London project marks world first in cement-free concrete

UK-based National Grid and its contractor Hochtief-Murphy Joint Venture (HMJV) have completed what is believed to be the world’s largest ever continuous pour of cement-free Earth Friendly Concrete® at the GBP1bn (US$1.25bn) London Power Tunnels (LTP) project. Approximately 736,000l (enough to fill around two 25m swimming pools) of cement-free concrete was poured to fill the base of the 55m-deep tunnel drive shaft at National Grid’s Hurst Substation in south London. 

The cement-free solution was developed by Wagners and supplied by Capital Concrete and uses a binder of ground granulated blastfurnace slag and fly ash geopolymer concrete system chemically activated by the use of industrial waste products instead of cement. The concrete reduces carbon by around 64 per cent saving an estimated 111kg of CO₂ per cubic metre poured in comparison to concrete that would have been used traditionally. The pour forms part of National Grid’s ambition to achieve net zero construction across all its projects by 2025-26. 

Andy Izod, Wagners UK regional manager, said, “We are delighted that National Grid and Hochtief-Murphy Joint Venture have chosen to use Earth Friendly Concrete (EFC) at their LPT project as by using an ultra-low carbon concrete for this application they have saved an estimated 82t of CO₂, which is roughly the equivalent of driving a new car 18 times around the world. This is the largest continuous EFC pour that has ever been undertaken and to do it on Earth Day, the 22nd of April, is quite fitting. We hope that other major clients will follow National Grid’s example in helping us to decarbonise the construction sector.”