Dielectric Sensors Used in Environmental and Construction Engineering

Abstract

ABSTRACTDielectric properties of materials can give insight into the microstructure or concentrations of their constituents and can be determined by measuring the complex impedance of a capacitor formed by a set of electrodes with the material as the dielectric. Measuring frequencies between 1 MHz and 1 GHz appeared to be most informative for soil and concrete. A new dielectric sensor containing an integrated circuit that includes all analog and digital circuitry is described briefly. This sensor is used to demonstrate the potential of dielectric sensor technology for applied materials research in the field in two recently developed applications. One application concerns the determination of the state of hardening of young concrete. The relationship shown is between changes in the dielectric properties and changes in the structure for curing concrete. The other application is a dielectric probe for contaminated site investigation. It appeared to be possible to locate chemically polluted soil layers, such as with chlorinated solvents or oil, using small changes in their dielectric properties.