An Electromechanical Impedance Measurement-Based Solution for Monitoring Fresh Concrete Maturity

This paper proposes an electromechanical impedance measurement (EIM)-based solution for monitoring concrete maturity that refers to concrete strength development at the early stage.

A smart aggregate (SMA) that consists of a waterproofed piezoelectric patch is developed. The working principle is explained based on the impedance theory of an electromechanically coupled system. A finite element (FE) model of the EIM-SMA unit is established. The stiffness of the applied spring foundation is varied to emulate the concrete hardening process.

The simulation results reveal that a peak located between 60 kHz and 70 kHz in the impedance plot could be used as an indication to reflect the stiffness variation of the spring foundation. A 3D-printed mold is designed for rapid production of the EIM-SMA units. In the experiment, two sample EIM-SMA units are used to monitor fresh concrete maturity in the first six hours after casting. The results of the two sample EIM-SMA units agreed well. The experimental results matched the simulation prediction.

Compared to a bar-dropping test that is widely adopted at construction sites, the impedance evolution of an EIM-SMA unit is much smoother and has better monotonicity.

In general, the proposed method has been proven to be a reliable solution to monitor the maturity development of concrete.