Rebar Corrosion Monitoring in Concrete Using Piezoelectric Cement Sensors

In this study, the piezoelectric cement (PEC) sensor, a sensing element of lead zirconate titanate (PZT)/cement piezoelectric composites, was used to monitor rebar corrosion in concrete. The strength of the concrete was 21 MPa. A rebar was placed in the center of the concrete specimen. The piezoelectric cement sensor was attached to the concrete surface with epoxy resin to monitor rebar corrosion. An impressed current was applied to accelerate the rebar corrosion in concrete. The weight loss of the rebar was directly measured after removing the rusted parts in the acid solution. The results showed that the piezoelectric cement sensors, through the electromechanical impedance (EMI) technique, can monitor rebar corrosion in concrete. The conductance curve of the RC specimen monitored by the PEC sensor is smooth, and the applicable frequency is easy to identify. The frequency bandwidth for rebar corrosion monitoring is between 1000 and 2000 kHz. The broader bandwidth of the PEC sensor is beneficial for monitoring rebar corrosion. The regression analysis of the rebar’s weight loss rate (WL) and the sensor conductance root-mean-square deviation (GR) indicated that WL is linearly correlated with GR. This linear behavior allows the assessment of rebar corrosion when piezoelectric sensors are used for RC structure monitoring.