DARPA-funded Cornell robot 3D prints concrete underwater in lab tests

Researchers at Cornell University, funded by DARPA, have made significant progress in developing a method to 3D-print concrete directly underwater, a breakthrough that could transform the construction and repair of ocean infrastructure such as undersea cables and ports. This initiative responds to a DARPA challenge issued in late 2024, which called for concrete printing several feet underwater within a year. Led by assistant professor Sriramya Nair, the team adapted an existing large-scale industrial robot and modified their concrete mixture to withstand continuous water exposure, successfully printing stable layers underwater. Their approach aims to minimize environmental disruption and reduce construction time and costs by enabling construction with minimal disturbance to marine ecosystems. A major challenge addressed by the team is preventing washout, where cement particles separate in water and weaken the structure. By balancing chemical additives that prevent washout with the need for pumpability and layer bonding, the researchers optimized the concrete mixture for underwater printing. Additionally, DARPA required the concrete to be primarily composed of seafloor