Issues in identifying damage progression in corroded post tensioned concrete beams under flexural loads by Acoustic Emission technique

Acoustic Emission technique was used to evaluate damage progression during increasing flexural loading tests of six meters long (0.4 x 0.25 m section) twelve years old post-tensioned concrete beams characterized by corrosion damage of the prestressing tendons. Acoustic emission signals have been recorded by sensors placed directly on prestressing strands and on concrete surface. Due to the high sensitivity of the acoustic emission technique a proper data mining procedure has to be adopted to avoid false assignations and erroneous interpretation. By using proper algorithms, it was possible to differentiate acoustic emission hits in different clusters characterized by specific recognition patterns. A tentative assignation to different damage mechanisms (e.g. tensile or shear crack propagation) was carried out.