The Gotthard Tunnel, part of the A2 Basel-Chiasso motorway in Switzerland, runs through the Swiss Alps to connect the Swiss cities of Goschenen and Airolo. One of the longest tunnels in the world, the 16.9-km long reinforced-concrete structure is the shortest passage through the central Alps and the quickest connection between northern Europe and Italy. As a result, the two-lane tunnel handles a significant amount of traffic.~1 During the winter months, thousands of vehicles carry chlorides into the tunnel when water spray that contains road salt residues is thrown from tires onto the walls and ceiling. The tunnel walls are shielded by special concrete elements that are coated with an acrylic paint; however, the ceiling needed to be protected.
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