Evaluation of destructive processes in FRC composites using time-frequency analysis of AE signals

Modern fiber-cement boards currently used in construction are made of natural raw materials such as cement, cellulose fibers and of polyvinyl alcohol (PVA) and water. They replaced the eternitic plates, which were harmful to health, originated by Ludwig Hatschek. Materials made of fiber-cement are used in construction industry as a building and finishing material for facades, internal walls and roofs. Therefore, they are exposed to environmental conditions including rainfall and temperature changes, and in particular to frequent temperature transition through 0 degrees C in a 24-hour cycle (cyclic freezing-thawing). In addition, fibrous cement materials, primarily used as cladding elements, are exposed to exceptional conditions, which include the high temperature caused by fire. The article presents the results of experimental tests of flexural strength of cement - fiber boards subjected to exceptional conditions, to which the operation of fire belongs. The paper also presents a proposal to use a non-destructive method of acoustic emission based on time-frequency analysis for testing fiber-cement boards. Interesting research results were obtained that allowed to trace the differences in the mechanisms of material destruction under the influence of the changing time of external factors.