Detection of Water and Ice on Bridge Structures by AC Impedance and Dielectric Relaxation Spectroscopy (Phase I) - FY08 NATSRL

Principal Investigator:

John Evans, Professor, UMD-Chemistry and Biochemistry

Project Summary:

This research project aimed to develop low-cost sensing systems for monitoring ice and water on bridge deck surfaces. These sensing systems are based on the measurement of impedance of the sensor in contact with or close proximity to ice, water, or aqueous solutions of deicing chemicals. Researchers explored two alternative technologies: impedance analysis at lower frequencies determined the presence of deicing electrolyte solutions (a sort of "conductivity measurement"), while high-frequency dielectric relaxation using time domain reflectometry (TDR) probed the physical state of precipitation and deicing chemicals on the deck or road surface (via dielectric relaxation). In both approaches, the methodologies used low-cost electrodes in the impedance analysis schemes. While it was originally expected that both measurements would be required to reliably determine the condition of a bridge deck surface with regard to the presence of frozen water or deicing solutions, researchers found that the TDR approach is adequate for this task, which suggests that a significant reduction in both the cost of development of practicable sensors and supporting software/electronics is possible, as well as the ultimate cost of deploying a system based on TDR alone. Due to these findings, TDR has become the focus for the next phase of development of these sensors.

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