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|Title:||Durability of post-tensioned concrete beams exposed to severe natural weathering|
|Authors:||O'Neil, Edward F.|
|Publisher:||Structures Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; SL-82-2.|
Abstract: A study of the durability of post-tensioned concrete beams and of the types of end caps used to protect the anchorage systems from deterioration when subjected 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, Maine. The beams were subjected to twice daily wetting and drying cycles plus an average of 130 freezing and thawing cycles per winter for a period of 12 to 13 years. During this exposure period, the beams were inspected annually to determine 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 being protected. The results of the durability investigation indicated, among other findings, that the end protective caps attached to the beams by reinforcing bars across the cap/beam joint experienced no cap 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.
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