The Evolution of Freezing Stress in Concrete Under Freeze-thaw Condition and Its Influence on Frost Resistance

In order to explore the freezing damage mechanism of concrete in severe cold area and the action mechanism of freezing stress affecting the frost resistance of concrete, based on the simulation of -40 ℃ low-temperature freezing damage condition by large-scale extreme climate simulator, the freezing stress and frost resistance of F300 high frost resistance design concrete under single cooling stage and cooling heating freezing and thawing cycle were studied by using the developed freezing stress test system. At the same time, the microstructure of concrete under freeze-thaw cycle was studied by environmental scanning electron microscope. The experimental results demonstrate that in the single cooling process under -40 ℃ low-temperature, the faster the cooling rate is, the earlier the freezing stress appears, and the greater the increase of freezing stress in the concrete. The freezing stress generated in the cooling stage will accumulate and increase with the continuous cycle of freezing and thawing, and there is a transition inflection point in the development of freezing stress. Under the same low temperature condition in the center of the specimen at the end of cooling, the greater the cooling rate in the cooling stage, the earlier the inflection point from growth to reduction of freezing stress appears. There is a good correlation between the freezing stress in the process of freezing and thawing and the two commonly used evaluation indexes of concrete quality loss and relative dynamic elastic modulus. The freezing stress gradually causes damage to the cement paste, which is manifested in the formation and development of micro cracks, and the damage accumulation produces freezing damage. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.