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51318-10861-An Indirect Impedance Measurement for Corrosion Detection in Structural Bridge Tendons

An indirect impedance technique is assessed as a possible method to detect corrosion within external post-tensioned bridge tendons. The method aims to extract the impedance of the steel-grout interface from the impedance measured at the surface of the grout.

Product Number: 51318-10861-SG
Author: Christopher L. Alexander / Mark E. Orazem
Publication Date: 2018
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$20.00
$20.00

An indirect impedance technique is assessed as a possible method to detect corrosion within external post-tensioned bridge tendons. The indirect impedance aims to extract the impedance of the steel-grout interface from the impedance measured at the surface of the grout. However, the electrode configuration required for the indirect impedance measurement yields geometry-induced frequency dispersion that confounds interpretation. A proof of concept was established for using indirect impedance to detect corrosion in post-tensioned tendons. Bench-top experiments were performed to show that the indirect impedance was sensitive to the properties of the steel and grout interface. Finite-element models were used to simulate the indirect impedance and determine how the geometry of the unusual electrode configuration influences the impedance. The indirect impedance was able to distinguish between locations of corroding steel and locations of passive steel, even if the actual damage to the steel was minimal. However, the complex nature of the grout impedance limits the indirect impedance measurement to providing only a qualitative assessment of the corrosion of bridge tendons.

 

Key words: Impedance, Corrosion Detection

An indirect impedance technique is assessed as a possible method to detect corrosion within external post-tensioned bridge tendons. The indirect impedance aims to extract the impedance of the steel-grout interface from the impedance measured at the surface of the grout. However, the electrode configuration required for the indirect impedance measurement yields geometry-induced frequency dispersion that confounds interpretation. A proof of concept was established for using indirect impedance to detect corrosion in post-tensioned tendons. Bench-top experiments were performed to show that the indirect impedance was sensitive to the properties of the steel and grout interface. Finite-element models were used to simulate the indirect impedance and determine how the geometry of the unusual electrode configuration influences the impedance. The indirect impedance was able to distinguish between locations of corroding steel and locations of passive steel, even if the actual damage to the steel was minimal. However, the complex nature of the grout impedance limits the indirect impedance measurement to providing only a qualitative assessment of the corrosion of bridge tendons.

 

Key words: Impedance, Corrosion Detection

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