Piezoelectric cement sensor-based electromechanical impedance technique for the strength monitoring of cement mortar

Piezoelectric cement is a 0-3 type cement-based piezoelectric composite comprising 50% lead zirconate titanate (PZT) particles. Piezoelectric cement sensors, which are based on the electromechanical impedance (EMI) technique, are applied for the structural health monitoring (SHM) of cementitious materials. The compressive strength (f(c)) of three cement mortar types with water-to-cement ratios of 0.4, 0.5, and 0.6 were monitored for 56 days using an embedded piezoelectric cement sensor (PEC sensor). The PZT sensor was used as a counterpart in the experiments. The results indicate that the strength monitoring capability of the PEC sensor is similar to that of the PZT sensor. However, the monitoring capability of the PEC sensor is superior to that of the PZT sensor because the electrical impedance change of the PEC sensor is more evident. The PEC sensor is easy to find an effective monitoring frequency at which the conductance decreases with the age of the cementitious materials because it has the advantage of a broader frequency bandwidth that provides higher recognizing ability than the PZT. For the PEC sensor, a conductance root mean square deviation G(R) in a high frequency region, such as that higher than 800 kHz, can promote the reliability of mortar strength monitoring. Based on the G(R) value calculated at the effective monitoring frequency, the relation between f(c) and G(R) in the mortar presents a logarithmic behavior. The PEC sensor is suitable for monitoring the change in material properties, especially for cementitious materials. (C) 2020 Elsevier Ltd. All rights reserved.