Study on Damage Mechanism and Residual Life of Clay Brick in Central Plains of China Under freeze–Thaw Environment

The paper scientifically evaluates the durability of masonry structure, reasonably predicts the residual life, and effectively protects the architectural heritage of masonry structure under the freeze–thaw cycle; investigated the deterioration law of traditional clay blue bricks comprehensively systematically. Through indoor experiments on clay blue bricks after freeze–thaw cycles, we investigated the changes in appearance, microstructure characteristics, quality and water absorption, changes in compressive strength, damage degree, and residual life of traditional clay blue bricks. The results showed that the damage caused by the freeze–thaw process to the blue brick reflected the decay of the macro-mechanical properties, the expansion of the microstructure, and the development of micro-defects is the intrinsic reason for the devolution of the mechanical properties. Furthermore, the water absorption rate of the blue brick increased rapidly at the beginning of the freeze–thaw cycle. In contrast, the mass-loss rate was low, and the opposite was the case in the late freeze–thaw period. We obtained the damage value of the blue clay brick according to the basic concept of macroscopic phenomenological damage mechanics and established the damage evolution equation. Under the action of the freeze–thaw process, the paper proposed a method of predicting the residual life of blue bricks. The analysis of compressive strength, freeze–thaw processes, and the service life calculated the relationship with the number of freeze–thaw cycles. Assuming that 10.0 MPa, 8.5 MPa, and 7.5 MPa are the failure strengths of blue bricks, the corresponding remaining service life is calculated as 36.5 years, 67.78 years, and 104.26 years. The research results provided the primary basis and essential reference for the scientific evaluation of the durability of buildings and the prediction of residual life under the action of freeze–thaw cycles.