London Tunnels Undergo Record Cement-Free Pour

MONDAY, MAY 15, 2023

Earlier this week, energy company National Grid announced that it has completed the world’s largest continuous pour of cement-free concrete at the 1 billion pound (about $1.25 billion) London Power Tunnel project.

According to the release, alongside its joint contractor Hochtief-Murphy Joint Venture, National Grid poured 736 cubic meters (about 194,431 liters) to fill the base of the tunnel drive shaft at the Hurst Substation in South London.

About the Project

National Grid reports that the cement-free concrete was developed by Wagners and supplied by Capital Concrete, using a binder of ground granulated blast furnace slag and fly ash geopolymer concrete. This system is then chemically activated by the use of industrial waste products instead of cement.

The record-breaking pour reportedly took place at the substation site on Earth Day (April 22), filling the 55 meter (180 feet) deep tunnel shaft to its permanent level. This followed the completion of 9.2 kilometers of tunnelling over two tunnel drives from Hurst to Eltham and Crayford.

The concrete is anticipated to reduce carbon by about 64%, National Grid reports, saving an estimated 111 kilograms of CO2 per cubic meter poured in comparison to concrete, which would have traditionally been used.

“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,” said Onur Aydemir, National Grid Project Director.

“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.”

National Grid adds that, in addition to the cement-free concrete pour, several other measures are in place to reduce the environmental impact of construction on the London Power Tunnels project, including:

  • Optimization of designs and construction methodologies of the tunnel and shafts network by HMJV saving approximately 50,000 tons of CO2, leading to a 30% reduction against baseline;
  • 99.98% of project waste being diverted away from landfill, a 21% reduction against the carbon reduction pre-project baseline for shafts, tunnels and headhouses, equivalent to 25,250 ton of CO2; and
  • A new 400kV substation at the heart of the project in Bengeworth Road, Lambeth, will be built using SF6 free gas insulated switchgear technology in a U.K. first.

“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,” said Raj Kundan, HMJV Technical Lead.

“Completing the largest ever continuous cement free concrete pour is testament to the ingenuity and collaboration of all involved working as part of this Project 13 Enterprise scheme, 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.”


Tagged categories: Carbon footprint; concrete; EMEA (Europe, Middle East and Africa); Emissions; Energy efficiency; Environmental Controls; Environmentally friendly; EU; Ongoing projects; Program/Project Management; Tunnel; Utilities

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