An architecture doctoral student at ETH Zurich has printed lightweight and insulating wall elements using cement-free mineral foams made from industrial waste. These could one day reduce the heating and cooling costs of buildings and help to use building materials more efficiently.
In the large hall of the Arch Tec Lab research and robotics laboratory on the Hönggerberg: several robot arms hang from the ceiling, and on the floor are half-finished beige-colored curved shapes that resemble sculptures made of sand. Enigmatic elements protrude from wooden crates on one side of the room.
Patrick Bedarf is standing in front of one of these boxes. He works in Professor Benjamin Dillenburger's Digital Construction Technologies group and completed his doctorate at the end of September. As part of his dissertation, he investigated how lightweight and insulating components, especially more complex shapes, can be produced in a material-saving manner. To do this, he used sustainable insulation material, which the ETH spin-off FenX produces from industrial waste. "Their mineral foam is an innovative building material that contributes to a more climate-friendly industry," says Bedarf.
The foam is mainly made from fly ash - a waste product from the blast furnace industry. "So the material has already gone through its first material cycle. And it can be easily recycled again after use," says Bedarf, crumbling the small piece he has dug out of the wooden box between his fingers. "The material can now be reused for a new foam."
The production of the insulating components also had to be sustainable: In order to use less material and reduce CO2 emissions, the doctoral student opted for 3D printing. "Unlike pouring concrete, you don't need formwork for this. This is very time-consuming to produce and can only be reused to a limited extent in the end," says Bedarf. Waste is a major challenge, especially in the production of complex geometries.
"Without automation, resource-saving construction is very time-consuming and expensive."
- Patrick need
By combining 3D printing with robotics, even complex components can be produced cost-effectively, says Bedarf. "Without automation, resource-saving construction is very time-consuming and expensive, especially because of the labor costs."
The researcher shows the first tests of printed and hardened foam. "For example, this slice here, which looks like a pizza," he says, pointing to a flat slice. "In the beginning, we printed various small
Anyone expecting to find a standard 3D printer in the robotics lab will be looking in vain - the entire room functions as a 3D printer. Flexible mixing chambers ensure that the raw material is mixed correctly. At the end of the robot arms, which hang from the ceiling, are print heads from which the material is applied layer by layer to the print bed. "The robots can precisely control any previously defined point in the room," explains Bedarf. "We program the path and tell them where to go and how fast. And how much material should come out of the print head at what point and in what time."
For the first tests, Bedarf stabilized the special components with concrete. He then managed to produce stable components using the foam alone, as the prototype of the Airlements project shows: a two-meter-high corner piece made of four 3D-printed segments. The four individual parts were glued together with mortar and sprayed with a white cement-free plaster.
Airlements - a play on the words air and elements - consists of lightweight individual parts that can be lifted and stacked by hand. "The components can be printed in a factory, then brought to the construction site and placed in the intended position," says Bedarf. "To make the component more stable, the hollow core would be filled with denser foam. This would allow the component to take on load-bearing functions one day." So far, Airlements can only be used as an insulating outer or inner wall.
Each individual part of the prototype was printed in less than an hour and cured for a week in the production environment at a controlled temperature of 20 to 28 degrees Celsius and a relative humidity of 20 to 70 percent. It was important to regulate the humidity and temperature so that the material could harden easily and not crack.
Bedarf had developed a special climate chamber for this purpose: a large transparent tent in which the robot followed the specified pressure path. "There was fumes and dust everywhere, and it was as hot as a sauna," he says, pointing out that this production method eliminates the need for energy-intensive processing. "This is an advance on previous work with cement-free mineral foams, which were cured either with cement or by subsequent firing in an oven." The corrugated texture of Airlements provides additional strength during curing and in the final state.
Airlements could one day contribute to sustainable construction: on the one hand, insulating elements reduce the energy consumption of a building. Secondly, 3D printing produces much less waste than the conventional production of components and there is no need for climate-damaging concrete formwork. And finally, Airlements is completely cement-free, which enables recyclable construction. "When the element is no longer needed, it can be completely shredded and turned back into dust and new foam."
Airlements would now like to develop this requirement further together with FenX. A production unit is to be set up in their factory in Turgi for this purpose. "We will precisely analyze the load-bearing capacity and insulation behavior to find out how this material behaves as a wall element in an enclosed space. We want to use infrared measurements to find out where the thermal insulation could be even better. And how weak points can be eliminated by making adjustments to the pressure path."
After his doctorate, Bedarf is working on the Bachelor course "Computational Design I&II". He is looking forward to inspiring the next generation of architects to think geometrically, but also to be able to communicate with machines. "My work with Airlements has taught me a lot about building materials and the use of information technology. And I've really enjoyed testing the geometries that are possible as a result. It would be great if I could inspire others."