Monitoring bond strength of adhesively planted rebars in concrete using electro-mechanical impedance (EMI)

Electro-mechanical impedance (EMI) is among the many types of gauges that can be used for structural health monitoring (SHM) of concrete structures. The bond strength between concrete and planted rebar plays an important role in the integrity of concrete structures strengthened by post-installed anchors. This paper presents a method to monitor the development of epoxy bond strength between concrete and a planted rebar by the EMI technique. Three concrete cubes each with a planted rebar were fabricated and used for a set of monitoring experiments. To conduct experiments, a lead zirconate titanate (PZT) patch was attached to the polished side surface of the planted rebar. During the monitoring test, conductance spectra signals from three PZT patches were acquired at the 0th, 20th, 40th, 60th, 80th, 100th, and 120th min of the experiment. Furthermore, a pull-out test was conducted on two concrete beams with three planted rebars each. The root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were applied to compare instantaneous conductance signatures with the initial, baseline conductance signature across different frequency ranges to ascertain the growth of bond strength during the curing process of epoxy. The results of the monitoring experiments and the pull-out test demonstrate the effectiveness of EMI technique in monitoring bond strength development between concrete and planted rebars. The results also show potential application prospects of the EMI technique in the SHM of reinforced concrete structures.