A world first: VINCI Construction completed the first tunnel in France to be created exclusively using pipes made of Exegy® ultra-low-carbon concrete

Credit: Yves Chanoit

10 August 2022 - Events - France

The consortium composed of Bessac (leader), Soletanche Bachy Fondations Spéciales (both VINCI Construction) and Setec Hydratec completed the construction of an entire tunnel for the discharge of treated water using pipes made of Exegy® ultra-low-carbon concrete.

This structure, 912 m in length and 1.6 m in diameter, at the wastewater treatment plant in Bonneuil-enFrance (Val-d’Oise) relies on a concrete formula developed by Soletanche Bachy’s integrated materials laboratory, with the involvement of the Tunnel Factory. The carbon footprint of the pipe prefabrication process was a quarter of that of the usual concretes used. And the pipes were prefabricated locally, thus limiting transport-related CO² emissions. As for the retaining structures of the two entry and exit shafts for the microtunneling machine, these were created using the Starsol® process, enabling earthworks and excavation works to take place while sheltered from the water table. This project was designed and implemented in a way that took account of the environmental challenges posed by the site, which includes natural spaces classified as Natura 2000 areas and limited the impact of the works by using compact worksite installations within the still operating treatment plant. And finally, on 31 May 2022 this project was awarded the trophy, in the Innovation category, of the FSTT (French association promoting no-trench techniques for underground network operations)