Glass is remarkable because as long as it isn’t contaminated, it can be infinitely recycled without properties changing. That’s part of the appeal of its use in additive manufacturing, and compared to traditional glass casting, AM methods may allow for greater design flexibility and reduced costs. With these characteristics in mind, engineers at MIT wanted to test the viability of using AM glass to produce structural building components. So, they are developing 3D printed glass masonry units that can be stacked and interlocked like LEGO bricks.
The research was conducted by MIT engineers Daniel Massimino, Ethan Townsend, Charlotte Folinus, Michael Stern, and Kaitlyn Becker. Together, they fabricated strong, multilayered bricks, out of soda-lime glass, each shaped like a figure eight. Each block has two round pegs like a LEGO, enabling them to be arranged and rearranged endlessly, allowing for a rich composition diversity and a long-lasting lifecycle. If not rearranged, the bricks could be melted down to be printed again.
Printing the glass brick with the custom 3D printing process (photo credits: Ethan Townsend)
In an article by MIT News, Massimino explained, “With the figure-eight shape, we can constrain the bricks while also assembling them into walls that have some curvature.” The engineers’ reconfigurable glass masonry aligns with the concept of circular construction, the idea that building materials should be reused, wherever possible, to reduce carbon emissions associated with a building’s total construction. The glass blocks’ sustainability was a driving factor for the research.
A Focus on Material
The MIT engineers used a custom glass 3D printer called Glass 3D Printer 3 (G3DP3) provided by MIT spinoff Evenline. The machine implements a furnace to melt crushed glass bottles into a printable form and then deposits it in layers. The machine can print a maximum volume of 32.5 x 32.5 x 38 cm–suitable for producing full-size masonry units.
The team printed three types of blocks—fully hollow, print-cast, and fully printed— and found that “Hollow masonry units provide a more immediate path to implementation, while fully printed units have the potential to provide an entirely glass, transparent, and circular building component fabrication method.”
They tested the blocks’ strength with an industrial hydraulic press and found that the strongest blocks could withstand the same pressures as a concrete block. The strongest blocks were those with a separate, interlocking feature at the bottom of the block made from a different material. “Glass is a complicated material to work with,” Becker said in the same article by MIT News. “The interlocking elements, made from a different material, showed the most promise at this stage.” According to the article, they are looking into printing more of the interlocking element with glass, but it is not a deal breaker in scaling up the project.
The engineers built a glass wall on MIT’s campus to showcase the 3D printed bricks’ potential. Going forward, they plan to build bigger and more complex structures with the blocks and believe they could be used for facades and interior walls. For more, read MIT News’ article or read the study published here.
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*Cover Photo Credits: Ethan Townsend/MIT News