Effect of Voids in Grouted Post-Tensioned Concrete Bridge Construction: Inspection and Repair Manual for External Tendons in Segmental, Post-Tensioned Bridges

摘要

Segmental, post-tensioned (PT) bridges are major structures that carry significant traffic. These bridges are designed and constructed because they are economical for spanning long distances. In Texas, there are several signature PT bridges. In the late 1990s and early 2000s, several state highway agencies identified challenges with the PT structures, mainly corrosion of the PT strands. The Texas Department of Transportation (TxDOT) performed some comprehensive inspections of their PT bridges. A consultants report recommended that all ducts be re-grouted. However, the environment in Texas is very different than the environments in which the corrosion of the PT strands was observed in the other bridges. Report 0-4588-1 summarized the research findings from a comprehensive study on the corrosion characteristics, reliability, materials, and repair for PT bridges. This document, an inspection and repair manual, was developed from information from this research program. This document provides an efficient approach to inspect and repair PT bridges. However, it should be noted that in this manual, repair does not include filling the voids in the tendons with grout. A recent failure of a tendon in a bridge in Virginia was suspected of being caused by repair grouting of the tendon, possibly due to the formation of a galvanic couple between the new repair grout and the original grout. Although a procedure for pressure-vacuum grouting of tendons is provided in Appendix A of this manual, this method should not be used until the potential issue associated with galvanic corrosion of the strands after repair is resolved.