Nondestructive measurement of concrete strength development and damage assessment using smart PZT transducers

Abstract

The objective of this research work is to investigate the feasibility of using electro-mechanical impedance technique for non-destructive evaluation (NDE) of concrete, covering both strength prediction and damage detection. The impedance method is based on monitoring the changes in the electrical impedance which are due to the electro-mechanical coupling property of the PZT and the host structure and contain vital information concerning the phenomenological nature of structure. In this study, the PZT patches bonded on the concrete surface are used for actuating and sensing purposes simultaneously. This research work is divided into two parts. In the first part, the strength development of early age concrete is monitored by performing a series of experiments on early age concrete specimens with various curing conditions. The PZT patch bonded onto the specimen is periodically interrogated for the acquisition of electrical admittance signatures for 3, 5, 7, 14 and 28 days. The electrical admittance signatures for the curing state at 3rd day are then compared with the signatures at 5, 7, 14 and 28 days. The shifts of resonant frequency with increasing days is observed which is on account of the additional stiffening action due to bonding with concrete and the level of stiffening being directly related to strength. In the end a relationship is proposed between resonant frequency shift and compressive strength and also between RMSD values and compressive strength. In the second part of this research work damage detection in concrete cube specimen is done by using active admittance signatures instead of raw signatures. This is done by filtering off the passive components from the coupled electromechanical admittance equation. In order to assess the different damage states, the shifts of resonant frequencies and root mean square deviation are used as damage indicators. The active admittance signatures show relatively greater sensitivity to damage than the conventi...