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Use of Electrochemical Impedance Spectroscopy to Monitor Delamination and Moisture Uptake in CFRP-Reinforced Concrete Structures
Abstract
Electrochemical impedance spectroscopy (EIS) electrodes have been used to inspect carbon fiber-reinforced polymer (CFRP)-reinforced concrete structures exposed to a variety of laboratory test conditions (salt fog, alternate immersion in fresh water, alternate immersion in salt water, 100% relative humidity, 50% relative humidity, elevated temperatures, and below-freezing temperatures). Other specimens were used to investigate the detection of delamination between the CFRP and the concrete using a wedge test. External electrodes, coupled with the embedded rebar, provided the best results. Equivalent circuit modeling was used to analyze the impedance spectra. Several circuit parameters, especially the capacitance and constant phase element (CPE) magnitude, correlated very well with both bonded area/ delamination and moisture content. The different relationships between the different circuit parameters and moisture uptake or bonded CFRP-concrete area should allow these two material characteristics to be separately determined. Differences in the different exposure conditions were seen and explained. Coupled with a commercially available portable potentiostat, these measurements can be made in the field to facilitate inspection of concrete structures reinforced with CFRP, such as bridges.