The Post-Tensioning Institute (PTI) has announced a new specification update approved by the PTI Board of Directors and the Technical Advisory Board. Addendum #3 to PTI M10.2-00 Specification for Unbonded Single Strand Tendons requires the following:
All unbonded single strand post-tensioning tendons used for structures designed in accordance with the Building Code Requirements for Structural Concrete (ACI 318) must be encapsulated. The encapsulation of the tendons shall be in accordance with the material requirements for aggressive environments in the PTI Specification for Unbonded Single Strand Tendons (PTI M10.2-00).
The intent is to augment the durability of the post-tensioning systems used for all applications governed by ACI 318. Encapsulated systems provide additional protection of the prestressing steel regardless of location of the structure or exposure to moisture intrusion from any source.
Addendum #3 to PTI M10.2-00 Specification for Unbonded Single Strand Tendons is available for free download on PTI's website at http://post-tensioning.org/Uploads/Addendum3.pdf