Damage degradation model of aeolian sand concrete under freeze-thaw cycles based on macro-microscopic perspective

At present, the existing freeze-thaw damage models are mostly phenomenological damage models that use macroscopic indicators as variables, and there is a lack of a multi-scale freeze-thaw damage model that combines the macroscopic and microscopic perspectives. In this study, eight types of aeolian sand concrete (ASC) at the aeolian sand replacement rates of 0%, 10%, 20%, 30%, 40%, 60%, 80%, and 100% were subjected to freeze-thaw cycle test. Comprehensive analysis and evaluation were done of the frost resistance durability of ASC from the dynamic elastic modulus at the macro-scale and the pore structure at the micro-scale. The evolution law of the freeze-thaw damage characteristics of ASC was studied from a macroscopic and microscopic perspective. The freeze-thaw damage degradation model for ASC was established by transforming the irreversible energy dissipation into cumulative fatigue damage, and the applicability and reliability of the model were verified from the macro and micro multi-scale perspectives. The findings indicate that the introduction of aeolian sand could inhibit and delay concrete damage and deterioration, thus reinforcing the frost resistance durability of concrete. The decrease in the percentage of gel pores and transition pores and the increase in the percentage of large pores deteriorate ASC in freeze-thaw cycles. Whereas, increasing the percentage of gel pores and transition pores and decreasing the percentage of large pores could reinforce the frost resistance of ASC. The damage evolution model can manifest the development law for freeze-thaw deterioration in ASC from the macroscopic and microscopic perspectives. The model can be used as the theoretical foundation for the application of ASC in cold regions.