Embedded piezoelectric sensor-based real-time strength monitoring during curing process of concrete

Recently, novel methods to monitor the strength development of concrete during curing process have been reported based on electro-mechanical impedance measurement using piezoelectric sensors. However, the previous research works could not provide the information about the absolute strength of concrete. In order to estimate the absolute strength directly, an embedded piezoelectric sensor system based strength monitoring technique was proposed in this study. To avoid the degradation of a piezoelectric sensor due to external and internal impacts and/or environmental variations, the piezoelectric sensor soldered with a lead wire is inserted into a small concrete block and then this block is embedded in larger concrete specimen. While the concrete is cured, the electro-mechanical impedance and guided wave signals, self-measured from the embedded piezoelectric sensor, would be changed because those are related to the material properties of the concrete such as the strength and the stiffness. Hence, the strength of concrete can be monitored by analyzing the root-mean-square-deviation (RMSD) of the impedance signals and the amplitude variation of the guided wave signals. Specific equations to estimate the strength of the concrete are derived using a regression analysis based on the features extracted from the signal variations. Finally, to verify the effectiveness of the proposed approach, a series of experimental studies using miscellaneous concrete specimens are conducted and further research issues will be discussed for real-world implementation of the proposed approach.