Characterization of fracture development in geometrical similar ultra-high-performance concrete (UHPC) beams using acoustic emission (AE) technique

Abstract

The acoustic emission (AE) technique is a common method for evaluating the fracture and damage properties of materials. This study utilized the AE technique to analyze the fracture behavior of ultra-high-performance concrete (UHPC) beams. Experiments were conducted on three differently sized beam specimens that were geometrically similar. The center point bending tests were carried out under crack mouth opening displacement (CMOD) control to study the fracture properties of the UHPC beams. Based on the experimental study, the fracture properties such as crack propagation, parametric-based properties, and fracture process zone (FPZ) length and width were predicted in the present work. The AE waves generated during the cracking can readily differentiate between the concrete matrix failure and fiber bridging following the post-peak response in the UHPC beam. In this work, the AE parameters were used to detect the source location, fracture mode, the position of the crack, and strain localization near the crack tip. The presence of steel fibers in concrete provides complexity in identifying the source localization, and wave dispersion results in attenuation and distortion of the AEs. The occurrence of AE events was observed to increase in the post-peak part compared to pre-peak possibly due to fiber bridging, demonstrating the energy absorption capacity. Based on AE results, the length and width of the fracture process zone were found to increase with the specimen size.