Tensile behaviour of distinct hooked end steel fibre shape and geometry on material properties of self-compacting concrete

The influence of steel fibres in fibre reinforced concrete application has shown improvements in the mechanical properties most especially in tension. Hooked end steel fibre amongst other types of steel fibres exhibits better performance in crack resistance as well as bridging crack(s) at crack localisation point(s) resulting in increased pre and post cracking behaviour, ultimate load carrying capacity, energy absorption and ductility. Fibre distribution and orientation is more pronounced when used in self -compacting concrete thereby reducing the scatter of material properties with further improvement in its mechanical performance.

The aim of this study is to investigate the effect of new innovative multiple hook ends steel fibres as against existing single hook end steel fibre on the material properties and scatter when used in Self-compacting concrete. A laboratory investigation was carried out using different steel fibre hooked-end shapes and geometries at 0.25%, 0.5%, 0.75% and 1% fibre content in self-compacting concrete to obtain material properties. Uniaxial direct tension test and single fibre pull-out test were used as the test methods. The results show that alteration in the hooked end shape and geometry from single hook to multiple hooks influences positively the pull-out response (peak pull-out load and energy dissipated) during pull-out test. There is a decrease of up to a maximum of 20% in tensile strength for S1, M1 and M2 steel fibre types when compared to plain concrete. The fracture energy and ultimate tensile strength increased up to a maximum of 14% and 36% with M2 when compared to S1. However, the post- cracking response of steel fibre reinforced self-compacting concrete is not only influenced by the percentage steel fibre content but also by the embedment length of the fibres and extent of individual hooks across the crack.