Influence of hooked-end steel fibres on the fresh and hardened properties of concrete using Dreux–Gorisse mix design method

This study investigates the effect of hooked-end steel fibres on the fresh and hardened properties of concrete designed using the Dreux–Gorisse method. Locally sourced Moroccan aggregates were characterised using standard physical and mechanical tests before concrete production. A reference concrete mixture was prepared, and three hooked-end steel fibre dosages of 20, 30, and 40 kg/m³ were investigated. Workability, hardened density, and compressive strength were evaluated at 7 and 28 days. Increasing fibre dosage progressively reduced slump, from 6.0 cm for the control concrete to 1.5 cm at 40 kg/m³. In contrast, hardened density increased with fibre content, reaching 2.53 g/cm³ at 28 days. Compressive strength also increased progressively with fibre dosage. At 28 days, the compressive strength increased from 26.0 MPa for the control concrete to 34.5 MPa for the mixture containing 40 kg/m³ of fibres, corresponding to a maximum increase of 32.7%. The observed improvement is plausibly associated with fibre bridging, stress transfer, and mechanical anchorage, although these mechanisms were not directly investigated in the present study. The results indicate that hooked-end steel fibres can improve the compressive performance of conventional concrete produced with locally sourced aggregates, but their incorporation substantially reduces workability. The study provides a controlled reference dataset for further investigation of tensile, flexural, post-cracking, and microstructural behaviour.