Acoustic Emission-based crack tracking for existing concrete structures: Influence of number of load cycles and loading speed

Acoustic Emission (AE)-based crack tracking is a promising approach to locate cracks in concrete structures. Different from conventional AE, this approach uses AE activities during crack closure. But, AE activities during crack closure may be influenced by the number of load cycles and loading speed. This may challenge the applicability of AE-based crack tracking, especially for existing concrete structures with many load cycles in the service life. This paper investigates the influence of the number of load cycles and loading speed on AE-based crack tracking. A total of 80 load cycles were applied on a pre-cracked concrete beam. The last 5 cycles had increasing loading speeds. AE-based crack tracking was carried out in each load cycle. For calibration, Digital Image Correlation (DIC) was performed to measure the crack opening and closure. We found that AE-based crack tracking can locate the cracks, while, with many load cycles, it cannot indicate the crack width. Loading speed had little influence on AE-based crack tracking. The results of this paper put forward the applicability of AE-based crack tracking for existing concrete structures.