During the inspection of the Riddes viaduct structures, numerous deteriorations inside the structure were noted. The watertightness and the water flow were deficient, and the reinforcement and prestressing cables were heavily corroded. In addition, the concrete was degraded by a very significant alkali aggregate reaction (AAR). The capacity of the viaducts was limited to 3.5 tons as soon as these degradations were discovered. A complete upgrade of the 2 viaducts was deemed too expensive.
An emergency intervention was used to reinforce one of the two viaducts only with a 5 cm layer of UHPC. This UHPC solution as reinforcement, waterproofing, and as local reinforcement of the caissons. Only 22,000 m2 of the 33,000 m2 will be rehabilitated over a period of 15 years. One of the two bridges will be closed to traffic and will be left for observation to assess the progression of the AAR.
Phases 1 and 2 are currently underway, with over 550 m3 of UHPC already laid. A further 1,500 m3 will be laid in phase 3 from August.
Length: 2x 1,250 m + 4 ramps at about 200 m
Width: between 7 and 10 m
Volume: laid 550 m3 - total about 1500 m3
No. of installation days: 8 days in the caissons / 11 days on the deck
The Kanderviadukt near Frutigen was built in 1911 as part of the construction of the Spiez - Brig railway line and was completed in 1958/59 with a ballast trough. It is a single-track natural stone viaduct with 11 spans and a length of 280 m, spanning the main Spiez - Kandersteg road and the Kander river.
The bridge experienced a lot of damage over the years. The concrete trough, the joints between the stones of the structure, and the drainage system had to be repaired. The entire rehabilitation of the bridge deck was carried out in an intensive two-month construction phase under a complete bridge closure .
After the damaged concrete was removed using hydrodemolition, our teams concreted the kerbstones in 25m sections with a clean floated surface. The filling of the formwork was complicated due to the small thickness of the UHPC , the geometry of the curbs at several levels and the longitudinal slope of the bridge. This application required the use of both self-consolidating and thixotropic UHPC. Once all the kerbs had been completed, the entire deck was cast in one day to ensure water tightness without joints.
The rehabilitation of the bridge was a major challenge due to the limited space available and the 8 weeks closure . The supporting concrete was much further degraded than originally estimated resulting in the quantities of UHPC to be over 120 m3. Despite this significant change in project scope, our teams were able to complete the project on time. This would not have been possible with a traditional waterproofing solution.
Length: 280 m
Width: 5.3 m
Speciality: trough coating with UHPC
Volume: 120 m3
25 m steps for borders
Deck installation in one day
The wooden bridge over the Kallenmatt residential area was in a very poor condition. Due to the lack of waterproofing, the bridge had to be completely replaced.
The consultant of the project was impressed by the mixed Wood-UHPC bridge solution that we had produced in the spring and published in several magazines. We then worked together to study the feasibility of transposing this system to the present site.
The glued laminated timber beams were laid and the UHPC deck was poured directly on top of the timber beams . The top surface of the UHPC was smoothed providing a drivable and acceptable surface for users. The replacement of the bridge was completed in a very short period of time, despite the winter conditions (completed in December).
Length: 12.6 m
Volume: 6 m3
Number of days of installation: 1