Abstract
Unbonded post-tension (PT) tendons have been used for many years to reinforce concrete structures. Generally, these structures have performed well except where unbonded PT tendons have suffered from corrosion due to moisture penetration or protective grease deficiencies.
Like other technologies, unbonded PT systems have evolved and improved over the years from “paper-wrap” to “push-through” to “heat sealed” to “extruded” to “fully encapsulated” systems. Consideration should be given to the type of system when selecting the appropriate evaluation and corrosion mitigation methods for these systems.
Evaluation of unbonded post-tensioned structures is important to determine the current condition and to determine if corrosion and deterioration is likely to occur. If broken tendons or corrosive conditions are identified, a suitable mitigation strategy should be implemented such that the structural integrity can be maintained, and the service life of the structure can be met or extended.
This paper will discuss the types of unbonded PT structures which exist, evaluation techniques which can be used to identify the presence of corrosion, and mitigation methods which have been developed to mitigate corrosion of unbonded PT tendons. Project case studies will be presented to demonstrate the applicability and effectiveness of these techniques.
