It is critical to evaluate the quality of cementitious materials at its early age. Lead Zirconate Titanate (PZT) sensors, coupled with the electromechanical impedance (EMI) method, have proven to be a promising method for instantaneously monitoring the mechanical properties of cementitious materials. PZT is a piezoelectric ceramic with high piezoelectric properties and sensitivity, but its inherent brittleness limits its potential application in construction environments. To enhance the robustness of the sensor, this work has studied the use of two types of polymer coating as protective layers on the sensor, specifically Polydimethylsiloxane (PDMS) and polyester. The effectiveness of piezoelectricity in polymer-coated sensors is evaluated using a scanning laser Doppler vibrometer and an impedance analyzer. Finite element analysis has been conducted to simulate the frequency response of sensors with different coating configurations. Moreover, this study has evaluated the feasibility of monitoring the growth of mortars’ mechanical properties over time using the proposed sensors with EMI technique. Based on the results, both polymer-coated sensors have shown adequate sensitivity in capturing the change of mechanical properties in cementitious materials. The polyester coating performed better durability than PDMS coating as encapsulating materials. It has been concluded that the polymer-coated, sensor-based EMI method can be an effective nondestructive evaluation method for monitoring concrete properties in practical applications.