Norway: a bridge installed in one night

When engineers from the Norwegian Public Roads Administration set out to replace the Kobbervoll Bridge on the E134 highway in Kongsberg, they faced a major challenge: how to replace the infrastructure without disrupting weekday traffic.

Rather than demolishing and rebuilding on site, the teams opted for a more efficient method. They built the new bridge nearby, then lifted it into place over the weekend. However, this required the structure to be significantly lightened so that the cranes could safely lift it into place.

Weight, a decisive factor

This is where Leca had a crucial role to play. By replacing traditional gravel with Leca® 800 LWA expanded clay aggregate, the teams were able to formulate lightweight aggregate concrete (LWAC) with 20% lower density at 1,930 kg/m³, while maintaining the same mechanical performance.

“Leca® LWA has an excellent strength-to-density ratio, which helps maintain the mechanical properties of the concrete,” explains Geir Norden, product expert at Leca International. “Where weight is an obstacle, Leca® LWA is the solution. That’s why it has been used for decades on the most complex construction projects, from bridges to floating structures.”

100 t mega-lift

On site, the operation was a sight to behold.  A crawler crane handled the heaviest lifting: first removing the old bridge (80 t), then removing a temporary bridge positioned above it, before installing the permanent structure. In total there were three lifts ranging from 95 to 100 t, made possible by the light weight of the Leca concrete.

As a result, the new Kobbervoll bridge was installed on Sunday, November 3, and opened to traffic at 3 a.m. on Monday, November 4, without any weekday closure. A rapid achievement showing how material innovation can transform the performance of major infrastructure projects.