Fast-curing clay mix: Researchers test 3D-printed building material as an alternative to concrete

A team at Oregon State University has developed a clay-based material for construction 3D printing that hardens directly during extrusion and produces significantly lower CO₂ emissions than cement-based concrete. The material is intended to be used in the future for printed residential buildings and infrastructure in order to shorten construction times and reduce the share of cement in the construction sector.

At the core of the development is a clay mixture that is combined with sand, hemp fibers and biochar – a carbon-rich product from pyrolyzed biomass. Instead of cement, an acrylamide binder is used, which cures via so-called frontal polymerization. The reaction front travels along the extruded filament so that the material becomes load-bearing as it exits the nozzle and even allows short spans, for example over window and door openings.

“The printed material has a buildable strength of 3 megapascals immediately after printing, enabling the construction of multilayer walls and freestanding overhangs like roofs,” said Devin Roach, assistant professor of mechanical engineering in the OSU College of Engineering. “It surpasses 17 megapascals, the strength required of residential structural concrete, in just three days, compared to as long as 28 days for traditional cement-based concrete.”

Because the material consists largely of locally available soil and plant-based additives and does not require energy-intensive clinker production, its climate impact is significantly more favorable than that of concrete. Roach also emphasizes the benefits for rapidly setting up shelters after natural disasters, when material availability and construction speed are crucial.

“I’m incredibly proud of our innovative, transdisciplinary team for coming up with a material that can make a difference in people’s lives in multiple ways,” Roach said. “Especially with the frequency of destructive natural disasters, we need to be able to get shelter and other structures built quickly – and we can do that with a material that’s readily available and is associated with comparatively little emissions.”

“Currently, our material costs more than standard cement-based concrete, so we need to bring the price down,” Roach said. “Before it can be used we also need to follow American Society for Testing and Materials standard tests and prepare a report that professional engineers can review and approve if it is proposed to be included in construction projects.”

The mixture is still more expensive than standard concrete. According to the team, before it can be used in conventional construction it must undergo standardized tests in accordance with ASTM standards, and engineering firms must approve its use in projects. Further development is being supported by funding from the U.S. Department of Agriculture and by university research programs that are examining in particular the use of hemp and other renewable raw materials in the construction industry.