A Survey of the Durablity Performance of Post-Tensioning Tendons

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Title: A Survey of the Durablity Performance of Post-Tensioning Tendons

Author(s): Morris Schupack

Publication: Journal Proceedings

Volume: 75

Issue: 10

Appears on pages(s): 501-510

Keywords: bridges (structures); concrete constrution;corrosion;corrosion resistance; durablity;post-tensioning;prestressed concrete;prestressing steels; stress corrosion resistance.

Date: 10/1/1978

Abstract:
Information on the actual performance of stress-relieved post-tensioning tendos in completed structures, both bonded and unbonded, is presented. This is based on known incidents of corrosion and oppurtunites to inspect post-tensioned tendons in completed structures which were exposed for various reasons after a period of time. This report is directed toward North American, Western European, and Japanese experience in tendons made of stress-relieved wires, strands, or high-strength bars, which are the types of prestressing steel primarily used in Canada and the United States. The survey indicates that the general durablity performance of post-tensioning tendons, since the inception of post-tensioned prestressed concrete construction in the 1930s, has been excellent. With proper choice of materials and details, and with good construction practices, excellent corrosion protection is provided for both bonded and unbonded post-tensioning tendons. The relatively small number of corrsion incident that have occurred have been the result of poor design details, inadvertant exposure to known corrosive agents, or poor construction practices. It is estimated that over 2.7 million tons (2.5 metric tons) of stress-relieved prestressing steel, which is equivilant to about 30 million tendons, have been used in the western world. Only some 28 corrsion incidents, comprimising some 200 tendons using stress-relieved steel, have been reported for complete structures. These incidents could have been avoided if proper procedures had been used. To date, there has been no known catastrophic collapse of permenant structures in the western world due to corrosion of of post-tensioning tendons utilizing stress-relieved wire, strand, or high-strength stress-relieved bars conforming to ASTM specifications.