A concrete shrinkage monitoring technique using embedded piezoelectric impedance transducers

Concrete shrinkage directly affects the durability and integrity of concrete structures. The traditional shrinkage monitoring techniques have many limitations such as low accuracy, complicated operation, and size limitation of the specimen. This study proposes a novel monitoring technique for concrete shrinkage based on electromechanical impedance, which is expected to improve the precision and operability of concrete shrinkage monitoring. Embedded-type PZT (lead zirconate titanate) transducers encapsulated with cement paste were used to monitoring the shrinkage development of concrete specimens in 400 days by observing the variations of resonant frequency extracted from the piezoelectric admittance curves. Experimental results show that the resonant frequency increases with the increase of concrete shrinkage and appears approximately linear changes in two different stages. Both line and bilinear models are proposed to correlate the resonant frequency of admittance curve with concrete shrinkage based on the experimental data. Compared with the results measured by traditional vibrating wire strain gage, it is found that the bilinear model predicts concrete shrinkage better than the line model.