A study of the saturation levels of concrete at different depths on the downstream zone of a dam under low-temperature conditions

For concrete dams, the saturation level before freezing is an important factor influencing freeze-thaw deterioration of the downstream area of the dam. The integrated method of laboratory test-numerical inversion-feedback verification-engineering prediction was used to obtain concrete saturation levels at different depths within the concrete on the downstream zone of a dam under low-temperature conditions. First, tests were designed and carried out on capillary water absorption of unsaturated concrete under controlled and low-temperature conditions. Then, based on measured saturation levels in a controlled low-temperature environment, an optimization algorithm was used to identify key parameters in a capillary water absorption-water transport model for unsaturated concrete. Afterward, the measured saturation levels of previously unsaturated concrete under practical low-temperature conditions were utilized for feedback verification of the proposed model. Finally, the distribution of saturation levels of concrete on the downstream zone of a typical dam under low-temperature conditions was predicted. The study demonstrated in three geographic locations (northeast, northwest, and central China) that when the capillary water absorption before freezing continued for 5 d, 6 d, and 10 d, the saturation level of concrete on the downstream zone of a dam which exceeds 91.7 % was only near the water absorption surface for the sections of the dam. The critical depths within the concrete were 1.2 cm, 1.3 cm, and 1.8 cm at dams in northeast, northwest and central China, respectively.