A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Corrosion Characteristics of Post-Tensioning Strands in Ungrouted Ducts
Present FDOT construction specifications require post-tensioned ducts to be grouted within seven days of strand placement, to prevent corrosion. This specification may be too conservative under some mild service environments. The project had as objectives determining the relevant issues to establish fact-based guidelines for the duration of the ungrouted period for post-tensioning strand in FDOT construction and propose for consideration updated guidelines if appropriate. A literature review indicated that a 7-day limit is often specified by transportation agencies but that also allowable periods of up to 40 days are proposed for environmental conditions that are deemed to be not aggressive. Field tests with unstressed ungrouted strand, showed conspicuous corrosion only if free water had been contained in closed ducts. Even in those cases the corrosion was mostly in the form of shallow pits after as much as 8 weeks of exposure, with no clear loss of strength revealed by subsequent tensile tests. There was no discernable effect from having one end of the duct continuously open to the external environment even in a seashore facility. Inhibitor presence had no well-defined effect on mitigating corrosion. Possible approaches for consideration in updating FDOT exposure duration guidelines were formulated, including extending the current limit to 2 weeks and 4 weeks depending on environmental classification, if assurance can be made that in-duct or on-strand free water is absent.
Corrosion Characteristics of Post-Tensioning Strands in Ungrouted Ducts
Present FDOT construction specifications require post-tensioned ducts to be grouted within seven days of strand placement, to prevent corrosion. This specification may be too conservative under some mild service environments. The project had as objectives determining the relevant issues to establish fact-based guidelines for the duration of the ungrouted period for post-tensioning strand in FDOT construction and propose for consideration updated guidelines if appropriate. A literature review indicated that a 7-day limit is often specified by transportation agencies but that also allowable periods of up to 40 days are proposed for environmental conditions that are deemed to be not aggressive. Field tests with unstressed ungrouted strand, showed conspicuous corrosion only if free water had been contained in closed ducts. Even in those cases the corrosion was mostly in the form of shallow pits after as much as 8 weeks of exposure, with no clear loss of strength revealed by subsequent tensile tests. There was no discernable effect from having one end of the duct continuously open to the external environment even in a seashore facility. Inhibitor presence had no well-defined effect on mitigating corrosion. Possible approaches for consideration in updating FDOT exposure duration guidelines were formulated, including extending the current limit to 2 weeks and 4 weeks depending on environmental classification, if assurance can be made that in-duct or on-strand free water is absent.
Corrosion Characteristics of Post-Tensioning Strands in Ungrouted Ducts
A. A. Sagues (author) / F. C. Karins (author) / K. Lau (author)
2011
60 pages
Report
No indication
English
SIBIE procedure for the identification of ungrouted post-tensioning ducts in concrete
| British Library Conference Proceedings | 2007
Imaging of ungrouted tendon ducts in prestressed concrete by improved SIBIE
| Tema Archive | 2007