Tarmac develops new CO2-low concrete with HS2
New ultra low carbon concrete trialled for HS2 rail.
Tarmac is already pouring concrete for Align, the joint venture delivering the Central 1 (C1) section of HS2 Phase One.
Both organisations are working towards net zero carbon construction and after extensive laboratory design Align tested at full scale using one of three Tarmac concrete batch plants at a Chalfont Lane construction site in Hertfordshire.
A structural slab forming part of the new viaduct pre-cast factory and a vertical wall were poured.
The mixes, designed to Align concrete specification, exceeded expectations in both fresh and hardened properties, and proved that the new concrete can be produced by normal plants and placed via mixer truck and by skip with tremie pipe.
The concrete's carbon footprint, following industry BSI PAS2050 calculation rules, has a 62% reduction in CO2e per m3, compared to a standard CEM I concrete, meeting the same specification in the same raw materials.
The footprint covers all aspects of the 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.
There is potential to use very high ground slag (GGBS) contents of more than 90%, as an alkali activated cementitious material conforming to BS EN197 – the standard for cementitious materials allowed to be used in ready mixed concrete – to significantly reduce carbon emissions, whilst still producing a quality finish and allowing normal construction and demoulding times.
