Piezoelectric-based non-destructive monitoring of hydration of reinforced concrete as an indicator of bond development at the steel–concrete interface

Advances in piezoelectric materials have attracted interests among researchers to develop new non-destructive evaluation and monitoring techniques. In this study, piezoceramic (PZT) sensors were embedded in concrete by bonding the sensors on steel reinforcing bars to perform non-destructive monitoring. To evaluate the performance of the PZT sensors and electromechanical impedance (EMI) sensing technique, a series of experiments was carried out to monitor the bond development between steel rebar and concrete by measuring the electrical response of the PZT bonded to the steel rebar using an impedance analyzer. From the EMI measurements, the gradual adhesion between the steel rebar and fresh concrete could be detected via the measured changes in the conductance spectra of the PZT sensor bonded to the steel rebar. The bond development could be attributed to the transformation of concrete from liquid to solid state controlled by the hydration of cement and by monitoring the hydration of concrete with respect to time, the status of bonding can be estimated. The results show that the early-age development of bonding between steel rebar and concrete is affected by various factors such as varying water–cement ratio, low curing temperature and poor compaction.