Innovative Corrosion Evaluation System for Unbonded Post-Tensioned Cables, Fallis, Ball & Moad

Unbonded post-tensioned tendons may corrode for a number of reasons, even though they are encapsulated by a plastic duct. This is primarily due to voids in the protective grease, which allow moisture to accumulate adjacent to the post-tensioned tendon. Corrosion may go undetected for years until eventually significant structural deterioration, leading to a loss in structural capacity and, eventually, extensive and costly repairs. Increasingly, however, cases have been reported where corroded (failed) cables have erupted from the concrete, thus also posing a risk of damage or injury from ejecting cables, falling concrete, and/or dislodged claddings.

Existing methods typically used to evaluate corrosion of steel in concrete structures such as half cell corrosion potentials and corrosion rate testing are not practical to use on these types of unbonded post-tensioned structures due to the presence of the non-conductive plastic ducts. In response to the need to determine the probability of corrosion activity within unbonded post-tensioned cables, the Post-Tech® PT Corrosion Evaluation Method was developed.  (read more)