The vast changes in temperature are what produce thermal fatigue damage to concrete. In this study, concrete specimens in three different categories—C20, C40, and C60—are tested for thermal fatigue at temperatures ranging from 10°C to 80°C in an atmosphere with constant relative humidity. Utilizing ultrasonic nondestructive testing, the elastic modulus of concrete is determined. After thermal cycling, the mass reduction and appearance of samples are also recorded. The results demonstrate that the degrading effects of thermal fatigue clearly influence concrete. As the thermal cycle lengthens, the elastic modulus of concrete rapidly decreases, and C60 concrete experiences a greater reduction in elastic modulus than C20 concrete. With thermal cycles, the damage factor increases and the ultrasonic wave velocity steadily decreases, suggesting a propagation of the concrete’s interior microcracks. Additionally, the micromechanical thermal fatigue model is developed based on the experimental results. The ability to simulate and describe the physical behavior of concrete under thermal fatigue stress on the microscale is validated by the proposed micromechanical damage model.

中文翻译：

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混凝土的实验研究和微机械热疲劳模型


温度的巨大变化会导致混凝土产生热疲劳损坏。在这项研究中，在相对湿度恒定的大气中，对三种不同类别（C20、C40 和 C60）的混凝土试件在 10°C 至 80°C 的温度范围内进行热疲劳测试。利用超声波无损检测测定混凝土的弹性模量。热循环后，还记录样品的质量减少和外观。结果表明，热疲劳的降解效应明显影响混凝土。随着热循环的延长，混凝土的弹性模量迅速下降，C60混凝土的弹性模量下降幅度比C20混凝土更大。随着热循环，损伤因子增加，超声波速度稳定下降，表明混凝土内部微裂纹的扩展。此外，根据实验结果开发了微机械热疲劳模型。所提出的微观机械损伤模型验证了在微观尺度上模拟和描述混凝土在热疲劳应力下的物理行为的能力。