Study on the AE Characteristics and Wave Velocity of Concrete during the Total Failure Process

This paper introduces an example on AE monitoring and ultrasonic wave velocity measurement of concrete (C20). Experiment on AE characteristic of the full failure process of concrete is carried out on the pressing machine. AE sensors can be surface mounted. A system (the 8-channels, high-speed acquiring and analyzing AE signal), called HUS (Hyperion Ultrasonic System), was employed to acquire and record AE characteristics. AE signals were recorded during loading (fracture propagation) subject to the uniaxial compressive loading until failure. Using a simplex location algorithm allows AE event location from first arrival times to be determined by the AE sensors. The mechanical properties of concrete and acoustic emission characteristic, including the full stress-strain curves, AE counts, and AE rate and ultrasonic wave velocity, were obtained. The relations among AE counts, AE rate, stress levels, ultrasonic wave velocity and time are analyzed in detail. This paper reports AE observations made with an array of this new high-fidelity. Crack initiation and crack propagation due to the uniaxial compressive loading were monitored for AE activity and compared with visual observation. Meanwhile, stress changing influence the wave velocity of concrete; with the initial crack expands, up to the rock sample failure, the wave velocity falls gradually. Some insight into the percentage of AE events that must actually be detected to describe the health of concrete sample was gained.