Ultra-high-performance concrete: Impacts of steel fibre shape and content on flowability, compressive strength and modulus of rupture

The impact of three-shaped steel fibres (straight, hooked end, and corrugated) with varying steel fibre (SF) contents (0.75 %, 1.5 %, and 2.5 % by volume fraction) on the fresh and mechanical characteristics of ultra-high-performance concrete was investigated in this investigation. The characteristics concerned included flowability, compressive strength, and modulus of rupture. The findings showed that using deformed fibres and increasing the fibre volume could gradually reduce the flowability of ultra-high-performance concrete. It also had a substantial impact on the compressive strength and modulus of rupture of ultra-high-performance concrete. At 28-d, its compressive strength and modulus of rupture were greater than 155 and 37 MPa, respectively, with the introduction of 2.5 % straight SFs. Moreover, the compressive strength increased by 50 % and 65 % for concrete comprising 2.5 % hooked end fibre and corrugated fibre, respectively, when compared to concrete with the same volume of straight fibre.