EXPERIMENTAL STUDY ON THE TEMPERATURE FIELD OF CONCRETE DURING COOLING FROM ROOM TEMPERATURE TO -196℃ AND THEN RETURNING TO ROOM TEMPERATURE

Through experiments on the temperature field of concrete specimens with different shapes and sizes during cooling from room temperature to -196℃ and then returning to room temperature, the changing pattern during cooling and returning temperature (CRT) and the impacts of exerting CRT rates, specimen sizes and shapes on the changing pattern were discussed. The results show that the internal temperature of concrete exhibits remarkable hysteresis and there are significant differences between CRT duration. Concrete has a significant thermal inertia at ultralow temperatures, but some properties are not the same as those under high temperatures. The internal temperature variation of specimens and the difference with exerting temperature are affected by exerting CRT rates, and specimen sizes and shapes, and they present non-linear relationships. The temperature difference between inside and outside of the specimen with a minimum size no less than 100 mm can reach 100℃ when the exerting temperature ranges from room temperature to -196℃. The cooling rate of internal concrete can reach and exceed the exerting rate when the internal temperature is lower than the inversion temperature, but the returning temperature rate of internal concrete is lower than the exerting rate. These test results can provide reference for designing concrete structures like liquefied natural gas (LNG) tanks.