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Even 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. [ABSTRACT FROM AUTHOR]

This study investigates the use of a modified statistical model to quantitatively analyze and assess the current operation status of an RCC (Roller Compacted Concrete) gravity dam in an alpine region. Initially, combined with the measured temperature analysis and temperature field simulation results of a typical dam block, it is demonstrated that frost heaving data are essential to monitor dam crest deformation. The frost heaving factor is introduced using an engineering analogy method, and a modified statistical model considering frost heaving based on the Heaviside step function adaptive model is established. The analysis shows that (a) in the low-temperature season, the deformation near the dam crest is affected due to a wide range of negative-temperature zones; (b) the frost heaving component identified using the novel statistical model shows that the dam crest frost heaving deformation presents a variation law of periodic pulsed fluctuation and a ten-day cycle of hysteresis. The safety assessment of concrete dams crest without any insulation measures in alpine regions should thoroughly consider the displacement caused by frost heaving, which is highly relevant to improving the accuracy of dam safety evaluations over long-term service periods. [ABSTRACT FROM AUTHOR]

Shape is an important physical property of aggregates. However, the large amount of work required to measure with precision the size of coarse aggregate and the lack of relevant tests obscure how the shape of the coarse aggregate affects the strength of concrete. In this work, granite coarse aggregate was first divided into flaky stone and massive stone by manual screening. Next, the coarse aggregate was selected at random for size and volume measurements to obtain and analyze the aggregate shape parameters such as sphericity and flatness. Based on the selected aggregate, three aggregate combinations were designed according to the content of flaky stone. Finally, we measured the compressive strength and splitting tensile strength of hydraulic concrete (7, 28, and 60 days) with water‐binder ratios of 0.33, 0.41, and 0.5. The results show that the three aggregates clearly differ in shape, and the measured compressive strengths and splitting tensile strengths of the concrete with water‐binder ratios of 0.41 and 0.5 are similar. However, the compressive strength of the concrete with water‐binder ratio of 0.33 is significantly correlated with the three selected aggregate combinations. [ABSTRACT FROM AUTHOR]

Since research on the freezing‐and‐thawing damage experienced by hydraulic concrete subjected to variable temperatures is currently rudimentary, it is difficult to use existing models to quantitatively reflect the damage of actual hydraulic engineering concrete under such conditions. This study first presents a formula to calculate the equivalent damage age through an analogy with the equivalent age theory, and the results of this formula can comprehensively reflect the relationship between the freezing‐and‐thawing process at variable temperatures and concrete damage. Then, this study establishes a fractional freezing‐and‐thawing damage model for hydraulic concrete subjected to freezing‐and‐thawing cycles at variable temperatures according to fractional calculus theory. New model parameters for freezing‐and‐thawing damage are identified and optimized with existing testing data acquired under variable freezing‐and‐thawing temperatures. Moreover, the applicability of the new model is verified with different freezing‐and‐thawing temperature data obtained from supplemental freezing‐and‐thawing tests performed in this study. The analysis results show that the new concrete freezing‐and‐thawing damage model can accurately reflect the changes in concrete strength during freezing‐and‐thawing cycles at variable temperatures. [ABSTRACT FROM AUTHOR]