Experimental investigations and micromechanical thermal fatigue models of concrete.

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. [ABSTRACT FROM AUTHOR]