Carbon-busting concrete trials launched

Skanska is trialling an 'industry-first low carbon-reinforced concrete solution' on a major National Highways scheme.

Production of cement, a key ingredient in concrete, currently accounts for around 7% of the world’s CO2 emissions, although in the UK this figure is less than 1.5%.

The £282m M42 Junction 6 improvement project is trialling the use of low carbon concrete and basalt fibre reinforcement on a temporary haul road for construction vehicles, comparing it against traditional steel-reinforced concrete.

The trial is led by Skanska in partnership with the National Composites Centre.

Glennan Blackmore, Skanska UK’s operations director (highways), said the combination of low carbon concrete and the replacement of the steel with a lightweight composite reinforcement reduces the carbon footprint by more than 50%.

‘With support and funding from customer National Highways, we have been able to bring together the knowledge, skills and innovative thinking from expert teams within Skanska, the National Composites Centre and supply chain partners Basalt Technologies and Tarmac to carry out this exciting trial,' he said.

‘Through using a unique combination of materials, we are working to not only cut carbon but also aiming to improve the structural performance of reinforced concrete and deliver better productivity, safety and cost outcomes.

‘We are thrilled at the progress achieved to date and we are very excited to see the results.'

Tarmac provided two types of concrete for the trial: a mix comprising conventional blended cementitious material and a low carbon alternative mix incorporating an Alkali Activated Cementitious Material (AACM) in place of the cement.

Its head of commercial engineering, Robert Gossling, said: 'Tarmac has developed new low carbon concrete technology and this trial is a great opportunity to collaborate with industry-leading project partners to test its performance through an ideal, real-life application.

‘Manufactured at a conventional concrete plant located close to the project and installed in exactly the same way as traditional materials, this new sustainable product delivers a carbon footprint up to 80% lower than a standard CEM I concrete. We hope this demonstration will help to accelerate the development of innovative low carbon materials.’

Malcolm Newton, director at Basalt Technologies, said: ‘Basalt is a lightweight composite material consuming 62% less CO2e than steel during its manufacture. It comprises a non-metallic inert material that does not corrode, making it more durable than steel. Basalt Fibre reinforcement is also four to five times lighter than steel, making it safer to handle, fix and transport with fewer lorry movements.'

More about the trial

Following the start of the trial in early December 2021, field and laboratory tests will be carried out over the coming months.

Four reinforced concrete slabs were cast at the M42 Junction 6 site as part of a temporary haul road that will be heavily used by construction vehicles and will be monitored over the duration of the works.

The slabs are made up of:

  • Slab A – Conventional concrete + steel reinforcement
  • Slab B – Low carbon concrete + steel reinforcement
  • Slab C – Conventional concrete + basalt reinforcement
  • Slab D – Low carbon concrete + basalt reinforcement

The project team is now monitoring the slabs in-situ. Full scale test slabs have been sent to a specialist laboratory for bending and shear testing.

Skanska said all the collected test results will build knowledge of the curing process, ease of construction, safety benefits, functional properties and structural behaviour of the various concrete and reinforcement combinations, which will provide insight into the future use of longer lasting materials in construction.

It added that the trial will also provide a better understanding of the impact of the use of these materials ahead of the proposed revision to Eurocode 2 standards that will include the use of composites in the design of concrete structures. This is currently being developed.

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