Calculation of Expansion Stresses and Strains in Concrete under Sulfate Crystallization Attack in Dry–Wet Cycles Environments

This paper analyzed the deterioration model of concrete in dry–wet cycles and sodium sulfate solution. The calculation method of stress transformation from dry–wet cycle and salt crystallization was established from the aspects of water saturation, salt accumulation concentration, and salt supersaturation. The results showed that the calculation results of concrete strain caused by dry–wet cycles and sodium nitrate crystallization are in good agreement with the experimental results, which proves the reliability of the stress calculation method. The calculation method of concrete strain caused by dry–wet cycles and sodium nitrate crystallization was extended to the deterioration process of concrete caused by dry–wet cycle sodium sulfate crystallization, and the strain caused by dry–wet cycle sodium sulfate crystallization is calculated. The results of strain comparison showed that the strain of mortar produced by each action increases with the increase of cycle times after degradation by dry–wet cycle sodium sulfate solution, but because mortar with a higher water to cement ratio has weaker resistance to sulfate attack, a large number of cracks appear in the later stage of degradation, and the calculation method of strain caused by dry–wet cycle salt crystallization is therefore no longer applicable.