Visual damage identification of concrete cylinders with steel‐fiber‐reinforced composite bars based on acoustic emission

Steel-fiber-reinforced composite bar (SFCB) is a composite bar composed of a crescent-rib steel bar and an outer protruded fiber-reinforced polymer (FRP) layer. Due to its unique post-yield stiffness and superior anti-corrosion behavior, the SFCB is except to be an ideal reinforcement for concrete structures subject to a high corrosion environment. For SFCB-reinforced concrete cylinders, their internal damage mechanism has never been experimentally studied but was usually speculated with the brittle failure due to the potential brittle fracture of the SFCB. To reveal the compression damage mechanism of SFCB-reinforced concrete cylinders, a uniaxial compression test for SFCB-reinforced concrete cylinders was carried out at first. The entire damage process of SFCB-reinforced concrete cylinders was monitored in real-time by acoustic emission (AE), a widely used nondestructive testing method. The test result shows that the SFCB-reinforced concrete cylinders fail after the buckling of longitudinal SFCB or the fracture of the stirrup. The intensity signal analysis of AE proves the failure mode of the SFCB-reinforced concrete cylinder was close to a plastic failure instead of a brittle failure. Furthermore, a new damage visualization method is proposed to analyze the internal damage of the concrete cylinders by using the spatial b value of AE. The T value was constructed by combining the spatial b value with the density distribution of AE events. It is proven that the T value is highly sensitive to the serious damages of the concrete cylinders and can be used to identify the damage locations inside the concrete cylinders.