HMJV has overseen pouring of 736,000 litres – enough to fill around two 25m swimming pools – 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 blast furnace slag and fly ash geopolymer concrete system chemically activated using industrial waste products instead of cement.

The concrete reduces carbon by around 64% saving an estimated 111kg of CO2 per cubic metre poured in comparison to concrete which would have traditionally been used.

The use of Earth Friendly Concrete was driven forward by a team of young engineers on the project and supported by HMJV’s engineering experts and AECOM, Mott MacDonald and WSP, following several trials at different London Power Tunnels sites.

National Grid Project Director, Onur Aydemir said: “We are always looking for new ways to innovate and to now be using this carbon saving cement-free alternative to conventional concrete at scale and on site is exciting.

“This world record-breaking pour also offers the opportunity to evaluate the technology ahead of future possible rollout across our network in England and Wales, demonstrating our ambition to achieve net zero construction across all our projects by 2025/26.”

Raj Kundan, Technical Lead for HOCHTIEF-MURPHY Joint Venture said: “At HMJV, in conjunction with our supply chain family, we strive to advance innovative and cutting-edge solutions – and the incredible work the team have done on the project in the trialling and large-scale use of Earth Friendly Concrete in temporary as well as permanent applications is a great example of that.

“Completing the largest ever continuous cement free concrete pour is testament to the ingenuity and collaboration of all involved and shows how a client, contractor and the supply chain can work together to help take a major step moving the industry forward in reducing carbon emissions.”