Optimal dimension of arch-type steel fibre-reinforced cementitious composite for shotcrete

In this study, the optimal dimension of arch-type steel fibre for cementitious shotcrete was derived based on the bond properties with a cement matrix, as a function of the length of the steel wire, the radius of curvature of the arch, and bend length at the fibre end. Our results indicated that a smaller radius of curvature of the arch-type steel fibre was able to withstand a higher maximum load, without fibre fracture or pullout. Pullout was evident for a larger radius of curvature of the fibre; however, fibre fracture was not observed. Additionally, the arch-type steel fibre end with a longer bend length showed excellent bond properties and pullout behaviour as the radius of curvature increased, due to stable anchoring within the cementitious composite. Statistical analysis of the experimental results indicated that the steel wire length had no effect on the bond properties of the fibre; also, a bend length >2.0 mm was identified as optimal for a radius of curvature of 20 mm. Our optimised fibre configuration was compared with a 35-mm hooked-end-type steel fibre, which is commonly used as reinforcing material in shotcrete.