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Carbon concrete Cube cuts emissions and expands design options

Words:
Stephen Cousins

Carbon mesh and thinner structure slash embodied CO2 in Dresden’s concrete showcase Cube building by up to 70%

The Cube is the culmination of Germany’s largest construction research initiative.
The Cube is the culmination of Germany’s largest construction research initiative. Credit: Stefan Gröschel, IMB, TU Dresden

The world’s first ‘carbon concrete’ building, with roughly 70% less embodied carbon than a regular reinforced concrete building and four times the strength, is taking shape on site in Germany. Dresden’s Cube exhibition centre is the culmination of the C³ – Carbon Concrete Composite project, the largest research initiative in German construction, financed by the Federal Ministry of Education and Research.

The 220m2 building will serve as a showcase and testbed for the long-term viability of the innovative construction material – a composite of flexible carbon mesh and concrete – as a more sustainable method of construction. It features super-thin outer walls just 4cm wide and expressive double curved geometry built without the need for conventional formwork. 

A ground floor orthogonal ‘box’ will be used to monitor carbon concrete facade panels, wall elements and multifunctional reinforced concrete elements. Two double curved shells, arranged symmetrically, twist out of the wall and merge into the roof to form the side and upper room enclosure.

Manfred Curbach, director of The Institute of Concrete Structures at Dresden University of Technology, believes the project could signal a more sustainable trajectory for the world’s most commonly used, but environmentally damaging, construction material.

‘Cement production is responsible for about 6.5% of global CO2 emissions, so the potential benefit of using this carbon reinforced concrete is huge,’ he said. ‘A thinner structure means we are able to reduce the volume of concrete by more than 50%, but overall CO2 reductions will be up to 70%, because we do not use clinker [the binder in cement associated with high emissions in manufacture].’

  • Carbon concrete is much lighter and stronger than regular reinforced concrete, enabling thinner freeform structures.
    Carbon concrete is much lighter and stronger than regular reinforced concrete, enabling thinner freeform structures. Credit: Lurii Vakaliuk, IMB, TU Dresden
  • The Cube is under construction and due to complete in February 2022.
    The Cube is under construction and due to complete in February 2022.
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Whole life carbon is expected to be significantly lower because carbon fibre does not corrode like steel, giving the concrete more resistance against, for example, chemical attack, extending its longevity. The Cube’s structure, a combination of precast panels and shotcrete sprayed to carbon fibre mesh to form the twisted shell, has a predicted lifespan of 200 years, against 70-80 years for conventional reinforced concrete buildings.

Researchers anticipate carbon concrete being applied to existing buildings and structures as part of a more effective campaign of refurbishment. They have yet to measure and calculate the actual carbon impacts of the material, as a Eurocode to meet EU building regulations is in development.

The flexibility of the mesh opens new avenues for architectural expression, said Curbach: ‘Steel reinforcement is very stiff so making any curved reinforced concrete structure is difficult because you have to bend steel elements. Our carbon reinforcement grids are soft so you can bend them without any problem, making it much easier to build double curved structures. We have a new aesthetic language of forms for architects to explore.’

With the global population increasing by over 80 million every year, carbon concrete could provide a more sustainable way to keep pace with demand for new buildings. But a global roll out of the material will depend in part on the ability to scale up carbon fibre production.

‘Companies worldwide are producing enough carbon for today's demand and now looking to the building industry and planning to increase capacity,’ said Curbach. ‘Interest in carbon  reinforcement is very high in China and manufacturers know there is a market for the material. We will have enough carbon for the building industry,’ he concludes.

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