THE NEW ATLANTIS

Underwater 3D printing could transform maritime construction

Cornell University

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

ITHACA, N.Y. – A group of Cornell researchers is developing a way to bring the technology to the ocean. By 3D-printing concrete underwater, the new approach could transform on-site maritime construction and the repair of critical infrastructure that connects continents.

“We want to be constructing without being disruptive,” said Sriramya Nair, assistant professor of civil and environmental engineering, who leads the effort. “If you have a remotely operated underwater vehicle that shows up on site with minimal disturbance to the ocean, then there is a way to build smarter and not continue the same practices that we do on the land.”

The project got its start in fall 2024, when the Department of Defense’s Defense Advanced Research Projects Agency (DARPA) issued a call for proposals to design 3D-printable concrete that could be deposited at a depth of several meters underwater – and to do so in a radically truncated timeframe of one year.

“When the call for proposals came out, we said, ‘Hey, let’s just do this and see, so that we will at least understand what the challenges are,” said Nair, whose group had already been working with a roughly 6,000-pound industrial robot to 3D-print large-scale concrete structures. “And it turned out, with our mixture we could actually 3D-print underwater by making adjustments to account for continuous water exposure.”

Underwater printing faces numerous challenges. Chief among them is preventing washout, in which cement particles fail to bind together during deposition, weakening the material. The typical solution is introducing admixture chemicals, but these create complications of their own.

“When you add those chemicals, it makes your mixture really viscous, and you can’t pump. So you’re balancing that pumpability with these anti-washout agents,” Nair said. “When it extrudes, even if you don’t have washout, you still want it to be able to hold the shape and bond well with the other layers. There are multiple parameters at play.”

DARPA added one more hurdle: The concrete needed to consist primarily of seafloor sediment and only include a small amount of cement. Incorporating material from the bottom of the ocean would minimize the logistical difficulty of transporting large quantities of cement by ship.

In September, the Cornell team successfully demonstrated to a group of visiting DARPA officials that they were getting close to meeting the agency’s high sediment target. It was a huge milestone, according to Nair.

“Nobody is doing this right now,” she said. “Nobody takes seafloor sediment and prints with it. This is opening up a lot of opportunities for reimagining what concrete could look like.”

The second phase of the DARPA challenge will culminate in a bake-off of sorts, with multiple teams 3D-printing an arch underwater, in March. For months, Nair’s team has been conducting test prints in a large tub of water – often producing multiple samples every week. The lab setting allows the researchers to closely monitor how the layers are deposited and the strength, shape and texture of each arch.

For additional information, read this Cornell Chronicle story.

Cornell University has dedicated television and audio studios available for media interviews.

Media note: Pictures and video can be viewed and downloaded here: https://cornell.box.com/v/3Dunderwaterconcreteprinting

-30-