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Corrosion detection in structural tendons

  • US 9,829,452 B2
  • Filed: 10/08/2014
  • Issued: 11/28/2017
  • Est. Priority Date: 10/08/2013
  • Status: Active Grant
First Claim
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1. A method, comprising:

  • injecting alternating currents through a portion of a tendon assembly including a tendon extending through a duct, the tendon at least partially encased in grout filling the duct, where access to a surface of the grout is established through small holes drilled into the duct, and four electrodes are placed into the small holes with a conductive gel to establish electrical contact with the grout, the four electrodes comprising a pair of supply electrodes and a pair of reference electrodes, where the alternating currents are injected over a range of frequencies through the pair of supply electrodes on the surface of the grout;

    measuring potential differences across a portion of the grout surface between the pair of reference electrodes on the surface of the grout, the potential differences measured over the range of frequencies;

    determining a total impedance (Ztotal) based upon the injected alternating currents and the measured potential differences, the total impedance comprising;


    Ztotal=Zelectrode,1+Zgrout,1+Zinterface,1+Zsteel+Zinterface,2+Zgrout,2+Zelectrode,2,where Zelectrode is an impedance associated with the electrical contact of each of the pair of supply electrodes in contact with the grout, Zgrout is an impedance associated with the grout between each of the pair of supply electrodes and the tendon Zinterface is an impedance associated with an interface between the grout and a surface of the tendon adjacent to each of the pair of supply electrodes, and Zsteel is an impedance associated with the tendon; and

    determining a condition of the tendon based at least in part upon the total impedance.

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