Corrosion monitoring of the reinforced concrete by using the embedded annular piezoelectric transducer

Abstract

It is an important issue to ensure the long-term reliable service of the reinforced concrete structures by developing effective online monitoring techniques. In this paper, three different accelerated corrosion experiments were conducted by using the electrochemical method, and the ultrasonic pitch-catch and the electrochemical impedance spectroscopy methods were employed to discuss the corrosion phenomena by using the embedded annular piezoelectric ultrasonic transducer. The results show that the capacitance arc length in the high frequency zone of the electrochemical impedance spectra increases gradually with increasing the corrosion rate. When the corrosion rate is larger than 3%, obvious corrosion products can be found on surface of the reinforced concrete, and there exist two capacitance arcs in the corresponding electrochemical impedance spectra. The ultrasonic analysis results show that there is an obvious longitudinal mode wave packet in the time domain spectra, and the peak-peak value shows a linear decreasing trend with increasing the corrosion time. The dominant frequency peak value also decreases with increasing the corrosion time accompanying with the appearances of the new peaks in the low frequency zone. The wavelet transform method was also employed for the ultrasonic time-frequency domain analysis. Based on variations of the acoustic energy and dominant frequency components of the ultrasonic wave, the corrosion extent of the reinforced concrete can be qualitatively evaluated.