Walensee Highway A3, Murgwald Tunnel North

Situation

As part of the annual tunnel cleaning and maintenance work on fire alarms, ventilation, sewage, and lighting along the A3 highway near Walensee, repair work was also carried out on the concrete roadway in the Murgwald North Tunnel. The section of the Walensee highway from Walenstadt to Murg in the direction of Zurich was closed to all vehicle traffic from approximately 8:30 PM to 4:30 AM.

During this closure, damaged manhole covers, including frames, were to be replaced. The goal was to remove and replace the damaged sections within the night closure and re-pour the manhole frame with concrete. Before the motorway could be reopened at 4:30 AM, sufficient concrete strength needed to be ensured.

Solution and Evaluation

For the new manhole frames, the rapid-hardening dry concrete Concretum® Q-CON was used. This concrete achieves a strength of 20 N/mm² within one hour after setting begins.

The work was carried out in a single night shift. The dry concrete was mixed on-site using a batch mixer and produced with a spread of approximately 55 cm. The mixture was directly poured from the batch mixer into the formwork. This approach ensured a sufficient safety margin, allowing the concrete to be placed within the open time, despite the high temperatures in the tunnel. One hour before the road was reopened to traffic, a strength of 20 N/mm² was achieved.

The construction time for the affected tunnel section was optimized with the chosen solution, and it was ensured that the other maintenance teams were only minimally affected by the concreting work.