Impedance based Concrete Monitoring using Embedded PZT Sensors

This paper presents a health monitoring study of concrete specimens using embedded piezoelectric transducer (PZT) via electromechanical (EM) impedance technique. The main objective of this research is to present a very easy method of embedding PZT sensor in concrete for monitoring either fresh or cured concrete. The basic principle; is to record EM admittance signatures resulted from the actuations of PZT in the presence of electric field. Any deviations in these signatures during the monitoring period indicate disturbance/damage in the concrete structure. The PZT can be either surface bonded or embedded, however the important features of embedding PZT inside the host structure are durability and protection from surface finish, vandalism etc. The embedment of PZT in the structure is not as simple as surface bonding because there are several issues such as bonding between PZT and host structure. Moreover, it should withstand the curing pressures and temperatures of the host material, etc. The PZT was found to be more effective for metals as compared to non metals like concrete. Thus, this paper presents a double protection wrap method employing both metal and non metal, where the first protection is provided by a steel wire mesh and the second is by cement paste. The wire mesh serves as bonding connector between the host structure and the PZT, where as cement paste provides connection between concrete and mesh. The implementation was verified on various lab sized concrete cubes and the observations were examined by statistical analysis.