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3D-printed bridge points the way to greener construction
3D-printed bridge points the way to greener construction
MIT researchers developed a framework that folds a printer’s real-world limits into the optimization, while revealing that better hardware could sharply reduce material use.
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Stephanie Martinovich<br>Department of Civil and Environmental Engineering
Publication Date:
July 15, 2026
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Stephanie Martinovich
Email:<br>smartino@mit.edu
MIT Department of Civil and Environmental Engineering
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Caption:
MIT Department of Civil and Environmental Engineering postdoc Hajin Kim-Tackowiak (left) and graduate student Zane Schemmer pose with the 3D-printed concrete bridge they designed and load-tested.
Credits:
Photo courtesy of the researchers.
Caption:
A close-up of the bridge shows the stacked layers, or beads, of extruded concrete, laid down in a single continuous path with no molds.
Credits:
Photo courtesy of the researchers.
Caption:
During testing, the roughly 900-pound bridge held more than 2,000 pounds of concrete blocks spread across its top without measurably bending, closely matching the team's simulations.
Credits:
Photo courtesy of the researchers.
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Concrete is the most widely used building material on Earth, and producing it is one of the largest single sources of carbon emissions. One promising way to reduce its environmental footprint is to 3D-print concrete, laying it down bead by bead like a giant icing-piping robot. This process eliminates the labor-intensive formwork of pouring it into molds, and places the material only where a structure needs it.<br>But many of the most efficient designs created by computers are impossible for today’s printers to build. Engineers use a technique called topology optimization to find the strongest structure that uses the least amount of material. But those mathematically ideal designs, with their intricate, spider-web shapes, don’t account for the physical limitations of large-scale concrete printers with their thick nozzles, limited turning, and need to print in one continuous motion.<br>Now a team of MIT researchers has developed a way to close that gap. Their framework, described in a new article in Additive Manufacturing, bakes a printer’s real fabrication limits directly into the optimization, so the design that comes out is one a machine can build and print with little or no manual redesign. They demonstrated it by designing, printing, and load-testing a 2.3-meter concrete bridge and found that today’s printing hardware, not the concrete itself, limits how light a structure can be.<br>“We were finding a lot of cracks you can fall through when it comes to translating these super-optimal designs into manufacturable designs,” says co-first author Hajin Kim-Tackowiak PhD ’26, a postdoc in MIT’s Department of Civil and Environmental Engineering (CEE). “Those cracks were like chasms.”<br>Designing for what can be built<br>To pin down the constraints, the team worked with the people who run the large-scale printing machines at Autodesk’s facility in Boston.<br>“They pointed at some of our sharp angles, and they went, 'I don't feel safe printing something like that,'” Kim-Tackowiak recalls.<br>Those conversations surfaced three key limitations: how thick each printed bead must be, how sharply the nozzle can turn, and the need to print in a single continuous line. The researchers translated each constraint directly into the mathematical rules of their framework.<br>Existing 3D-printed structures are typically produced with older methods that optimize the shape first, and then require “a massive amount of post-processing,” taking days to run, Kim-Tackowiak explains. By contrast, the team’s framework generated fully printable designs in about two minutes on a laptop. When the team needed to slightly reduce the bridge’s size...