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Low-carbon reusable cassette.

Circular economy approach.

A team, led by MACE, includes AKT II, DB Group, William Hare Group, Oranmore Precast, Converge and UCL, and has currently finished the design phase of a low-carbon structural system making net-zero carbon structures deliverable. 


The low-carbon reusable cassette is the result of collaborative work with the teams, designed to drive down embodied carbon and promote a truly circular economy in the built environment.

A circular economy approach involves designing out waste, utilising resources more efficiently, and keeping materials and assets in use for as long as possible. When implementing this approach, assets can retain their value, while the effects of man-made climate change, resource depletion, deforestation, loss of biodiversity, and pollution are reduced.

Structural materials are often accountable for more than half of embodied impacts on most new buildings. As structural engineers, we must lead positively in the transition to net-zero embodied carbon.

The reinforced concrete slab is achieved by using Cemfree, a low carbon alternative to traditional cement. In the below video, you can see that this cement-free alternative has been cast on top of the steel beams as a precast. The connections between the structural elements are mostly ‘dry’ to improve the opportunities of adaptability, as well as allowing the structure to be demountable. Offsite manufacturing of the structural elements in this design has been maximised to improve logistics both in the factory, during transportation, and at the installation phase on-site. Compared to traditional construction, the system will reduce:

• Weight of the structural frame by 10%

• Structural steel content by 15-20%

• Deliveries to site by 40%

• Labour resources for steel frame erection and following trades by 60%

• Reduced embodied energy (and therefore carbon reduction) of 80%

• Cement content in floors by 100%

The structure of this animation mock-up is currently being installed and tested for structural performance. Other structural components will be tested in the facilities at Here East, the centre for cross-disciplinary research and teaching at UCL.

Testing is pivotal for the design team to achieve an innovative design. Any information collected during this process will be stored in the material passport, with the results used to enhance the structure’s value for recovery, recycling and re-use. By using a circular economy design and approach, we can improve environmental outcomes, boost economic opportunities and enhance well-being for all, and this project aligns well with this philosophy.