Active and passive monitoring of corrosion state of reinforced concrete based on embedded cement-based acoustic emission sensor

Abstract

In this paper, a cement-based acoustic emission sensor is embedded in reinforced concrete, and the corrosion damage inside the concrete is activated by swinging ball impact. The changes of low frequency and high frequency acoustic emission signals are captured and analyzed by the sensor, and the concept of low-high-frequency (LH) is proposed. The changes of acoustic emission characteristics during the corrosion of steel bars were studied, and the effects of protective layer thickness and activation site on the ratio of LH were analyzed. The results show that with the increase of the corrosion degree, the amplitude of the frequency signal in the range of 13 kHz–22 kHz decreases gradually, from 2.59 mV to 1.29 mV. The amplitude of the frequency signal near 170 kHz increases first and then decreases with the increase of corrosion time. The frequency signal near 22 kHz is used as the low frequency signal, the amplitude of the frequency signal near 170 kHz is used as the high frequency signal, and the ratio of the two is used as the low-high-frequency (LH). The evaluation result of this ratio is consistent with the ultrasound test results. As the sound source continues to move to both ends of the concrete sample, the distance between this sound source and the sensor gradually increases, the low frequency signal decreases significantly, and LH changes significantly, influenced by the reflection of the boundary.