An interdisciplinary team at Cornell University is developing a method to 3D print concrete directly underwater, aiming to enable faster, lower-impact construction and repair of critical subsea infrastructure such as ports, pipelines, and offshore energy assets.
Supported by the U.S. Defense Advanced Research Projects Agency (DARPA), the project combines materials science, robotics, and 3D printing to overcome technical challenges in remote or contested maritime environments, where traditional construction is slow, costly, and logistically complex.
Bringing Additive Manufacturing Beneath the Surface
The project is led by Sriramya Nair, assistant professor of civil and environmental engineering, who envisions underwater building methods that minimize environmental impact and logistical complexity. “We want to be constructing without being disruptive,” said Nair. “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 initiative began in late 2024 when DARPA released a call for proposals to develop concrete formulations that could be 3D printed several meters underwater within a one-year timeline. Nair’s group, which already operated a roughly 6,000-pound industrial robot for large-scale concrete printing, decided to take on the challenge.
“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. “And it turned out, with our mixture we could actually 3D print underwater by making adjustments to account for continuous water exposure.”
In May 2025, the team secured a one-year, $1.4 million DARPA grant tied to milestone performance, competing alongside five other research groups.
Designing Materials for Subsea Printing
The researchers explained that developing concrete that can be reliably printed underwater presents multiple engineering constraints. One major issue is washout, where cement particles disperse before bonding properly, weakening the final structure. Chemical additives can reduce washout but often increase viscosity, making pumping and extrusion more difficult.
“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’s requirements further complicated the process by mandating that most of the material be derived from seafloor sediment rather than traditional cement, reducing the need to transport large quantities of raw material by ship. During a September demonstration, the Cornell team showed progress toward achieving this high sediment content.
“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.”
To address the project’s complexity, researchers formed specialized sub-teams focused on material formulation and fabrication processes. The collaboration spans multiple disciplines, including electrical engineering, architecture, robotics, and materials science, with additional partners from University of Michigan, Clarkson University and University of Arizona.
Automation, Monitoring, and the Path to Deployment
The next phase of the DARPA program will culminate in an underwater arch-printing demonstration scheduled for March. In preparation, the Cornell team has conducted frequent test prints in large water tanks, analyzing layer adhesion, structural integrity, and overall print quality.
Real-world marine environments, however, introduce challenges that make direct human monitoring impractical. “Let’s say you want to print underwater in the real world – we can’t send somebody down with a scuba suit, right? We have to be able to detect those things and adjust our tool path in real time,” Nair said. “The overall goal is to achieve good print quality, because if you don’t place your material where it needs to be, you’re not going to get the strength you need.”
Limited visibility caused by disturbed sediment is another obstacle. “The problem is sediment is super fine, and as soon as you stir it up, you can have zero visibility,” said Napp. “We didn’t know how much turbidity – or murkiness – there would be in the water.”
To address this, the fabrication team developed a sensor-equipped control system that integrates with the robotic printing arm, enabling real-time monitoring and adaptive toolpath adjustments. As the final demonstration approaches, researchers are combining advances in materials design with autonomous fabrication technologies.
3D Printing Is Becoming Essential for Underwater Concrete Repairs
Underwater construction and repair is growing in demand, but traditional methods are slow, costly, and limited by diver depth, poor visibility, currents, and heavy equipment needs. Even small repairs require specialized crews and repeated operations, increasing downtime and risk. 3D printing solves these constraints by enabling robotic, layer-by-layer fabrication directly in place, with precise material control and automation that reduce costs, time, and logistical complexity.
In 2022, Norwegian projects began exploring robotic 3D printing to perform concrete repairs directly on submerged assets, enabling layer-by-layer fabrication without removing the structure to the surface. Other projects producing submerged structures, such as Florida’s 3D printed artificial reef modules and Jordan’s coral reef restoration units, demonstrate how additive manufacturing enables precise placement, controlled material properties, and automated fabrication in environments where conventional casting or molds cannot perform. Despite these advances, technical and environmental challenges remain.
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Featured image shows Underwater 3D Concrete Printing. Photo via Cornell University.
