Sensor to Detect Corrosion in Post-Tensioned Bridges and Buildings

Technology #14692

Device Uses Electrochemical Impedance Spectroscopy to Inspect Structures

This sensor uses electrochemical impedance spectroscopy to detect corrosion in bridges and buildings supported by post-tensioned structural tendons. The Federal Highway Administration has rated nearly one in nine U.S. bridges as structurally deficient. With the average age of the nation’s more than 600,000 bridges at 42, bridge refurbishment costs upwards of $13 billion each year. Post-tensioned construction, common in bridges, has been a concern since cable corrosion caused bridges and buildings to collapse in the 1980s. Cable used in post-tensioned bridges usually consists of multiple strands of steel encased in a plastic sleeve. That plastic sleeve is filled with grout to protect the steel from corrosion; however, factors such as faulty grouting, inadequate waterproofing, and air voids can prevent the grout from protecting the wire strands. The loss or weakening of just a few wires could compromise the structural integrity. Available techniques including magnetic flux, ground-penetrating radar, impact echo, ultrasonic sound waves, and gamma-ray spectroscopy have been used to detect defects such as air voids or loss of steel due to corrosion. The results of these tests were not very accurate and were difficult to interpret. University of Florida researchers have developed an effective device. This sensor uses non-destructive, electrochemical impedance spectroscopy to detect corrosion in post-tensioned construction.

Application

Sensor to detect corrosion in post-tensioned bridges and buildings

Advantages

  • Detects damage to structural cables, potentially averting catastrophe in post-tensioned bridges and buildings
  • Senses steel properties through grout, allowing for non-invasive evaluation
  • Allows for early intervention, reducing construction costs
  • Displays well-defined detection information, facilitating interpretation of results

Technology

The sensor developed by UF researchers uses electrochemical impedance spectroscopy to detect regions in which corrosion has compromised the strength of the supporting cables. Inspectors drill holes into the protective plastic duct covering so that sensors can be placed in the holes, providing data without damaging the internal cables. By sending a sinusoidal current of different frequencies through the post-tensioned structure, the device can detect properties of the steel. A sinusoidal perturbation is applied at the grout surface and the potential response is measured to determine if corrosion or the conditions that might cause corrosion are present.