Frost Damage of Roof Tiles in Relatively Warm Areas in Japan: Influence of Surface Finish on Water Penetration
In Japan, frost damage has been observed in relatively warm areas such as Kyoto. Spalling and fine flaking of roof tile surfaces are a typical examples of frost damage in warm areas.
In this study, the characteristics and causes of frost damage in roof tiles were investigated through water penetration experiments, freezing–thawing tests, and a numerical analysis by focusing on the moisture accumulation and freezing.
First, the methods and results of water penetration experiments were reviewed. The distribution of water in tiles was experimentally examined, and the results showed that the water content might increase in particular small areas. As the results, non-uniform moisture distributions are observed in the specimens.
Second, a new freezing–thawing test method using different water supplies was reviewed. The results of new test showed that even small water droplets could penetrate the finish and could cause spalling similar to that found in the field. These experimental results suggested that small spallings or fine flakings may occur due to the increase in water content in particular small areas due to water penetration through invisible pinholes.
The influence of pinhole on the water penetration was investigated by numerical analysis. In the analysis, the time profile and distributions of liquid water and ice contents in the freezing–thawing process were analyzed. The influence of the position of the surface finish and water permeability of the tile body was also considered. The results showed that when the water permeability was low, high local water content tended to occur, and this high water content increased the risk of frost damage.