Led by Dr Paul Shepherd and with its origins at BRE Centre for Innovative Construction Materials, a research partnership across the Universities of Bath, Cambridge and Dundee is working together to create more sustainable and productive behaviours in the construction industry, particularly around use of materials.

The production and use of concrete is one of the world's biggest sources of carbon emissions. Worse, is that up to half of the concrete being used in buildings is unnecessary. Concrete is used so often because it can be shaped into easy-to-make beams, columns and floor slabs. But while easy to make, these prisms are inefficient to build with, create waste and are a major driver of embodied carbon in construction.

The ACORN team has completely rethought the way that concrete is used in our buildings. It has combined offsite manufacturing processes, robotics, and a highly automated, quality-controlled environment to help design concrete out of construction. It only uses concrete where it is absolutely needed, such as fulfilling the structural requirements of the building, and it creates concrete beams, columns and floors in more optimised, efficient shapes. It also uses concrete in structure where it takes forces in compression - rather than flat slabs which resist loads in bending and need to be highly reinforced. This means that just enough concrete is used. The added introduction of cement-free alternatives together helps realise the carbon efficiencies required for the UK to achieve net zero by 2050.

The team were initially researching fundamentals about how concrete structures are designed and manufactured. Appreciating that concrete is initially a liquid and can form structures of any shape, given the right mould, they were reimagining the ways concrete is used on a building and introducing brand new processes and behaviours that would bring down its use and reduce this waste. This insight initiated a project to Automate Concrete Construction, or ACORN.

Project ACORN wanted to create new industry behaviours around concrete use to reduce waste so brought together twelve industry partners including Architects, Engineers and Contractors, both large and small, to help guide the project and ensure the outputs are fit for purpose. The partners noted that reducing material doesn't always reduce carbon. So as well as reducing concrete usage, ACORN also wanted to quantify the carbon savings that could come from reduced waste. ACORN carried out life cycle analyses across several construction projects to categorise and quantify different instances when material is wasted in the construction of a building. It found that half of projects are over-designed and use materials that are simply not required. In the instance of one project, 14% of the concrete ordered was wasted. 

Our modern day approach to pre-casting prism shaped concrete slabs hasn't changed since Roman times. It yields reliable and highly repeatable results, but creates waste and does not work for an industry looking to invest its carbon sparingly and for the right reasons. New approaches to concrete use and manufacture are needed, and the value of them needs to be evidenced if more of the industry need to adopt these new behaviours.

ACORN is a proof of concept project looking to move the concrete construction industry to use automation and robotics at scale by creating segmented structures that are produced in a factory and assembled onsite. The project team is continuously prototyping new manufacturing techniques in the University of Cambridge’s new NRFIS Lab to gain a better understanding of performance. Several technologies and techniques are being used to produce structures that only use the right amount of material:

• Reconfigurable moulds that consist of a set of vertical pins holding flexible form-work and fitting a doubly-curved target surface on which the concrete element is cast.
• Robotic concrete spraying arms that project concrete on to the curved form-work, which adheres to the surface thanks to self-compaction. Robotic spraying enhances the quality of the spray by carefully following a path with the appropriate position and orientation from the surface, and also allows the thickness to vary across the finished object.
• Robotic filament winding that breaks the constraint of high utilisation of steel reinforcement bars and produces complex, optimal reinforcement layouts that can follow the curved formwork.
• Connected Segments allow large span floors to be made in transportable pieces and then joined together on-site. This also allows them to be disassembled for recycling, reuse, reassembly, or reconfiguration of the structure at the end-of-life, supporting a circular economy.

Digital fabrication is needed to build advanced shapes in concrete efficiently and sustainably. To design geometrically complex structures, the ACORN team is developing a digital design framework that can be integrated with existing 3D CAD tools. Parametric modelling enables architects and engineers to create and optimise designs that consider constraints from fabrication, transport and assembly, towards construction-aware design.

The trio of university research centres that make up ACORN are:

• University of Bath leads on the digital work and overall project management
• University of Cambridge leads on physical experimentation of the innovative-shaped floors where most of the robotics work lies, and also researching Whole Life Cost
• University of Dundee leads on materials development and, as a reaction to COVID-19, has also taken on the complex-shaped beams physical experimentation.

