Parametric analysis of RSB sensors for concrete strength monitoring using hybrid EMI and WP techniques: Numerical investigation

The strength of concrete after its casting increases with time up to a certain limit due to continuous hydration reactions in the cement matrix. To measure the rate of strength development and ultimate capacity of concrete, a novel health monitoring method using Reusable smart bolt (RSB) piezoelectric sensor is proposed in the present paper. The smart piezoelectric Lead zirconate titanate (PZT) patch-based Electro-mechanical impedance (EMI) and Wave propagation (WP) techniques are utilised for accessing the health of concrete at 1, 3, 5, 7, 14, 21 & 28 days of concrete hydration. Firstly, the PZT patch-based sensing capabilities are validated with the experimental results from literature by modelling concrete cube for EMI and beam for WP results. Then, a total of 31 finite element models of concrete cubes having different RSB configurations were taken into consideration for sensor design and optimization. In EMI technique, the shifting of conductance signatures and relative resonance frequency are measured, whereas in WP technique, the shift of P-wave velocity peaks between actuator and sensor is estimated for all the models. The sensitivity of outputs is measured by plotting statistical Root mean square deviation (RMSD) index which proven the efficacy of employing RSB sensors for monitoring concrete strength-development during early-hydration ages with good correlations. Overall, the EMI-identified RMSD plotted for conductance shows 327 % more sensitivity than WP-identified relative change of P-wave velocity in monitoring concrete strength development using RSB sensors.