Damage assessment of concrete via acoustic emission and mesoscopic damage constitutive model

This paper experimentally investigated the acoustic emission (AE) behavior of concrete specimens. By using the MTS810 servo hydraulic testing system and the multi-channel AE system, a series of specimens graded C40, C50, and C60 were loaded under uniaxial compression. The spatial distribution of the AE events, AE events rate, and AE energy rate were recorded. Additionally, a theoretical mesoscopic damage constitutive (MDC) model, which defines the theoretical mesoscopic damage variable as the ratio of the fractured micro-elements to the total microelements, was introduced. The results indicated that the spatial distribution of AE events resembled the shape of failure modes. Moreover, the theoretical mesoscopic damage calculated by the MDC model matched well with the observed experimental damage, represented by the AE events. This association not only related the theoretical mesoscopic damage with experimental macroscopic damage, but also revealed that the macroscopic damage of concrete stemmed from mesoscopic fracture. Additionally, the AE energy was related both to the energy of fractured micro-elements and its derivative in the MDC model.