Time-frequency analysis of acoustic emission signals generated by cement-fiber boards during bending test

Fiber-cement building materials have been used in civil engineering for over one hundred years. Contemporary fiber-cement boards are made of natural raw materials such as cement, cellulose fibers, PVA and water. Materials made of fiber-cement are used in construction as a building and finishing material for elevations, internal walls and roofs, hence are exposed to environmental conditions such as rainfall and temperature changes, in particular, frequent temperature transition through 0°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 bending strength of cement-fiber boards subjected to environmental factors and exceptional factors. The paper also presents a proposal to use a nondestructive method of acoustic emission (AE) based on time-frequency analysis for testing fiber-cement boards. Interesting research results were obtained, which allowed to trace the differences in the mechanisms of material destruction under the influence of various factors