Deterioration with years in service of corrugated asbestos cement sheet (slate) is investigated experimentally. This material is widely used for roofing of factories. The present paper provides the properties of the slate being used for up to 35 years. Following experimental items are discussed, based on the experimental data. 1. Appearance changes : thickness, cross sectional density, interlayer segregation 2. Change in water absorption 3. Change in chemical property : pH, chemical composition 4. Change in mechanical property : flexural strength, Charpy impact value From the obtained experimental data, it is assumed that the flexural strength of the slate almost constantly decreases with years in service. Such tendency coincides with the fact reported by users, while that can not be predicted from the experimental data reported earlier.
