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The Krk Bridge in Croatia recently embarked on extensive preservation efforts. A reinforced concrete arch bridge connecting the Croatian island of Krk to the mainland, the Krk Bridge carries over a million vehicles a year. As a result of strong wind and sea salt, the bridge needs to be constantly maintained.

The entire reinforced concrete structure of the bridge is continuously monitored and maintained, and the current cost of regular and extra maintenance of Krk Bridge is around EUR 1 million annually. The strong wind in the area has helped sea salt accumulate on the surface of the reinforced concrete structure, and chlorides have penetrated through the protective layer of concrete to attack the reinforcing. This was the main reason that the current preservation effort was initiated. The repair, which will be carried out in several phases, is expected to take around 30 years.

Renewing corrosion damages

The field investigation and the preservation project design was done by IGH, the Institute for Civil Engineering in Zagreb. According to the results of the exploratory works, the concrete is mainly contaminated to the depth of the main reinforcement, so the existing concrete is being removed to this depth. After the removal of the contaminated concrete layer, the cleaned concrete surface is treated with a surface corrosion inhibitor.

Before the repairs on the bridge commenced, an experimental study to establish the best products for use in the project was carried out. After a number of field and laboratory tests, the Cortec’s MCI 2020 corrosion inhibitor was selected. The product met all the technical requirements of the project, and is economical and easy to apply.

Detailed visual inspection of the condition of the concrete and reinforcing are performed to establish where there are crack or any other issues. The concrete is then removed and the rebar cleaned. If corrosion is found to have already started, MCI 2020 is applied. Before applying the mortar, the surface must be saturated with water and any excess water from the surface must be removed.

Prepared repair mortar that is applied by spraying it onto the surface treated with the MCI 2020 inhibitor in a single layer has shown excellent adhesion. No binding layer is required.

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