Monitoring hydration and strength development of E-waste concrete: A passive sensing approach using piezo sensors

This study investigates the monitoring of hydration and development of compressive strength at different stages during the curing process of conventional concrete and electronic waste (E-waste) concrete using the electro-mechanical impedance (EMI) technique with embedded piezo sensors (EPS). The experiment was carried out on concrete cube specimens in which the EPS was placed inside the conventional concrete (CC) and E-waste concrete specimens to monitor the changes during hydration and different stages (early age, later age and delayed age) of compressive strength development. Simultaneously, a destructive analysis was performed to identify the compressive strength. Statistical indices, namely root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) have been established for the quantification of EMI signatures. The results revealed that with the 15% replacement of coarse aggregate with E-waste, the compressive strength of E-waste concrete decreased by 8.15 % after 28 days. The EPS sensor effectively captured the changes during the hydration and different stages of compressive strength development. The RMSD values indicate that the early-age strength development of CC and E-waste concrete is significantly higher than later-age and delayed age, and the same observations are also observed in destructive analysis with the increase in compressive strength at early age, followed by late age and delayed age. Hence, it was concluded that EPS can be used in monitoring the hydration and strength development of concrete in real time.