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 DIF model suitable for UHPC under strain rates of 37 s to 212 s was proposed.

中文翻译：

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一维应力波下 UHPC 的动态压缩性能：钢纤维形态和固化方式的影响

常规混凝土结构基体强度低、韧性不足，严重威胁其在强烈压缩波作用下的使用性能。本研究旨在全面研究一维应力波下钢纤维形态和养护方式对超高性能混凝土（UHPC）动态压缩性能的影响。力求在不改变配合比的情况下提高其抗冲击性能。选择三种钢纤维类型（直纤维、波浪纤维、钩状纤维）和两种固化方式（90°C 蒸汽，180°C 干热）作为实验变量。最初校准 UHPC 的准静态机械性能，然后利用分体式霍普金森压力棒 (SHPB) 系统进行动态压缩测试。计算了6种UHPC在5种冲击速度（8.5 m/s、10.8 m/s、13.1 m/s、15.2 m/s、17.3 m/s）下的压缩应力-应变关系和相应的动态力学参数。此外，高速相机细致捕捉了UHPC在高速冲击下的动态失效模式和演化过程。利用CT扫描观察低应变率下的裂纹扩展路径和损伤模式。最后，进行了 SEM 和 EDS 测试，以揭示固化方式和纤维形态对 UHPC 动态压缩性能的潜在机制。提出了适用于应变速率为 37 s 至 212 s 的 UHPC 的重新校准经验 DIF 模型。