Analysis on Moisture Stress in Building Walls of Porous Media

According to the characteristic of moisture expansion in porous media, action mechanism and influencing factors of moisture stress in building walls were analyzed and moisture expansion experiments were carried on commonly used porous media such as tiles and cement mortar. The results and analysis of the experiments indicate that: The moisture content and gradient inside the wall are affected by thermal and moisture environment. The physical parameters of the material layers such as elastic modulus, moisture transfer rate, coefficient of moisture expansion are different and in this case moisture stress will occur due to restraint among material layers when moisture content changes. In a certain layer, even if physical parameters are the same, the restrained bending deflection caused by moisture gradient would generate moisture stress in the material. Under the thermal and moisture environment, variations of moisture content moisture gradient and variation of moisture stress on the surface of the wall is larger than that of the inside. Thus the surface of the building wall is the part more likely to be damaged by moisture stress.