The motorway viaduct features some of the heaviest traffic levels in France. The external steel struts had recently shown severe signs of corrosion, mainly due to their high level of exposure to de-icing salts. Installation of a cathodic protection system was therefore necessary.

  • Name of the owner
    Regional and Interdepartmental Authority for Equipment and Town Planning for Ile-de-France (DRIEA IF)
  • Name of the client
    Ile-de-France Highways Authority (DiRIF)
  • Delivery date of the project
    July 2017
Cathodic protection of the viaduct

Painstaking preparation

Preparations were required before the teams could fit the impressed current cathodic protection system (ICCP). A radar was used to determine the exact position of the prestressing tendons and steel components before the damaged concrete was removed to ensure a clean and healthy substrate. After carrying out electrical continuity testing on the steel elements, any damage to the reinforcement coatings was repaired with dry process shotcrete. Once the structure had been properly prepared, the ICCP system was fitted.

The challenge

Access to the work areas represented one of the main challenges facing our operations teams. Prestressing tendons inside the segments and the high density of services hampered the teams’ progress. Two custom-designed suspended platforms were required on the outside to access the caisson struts.

Cathodic protection of the viaduct

The largest cathodic protection project in France

Over 45,000 discrete titanium anodes (37,000 on the inner faces of the caissons, and 8,000 on the outer faces) were installed in the pre-drilled holes. Once checks had been carried out to ensure that there were no short-circuits, the system was wired, connected and commissioned, following which the setpoints were defined. Note that the large amount of drilled anodes used for the project broke a record in France for cathodic protection systems.

  • 45,500
    Discrete anodes fitted
  • 800
    Points measured across the entire viaduct
  • 50,000
    Working hours to install the cathodic protection system
Cathodic protection of the viaduct

Structural monitoring by our teams

Freyssinet is keeping a close eye on the installation as part of a long-term maintenance contract awarded by the client. This additional monitoring service is being carried out by the corrosion team within Freyssinet’s technical operations division. The team is keeping a close eye on the structure remotely with a GSM link, which provides direct access to the PLC and allows the team to read the measurement data provided by the 800 measurement points that Freyssinet has fitted across the entire viaduct. Operators can also modify the setpoints if necessary.

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