Analysis of the process of crack initiation and evolution in concrete with acoustic emission testing

Application of the acoustic emission method (IADP), to the analysis of crack initiation and growth in concrete and reinforced concrete beams is presented in the paper. This method is based on the idea that every active destructive process becomes a source of acoustic emission. Comparing AE signals, generated within structures under service load, with previously created database, one can identify the processes of active deterioration occurring in an element. They can be located on the basis of the difference in the time, that AE signal reaches the sensors with known wave velocity. Because the cracking process (micro-cracking) occurs in concrete already at the maturing stage, experiments were performed on unloaded concrete members just after concreting (when shrinkage occur) as well as on concrete beams (in technical scale) subjected to continuous loading. It was found that using the IADP method, it was possible to detect and locate creation of micro-cracks (not visible on the member surface) and initiation and growth of cracks, which are visible on the element surface.