Zeelandbrug must last at least another sixty, preferably one hundred years

Concrete skin preserved, now the caissons

After its construction in 1965, it was the longest bridge in Europe, now it is still the longest in the Netherlands: the Zeeland Bridge. Meanwhile, the 55-year-old connection between North Beveland and Schouwen-Duiveland is a National Monument (2016). It should come as no surprise that this more than five-kilometer-long work of art needs maintenance.

Cross-section of the old coating showing the (old) top coat.

Commissioned by the Province of Zeeland, a few years ago Bjond, a materials expert firm, started an investigation into the condition of the coating system that should protect the concrete of the bridge and the condition of the concrete itself. Owner Jo van Montfort: "The bridge consists of 54 piers and girders, two abutments and contains two bascule bridges. On my birthday (May 29, 1962), the bridge company commissioned the construction. The concrete from which the piers were made was in poor condition fairly soon after construction. To stop the corrosion that had occurred, it was decided about 30 years ago to apply a coating system. Since then, the trick has been to maintain that coating system. As long as the coating is functioning, the bridge can survive. We have extensively studied the condition of the protective coating. The goal was to gain insight into the lifespan of the current coating and what measures are optimal for extending the lifespan."

Scratch tests with adhesive strips give an indication of whether the top coat is properly attached.

Concrete skin

The concrete of the Zeeland Bridge has long been protected from sun, water, salt and wind by a single polyurethane coating and a top coat. Van Montfort: "To get a good picture of especially the concrete skin  - which is everything above the reinforcement - we inventoried all the damages, took borings and depth measurements, and tested the quality of the top layer. The polyurethane coating turned out to have remained surprisingly good, and the concrete skin was also in good shape except for a limited number of damage spots. Based on this, it was decided to undertake a repair program, which was carried out in 2018. In it, the damage to the concrete was repaired and the entire structure was cleaned with high-pressure water."

Polyurethane coating

Then came the most important operation: preserving the 40,000 m² of concrete. Van Montfort: "We keep that polyurethane coating alive with a new top coat that protects against UV radiation and salt. After extensive testing, we ended up with a product from Mapei, Elasto Color Waterproof, an acrylate-based agent that adheres very well to the existing coating and meets all the stringent physical properties. Consider that it will be applied offshore from pontoons and aerial platforms, in wind, sun and rain. There are not many products that can handle that."

Bjond can use the original drawings, in this case from Van Hattum and Blankevoort.

Research caissons

Bjond recently received a follow-up order from the province of Zeeland. Van Montfort: "We may examine the condition of the caissons. These are the oval-shaped containers of prestressed concrete on which the piers stand. They have never been properly looked at and we will probably start an exploratory investigation in the near future. The tension cables run all around in the caissons and hold the concrete structures together. If the cable breaks, you have a problem. The idea is to use radar to see exactly where the strands are and to perform sightings to see the condition in the caissons. We are also crawling into some of the piers."

Next turn

The aim of all these operations is to prevent reinforcement in these structures from corroding. Van Montfort: "The Zeeland Bridge has to last at least another sixty and preferably one hundred years. With the current protection, I expect that the next major maintenance will not be needed for another twenty to twenty-five years. In any case, we are proud to play a crucial role in the preservation of this beautiful bridge."