Effect of shrinkage-induced initial damage on the frost resistance of concrete in cold regions

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The shrinkage-induced initial damage poses a threat to the frost resistance of concrete in cold regions with low relative humidity (RH). However, the progression of freeze–thaw damage in concrete affected by this initial damage, along with the quantitative relationships among RH, freeze–thaw damage, and the number of freeze–thaw cycles (FTCs), remains unexplored. This study employed combination of experimental and numerical simulation approaches to address these challenges. Experimentally, the freeze–thaw damage of concrete cured at low RH (40 ± 5 %) was compared with that cured at standard RH (95 ± 5 %) after varying FTCs. Results indicated that the former experienced more severe freeze–thaw damage, characterized by increased surface peeling, higher mass loss rate, and greater compressive strength attenuation. For the simulation aspect, a numerical model incorporating cohesive elements was firstly proposed to study the evolution of freeze–thaw damage in concrete cured at different RH under FTCs, of which the rationality was confirmed through experimental data. Additionally, the effect of FTCs and curing RH on freeze–thaw damage was investigated, revealing a negative correlation between freeze–thaw damage and curing RH, resulting in opposite evolution trend for residual mechanical properties of concrete. Finally, the freeze–thaw damage prediction model was proposed based on simulation results, and the error between the predicted and actual values was only 2.1 %, which confirmed that this model can be adopted to accurately assess the freeze–thaw damage degree of concrete cured by different RH after different FTCs. In conclusion, this study aims to better understand the freeze–thaw damage evolution of concrete cured under low RH, which provides a feasible scheme for the frost resistant design of concrete construction in cold regions.