Record-breaking EFC pour for permanent works

Capital Concrete supply largest-ever continuous pour of cement-free Earth Friendly Concrete

CAPITAL Concrete have supplied the largest ever continuous pour of their cement-free Earth Friendly Concrete to the London Power Tunnels project.

A total of 736m³ of Earth Friendly Concrete (EFC) was used to fill the base of a 55m deep tunnel drive shaft at the National Grid’s Hurst substation in South London. The pour, supplied to contractor Hochtief-Murphy joint venture (HMJV), took place in April and is the first time EFC has been used in large-scale permanent construction.

The cement-free solution uses ground granulated blast-furnace slag (ggbs) and fly ash instead of Portland cement and reduces embodied carbon levels by up to 87%, saving around 180kg of CO₂ per cubic metre in comparison with traditional concrete.

Throughout the construction of the £1 billion project, National Grid have been utilizing sustainable construction measures to achieve their net-zero target, and after trials at different London Power Tunnels sites by engineering professionals from HMJV, AECOM, Mott MacDonald, and WSP, the green light was given to use Earth Friendly Concrete in construction of the permanent works.

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 roll-out across our network in England and Wales, demonstrating our ambition to achieve net-zero construction across all our projects by 2025/26.’

Luke Smith, managing director of Capital Concrete, commented: ‘We have been supplying Earth Friendly Concrete since January 2020 as a low-carbon, high-performance alternative to standard cement-based concrete.

‘We are delighted that the Capital Concrete team could work together with Hochtief-Murphy to provide the technical expertise and focus on customer service to deliver the biggest EFC pour globally to date over an 11-hour period for the London Power Tunnels project.’

Capital Concrete have previously supplied EFC for use on other London-based projects, such as HS2, Plaistow Wharf, and Nova East Development, where the material’s low levels of embodied carbon, high tensile strength, and low shrinkage have helped meet project requirements.