Abstract Concrete with two types of steel fibres and a polypropylene fibre prevented spalling and preserved the compressive strength at 300 °C, which makes these concretes suitable for long-term applications up to 300 °C, such as for steam collectors or thermal energy storage systems. The compressive strength behaviour of three types of ultra-high-performance fibre-reinforced concrete manufactured with the same matrix was investigated. For this purpose, a complete characterisation of all the raw materials and the three types of fibres used was performed. The morphology of all concrete mixtures at room temperature was analysed using scanning electron microscopy–energy-dispersive X-ray spectroscopy. From the results, it was ascertained that the steel fibres and coarse siliceous aggregates were not in contact (being separated by ≥3.41 μm) and were surrounded by the binder (of ≥1 μm in thickness) for all the mixtures studied. Rosenhahnite and/or quartz Dauphine-twinned phases improved the compressive strength (as determined by X-ray diffraction).

中文翻译：

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中等温度对超高性能混凝土抗压强度的影响：微观结构分析

摘要 含有两种钢纤维和一种聚丙烯纤维的混凝土在 300 °C 时可防止剥落并保持抗压强度，这使得这些混凝土适用于高达 300 °C 的长期应用，例如蒸​​汽收集器或热能储存系统. 研究了用相同基体制造的三种超高性能纤维混凝土的抗压强度行为。为此，对所有原材料和所用的三种纤维进行了完整的表征。使用扫描电子显微镜 - 能量色散 X 射线光谱分析室温下所有混凝土混合物的形态。结果表明，钢纤维与粗硅质骨料没有接触（相隔≥3. 41 μm）并被所有研究的混合物的粘合剂（厚度≥1 μm）包围。Rosenhahnite 和/或石英 Dauphine 孪晶相提高了抗压强度（由 X 射线衍射确定）。