When you’re designing a new office building, the flat floor slab is the default option. It can be built quickly, and it makes it easy to install services and partitions. But most of the embodied carbon in a building’s structure is in the floor slab. So it makes sense to reduce the impact of that part of the building. That’s what has led to researchers coming up with a vaulted arch-type structure as a floor slab alternative.
Vaulted structures constructed from bricks have been used for centuries, but this new system is made from concrete. It’s called Acorn and is a thin shell, shallow vaulted structure with a column supporting each of its four corners.
It’s made in segments, off-site, by spraying concrete onto formwork with a robotic arm. The formwork is not unlike the kind of 3D pin-art where you leave an imprint of your face or hand. The pins are controlled by computer and can be moved depending on which segment you’re making.
This system has been developed in a partnership between Dundee, Cambridge and Bath universities, with the help of UK Research and Innovation funding, plus involvement from Laing O’Rourke.
Researchers have built a test version at the University of Cambridge’s civil engineering department and found that the 4.5m square prototype could be built with 60% of the embodied carbon of a flat slab. But they believe there’s the potential to reduce embodied carbon by up to 75%.
The prototype has a column at each corner and is made up of nine curved segments that fit together. The central segments have glass fibre reinforcement and are 40mm thick, whereas the corner segments are 60mm thick. Some segments are a little deeper so they can accommodate ribs for extra strength.
There is more work needed on this, and it may take two to three more years to develop the concrete mix, to work on the digital side of things and to improve the segment connection system.
One of the downsides of the vaulted structure is that fixing services becomes more of a challenge. But with so much less embodied carbon, it’s something worth exploring. It may not work economically as things stand, but as net carbon zero targets get ever closer then things may change. Either way, it’s an interesting and innovative solution.
Meanwhile, if you need assistance with the structural elements of an upcoming project, please do get in touch.