Study on dynamic properties of lightweight ultra-high performance concrete (L-UHPC)

•A lightweight ultra-high performance concrete (L-UHPC) with a compressive strength exceeding 120 MPa and a density less than 2100 kg/m3 was developed.•The developed L-UHPC shows obvious sensitivity to variation of strain rate.•The fiber shape has little impact on the dynamic compressive strength of L-UHPC.•The fiber length is beneficial to the dynamic properties of L-UHPC.•The reinforcement mechanism in L-UHPC is due to the combined effect of lightweight aggregates and steel fiber. Ultra-high performance concrete (UHPC) is being considered as a potential material for concrete structures subject to impact and blast loads due to its exceptional strength and ductility characteristics. In this study, a lightweight ultra-high performance concrete (L-UHPC) was developed using fine lightweight aggregate. To further understand the mechanical response of L-UHPC at high impact velocities, the dynamic properties (such as failure pattern, peak stress, DIF, stress–strain curve, and toughness) of L-UHPC were investigated and the effect of steel fiber type on dynamic properties was analyzed. According to the research findings, the L-UHPC exhibits significant sensitivity to variation of strain rate, it experiences more damage, exhibits a higher peak stress, and absorbs more energy when subjected to a higher strain rate. The steel fiber shape exhibited little effect on both quasi-static and dynamic properties. Furthermore, an empirical formulate of dynamic increase factor (DIF) for L-UHPC with different steel fiber was proposed. At last, the failure mechanism of L-UHPC was analyzed. The experimental findings can provide a valuable reference for the further understanding and studying the dynamic characteristic of concrete with ultra-high strength and low density.