Investigation of the freeze-thaw deterioration behavior of hydraulic concrete under various curing temperatures

To address the issue of damage and deterioration of hydraulic concrete materials in cold regions, experiments were conducted to investigate the microstructural and mechanical properties of concrete under the combined effects of various curing temperatures and freeze-thaw (F-T) cycles. The results indicate that as the curing temperature decreases, the peak compressive strength of concrete decreases, while the peak strain increases and the elastic modulus decreases. These trends become more pronounced with the progression of F-T cycles. Additionally, during the compression failure process of concrete, the amplitude of the acoustic emission exhibits a more significant and rapid increase as it approaches the critical state, indicating a stronger brittle characteristic of concrete after F-T damage. Microscopic test results demonstrate that the influence of curing temperature on the pore structure of concrete after F-T primarily manifests in the mesopores and large pores. Moreover, the reduction in curing temperature increases internal defects in concrete, deteriorates the crystallinity of hydration products, and leads to the aggregation of unhydrated cement particles. Insufficient curing temperatures slow the hydration rate of cementitious materials, affecting the density and overall performance of concrete. Finally, damage prediction models based on the Weibull distribution were established, using the relative dynamic modulus of elasticity, compressive strength loss rate, and mass loss rate as damage factors. The model based on the relative dynamic modulus of elasticity was more sensitive to the number of F-T cycles. All models exhibited a goodness of fit exceeding 0.89, indicating that they accurately reflect variations in the observed data and can be used to predict the service life of concrete under F-T cycles. This provides theoretical references for the degradation and damage of hydraulic concrete in cold regions.