A study of the durability of post-tensioned concrete beams and the types of end caps used to protect the anchorage systems from deterioration due to severe environmental conditions was conducted. Twenty post-tensioned concrete beams 254 by 406 mm (10 by 16 in.) in cross section and 2.44 m (8 ft) in length were cast, post-tensioned, and placed at the mean tide elevation on the beach at Treat Island off the coast of Eastport, Me. Here the beams were subjected to wetting and drying cycles twice daily, plus an average of 130 freezing and thawing cycles per winter for a period of between 12 and 13 years.

During this exposure period the beams were inspected yearly by a team of raters who judged the condition of each end cap or plug, the joint between beam and cap or plug, and the beams themselves.

At the end of the exposure period eight representative beams were returned to the laboratory for autopsy and analysis of the protective caps, the method of joint preparation, and the post-tensioning steel.

The results of investigation indicated, among other findings, that the protective end caps attached to the beams by reinforcing bars across the cap/beam joint experienced no failures, the epoxy concrete end caps provided the best protection to the end anchorages of all methods tested, and the post-tensioning wires in the beams experienced no structural damage over the exposure period provided they were encased in a flexible metal conduit and protected with portland cement grout.