Monitoring of the strength gain of concrete using embedded PZT impedance transducer

Piezoelectric lead zirconate titanate (PZT) impedance transducer in the electro-mechanical impedance (EMI) technique has emerged as a potential sensing tool for structural health monitoring. In the EMI technique, PZT acts as both sensor and actuator simultaneously due to its direct and inverse piezoelectric effects. The PZT impedance transducer provides a new alternative for monitoring the compressive strength gain of concrete since the conventional nondestructive detection techniques have many limitations. This paper briefly presents a waterproof process for PZT patches using asphalt lacquer material in order to use PZT patches as embedded transducers into concrete, and also presents a new monitoring technique of concrete strength based on embedded PZT impedance transducers. In the technique, a PZT patch covered with asphalt lacquers are embedded into one of concrete cubes. By monitoring the PZT admittance (inversion of impedance) signals and measuring the compressive strength of concrete cubes in different ages, and by combining with the indexes of the root mean-square deviation (RMSD) and the mean absolute percentage deviation (MAPD), the correlations between concrete strength gain and RMSD as well as its correlation with MAPD are founded. The feasibility of the new EMI method based on embedded PZT transducers for monitoring the concrete strength development in early ages is verified.

► The proposed technique can monitor and predict the earlier age strength of concrete, even the first day strength, which is difficult to implement by the surface-bonded PZT transducers.
► The indexes of MAPD and RMSD are introduced to further evaluate the correlation between the compressive strength of concrete and the electric admittances of PZT embedded into concrete.
► A waterproof process for PZT patches using asphalt lacquer material is briefly addressed in order to use PZT patches as embedded transducers into concrete.