High temperature mechanical property data are needed for evaluating fire resistance of structural members. Being a relatively new construction material, there is a lack of temperature-dependent mechanical property data on ultra-high performance concrete (UHPC). To address this knowledge gap, this paper presents results from an experimental study on the effect of temperature on mechanical properties of UHPC. Specimens made of two UHPC mixes: one with only steel fibers (UHPC-S) and the other with hybrid fibers, that is, both steel and polypropylene (UHPC-H), were tested under different heating conditions in 20 to 750°C temperature range. Compressive strength, tensile strength, stress-strain response, and elastic modulus of UHPC were evaluated at various temperatures. Results generated from these property tests on UHPC were compared with property relations specified in design codes for conventional normal strength concrete (NSC) and high strength concrete (HSC). The comparisons show that UHPC experiences faster degradation in compressive strength and elastic modulus as compared to conventional concrete. However, UHPC exhibits slower degradation in tensile strength and ductility at elevated temperatures due to the presence of steel fibers. Data generated from these property tests were utilized to propose relations for expressing the mechanical properties of UHPC as a function of temperature and these relations can be used as input to numerical models for evaluating fire resistance of structures made of UHPC.

中文翻译：

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温度对超高性能混凝土力学性能的影响

评估结构构件的耐火性需要高温力学性能数据。作为一种相对较新的建筑材料，超高性能混凝土 (UHPC) 缺乏与温度相关的力学性能数据。为了解决这一知识空白，本文介绍了温度对 UHPC 机械性能影响的实验研究结果。由两种 UHPC 混合物制成的样品：一种仅含有钢纤维 (UHPC-S)，另一种含有混合纤维，即钢和聚丙烯 (UHPC-H)，在 20 至 750°C 的不同加热条件下进行了测试范围。在不同温度下评估了 UHPC 的压缩强度、拉伸强度、应力应变响应和弹性​​模量。这些 UHPC 性能测试的结果与常规普通强度混凝土 (NSC) 和高强度混凝土 (HSC) 设计规范中规定的性能关系进行了比较。比较表明，与传统混凝土相比，UHPC 的抗压强度和弹性模量退化速度更快。然而，由于钢纤维的存在，UHPC 在高温下表现出较慢的拉伸强度和延展性退化。从这些性能测试中产生的数据被用来提出将 UHPC 的机械性能表示为温度函数的关系，这些关系可以用作数值模型的输入，用于评估由 UHPC 制成的结构的耐火性。