Title: Faroe Bridges-Chloride Penetration Rate Estimated on Basis of Measurements from 1988 to 1997

Author(s): E. Stoltzner, B. Buhr, and S. Engelund

Publication: Symposium Paper

Volume: 192

Issue:

Appears on pages(s): 471-486

Keywords: cathodic protection; chlorides; corrosion; diffusion; marine structures

DOI: 10.14359/5766

Date: 4/1/2000

Abstract:
The Faroe Bridges are two bridges connecting the Danish islands of Zealand and Falster crossing the island of Faroe. The bridges carry the southern motorway which connects Copenhagen with Germany and the rest of Europe. The total length of the bridges is 3.3 km. The bridges were constructed in the period from 1980 to 1997 several investigations were carried out on the columns. The objective was to evaluate the risk of initiation of reinforcement corrosion as a result of chloride penetration. The investigations included, inter alia, measurements of chloride content (in dust samples and on dust ground from drilled cores), measurements of reinforcement corrosion, concrete condition, etc. The future chloride penetration has been modeled using a probabilistic approach. It can be concluded that the decrease in chloride penetration ratio that might have taken place in the time span from 1988 to 1997 was insignificant in comparison with the random variation caused by the concrete characteristics. It has been calculated that corrosion initiates after 15-40 years in the tidal zone (level .5 m above water) and after 25-40 years in the splash zone (level 1.5m above water) given a critical chloride content of .5-.10% CI by mass of concrete and the specified cover of 50mm. As a pilot project cathodic protection was installed on one column using magnetite anodes in the sea. It was found that the conditions believed necessary to prevent corrosion were established below water level and in the tidal zone.