The ACORN Demonstrator

Researchers’ Reusable Thin-shell Floor will Transform the Construction Industry

An interdisciplinary team from the Universities of Bath, Cambridge, and Dundee have unveiled a full-scale demonstration of a new approach to the design and manufacture of concrete buildings, which can significantly reduce the carbon footprint of our built environment.

Achieving the net-zero targets recently agreed at the COP26 conference will require significant change by the Construction Industry, which is responsible for about half of the UK’s total emissions. Since concrete is the world’s most widely consumed material after water, and its production contributes more than 7% of global carbon emissions, the easiest way for construction to begin its journey to net-zero is to use less concrete.

The UKRI-funded research project Automating Concrete Construction (ACORN), has developed an innovative solution to this challenge, by rethinking how concrete floors are designed and produced. 

Currently most building floors use thick flat slabs of solid concrete, which is inefficient since it relies on the bending strength of concrete to support loads.  Since concrete isn’t very good at resisting the tension induced by bending, these floors also need lots of steel reinforcement.  Instead, ACORN’s approach is to use concrete for what it is good at - resisting compression.  By putting the material only where it is needed, and using it in compression, ACORN’s floors only need a quarter of the concrete of an equivalent flat slab to carry the same load.

This results in floors with a completely new shape, very thin and curved, which would be harder to make using traditional temporary formwork.  Therefore, in parallel the ACORN team have developed an automated adaptable mould and a robotic concrete spraying system that can be used in an off-site factory setting.  And to work out where to place the material for a given building design, the team have also developed bespoke software to seamlessly optimise the design of the floors and control the automated manufacturing system to produce them.  Since the floor is made off-site, it also needs to be transported to site and then assembled.  This brought some exciting challenges for the team, who had to split the large floor into 9 transportable pieces and develop a connection system to join the pieces together.  However, this also brings some advantages, in terms reducing time needed on-site for construction. The ACORN team were also able to design reversible joints, so that the floor can be disassembled and reused elsewhere at the end of the building’s life, promoting a circular economy for the construction industry.