British building materials company Tarmac has joined forces with Align to develop a new low-carbon concrete solution for HS2 Phase One, to help mitigate the climate crisis.
The innovation has been trialled by the two firms who are key partners in delivering the Central 1 (C1) section of HS2 Phase One, the new high-speed rain line in the UK. C1 consists of 21.6km of high-speed rail infrastructure in a rural environment which is being delivered by Align, while Tarmac supplies the concrete for construction.
The innovative concrete has undergone considerable research and design in the laboratory as the two companies work towards the joint goal of net zero carbon construction.
Align delivers high-profile infrastructure projects both in the UK and globally, and is a joint venture of Sir Robert McAlpine, Bouygues Travaux Publics (a subsidiary of Bouygues Construction) and VolkerFitzpatrick (a subsidiary of VolkerWessels). All three are international and privately-owned infrastructure companies.
Tarmac used its construction site in Chalfont Lane, Hertfordshire (one of three Tarmac concrete batch plants) for early demonstration and testing which was conducted at full scale.
The new low-carbon concrete has a carbon footprint following industry BSI PAS2050 calculation rules. It gives a 62 per cent reduction in CO2e per cubic metre of concrete, compared to a standard CEM I concrete, and meets the same specification in the same raw materials.
The footprint covers the entire concrete production and supply with no carbon off-setting applied, delivering an actual footprint of 133kg/m3 CO2e. This represents a saving of 220 tonnes CO2e for every 1000m3 produced.
A structural slab forming part of the new viaduct pre-cast factory and a vertical wall were poured. The mixes, designed to Align concrete specifications, exceeded expectations in both fresh and hardened properties, and demonstrated that the new concrete can be produced in normal concrete plants.
This showcases the potential to use very high ground slag (GGBS) contents in excess of 90 per cent, as an alkali activated cementitious material conforming to BS EN197 (the standard for cementitious materials allowed to be used in ready mixed concrete), to lower carbon emissions, yet still produce a quality finish.
Robert Gossling, Head of Commercial Engineering Solutions at Tarmac, said: “Against the backdrop of the climate emergency, this project underlines the clear benefits which can be unlocked when clients and contractors collaborate, in this case engaging to help understand and accelerate the adoption of this new low carbon concrete solution.
“Together we’ve shown this new concrete is fit for purpose in slabs and walls, with good repeatability and works with standard production and construction methods. This product is a great step along the industry zero carbon route map, and the demonstration will help accelerate adoption of this new concrete.”
Daniel Altier, Project Director for Align, said: “It is a strategic imperative for Align, reflecting the priorities of our JV partners and in line with HS2 commitments, to reduce carbon emissions by 50 per cent, to look for opportunities to improve our carbon footprint. The early results of this trial are very encouraging and highlight the benefits to be gained through close collaboration with our supply chain partners.”
Greg Walker, Senior Consultant, Sustainable Business - Construction and Infrastructure, at Acre said: “Two giants in the infrastructure sector are working together to tackle one of the major carbon issues in large-scale projects, concrete. The low-carbon concrete solution being developed by Align and Tarmac represents a great opportunity that will be first utilised on HS2. Whilst this will be a significant achievement, this is just the start of what could be done globally across major infrastructure projects."
Tarmac will expand the trial with Align on other available areas of the C1 project and will continue to focus on developing low carbon solutions.
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