Influence of crack orientation on propagation behavior of concrete by acoustic emission in compression test

The crack behavior of concrete needs to be understood to properly evaluate the damage in concrete specimens from in-service structures.The mechanical properties of heavily damaged concrete are unreliable due to variations in destructive behavior and damage localization.Therefore, a supplemental indicator is necessary for evaluating the damage in concrete with crack propagation behavior.Against this background, the damage behavior of concrete with cracks of different orientations is investigated using Acoustic Emission (AE) in uniaxial compression test.Concrete specimens were drilled from a dismantled weir pillar of a reinforced concrete (RC) structure.These concrete specimens were affected by freeze-thaw and salt damage due to the severe environmental conditions.Each concrete specimen has a crack distribution with vertical and horizontal orientations defined as the longitudinal and short directions of the concrete.In the experimental procedures, Xray Computed Tomography (CT), ultrasonic testing and uniaxial compression test with AE monitoring were performed.Based on the results of non-destructive testing, selected concrete specimens were subjected to uniaxial compression test.Pre-existing cracks were visualized and quantified based on their distribution and geometric features using X-ray CT.The geometric properties of the cracks were calculated in two dimensions and included parameters such as perimeter, angle, and circularity.The number of AE events was estimated using machine learning based on the relationship between the geometric properties of neighboring elements.The influence of these geometric properties on the number of AE events was investigated quantitatively.