Monitoring of cementitious materials hydration using 2-2 cement-based piezoelectric transducers based on electromechanical impedance method

Monitoring cementitious materials hydration enhances construction efficiency by providing crucial information regarding the optimal timing for shoring removal and pre-stress transferring. In recent years, many scholars have utilized the lead zirconate titanate (PZT)-based electromechanical impedance method (EMI) to monitor the cementitious materials hydration process. However, conventional piezoelectric transducers are less compatible with cementitious materials. In addition, the currently commonly used statistical-based metrics lack a clear physical meaning. The 2-2 cement-based transducer (2-2), composed of multiple PZT elements, demonstrates excellent electromechanical performance and good compatibility with cementitious materials. In this study, the 2-2 was employed to monitor the cementitious materials hydration, and an electromechanical impedance model for describing the interaction between the 2-2 and the structure was presented. Taking into account both resonance frequency and peak value of the conductance signatures, an objective function was defined. Genetic algorithm (GA) was employed to minimize the disparity between theoretical and experimental results, thus extracting equivalent stiffness and damping. The empirical relationship between equivalent stiffness, damping, and compressive strength was established to predict the compressive strength. The experimental results show that for the same monitoring process, the normalized equivalent stiffness and damping extracted from different 2-2 sensors are in some agreement. It is more sensitive to hydration processes than statistical indicators. More importantly, the equivalent parameters have a clear physical meaning and can better portray the hydration process of the cementitious materials.