A novel electromechanical impedance–based model for strength development monitoring of cementitious materials

Strength monitoring of early age concrete improves the efficiency of construction as it provides information on the optimum time for shoring removal and pre-stress transferring. Electromechanical impedance technique has been proven to be a useful tool for strength monitoring of cementitious materials. One of the key limitations of this technique is the lack of physical models, which resulted in strong reliance on statistical analysis tools to quantify the strength of structure being monitored. In this proof-of-concept study, a novel electromechanical impedance–based model with the potential of monitoring the strength of cementitious materials using the concept of Smart Probe is proposed. Instead of directly bonding a lead zirconate titanate patch on the host structure, a lead zirconate titanate was first surface-bonded on a pre-fabricated aluminum beam, which is termed Smart Probe. The Smart Probe was then partially embedded into cementitious materials for strength monitoring. The structural resonant frequencies of the Smart Probe can be identified from the conductance signatures measured from the lead zirconate titanate patch throughout the curing process and serve as strength indicator. By modeling the cementitious material as an elastic foundation supporting the Smart Probe, an analytical model was developed to predict the dynamic modulus of elasticity of cementitious materials based on the resonance frequency of the Smart Probe. Experimental study was carried out on a mortar slab specimen to verify the model and to investigate the performance of the Smart Probe. It was found that the dynamic modulus of elasticity of the host structure could be predicted from the conductance signatures using the proposed model. Compressive strength assessment was achieved by establishing an empirical relation with the dynamic modulus. The proposed electromechanical impedance–based model with Smart Probe is physically parametric in nature and shows high repeatability, which renders its superiority over the conventional statistical method–based electromechanical impedance technique for strength monitoring of cementitious materials.