Dynamic compressive properties of UHPC under one-dimensional stress wave: The influence of steel fiber morphology and curing regime

Abstract

The low matrix strength and insufficient toughness of conventional concrete structures seriously threaten the service performance when subjected to intensive compressive waves. This study aims to comprehensively investigate the impact of steel fiber morphology and curing regime on the dynamic compressive properties of Ultra-high performance concrete (UHPC) under one-dimensional stress wave. Seeking to improve its impact resistance without changing the mix ratio. Three steel fiber types (straight, wave, hooked) and two curing regimes (steam at 90 °C, dry heat at 180 °C) were selected as experimental variables. Quasi-static mechanical properties of UHPC were initially calibrated, followed by dynamic compressive tests utilizing the Split Hopkinson Pressure Bar (SHPB) system. The compressive stress-strain relationships and corresponding dynamic mechanical parameters of six types of UHPC were calculated under five impact velocities (8.5 m/s, 10.8 m/s, 13.1 m/s, 15.2 m/s, 17.3 m/s). Furthermore, the dynamic failure mode and evolutionary process of UHPC under high-speed impact was meticulously captured by a high-speed camera. CT scanning was utilized to observe the crack propagation path and damage patterns under low strain rate. Finally, SEM and EDS testing was conducted to unravel the underlying mechanisms of the curing regime and fiber morphology on the dynamic compressive properties of UHPC. The recalibrated empirical DIFfc model suitable for UHPC under strain rates of 37 s-1 to 212 s-1 was proposed.