Objectives and content
One of the most economic methods of constructing large span highway and railway bridges is by using post-tensioned concrete. This method of construction has now been widely in use for almost 45 years. During the last 10 years, it has become evident that durability problems due to inadequately grouted ducts may dramatically affect the expected long term performance of post-tensioned structures and may have been partially overlooked. In the case of inadequately grouted ducts, de-icing salts for instance, used to keep roads open to traffic during frost and snow, will start to corrode the particularly sensitive post-tensioning tendons. The electro-chemical attack is indeed concentrated at the voids of the ducts.
Dramatic collapses in both the UK and Belgium, premature demolitions and unforeseen extensive maintenance works all over Europe created great concern. It is clear that, as embargoes on the design of post-tensioned bridges exist already in the UK and in Italy and are expected in other countries, there is an urgent need to come forward with improved and reliable grouting processes to make possible a further prosperous development of post-tensioning applications.
Improvements on the current processes of grouting post-tensioning ducts require parallel developments in the field of grouting materials, grouting techniques and QA/QC systems. It, is therefore, the objective of this project to:
- introduce suitable QA procedures (with newly developed equipment for overall and local sensing systems) which can be applied during and immediately after grouting,
- develop grouts which show improved properties both in the fresh and hardened state (flowability, bleed, volume change,...)
- develop improved grouting techniques and specifications.
The results of this research program will not only be applied to the construction of post-tensioned bridges, but will also be applicable to the construction of other post-tensioned structures such as buildings, offshore rigs, nuclear reactors, aero generators, etc. Outputs of the research, i.e. the development of a new grout, QA and improved grouting techniques, will be directly exploitable.
Funding SchemeCSC - Cost-sharing contracts