Zeeland bridge

Zeeland Bridge is an imposing concrete bridge in the south-western part of Holland. It is supported by 54 upside-down, V-shaped pillars sitting on bases in reinforced concrete. The bridge has 52 spans, each one 95 m wide, as well as a mobile section 40 m long, and its two carriageways and cycle lane are suspended above the water.

It was built between 1962 and 1965 thanks to a decision of the Zeeland Provincial Government and, in 2015, it was declared a site of national interest by the Netherlands National Cultural Heritage Agency. The bridge has undergone maintenance work several times since 2000, with the most recent work carried out between 2017 and 2018.

During this intervention, which is described in edition No. 72 of Realtà Mapei International, several Mapei products were employed to restore the damaged concrete, such as MAPEFER 1K anti-corrosion cementitious mortar to protect steel reinforcement and MAPEGROUT T60 mortar to repair degraded concrete structures.

It was also important to make sure the surfaces of the bridge were well protected, by creating a finish with the capacity to resist the penetration of salts from the seawater (chlorides) and oxygen and carbon dioxide present in the surrounding air, elements that could otherwise trigger carbonation and corrosion of the steel reinforcement (including pre-stressed steel) in the underlying layers of concrete. The final coating also had to provide sufficient protection against the effects of UV rays and mechanical impact from floating timber on the lower part of the pillars which, in certain periods of the year, can be quite severe at high tide.

In 2016 Bjond Innovation (an engineering company specialised in the restoration of degraded structures) was commissioned by the Zeeland Provincial Government to analyse the bridge and to monitor its state of conservation, especially with regards to the existing finish. Once the analysis had been completed, a maintenance plan was drafted which focused on the finish protecting the previous layer of paint applied between 1992 and 1993.

Based on the results of these analyses, which were carried out twice at a distance of 6 months, ELASTOCOLOR WATERPROOF, an acrylic paint by Mapei suitable for permanent contact with water, was found to be the most appropriate product for this specific intervention, with work carried out between 2017 and 2018.

What is more, ELASTOCOLOR WATERPROOF complies with the requirements of EN 1504-2 regarding products and systems for the protection and repair of concrete structures, as specified by the Zeeland Provincial Government.

Since ELASTOCOLOR WATERPROOF meets the requirements of European standards, and the analyses carried out on prototypes gave positive results, this would normally have been sufficient to guarantee the durability and effectiveness of the maintenance work. However, since this is quite a unique bridge, the Zeeland Provincial Government decided it would be advantageous to carry out a five-year monitoring programme to analyse the effective performance properties of the coating system once exposed to the bridge’s real service conditions.

Bjond Innovation was commissioned to carry out the monitoring and the scope of the programme was to collect and analyse data about the level of degradation of the coating system in order to forecast its long-term durability and performance. The analyses carried out included:

• Adhesion of top layer, according to ISO 2049 (cross-cut) and EN 16276-2 (X-cut) and adhesion of the total system, according to ISO 4624 (EN 1504);
• Blistering (visual inspection according to ISO 4628);
• Cracking (visual inspection according to ISO 4628);
• Delamination/chipping (visual inspection according to ISO 4628);
• Determination of the glass transition temperature;
• Carbonation depth of concrete;
• Microscopical investigation with fluorescing day to determine micro cracking.