HS2 introduces carbon neutral concrete to ensure sustainable construction

Credit: HS2 Ltd

As part of its ambitions to build the most sustainable high-speed railway in the world, HS2 contractors in London have begun using a new low carbon concrete product which provides a reduction of 42 per cent in CO₂ in comparison to standard concrete.

In addition, the remaining carbon emissions from using the concrete are offset to provide a carbon neutral product, in accordance with The CarbonNeutral Protocol. The product, used for the first time in London, has been supplied to HS2’s enabling works contractor, the Costain Skanska joint venture, and Lydon Contracting Ltd by global building materials manufacturer CEMEX, from their plant based in Wembley.

After engineering carbon reductions into the concrete mix design, CEMEX calculates the embodied carbon generated from the extraction and processing of raw materials, product manufacturing and distribution. The residual carbon is then offset, making the concrete carbon neutral from manufacture to use.

To achieve carbon neutrality, carbon is offset by the removal or reduction of emissions of carbon dioxide or other greenhouse gases from the atmosphere in order to compensate for emissions made elsewhere. CEMEX facilitates this by investing in projects which physically remove CO₂ where possible from the atmosphere, such as planting more trees or protecting against deforestation through an independently audited and verified project. This is done in accordance with international standards for carbon neutrality.

The first use of the Vertua Classic Zero concrete in the capital recently took place at a HS2 site in North West London, ready to prepare the ground for an electricity substation which will power the tunnel boring machines excavating HS2’s London tunnels.

A further delivery of Vertua is planned at the same site by the end of October 2020. By using this low carbon concrete, a total of 12 tonnes of carbon should be saved once deliveries are complete, with an additional 17 tonnes of residual CO₂ offset. 

Discussions are continuing as to how this technology can be adopted on further sites across the HS2 route.

HS2 aims to build the most sustainable high-speed railway in the world and is driving innovation in design, construction and operation to minimise its entire carbon footprint. In order to become the UK’s most environmentally responsible infrastructure project, HS2 has set a carbon reduction target of 50 per cent for its contractors on construction baselines for Phase One’s civil assets (such as tunnels, viaducts and cuttings), stations and railway systems.

Environment Director at HS2 Ltd, Peter Miller, said: “We know that climate change is the greatest long-term threat to Britain’s security and prosperity. The government has set a target for net-zero emissions by 2050, and HS2 is playing its part in meeting that challenge. Using innovative techniques and products in the construction of the new high-speed railway, we can not only build HS2 more sustainably, but we can lead by example, showing how the construction sector can help deliver Britain’s cleaner, greener future.”

When operational, HS2 will offer people a cleaner, greener way to travel, with lower carbon emissions per passenger kilometre than cars and domestic air travel. HS2 trains will be highly energy efficient and powered by electricity from an increasingly decarbonised electricity grid. In the future, with electricity generation fully decarbonised, travelling on HS2 will be a zero-carbon activity. In addition, HS2 will free up extra space on the existing rail network. It will take cars and lorries off of the road and reduce the need for domestic air travel. This will reduce transport carbon emissions and improve air quality.