Effects of steel fiber content and pre-setting pressure on the dynamic compressive behavior of UHPC

Abstract

Owing to the high strength, high toughness and excellent durability of ultra-high performance concrete (UHPC), it can effectively resist the structural damage caused by strong impact and avoid structural instability. The static and dynamic performance of UHPC can be effectively improved by the combination of fiber reinforcement and preloading technology during its preparation. In this paper, the static mechanical properties and dynamic compression performance of UHPC were systematically tested by setting different volume steel fiber contents and different preloading loads. The stress–strain relationship and corresponding mechanical property parameters of UHPC under impact velocities of 3.2–17.5 m/s were determined, and the damage mode and failure mechanism of the UHPC samples were analyzed. In addition, the effects of the preloading load and steel fiber content on the evolution of cracks in UHPC at a low strain rate were characterized by micro-CT three-dimensional scanning technology. Moreover, the dynamic failure of the UHPC samples was recorded in detail by a high-speed camera, and the evolution of crack initiation, propagation and final failure was clearly determined. Finally, on the basis of the experimental data and empirical model, a DIF model of UHPC dynamic compression performance suitable for axial compressive strength in the range of 105.1 MPa to 239 MPa was constructed. The results of this study provide new solutions and ideas for the development and application of UHPC.