly influence their interaction with the cementitious matrix and, consequently, the overall mechanical performance of fibre-reinforced concrete. This study investigates the effect of hybrid steel fibre geometry on the performance of fibre-reinforced concrete, with particular emphasis on strength development, crack control, deformation behaviour, energy absorption, and post-failure response. The experimental programme considers concrete mixtures reinforced with different combinations of steel fibres having variations in length, diameter, aspect ratio, and geometry, such as hooked-end and straight fibres. A conventional plain concrete mixture is considered as the control specimen, while mono-fibre and hybrid-fibre mixtures are prepared to evaluate the synergistic effect of combining fibres with different geometrical characteristics. The specimens are subjected to compressive strength, split tensile strength, flexural strength, and load–deflection tests at specified curing ages. The post-failure behaviour is further assessed through crack propagation, residual load-carrying capacity, toughness, and energy absorption characteristics. The hybrid fibre systems are expected to provide improved fibre–matrix interaction and more effective crack-bridging mechanisms across different stages of fracture development. Shorter fibres are anticipated to control microcracks, whereas longer and hooked-end fibres are expected to enhance macrocrack bridging and improve post-peak resistance. The study provides an experimental basis for optimizing hybrid steel fibre geometry for structural concrete applications where enhanced ductility, toughness, and resistance to sudden failure are required. The findings can contribute to the development of more durable and damage-tolerant fibre-reinforced concrete for structural and infrastructure applications.