The Grouting of Five Prestressed Concrete Bridges During Construction

摘要

The grouting of five post-tensioned prestressed concrete bridges was monitored during construction. All bridges were of similar design, used the same stressing system and were grouted by the same sub-contractor. There was no evidence of voids apart from partially grouted vents (where grout had fallen back into the ducts) at some of the outlet anchorages. These voids did not extend into the anchorages. It was not possible to check whether the grout had penetrated radially between the strands. The specification was not always strictly adhered to: mixing times were frequently less than two minutes, the ducts were not always grouted continuously and the pressure at the pump often exceeded the maximum recommended in the specification. Other bad practice included leaving the ducts ungrouted after stressing for longer than was absolutely necessary, sealing the vents as soon as grout appeared, and grouting too quickly. Occasionally problems were encountered during grouting. These were due to blockages in both vents and ducts, and poor connections at the inlet anchorages. Many of the problems that did arise could have been avoided by more stringent preparations beforehand. (Copyright (c) Crown Copyright 1981.)