Prestressed vaults in a progressive circular construction project

Concrete fulfills sustainability promises

West Flanders-based Nerva, based in Harelbeke, is no newcomer to the concrete market. The company was founded in 1963. In 2013, three employees realized a management buyout, which immediately initiated further expansion. Nerva specializes in horizontal total solutions in precast concrete. The range of products includes concrete floors, floor slabs and prestressed concrete slabs. The prestressed floor slabs are made in thicknesses from 12 to 40 cm.

Since 2021, Nerva has been part of the French group Rector-Lesage, one of the most renowned manufacturers of building products in France. With a motivated team, Nerva can rely on decades of experience, 23,000 completed projects and more than 6 MIO m2 of vaulting.

Circularity first

For the Mobilis project in Anderlecht, she was approached by Alheembouw to make the prestressed vaults for the basement floor. A pilot project so to speak, given the circular approach in which the primary concrete structures were given a predetermined lifespan of 100 years. This was partly realized by the flexible approach of the building, which can be structurally adapted to changing needs in the future. In this project, this is expressed, for example, in two mezzanine floors that are adjustable in height.

Atypical approach

Erik Geerts, director and sales director of Nerva: "In total, we provided over 4,000 m2 of prestressed vaults here, which we produced and delivered over a period of 6 months according to the just-in-time principle. Unusually, we were only able to apply the basement after the above-ground primary structure was completed." This atypical approach was part of the planning and execution modalities of the project. "Here the vaults were retrofit onto steel beams, which are part of the above-ground concrete structure. This created a number of concerns. For example, in terms of logistics. It took some puzzling to get the vaults into place smoothly, within the spatial limitation of the already completed concrete superstructure."

Also, Nerva did not apply a conventional concrete compression layer above the vaults, as is usually the case. "After all, such a compression layer makes the floor permanent and that was not the intention here. In this case, only the joint ridges were filled," Geerts said. "The retrofit of the vaults on the steel beams and the absence of a compression layer make it possible to remove the precast elements relatively easily in the future, should the need arise."

The Mobilis project was yet another in a string of successful collaborations with Alheembouw for Nerva.