Impact printing employs a fast-moving jet of material, integrating it into a structure.
Recently, the construction firm ICON revealed that it is nearing the finish line for the
world’s largest 3D-printed neighborhood in Georgetown, Texas. This project isn’t the only one in the realm of 3D-printed housing; a multitude of 3D-printed homes are currently being built across the US and Europe, with many more projects on the horizon.
Several factors are driving the rise of 3D printing within the construction sector. It significantly cuts down construction time; a home that typically needs months to complete can be ready in just days or weeks when utilizing a 3D printer. Additionally, compared to conventional building techniques, 3D printing minimizes the amount of waste material produced during construction. These benefits contribute to lower labor and material expenses, making 3D printing an appealing option for construction firms.
However, a team of researchers from the Swiss Federal Institute of Technology (ETH) Zurich asserts they have created a robotic construction technique that surpasses 3D printing. This method is referred to as impact printing, utilizing Earth-based materials like sand, silt, clay, and gravel instead of typical construction substances to build homes. The researchers argue that impact printing is less carbon-intensive and significantly more sustainable and economical than 3D printing.
Earth-based materials are plentiful, recyclable, low-cost, and can often be excavated directly from the construction site. “We created a robotic tool and a method that can transform common excavated materials into usable building products, efficiently and at a lower cost, while significantly reducing CO2 emissions compared to traditional construction techniques, including 3D printing,” noted Lauren Vasey, a researcher and SNSF Bridge Fellow at ETH Zurich.
However, excavated materials cannot be utilized in their raw form. Prior to beginning the impact printing process, researchers must curate a mixture of Earth-based materials, balancing fine and coarse particles to ensure usability and structural integrity. Fine materials such as clay serve as binders to ensure that the particles adhere to each other, while coarser materials like sand or gravel enhance stability and strength. This carefully optimized mix is formulated to facilitate smooth movement through the robotic system, preventing clogs or blockages.
The following phase involves creating a digital blueprint. Much like a 3D printer’s requirements, the robotic impact printing system needs a digital model to direct the structure’s production. When this digital blueprint is finalized and uploaded to the system, the robotic tool is attached to a mobile platform, making it ready for use at the construction site. Subsequently, the Earth-based materials mix is loaded into a sizable volumetric hopper linked to the robotic tool.
Once the hopper is full, the system activates and carries out the essential functions—extruding, cutting, and spraying the material—to construct the structure according to the specifications of the digital model. This process will persist until the construction is complete.
The process of construction operates quite distinctively from standard building-grade 3D printing. In this context, the inherent properties of the materials are insufficient to support a structure on their own. To enhance the strength, additives such as cement are required to significantly increase the yield stresses (the maximum stress that a material can tolerate before permanent deformation) that the final structure can withstand.
The robotic tool employed for impact printing applies the construction material at a high velocity (reaching 32 feet/10 meters per second) in a precise manner. The resultant high-velocity impact promotes robust bonding between layers of Earth-based materials—even prior to the introduction of any binding agents. “Our material already possesses greater strength and stiffness (>28 kPa). Consequently, we have an advantage in the strength development of the material and depend less on additives to improve its properties,” explained Vasey.
Using this technique, the researchers successfully constructed walls that stand 6.5 feet tall (2 meters). Each of these structures is resilient enough to bear an additional structure of similar weight without the need for chemical additives like cement. “With our system, if you are fabricating a 2-meter-high structure, the material is already in a condition to support a load equivalent to 2 meters,” Vasey noted. However, this material may not be suitable for constructing much taller structures. “Our material has a compressive strength of about 2 megapascals, which is less than conventional concrete, but this is perfectly adequate for building walls and load-bearing capabilities up to two stories,” she remarked to Ars.
3D printing offers a reduction in labor expenses for businesses and holds the potential to make housing more economical. However, it is not necessarily a sustainable or environmentally benign process. It depends on cement as a component, a construction material contributing nearly 8 percent of global CO2 emissions. Furthermore, due to the incorporation of additives, 3D-printed structures are typically not recyclable.
“3D printing has the potential to conserve material by allowing for the precise placement of resources where they are most needed. Nevertheless, the typical mixture often contains a significant amount of mortars, additives, and accelerators, resulting in a high CO2 output per volume,” Vasey noted.
In contrast, structures built using impact printing avoid the need for cement and instead utilize naturally sourced, lower carbon materials. Currently, the researchers incorporate a small percentage, about 1 to 2 percent, of a mineral stabilizer, which is less detrimental to the environment and more recyclable than traditional cement. “In the future, our goal is to eliminate any additives or stabilizers entirely. We envision our method as fully circular, where the components can be disassembled and reused in future constructions, keeping them out of landfills,” Vasey shared with Ars Technica.
Vasey and her team are now looking to bring this innovative technology to the market. They anticipate launching their venture once they establish a prefabrication facility—essentially a factory where components will be manufactured for sale and transportation to building sites. “We are close to finalizing the technology for the prefabricated approach. We plan to incorporate as a startup within the next year, and we expect our product to be available on the market in approximately three years,” Vasey stated.
Circular Economy and Sustainability, 2024. DOI: 10.1007/978-3-031-39675-5_9 (About DOIs)
Rupendra Brahambhatt boasts extensive experience as a journalist and filmmaker. He specializes in reporting on science and cultural topics. Over the past five years, he has collaborated with a variety of cutting-edge news agencies, magazines, and media outlets from various regions around the world.