The effectiveness of cement grout, the most widely used corrosion-protection system for multistrand, bonded, post- tensioned tendons, has been under debate due to significant tendon-corrosion damage, several reported failures of individual tendons, and a few collapses of non-typical structures. Sixteen years ago, a comprehensive research program to examine the use of post-tensioning in bridge structures was initiated at the Phil M. Ferguson Structural Engineering Laboratory at the University of Texas at Austin to identify durability concerns and existing technology, develop and carry out an experimental testing program, and develop durability-design guidelines. Four experimental programs were developed: high-performance-grout studies, long-term macrocell corrosion test series, long-term beam corrosion test series, and long-term column corrosion test series. After performing comprehensive internal examinations, overall findings indicate unfavorable durability effects due to the use of mixed reinforcement (a combination of active and passive reinforcement), thin concrete cover, galvanized-steel ducts, grout voids, and both industry-standard (duct tape) and heat-shrink-galvanized duct splices. The width of cracks was shown to have a direct adverse effect on specimen performance, and local areas of severe corrosion were found on epoxy-coated and galvanized bars. Favorable behavior was observed, however, for specimens constructed with high-performance concrete, high post-tensioning levels, plastic ducts, and sound, epoxy-filled joints.
