An increasing number of critical infrastructures are built in cold and perma-frost regions, resulting in higher susceptibility to damage due to freeze-thaw (F-T) cycles. This paper assesses the mechanical properties and F-T damage evolution of compression-cast fiber-reinforced concrete (CCFRC) through rapid F-T cycling tests. Nine types of fiber-reinforced concrete (FRC) are experimentally investigated through 144 cubic and 39 prismatic specimens. The main parameters considered in the tests include the casting pressure applied during the compression casting procedure (between 0 and 15 MPa), type of the internal added fibers (polypropylene, end-hooked steel, or their combination), fiber content, and number of F-T cycles. The effects of these parameters on the failure modes, strength degradation rates, deterioration evolution, frost resistance durability, microscopic behavior, and F-T resistance of FRC specimens, are examined in detail. The microscopic performance of different specimens is further investigated using the X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and backscattered scanning electron (BSE) tests. Based on the test results, it is shown that: (i) compared with the mass loss rate, the relative dynamic elastic modulus can be a more suitable index to assess the F-T resistance of FRC; (ii) compression casting and addition of fibers can effectively enhance the F-T denudation resistance of CCFRC; (iii) compression casting reduces the compressive and flexural strength degradation rates of CCFRC, but at the expense of more brittle behavior; and (iv) compression casting and use of the mixed polypropylene and end-hooked steel fibers can effectively delay the F-T cycling induced damage, reduce porosity and internal defects, and enhance the micro-structural behavior and F-T resistance of CCFRC. F-T deterioration prediction models are also proposed and shown to provide accurate and effective representation of the behavior of CCFRC materials.

中文翻译：

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压铸纤维增强混凝土冻融劣化的试验评价


越来越多的关键基础设施建在寒冷和永久霜冻地区，导致冻融 （F-T） 循环更容易造成损坏。本文通过快速 F-T 循环测试评估了压铸纤维增强混凝土 （CCFRC） 的机械性能和 F-T 损伤演变。通过 144 个立方体和 39 个棱柱形试样对 9 种类型的纤维增强混凝土 （FRC） 进行了实验研究。测试中考虑的主要参数包括压缩铸造过程中施加的铸造压力（0 到 15 MPa 之间）、内部添加的纤维类型（聚丙烯、端钩钢或它们的组合）、纤维含量和 F-T 循环次数。详细研究了这些参数对 FRC 试件的失效模式、强度退化率、劣化演变、抗冻耐久性、微观行为和抗 F-T 性的影响。使用 X 射线计算机断层扫描 （X-CT）、扫描电子显微镜 （SEM） 和背散射扫描电子 （BSE） 测试进一步研究不同样品的微观性能。 基于试验结果表明：（i）与质量损失率相比，相对动弹性模量可以作为评价FRC抗F-T性能的更合适指标;（ii） 压缩铸造和纤维添加可有效增强 CCFRC 的抗 F-T 剥蚀性能;（iii） 压缩铸造降低了 CCFRC 的压缩强度和弯曲强度退化率，但以牺牲更脆的行为为代价;（iv） 压缩铸造和使用聚丙烯和端钩钢混合纤维可以有效延缓 F-T 循环诱导的损伤，减少孔隙率和内部缺陷，并增强 CCFRC 的微观结构行为和抗 F-T 性能。还提出了 F-T 劣化预测模型，并证明可以准确有效地表示 CCFRC 材料的行为。