Evolution of thermal parameters of wet‐screened dam concrete after different freeze–thaw deterioration

Abstract

AbstractEven with specialized equipment, it is difficult to measure the thermal parameters of dam concrete during freeze–thaw testing. In addition, numerical calculations usually assume that freeze–thaw cycling does not change the thermal parameters of the aggregate and mortar of dam concrete, which makes it difficult to accurately determine how these parameters evolve during freeze–thaw deterioration. To address this challenge, we propose herein a new method to determine the thermal parameters of wet‐screened dam concrete during freeze–thaw deterioration. This method involves freeze–thaw testing, temperature perturbation, numerical calculation, and optimization inversion. First, 200 rapid freeze–thaw tests and 5 temperature perturbation tests of 5 concrete specimens were carried out. Next, orthogonal design parameters were used to calculate the temperature field of the specimens via the finite‐element method. A neural network was then established based on the difference between the measured and calculated temperatures. The expected difference and measured density were fed into the model to invert the thermal parameters of the concrete for different water–cement ratios, ages, and content of the air‐entraining agent. The results show that, upon increasing the number of freeze–thaw cycles, the thermal conductivity of wet‐screened dam concrete gradually decreases, the specific heat remains relatively constant, and the surface heat‐transfer coefficient gradually increases.