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. (Author/publisher)
Samenvatting