Tarmac has demonstrated and tested an innovative new low carbon concrete solution with Align, the joint venture delivering the Central 1 (C1) section of HS2 Phase One, the new high-speed rail line in the UK.
The new low carbon concrete has a carbon footprint following industry BSI PAS2050 calculation rules which equates to a 62% reduction in CO2e per m3 of concrete compared to standard CEM I concrete, meeting the same specification in the same raw materials.
With all aspects of concrete production and supply and no carbon off-setting applied, the material delivers an actual footprint of 133kg/m3 CO2e representing a saving of 220 tonnes CO2e for every 1,000 m3 produced.
Align provided an early demonstration and full-scale testing applications using one of the three Tarmac concrete batch plants at its Chalfont Lane construction site in Hertfordshire.
Tarmac and Align have a common goal of working towards net zero carbon construction. This new concrete, which is only recently available following extensive laboratory design, can help achieve this objective.
A structural slab forming part of the new viaduct pre-cast factory and a vertical wall was poured. The mixes designed to Align concrete specifications exceeded expectations in both fresh and hardened properties and showed that the new concrete could be produced in normal concrete plants and placed via mixer truck and by skip with tremie pipe.
This has demonstrated the potential to use very high ground granulated blast furnace slag (GGBS) contents over 90%, as alkali-activated cementitious material conforming to BS EN197 standard.
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 the material 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 UK concrete and cement industry’s net-zero 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% and 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.”
Tarmac and Align will continue to collaborate by expanding the trial on other available areas of the C1 project and the development of low carbon concrete solutions.
Tarmac is currently providing concrete to construct the Central 1 section of HS2 Phase One that Align is delivering. This includes a 21.6km section of high-speed rail infrastructure incorporating a 3.37km viaduct across the Colne Valley, a 16.04km twin-bored tunnel, and five vent shafts handling intervention and tunnel ventilation facilities.
