Reactive powder concrete (RPC) is an advanced cementitious material with ultra-high strength, remarkable durability and excellent toughness. However, temperature dependent creep is a major concern as very little work has been reported in the literature. Therefore, systematic investigations are still missing in state of the art. This paper focuses on the impact of Polypropylene (PP) and hybrid (steel and PP) fibers on creep behavior of RPC at elevated temperature. Temperature-dependent creep is further characterized into free thermal strain (FTS), short-term creep (STC) and transient strain (TS), based on different thermo-mechanical regimes. Varying heating and loading schemes were considered such as steady-state and transient thermo-mechanical conditions. The target temperatures considered for steady-state thermal conditions and transient case are 120, 300, 500, 700 and 900 °C. Compressive strength was considered up to 60% load ratio of ambient and temperature dependency. The result shows that STC increases with increasing stress level and higher target temperature. The increase in STC becomes obvious above the transition stage of quartz aggregate. Furthermore, HRPC have significantly higher STC than PRPC and other traditional types of concretes. The evolution of FTS and TS was quite slow below 250 °C. However, at high temperature significant increase in FTS and TS were observed. Furthermore, increasing stress level and the addition of steel fibers results in high TS. Overall, the performance of PP fiber was better than the hybrid fibers on the creep behaviour of RPC. Finally, constitutive relationships were proposed for FTS, STC and TS, which will be used as input data in numerical models of fire resistance calculations.

中文翻译：

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温度和应力对聚丙烯和混合纤维增强活性粉末混凝土蠕变行为的影响

反应性粉末混凝土（RPC）是一种具有超高强度、卓越耐久性和优异韧性的先进胶凝材料。然而，温度相关的蠕变是一个主要问题，因为文献中报道的工作很少。因此，在现有技术中仍然缺少系统研究。本文重点研究聚丙烯 (PP) 和混合（钢和 PP）纤维对 RPC 在高温下蠕变行为的影响。基于不同的热机械状态，温度相关蠕变进一步表征为自由热应变 (FTS)、短期蠕变 (STC) 和瞬态应变 (TS)。考虑了不同的加热和加载方案，例如稳态和瞬态热机械条件。考虑稳态热条件和瞬态情况的目标温度为 120、300、500、700 和 900 °C。压缩强度被认为高达 60% 的环境和温度依赖性负载率。结果表明，STC随着应力水平的增加和目标温度的升高而增加。在石英骨料过渡阶段以上，STC 的增加变得明显。此外，HRPC 的 STC 明显高于 PRPC 和其他传统类型的混凝土。FTS 和 TS 的演变在 250 °C 以下相当缓慢。然而，在高温下观察到 FTS 和 TS 显着增加。此外，增加应力水平和添加钢纤维会导致高 TS。总体而言，PP纤维在RPC蠕变行为方面的性能优于混合纤维。最后，