Embedded piezoelectric transducers based early-age hydration monitoring of cement concrete added with accelerator/retarder admixtures

Abstract

Accelerator/retarder admixtures are often added into concrete to improve its early-age strength, which needs to be effectively monitored during its hardening process. The electromechanical impedance (EMI) technique has validated its effectiveness for concrete hydration monitoring, this study attempted to extend the EMI technique to monitor 28-day age of strength gain in concrete that added with accelerator/retarder admixtures. Two types of new piezoelectric (PZT) transducers namely cement/aluminum embedded PZT (CEP/AEP) were proposed for EMI monitoring. The feasibility of the CEP and AEP was first verified via finite element analysis, where hydration heat effect on the two types of transducers was comparatively evaluated by numerical modeling. In the experiment, CEP/AEP transducers were applied to monitor the strength gain in concrete cubes, where characteristics of EMI signature and its statistical indices including root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were analyzed and correlated to strength development in concrete. Monitoring results demonstrated that concrete hydration triggered by retarder/accelerator were successfully captured by EMI signature. RMSD and MAPD indices further indicated that AEP had preferable performance than CEP transducer for monitoring early-age strength gain of concrete, as it could immune from hydration heat effect.