ACORN approached 12 experts in the field of construction to be industry partners. These are: AECOM; AKTII; ARUP; BRE; Buro Happold; Byrne Bros; Cambridge Centre for Smart Infrastructure & Construction (CSIC); Foster + Partners; Laing O’Rourke; McKinsey & Co; OPS Structural Engineering; and Tonkin Liu. 

The project has been so well received by the construction industry that a further 14 project affiliates (and growing) have since joined to contribute to the project. They are: Format; Robert Bird Group; Tony Gee; London Structures Lab; Kilnbridge; Sci-Mode; Costain; i3P; National Composites Centre; Integral Engineering Design; Change Maker 3D; Versarien; HAL Robotics; and Power-Sprays. ACORN is seeking more partners and affiliates into the programme.

• AECOM
• AKTII
• Arup
• Buro Happold
• Byrne Bros
• Centre for Smart Infrastructure and Construction (CSIC)
• Change Maker 3D
• Costain
• Format
• Foster + Partners
• HAL Robotics
• Integral Engineering Design
• Kilnbridge
• Laing O'Rourke
• London Structures Lab
• McKinsey & Co
• National Composites Centre
• OPS Structural Engineering
• Power-Sprays
• Robert Bird Group
• Sci-Mode
• Tonkin Liu
• Tony Gee
• University of Bath
• University of Cambridge
• University of Dundee
• Versarien
• i3P

As well as supporting through Innovate UK funding, Transforming Construction has introduced the team to new industry stakeholders who have gone on to become project affiliates, as they see the value ACORN and what it can bring to construction in the future. ACORN partnered with the Centre for Smart Infrastructure Cambridge (CSIC) which is part funded by Innovate UK. This work is feeding into a broader CSIC project to identify underlying drivers of embodied carbon.

The UK must achieve net zero by 2050 and careful use of concrete in construction will play a big part in that. ACORN is transforming the way that concrete is used in our buildings by drawing on offsite manufacturing processes and robotics to help design concrete out of construction. By only using concrete where it is absolutely needed and by creating more optimised shapes - rather than the prisms seen in concrete beams, columns and floor-slabs - the industry can start to ensure just enough material is used, reducing waste and minimising carbon emissions.

Greater use of automated, factory processes means that the manufacture of concrete elements can be taken offsite and improve the conditions and safety of workers - ultimately taking them away from dangerous construction sites into highly-skilled jobs in safe efficient factories.

ACORN is continuously prototyping new offsite manufacturing techniques to gain a better understanding of building performance. By capturing performance data using sensors, the team can test different technologies, techniques and materials to produce structures that only use the minimum amount of concrete needed. This live iteration has attracted the interest of nearly 30 partners to the project who are keen to apply the findings to their real-world builds.

The construction industry in total is responsible for about 50%. of global carbon dioxide emissions. Research from ACORN showed that up to half of the concrete being used in buildings is unnecessary. ACORN-affiliated researchers carried out life cycle analyses across several construction projects and found that half of projects are over-designed and use materials that are simply not required. In one instance, 14% of the concrete ordered was wasted. ACORN estimates that its new approach could be part of a strategy that would cut embodied emissions by more than 90%. This will also involve the use of low carbon alternatives to cement, and reinforcement made from bio-based or recycled materials.

Emissions
The Cambridge Centre for Smart Infrastructure and Construction helped identify the underlying drivers of embodied carbon emissions in the construction and in-use phase of buildings. ACORN’s initial research found that existing approaches to reduce operational carbon wasn't on a big enough scale, or focused enough on embodied carbon. They concluded that emissions saved today – faster and on a bigger scale than currently – have a stronger saving longer term. ACORN estimates that if the construction industry adopted all of these potential carbon savings, including a move to offsite automated concrete construction using adaptable doubly-curved moulds, embodied carbon could be reduced by 90% compared to traditional concrete construction.

Safety
The new approach recommended by ACORN minimises the need for manual casting of concrete elements, moving fabrication offsite. This helps reduce the number of people onsite, especially those working at height. 

Whole-life Value
ACORN is developing an understanding of how whole-life cost, design value, carbon intensity and productivity should be defined and measured. This understanding has been developed through traditional research methods such as literature reviews, surveys, interviews and detailed analysis of case study data from its partners/affiliates. The team are introducing these calculations into the early stage design. By establishing whole-life value benchmarks against current practices, ACORN can help the industry compare the value of these new methods being proposed.

Changing the shape of floors could cut concrete usage by 75 percent