A European research consortium led by Empa (Swiss Federal Laboratories for Materials Science and Technology) and ETH Zurich (Swiss Federal Institute of Technology) – two of Switzerland’s most prestigious scientific institutions – is aiming to overhaul traditional construction by developing 3D-printed, carbon-negative concrete structures that eliminate the need for heavy steel reinforcement and conventional cement.
The research team is focusing on intelligent shapes, digital manufacturing, and alternative binders in a bid to create a climate-friendly building material that is delicate yet stable and can be custom-made using 3D printing, dismantled, and reused.
The project, titled CARBCOMN, focuses on “compression dominant” designs inspired by historic stone arches. By using digital manufacturing to create geometrically optimised shapes, the team can significantly reduce material mass.
The process utilises 3D printing to build components layer by layer, allowing robots to leave precise cavities where reinforcement is unnecessary, which reduces both resource consumption and seismic stress.
A critical shift in the project is the replacement of standard cement with alternative binders derived from industrial waste, specifically steel slag. These low-carbon components are placed in a CO2-injected chamber after printing, triggering a chemical reaction that hardens the material while simultaneously sequestering carbon dioxide.
“On the one hand, we are using digital manufacturing methods to build in a resource-efficient manner. On the other hand, we are replacing conventional cement with binders that have a lower carbon footprint,” says Empa researcher Moslem Shahverdi.
The structure was 3D printed at Ghent University in Belgium.
Shahverdi notes that while the goal is a cement-free mixture, small amounts may be added, if necessary, to meet civil engineering standards.
The low-carbon footprint concrete used in the CARBCOMN project consists exclusively of industrial waste. It is formed into individual components using 3D printing and later assembled into load-bearing structures.
“Concrete can withstand a lot of compression, but little tensile stress,” explains Shahverdi.
That is why the researchers are developing structures that are primarily subjected to compression – similar to historic stone bridges with their arches.
Digital manufacturing enables them to precisely plan such geometrically optimised shapes and significantly reduce the amount of material used. Since the concrete is printed layer by layer, the need for concrete formwork is eliminated. Cavities are deliberately left where no reinforcement is necessary.
“We plan these openings directly in the digital model so that the robot automatically leaves them open during printing,” explains Shahverdi.
Lighter elements not only reduce material consumption, but also seismic stress in proportion to the weight loss – a decisive advantage in earthquake-prone regions. “Even a 10 per cent reduction in weight makes a big difference,” says Shahverdi.
Surgically implanted steel reinforcement
However, the concept cannot do entirely without steel rebars, which are only used where they are necessary. This is where Empa brings one of its specialties to the project: iron-based shape memory alloys (Fe-SMA). These pre-stretched metals contract when heated – instead of expanding – and thus subsequently place components under compression.
“We have been working with these special alloys for around 20 years,” says Shahverdi.
The Empa spin-off re-fer is, therefore, also contributing its expertise in the field of shape memory alloys to the CARBCOMN consortium.
Conventional steel reinforcements have to be pre-stressed in a complex process; shape memory alloys, on the other hand, are simply inserted into the concrete after printing. This has several advantages: The printing process remains automated and undisturbed, and the Fe-SMA rebars can be placed precisely where they are actually needed. Moreover, they can be separated from the concrete again later – which is crucial for being able to dismantle the components at a later date.
According to the Empa researcher, these work steps are also to be automated in the long term. “In the future, a second robot could insert the Fe-SMA rebars directly after printing,” he says.
CO₂ as a hardening agent
After 3D printing, the concrete components are placed in a chamber where CO₂ is injected. This leads to a chemical reaction with the steel slag-based concrete mixture.
“This process hardens the concrete and binds CO₂ at the same time,” says Shahverdi.
The aim is to further increase strength with an optimised concrete mixture. If this is not sufficient, a small amount of cement could be added.
Parallel to the material, the teams are developing new digital tools: A common platform is to cover the entire process from design to production – including sustainability and life cycle analyses.
The initiative brings together 11 partners, including architectural firms Zaha Hadid Architects and Mario Cucinella Architects, alongside academic institutions such as Ghent University and TU Darmstadt. The collaborators are currently developing the unified digital platform.
While the architects design free-form structures, the Empa team investigates the technical feasibility, tests materials, and develops connection technologies that allow for later dismantling.
“We combine unique expertise here – 3D printing, structural performance, and our specialty: iron-based shape memory alloys,” summarises Shahverdi.
Funded by Horizon Europe with a budget of approximately six million euros ($6.93 million), the four-year project began in 2024. The consortium aims to produce a finalised prototype – a 3D-printed building module demonstrating climate-friendly, earthquake-proof, and recyclable residential construction – by 2028.