Evaluation of Embedded Dual-Piezoelectric-Based Transducer With Miniature Impedance Analyzer for Monitoring the Curing of Cement Mortar

A dual-piezoelectric-based embedded transducer employing an electromechanical impedance (EMI) technique is used for monitoring the curing of cement mortar. The transducer, comprising of two piezoelectric patches pasted on a metal plate, used with a miniature impedance analyzer having a simple peak-finding algorithm, results in an economical monitoring system. The effectiveness of the system has been tested in cement mortar cubes of various sizes and showed consistent results. The measurements obtained from the miniature impedance analyzer are validated with a laboratory impedance meter. The structural (plate) resonance peaks, which were found to be only marginally affected by temperature, are quite effective in monitoring the curing. The frequency shift of the resonance peaks, which provided the indication of curing, is compared with the heat of hydration curves of the cement used. The transducer system is evaluated for different plate dimensions. The resonant peaks are a function of the geometry of the plate, including thickness. The plate size has to be selected in such a way as to keep the resonance peak frequency within the operating frequency range of the impedance analyzer. The transducer system has also been evaluated for its reusability and long-term stability.