Marines from the 1st Marine Logistics Group at Camp Pendleton, California, 3D printed a concrete bridge with the help of the Marine Corps Systems Command Advanced Manufacturing Operations Cell and the Army Corps of Engineers.A Marine crosses a 3D-printed footbridge. Credit: U.S. Army Corps of EngineersA Marine crosses a 3D-printed footbridge. Credit: U.S. Army Corps of Engineers

Marines were trained to operate the Automated Construction of Expeditionary Structures (ACES) printer, incorporated new equipment into the process, and printed and assembled a usable foot bridge. The Army Corps of Engineers validated the bridge design to ensure it could bear the intended load.

The ACES printer uses concrete made with aggregate, rather than paste or mortar. The printer can also create other types of structures such as obstacles, protective structures, vaults, culverts and beams. Parts can be printed from computer-aided design models that can be either pre-loaded or up-linked from different locations.

The ACES program is intended to cut construction time from five days to one day per structure, and reduce the personnel required for construction from eight to three. The ACES program may also reduce the resources and logistics associated with material shipment that are required to sustain construction.

Sailors with a Naval Mobile Construction Battalion brought a volumetric mixer to the site, relieving six Marines from manually mixing the concrete needed for the print job. A print in August 2018 of a barracks hut was reportedly more difficult because Marines had to mix the concrete themselves using five-gallon buckets of gravel. They then used a fork lift to lift the buckets into a mixer. For the bridge project, which was completed in December, Marines used a volumetric mixer, which mixed the concrete for pumping into the printer.

The U.S. Army Engineer Research and Development Center, together with NASA’s Marshall Space Flight Center, Kennedy Space Center and Caterpillar, developed the additive 3D printing technology. Caterpillar is involved under a cooperative research and development agreement to explore commercializing the technology, with potential applications that include conventional construction and disaster relief.

Current plans call for additive manufacturing to become a program of record for the Marine Corps by fiscal year 2021.