Cornell’s Underwater Concrete Breakthrough Lets You 3D Print the Ocean Floor

Cornell researchers developed a method for printing concrete structures in the middle of the ocean, a development that has the potential to transform maritime construction. They’ve been printing homes, bridges, and even rocket parts on dry land with concrete for years, but taking the process underwater has its own set of challenges. Water damages the cement particles before they can bond together, makes the slurry too thick to pump when stabilizers are added too early, and creates a cloud of fine sediment that blinds all light.

When DARPA issued a call for a method of depositing 3D-printable concrete at depths of a few meters using local seafloor sediment rather than hauling in tons of cement from elsewhere, a group at Cornell University jumped right in. The agency issued the challenge in 2024. Cornell’s team, directed by assistant professor Sriramya Nair of the David A. Duffield College of Engineering, received a hefty $1.4 million grant in May 2025 to go out and figure it all out.

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Their method consists of a two-stage procedure that begins with a basic combination that is high in seafloor sediment and low in cement, allowing it to flow through the hoses while remaining fluid. Then, as it reaches the nozzle, they add certain unique mix-ins that cause super-fast solidification the moment it contacts the water. This ensures that the layers adhere effectively and do not wash away, even when there is a constant flow of water around them.

Photo credit: Charissa King-O’Brien | Cornell University
The researchers removed the printer system from a 6,000-pound industrial robot arm, which is commonly used on land for large concrete projects. They also included some sensors that monitor layer by layer how it is progressing, what form it is taking, and the texture, all in real time. This implies that no human diver needs to be lurking around checking on progress. Even when seafloor silt muddies the water as it is deposited, sensors continue to guide modifications.

Photo credit: Ryan Young | Cornell University
To put their theory to the test, they ran thousands of samples through a giant tub at the Bovay Civil Infrastructure Laboratory Complex, printing arches and other components week after week. They cured each one underwater before testing it for strength, shape, and surface quality. The good news is that the mixture remained together and formed relatively solid structures even when subjected to steady water flow.
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