Replacing solid panel floors with a ‘thin-skin’ domed alternative could help the construction industry meet its net-zero targets, according to a concept put forward by a British research team.
A multidisciplinary team of structural engineers, mathematicians and manufacturing experts from the Universities of Bath, Cambridge and Dundee have presented a large-scale demonstration of a thin-skinned floor that uses 60 per cent less carbon in its construction than an equivalent flat slab could carry the same load.
The new domed floor, developed in the UK, uses 75 per cent less concrete than a traditional flat slab floor and could help the construction industry reduce its carbon footprint. The curved vaulted structure is covered with standard raised floor panels to create a level surface.
Prepared funded by UKRI Research project Acorn (automation of concrete construction).The innovative vaulted floor design takes advantage of the inherent natural properties and strengths of concrete.
The team showed that the new process could significantly reduce the carbon footprint of our built environment.
dr Paul Shepherd, Lecturer at the Faculty of Architecture and Civil Engineering in Bath and lead researcher for Acorn, said: “To achieve the net zero targets recently ratified at the COP26 conference will require significant changes in the construction industry, which will last for around accounts for half of the UK’s total emissions.
“With concrete being the second most consumed material in the world after water, and its production contributing more than 7 percent to global carbon emissions, the easiest way for construction to start its journey to net zero is to use less concrete.
“That was the driving force behind this project, which we hope could make a big difference to the impact of construction.”
Innovations in robotics, automated design and offsite manufacturing are also key aspects of the project.
Most building floors use thick flat slabs of solid concrete, which are inefficient because they rely on concrete’s flexural strength to support loads. Concrete is not very good at resisting the stress caused by bending, so these floors also need a lot of steel reinforcement. Acorn’s approach is to use concrete for what it’s inherently good at – resisting pressure.
By only putting the material where it’s needed and ensuring it works under pressure, the Acorn design uses far less concrete. The new mold might prove impractical to fabricate with traditional temporary formwork, so the Acorn team have been working in parallel to develop an automated adjustable mold and robotic shotcreting system that can be used in an off-site factory setting.
Alongside this new manufacturing style, the team has also developed bespoke software to seamlessly optimize floors for a specific building design and control the automated manufacturing system used to manufacture them.
Since the floor is manufactured externally, it also has to be transported to the construction site and then assembled. This presented new challenges for the team, who had to disassemble the large floor into nine transportable parts and develop a connection system to connect the parts together. However, this approach also brought some advantages in terms of reducing the construction time on site.
The Acorn team was also able to incorporate reversible joints, allowing the floor to be dismantled at the end of the building’s life and reused elsewhere, promoting a circular economy for the construction industry.
The practicality of this integrated system was demonstrated to Acorn’s industrial partners with a full-size 4.5m x 4.5m thin-walled building erected in the NRFIS laboratory at Cambridge University’s Civil Engineering Department.
Initial results suggest that Acorn’s approach to using materials sparingly can already result in significant CO2 savings, with future research likely to lead to even more as the various processes are further optimized. Despite being the first of its kind, it took just half an hour to manufacture each part and a week to assemble the entire floor – future commercial versions could be manufactured much more quickly in dedicated industrial facilities, with on-site assembly times reduced accordingly.
dr Added Shepherd: “After three years of research, it is amazing to see the fruits of all our hard work dominating the lab and drawing interested looks from all passers-by. It’s not every day that you get to advance your research! I just hope that one day this type of low-carbon, automated building is so widespread that people walk by without noticing it.”
Adam Locke, program manager for the Europe Hub Technology and Innovation at Laing O’Rourke, one of Acorn’s industry partners, added: “The Acorn demonstrator is a very useful stepping stone on the ongoing journey to decarbonise our solutions and complements our very good work of our own in this area.”
The decarbonization of the construction industry and its heavy reliance on the use of concrete is a popular research topic.
In May 2021, a joint venture between graphene specialists from the University of Manchester and alumni-led construction firm Nationwide Engineering unveiled a graphene-enriched concrete that could revolutionize the concrete industry and its impact on the environment.
Meanwhile, in April 2021, first-time tenants of Holland’s first 3D-printed concrete house received their house keys. The house is the first of five structures of this type planned as part of Project Milestone – a joint construction and innovation project between Eindhoven University of Technology, Van Wijnen, Saint-Gobain Weber Beamix, Vesteda, the municipality of Eindhoven and Witteveen+ boss
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