The chemical processes and high temperatures required to produce traditional Portland cement – a key ingredient in concrete – create high levels of carbon emissions.

Metro Tunnel Project has committed to a 36% reduction in the Portland cement content of concrete across all its construction projects.

This has been achieved by using higher amounts of recycled materials, such as fly ash and blast furnace slag. Fly ash is a by-product of coal power production, while slag is a by-product of iron and steel production.

The Metro Tunnel’s construction partners are currently delivering well above this target. As at October 2022, they have achieved:

• 52% reduction in Portland cement across the Tunnels and Stations package of works
• 44% reduction in Portland cement across the Rail Network package of works.

Learn more about the works packages delivering the Metro Tunnel.