The pour was carried out by National Grid and its contractor HOCHTIEF-MURPHY Joint Venture (HMJV).
A total of 736,000 litres of more sustainable, 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 blast furnace 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% saving an estimated 111kg of CO2 per cubic metre poured in comparison to concrete which would have traditionally been used.
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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.
The record-breaking pour on Earth Day at National Grid's Hurst substation site was needed to infill the base of the 55m deep tunnel shaft to its permanent level, following the successful completion of 9.2km of tunnelling over 2 tunnel drives from Hurst to Eltham and Crayford.
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."
