Thermal and wet progressive micro damage of high falling risk in building external wall systems.

A fine -macroscopic scale computational model was constructed based on the numerical analysis of the fracture phase field method to simulate the internal temperature field and microscopic stress field in the case of a sudden cooling of the exterior wall surface after being subjected to hot sunshine. An evaluation model of heat and humidity progressive micro-damage was established, which was verified by the bonded mortar pull-out test. The results indicate that when the external surface of the external wall system is subjected to a temperature increase of 88.6 °C, in summer and then a sudden decrease to 20 °C, by hail and heavy rainfall, the maximum principal stress value of fine aggregate and net mortar subjected to 15 MPa, respectively. Cracks with a depth of 5 mm and a width of 100 microns in the direction of the thickness were developed, which means that this kind of extreme climate change has caused substantial damages to the structural integrity of the heat preservation system, and the structural integrity of the heat preservation system is substantially damaged by this kind of extreme climate change. The risk of "high fall" of the external wall system increases rapidly. [ABSTRACT FROM AUTHOR]