Cement-free concrete for £1bn London Power Tunnel

HOCHTIEF-MURPHY Joint Venture (HMJV) has delivered the world’s largest pour of cement-free concrete in the London Power Tunnels project.

National Grid (NG) and HMJV have completed the pour of 736,000 litres of Earth Friendly Concrete® at NG’s Hurst Substation for the London Power Tunnels project. 

The concrete was poured into a 55m deep tunnel shaft in the Hurst location on Earth day, 22 April. 

It is part of the wider tunnelling happening across the project, which aims to rewire London, from Wimbledon to Crayford. 

Cement-free concrete 

The concrete was developed by Australian construction material provider, Wagners, and supplied by Capital Concrete. 

Instead of cement, the concrete uses a binder of ground granulated blast furnace slag and fly ash geopolymer concrete system, chemically activated by the use of industrial waste products. 

HMJV, along with AECOM, Mott MacDonald and WSP, supported the trial of this concrete on other sites in the tunnel project. 

The concrete reduces around 64% of carbon, saving approximately 111 kg of CO2 per cubic metre poured compared to traditional cement concrete. 

Project trajectory 

The concrete pour followed the completion of 9.2 km tunnelling over 2 tunnel drives from Hurst to Eltham and Crayford. 

The next scheduled work involves cabling works and installation, led by Balfour Beatty. 

A new substation at Bengeworth Road in Lambeth is also set to start construction. 

Linxon are contracted for the latter substation, and will be using Hitachi Energy’s SF6 free gas insulated switchgear technology, enforcing NG’s decarbonising commitments to be SF6 free by 2050. 

It is understood that 90% of the tunnelling works for the project has been completed, with the final tunnel set to be completed by the end of this Summer. 

Enjoyed this? Check out IN PICTURES: AmeySRM JV lead 18-month M56 bridge replacement.