In this work we assess the effect of the addition of polypropylene (PP) fibers in a heated ultra-high-performance fiber reinforced concrete (UHPFRC). To this end, three sets of specimens with identical cementitious materials were manufactured: plain concrete, a concrete reinforced exclusively with steel fibers and a concrete reinforced with steel and polypropylene fibers. The mechanical and fracture properties of each concrete at temperatures ranging from room temperature to $$300\,^\circ $$ 300 ∘ C were determined. A thorough appraisal of the thermal effect on the microstructure was also carried out by means of an X-ray scan analysis. Based on the testing data, the relation between the macroscopic response, including mechanical and fracture behavior, and the microscopic structure, i.e., size and number of pores and their distribution, is ascertained. The results show that the addition of PP fibers significantly increases the maximum pore size and slightly increases the total porosity. Furthermore, the partial melting of polypropylene fibers at $$300\,^\circ $$ 300 ∘ C, in combination with the rise in porosity, reduces thermal damage and results in similar behavior at low and high temperatures, room temperature and $$300\,^\circ $$ 300 ∘ C, respectively.

中文翻译：

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聚丙烯纤维对加热超高性能混凝土断裂行为的影响

在这项工作中，我们评估了在加热的超高性能纤维增强混凝土 (UHPFRC) 中添加聚丙烯 (PP) 纤维的效果。为此，制造了三组具有相同胶凝材料的试样：素混凝土、仅用钢纤维增强的混凝土和用钢和聚丙烯纤维增强的混凝土。确定了每种混凝土在从室温到 $300\,^\circ $300 ∘ C 的温度范围内的机械和断裂性能。还通过 X 射线扫描分析对微观结构的热效应进行了全面评估。根据测试数据，宏观响应（包括力学和断裂行为）与微观结构（即孔隙的大小和数量及其分布）之间的关系，被确定。结果表明，PP纤维的加入显着增加了最大孔径，并略微增加了总孔隙率。此外，聚丙烯纤维在 $300\,^\circ $300 ∘ C 处部分熔化，结合孔隙率的上升，减少了热损伤并导致在低温和高温、室温和 $300\ 下的类似行为,^\circ $$ 300 ∘ C，分别。