Long-term corrosion testing and evaluation of partially submerged post-tensioned column specimens

Post-tensioned concrete piers may be partially submerged in sea water or exposed to deicing salts. In order to provide detailed observations to improve the durability design of columns under these exposure conditions, a research study was started with the dual intent to evaluate how to use post-tensioning to improve corrosion protection and how to protect the post-tensioning systems from corrosion damage. The information contained in this paper is part of a comprehensive research program developed at the Ferguson Structural Engineering Laboratory, at The University of Texas at Austin, which had the objectives to examine the use of post-tensioning in bridge substructures, identify durability concerns and existing technology, develop and carry out an experimental testing program, and conclude with durability design guidelines. This paper documents the final evaluation, conclusions, recommendations and implementation measures from the long-term column exposure series. Ten large-scale specimens were designed, constructed and placed under exposure testing in July 1996 and autopsied in January 2003. After forensic examination, overall findings indicate negative durability effects due to the use of small concrete covers, galvanized steel ducts and rubber gaskets at the duct ends. Relying on epoxy and galvanized bar coating was also found inappropriate because of local attack. On the other hand, very positive effects were found with the use of fly ash concrete, post-tensioning through the column-foundation interface, and plastic ducts.