Abstract
On the windward side of an existing box girder bridge exposed to aerosol and incidentally spray chloride profiles were determined at an age of 18 and 32 years as to obtain data on the development of chloride ingress over time and to predict the time to onset of reinforcement corrosion. According to the chloride contents determined at the level of the reinforcing steel for an age of 18 years corrosion was likely to be present, however neither visual inspections nor large scale potential mapping revealed any spots suspect of corrosion. Chloride profiling performed at an age of 32 years indicated that chloride ingress was much slower than was anticipated. A full probabilistic approach was adopted to predict the development of chloride ingress over time and onset of reinforcement corrosion using updated values for the so-called ageing factor and the critical chloride content. However, the results obtained with these predictions proved to be far more pessimistic than is shown by the actual condition of the bridge. As a consequence it was decided not to rely anymore on predictions based on numerical models using probabilistic calculations but in contrast to adopt a pragmatic engineering approach using common sense as a basis.
Highlights
For marine concrete structures reinforcement corrosion induced by penetrating chlorides is considered the major threat for durability
Condition assessment by regular visual inspections is the common procedure adopted in practice
During the time period 2002-2016 extensive investigations have been performed with respect to chloride ingress into the wall of a number of bridge elements
Summary
For marine concrete structures reinforcement corrosion induced by penetrating chlorides is considered the major threat for durability. More in-depth investigations are considered after a reinforced concrete structure shows clear visual evidence of distress caused by corrosion of the embedded reinforcement. Such in-depth investigations may comprise non-destructive techniques e.g. potential mapping and cover depth measurements. The more common approach is to drill a number of cores, determine the chloride penetration profile and, based on the chloride content at the level of the reinforcing steel, judge if corrosion is likely to be present or will occur in the near future. This paper presents and discusses the findings and interpretation of the chloride profile measurements obtained in 2002 and 2016 on the wall of a box girder bridge facing the North Sea (windward side)
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