Reducing construction carbon emissions via 3D printing
How 3D printing is revolutionising construction by reducing material use and carbon emissions for a more sustainable and resilient future.
Traditionally conservative, the construction sector must now demonstrate innovation given the climate emergency in order to improve the sustainability of the built environment. To achieve carbon neutrality, conventional construction methods must be transformed through innovative techniques including automation and robotics. 3D printing of concrete is an emerging technology with an immense potential to address sustainability challenges in the modern construction sector with carbon footprint reduction through design optimisation and use of low-carbon inks, as well as enhanced circularity and service life.
Building better with less
3D printing technology in construction offers a unique ability to minimise material use and create complex geometries that are difficult or impossible to achieve with traditional methods. The ability to print components with these geometries and properties tailored to specific load requirements enhances the overall performance of the structure while minimising material use. This approach ensures that the material is used only where it is needed, reducing both weight and embodied carbon.
One such design innovation was used in the Striatus, a pioneering example of 3D printed infrastructure. Unveiled at the Venice Biennale of Architecture in 2021, Striatus was the first 3D printed masonry bridge, in partnership between ETH Zürich – Block Research Group, Zaha Hadid Architects, Incremental3D and Holcim. In this prototype, the funicular block shapes naturally follow the paths of compressive forces and thus require less material to achieve the same structural integrity. As these vault structures are purely under compression, the use of steel reinforcement is not necessary.
Additionally, the modular nature of 3D printed components facilitates easier disassembly and recycling at the end of their lifecycle. This modularity means that parts of a structure can be upgraded without the need for extensive demolition, and no sorting of parts as the rebars have been removed from the project, further reducing waste and associated emissions. The lessons from this project provided Holcim with enough insights to launch a second iteration, the Phoenix bridge. Built in 2023 at the Innovation Centre in Lyon, France, the new bridge applies the same structural principles, combining them with specially-developed ink that aims for even further embodied carbon reduction through the application of circular design principles.
Specially tailored inks
The concrete ink used for Phoenix has been specially tailored to its application, while also minimising its carbon footprint. Structural tests used to validate the material performance of Striatus revealed that the new bridge required ink strength of ‘only’ 50 MPa instead of the earlier 90 MPa. Avoiding the trap of over-design helped Holcim save materials but also lowered the carbon footprint of the construction project. These low carbon concrete inks can also incorporate fly ash, slag, or ground granulated blast furnace slag (GGBS), which not only divert waste from landfills but also reduce the need for energy-intensive Portland cement. They may also include construction demolition waste and recycled aggregates for circular projects. In the case of the Phoenix bridge, the TectorPrint ink was composed of 40% of recycled material. These included a 100% recycled binder, and also demolition sand from the former project Striatus. Additionally, coarser sand used in the ink was sourced locally, further increasing the project’s circularity.
Shaping the future
Advancements in 3D printing technology have opened new avenues for sustainable infrastructure development. By optimising material use, developing low-carbon concrete inks, and enabling innovative structural designs, 3D printing addresses many of the environmental challenges associated with traditional construction methods. Combining funicular design and an arch in pure compression, the use of materials can be significantly reduced: by 35% for concrete and 50% for steel. Furthermore, a single material design allows for easier recycling and enabling circularity.
As this technology continues to evolve, it promises to play a crucial role in creating sustainable and resilient infrastructure for the future. The innovative techniques and materials being developed today are setting the stage for a new era of environmentally responsible construction, demonstrating that with the right approach, it is possible to significantly reduce the carbon footprint of our built environment.
Edelio Bermejo is Global Head of R&D at Holcim.