Fracture behaviour of ultra-high performance concrete

In this work, an attempt has been made to develop and investigate mechanical and the fracture behaviour of ultra-high performance concrete (UHPC). Geometrically similar notched beam specimens of different sizes made up of ultra-high performance fibre reinforced concrete (UHPFRC) have been considered for the experimental investigation. Centre point bending tests have been performed on beam specimens in crack mouth opening displacement control manner for investigating the fracture properties. Various fracture properties such as, fracture toughness, fracture energy, brittleness number etc. have been determined on the basis of non-linear fracture mechanics theory. The results of UHPC concrete have been compared with that of normal strength concrete available in the literature. It has been observed that addition of fibres increases the energy absorption capacity to a great extent for all size of specimens of ultra-high performance concrete as compared to normal concrete. Moreover, the brittleness number has been found to decrease due to the addition of fibers thereby enhancing the ductility. A decrease in nominal strength of UHPC based concrete with the increase in specimen size has been observed in similar fashion as normal strength concrete. However, the sensitivity to the size effect of ultra-high performance concrete is effectively reduced compared with normal concrete.