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Post-tensioned Concrete Bridges

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Title Document type Published Publisher
Management of Highway Structures Complementary Guidance

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Management of Highway Structures: A Code of Practice was published in September 2005. Since then Government Policy in respect to highway and structures management has developed and evolved in a number of areas, including the introduction of new statutory duties on highways authorities. There have also been developments/advances with regard to recognised good practice. To assist users of the Code, the Roads Liaison Group has prepared this complementary guidance which takes account of these changes and developments. Where appropriate, the complementary guidance provides details of where to find up-to-date information that can assist with the implementation of the good practice set out in the Code. Users of the Code should treat this complementary guidance as up-to-date and having the same status as the Code. Where paragraphs have been amended, they supersede the ones in the Code.

Primary Doc. 27/05/11 UK Roads Liaison Group Add icon
Corrosion protection of external tendons in post-tensioned concrete bridges

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A number of lengths of stressed post-tensioning strand, unstressed wires from post-tensioning strand and steel coupons, were exposed in the box sections of two externally post-tensioned concrete bridges. Samples were also exposed outside the structures. The temperature and humidity both inside the box sections, adjacent to the stressed samples, and outside the structures were also monitored. Time-of-wetness probes were positioned along the length of one of the structures. The objective was to determine the corrosivity inside the box sections and thus the degree of corrosion protection required by externally post-tensioned tendons. Results over five years indicate that although the corrosivity within a concrete box section is much lower than outside, bare tendons are not an option and some form of corrosion protection is required.

Research 01/01/02 Transport Research Laboratory Add icon
TRL LR 980 Conditions within ducts in post-tensioned prestressed concrete bridges

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an investigation was made of the grouting of twelve post-tensioned prestressed concrete bridges built between 1958 and 1977. ten of these structures were examined in situ and the other two had been demolished. voids were found in ten of the bridges including the most recently built structure. they were often continuous along the accessible length of a duct although they were not evenly distributed but tended to be concentrated at high points. local voids were found at anchorages in one of the demolished bridges in what were otherwise fully grouted ducts. the grout was usually dry and its quality ranged from soft and 'crumbly' to hard. exposed wires were observed in six of the bridges. they were usually covered with a thin film of cement paste indicating that grout had initially flowed through the duct at full, or nearly full bore. the cement film was intermingled with surface rust on some of the wires but, with the exception of one strand in a virtually empty duct, there was no evidence of pitting or loss of sectional area. the application of a low air pressure to the ducts showed that they were not completely sealed from the atmosphere. the grout should continue to protect the tendons provided it does not carbonate and chloride ions are excluded.

Research 01/01/81 Transport Research Laboratory Add icon
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