Galvanic Corrosion Protection
Corrosion Investigation & Testing of Post-Tensioned Cables, Fallis & Arnesen
The Post-Tech Corrosion Evaluation (CE) System provides a method for evaluating the potential for corrosion activity in un-bonded post-tension cables that if left untreated can be the cause of structural concerns with the un-bonded post-tensioned structures. This system has been successfully performed on several hundred structures in the past 15-years. It provides a method to restore the wet post-tension cables back to the environment for which they were originally designed. Un-bonded post-tensioned cables can not only be evaluated for their potential for corrosion, but also for identifying possible locations for un-bonded post-tension strand failure and the possible related structural deficiency.
The Post-Tech Cable Break (CB) system relies on the remanent magnetism method (RM-Method) to identify damaged or unsafe high strength individual or bundled pre-stress strands. This is a non-destructive test for evaluating the magnetic field or flux of externally magnetized tendons. Characteristic fracture readings of the magnetic leakage field are used to evaluate the extent of damage or amount of steel cross-section loss of the cables, which could include single or multiple wires in the strands. Wire or even strand fractures can happen abruptly and there are often no external visible signs of this type damage. (read more)
Galvanic Corrosion Protection of Reinforced Concrete Structures, Ball & Whitmore
In the past 10 years, there have been significant advancements in galvanic anode technology for reinforced concrete structures. Today, galvanic protection is the most commonly utilized form of corrosion protection for reinforced concrete in North America. The popularity of galvanic systems is due to many factors including ease of installation and little or no on-going system maintenance costs.
Distributed galvanic anode systems are used to provide targeted protection to specific structural elements as well as global protection to large areas in both marine and non-marine exposure environments. Examples of distributed galvanic protection technology include humectant-activated arc spray zinc and galvanic jacketing systems
Recent installations for distributed anode systems include a multi-million dollar rehabilitation of four cargo loading piers at Cape Canaveral, Florida. This project utilized a range of galvanic protection systems targeted to the varying needs of the structure. Distributed protection was utilized to protect over 5,000 m2 of prestressed concrete decks and 668 prestressed concrete piles in saltwater. (read more)
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)