Understanding the effects of hooked-end steel fibre geometry on the uniaxial tensile behaviour of self-compacting concrete

A series of uniaxial tensile tests on cylinders made from steel fibre reinforced self-compacting concrete (SFR-SCC) have been carried out to investigate the influence of fibre geometry and the combined effect of fibre content and distribution on the post-cracking behaviour. Three types of commercially available hooked end fibres (3D (single hooked), 4D double (double hooked) and 5D (triple hooked)) have been used in this study, which are added to the concrete mixture at two fibre dosages (0.5 and 1% by volume). The experiments show that the post-cracking strength increases significantly (P < 0.05) with the increase of fibre content for all mixtures. The combination of a unique shaped hook of high tensile strength demonstrates an optimum effect on the failure mode of concrete cylinders in which peak and post-peak strengths are raised. Notably, strain-hardening behaviour is observed only for cylinders reinforced with 5D hooked end fibres. A correlation between number of fibres exposed on fractured surfaces and post-cracking behaviour is established.