Investigating polymer coated piezo-ceramic sensor for the very early strength monitoring of cementitious materials (Conference Presentation)

Electromechanical impedance (EMI) technique coupled with the piezoelectric sensor has been explored as a promising non-destructive testing (NDT) method to determine the quality of cementitious materials. Among the piezoelectric sensors, Lead Zirconate Titanate (PZT) is the most commonly used piezo-ceramic materials for conducting the EMI because of the high sensitivity and high piezoelectric constant. However, the inherent brittleness of PZT limited their potential application as embedded sensors for in-situ monitoring of materials/structure properties. To improve the durability and flexibility of the PZT sensor, we have systematically investigated the effect of different polymer coating methods of PZT on their sensitivity and effectiveness of EMI sensors. Specifically, two polymer coating agents were used to encapsulate the PZT sensor including the flexible organic polymer compound - Polydimethylsiloxane (PDMS) and the rigid polymer compound- Polyepoxides (Epoxy) We have also investigated the feasibility of EMI technique with the surface bonded sensor and embedded sensor to test the compressive strength gain of mortars. The compressive strength test of samples was also conducted using conventional mechanical methods per ASTM C109 as a baseline at the first 5th to 8th hour. The EMI signatures were collected for all the samples at the same time. Our preliminary results have shown a high correlation of EMI methods’ results with the compressive testing results for two different polymers coated PZT sensors, which indicated the polymer-coated PZT sensors can be used as an effective NDT method for in-situ monitoring of concrete compressive strength gain at the very early age.