Acoustic emission characteristics of concrete cylinders reinforced with steel-fiber-reinforced composite bars under uniaxial compression

An experimental study of the acoustic emission characteristics of concrete cylinders reinforced with steel fiber-reinforced composite bars (SFCB) under uniaxial compression was performed. SFCB-reinforced concrete cylinders, plain concrete cylinders, and fiber-reinforced polymer (FRP) bar-reinforced concrete cylinders were tested under uniaxial compression. The entire failure process of different concrete cylinders was monitored in real time using acoustic emissions (AE). Damage characteristics of the cylinders were analyzed using the AE hit number distribution, Ib value analysis method, and AE event location and energy. The Ib value characteristics were closely correlated with the microcracks and their extension inside the concrete cylinders. For the reinforced concrete cylinders, the damages were predominantly microcracks of the concrete observed before the first turning point of the load-displacement curve. Subsequently, damage to the longitudinal SFCBs and FRP bars occurred. The AE characteristic of FRP reinforcement damage was similar to that of the macroscopic crack damage in concrete, that is, with a small Ib value. According to the AE event location analysis, the plain concrete cylinder demonstrated obvious shear failure, which was primarily suppressed in the reinforced concrete cylinders owing to the confinement effect of the spiral. The AE energy released by the compression damage of the longitudinal FRP bar was higher than that released by the tensile damage of the FRP spiral. This could trigger a distinguishable high AE location source amplitude for detecting the compression damage to the FRP bar. The analysis of the AE event distribution characteristics proves that the SFCB has a stable post-yield stage, and the compressive damage process of the SFCB is relatively stable and mild compared with the FRP bars in concrete cylinders.