Vinci piloting ‘world first’ ULC concrete segments at Grand Paris Express

6 October 2021

In what has been claimed a world first, tunnel segments made of ultra-low-carbon concrete are being used by Vinci Construction and Société du Grand Paris as part of a pilot project at a Line 18 worksite of the Grand Paris Express metro.

The ultra-low-carbon (ULC) concrete contains a cement-free alkali-activated slag. Cast in moulds, the resulting wedge-shaped segments have formed part of several years’ development by Vinci Construction over a variety of low-carbon concrete uses in building and other construction applications. The family of products are grouped under the Exegy brand.

Jointly funded with Société du Grand Paris, the Line 18 pilot project is designed to establish that the very low environmental impact concrete formula:

  • Can be used successfully
  • Can be poured into moulds at the required pace for a tunnelling operation and
  • Will perform successfully both in storage and over time under operating constraints.

The initial test phase established the concrete formula applicable to segments. The second phase, which began in September 2021, involves producing five full rings (comprising 40 segments) sized for the project, with the first units to be used for full-scale ISO fire and load tests.

Vinci stated that replacing conventional concrete segments with Exegy ultra-low-carbon concrete ones and Ecocem Ultra alkali-activated binder has a significant impact on the worksite’s environmental performance: emissions are reduced by 70% compared to traditional concrete, and 50% compared to very-low-carbon concrete (respectively 90kg of CO²/m3 for ULC concrete; 170kg of CO²/m3 for VLC concrete and 330kg of CO2/m3 for traditional concrete).

The company claimed that using ULC concrete segments could bring about a massive drop in the carbon footprint of tunnels built in France.