Ultra-high-performance concrete (UHPC) is prone to explosive spalling at high temperatures, which compromises the load-bearing capacity of the structures. In this paper, the effects of the content and length/diameter ratio of polypropylene (PP) fibers on the explosive spalling resistance of the steel and PP hybrid fiber-reinforced UHPC were investigated utilizing experimental method. First, the UHPC specimens were prepared using the conventional curing method. Second, the UHPC specimens were heated using the ISO-834 standard heating curve. Thirdly, the appearances, the first spalling time, the first spalling temperature, and the mass loss of the specimens were used to evaluate the explosive spalling resistance of the UHPC. The results demonstrated that the steel and PP hybrid fiber-reinforced UHPC has much greater explosive spalling resistance than the steel fiber-reinforced UHPC. The explosive spalling resistance of the hybrid fiber-reinforced UHPC is strongly influenced by the content and length/diameter ratio of the PP fibers. Generally, the explosive spalling resistance of the hybrid fiber-reinforced UHPC increases with the increase of the PP fiber content and length/diameter ratio.

超高性能混凝土（UHPC）在高温下容易发生爆炸剥落，这会影响结构的承载能力。本文采用实验方法研究了聚丙烯（PP）纤维的含量和长径比对钢和PP混合纤维增强UHPC抗爆炸剥落性能的影响。首先，使用常规固化方法制备 UHPC 试样。其次，使用 ISO-834 标准加热曲线加热 UHPC 试样。第三，利用试样的外观、首次剥落时间、首次剥落温度和质量损失来评价UHPC的抗爆炸剥落性能。结果表明，钢和PP混合纤维增强的UHPC比钢纤维增强的UHPC具有更高的抗爆炸剥落性。混合纤维增强 UHPC 的抗爆炸剥落性受 PP 纤维的含量和长径比的影响很大。一般来说，混合纤维增强UHPC的抗爆炸剥落性随着PP纤维含量和长径比的增加而增加。