Tunnel rehabilitation in Switzerland

In the Swiss canton of St. Gallen,two tunnels along the bypass around the town of Lichtensteig had to be renovated in response to the concrete coatings showing clear signs of ageing. And in this refurb campaign, Kinetic- Boost Technology® from MC once again proved invaluable in underpinning construction schedule reliability and shortening tunnel closures.
After 37 years, the inner walls of both the Flooz (290 m) and Aeuli (430 m) tunnels, which were each built and commissioned in 1982 as part of the Lichtensteig bypass, had to be rehabilitated in the summer of 2019. The St. Gallen canton authorities responsible chose the company Trauffer AG Bautenschutz to perform the work.

 

In the first refurbishment phase from May to July 2019, a one-way traffic system was introduced to redirect vehicles using this busy bypass. This enabled demolition work to start on the Flooz and Aeuli tunnels, with the surface layer of the concrete walls being removed and then repaired with sprayed mortar.

 

Full closure reduced to a minimum

The second refurb phase entailed repairing, reprofiling and whitewashing the tunnel walls. The new coating was to provide increased protection against attacks by CO2, road salt and the effects of freeze-thaw cycling. It was also designed to create an easy-to-clean and permanently bright surface, thus saving lighting costs and ensuring maximum traffic safety.

As problems with a high moisture load were expected during the work, all parties involved decided in favour of a tunnel coating solution from MC based on KineticBoost-Technology® that uses the moisture in the environment to strengthen and accelerate the curing reaction. The speed of coating application thus achieved also meant that full closure of the tunnels, which was essential for the coating work, was kept to a minimum. It also meant the full-closure period could be scheduled for the region’s summer holidays. Once the concrete surfaces of the tunnel walls were smooth, they were coated with the transparent primer MC-DUR 1177 WV-A. This was followed by a coat of MC-DUR 2496 CTP Tunnel, a pigmented high-performance waterproofing compound with integrated KineticBoost-Technology®. This two-component, low-solvent, UV-stable reactive resin cures particularly quickly regardless of the influence of moisture and temperature and also scores high in terms of its good mechanical and chemical resistance properties.

 

Coating completed in five days instead of eight

The coating work, which normally takes eight days for comparable projects, was executed within just five days. Although completed in record time, the result was nevertheless a high-quality, non-yellowing and extremely easy-to-clean tunnel interior coating with excellent concrete protection properties. This benefited not only the client and specialist applicators, but also the motorists, for whom the traffic restrictions were soon lifted.