This Hemp-Infused Concrete Alternative Cures Quickly Enough for 3D-Printed Homes and More

Researchers from Oregon State University have come up with an environmentally-friendly alternative to concrete that, they say, sets quickly enough that it could allow for direct 3D printing of homes and other infrastructure.

"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," says corresponding author Devin Roach of the research. "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."

A traditional desktop 3D printer uses some form of plastic as its material, heating it up and pushing the liquid through an extruder to form a two-dimensional layer — then lifts up to the next layer height and begins again, the first layer having cooled back down to being solid again. That's great for a Benchy, but not so great for large-scale structures like buildings — and traditional concrete is not only slow-setting but its production is responsible for a claimed eight percent of the planet's carbon dioxide emissions.

The team's answer: a soil-based alternative infused with hemp fibers, sand, and biochar created by heating wood chips and other organics in a low-oxygen environment. An acrylamide-based binding agent sets the clay-like material quickly enough after extrusion that it can even be printed with unsupported overhangs — and it can be produced with a fraction of the environmental impact of concrete.

"The printed material has a buildable strength of three megapascals immediately after printing, enabling the construction of multilayer walls and freestanding overhangs like roofs," Roach, an assistant professor of mechanical engineering in the OSU College of Engineering, explains. "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."

There's a catch, of course: cost. "Currently, our material costs more than standard cement-based concrete, so we need to bring the price down," Roach admits. "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 team's work has been published under open-access terms in the journal Advanced Composites and Hybrid Materials.