Engineers are developing 3D-printed glass bricks that fit together like Lego, claiming they can withstand similar pressures as their concrete counterparts
Imagine if construction took a leaf out of a popular children’s plaything; crafting buildings from materials that could be put together and taken apart again as easily as Lego bricks.
Sounds a little implausible, perhaps. Not to engineers at the Massachusetts Institute of Technology (MIT), in the United States; they’ve come up with a kind of reconfigurable masonry that they say can do pretty much that.
The approach is motivated by the ideas behind circular construction, where buildings can be disassembled at the end of their lifetime and the components re-assembled into a new structure.
Circular construction’s aim is to reuse and repurpose a building’s materials whenever possible, to minimise the manufacturing of new materials, and reduce the construction industry’s embodied carbon; the greenhouse gas emissions associated with every process throughout a building’s construction, from manufacturing to demolition.
That’s where the MIT engineers come in. Motivated by circular construction’s eco potential, they are developing a new kind of reconfigurable masonry made from 3D-printed, recycled glass.
Using a custom 3D glass printing technology provided by MIT spinoff, Evenline, the team says it has made strong, multi-layered glass bricks, each in the shape of a figure eight, that are designed to interlock, much like the aforementioned Lego bricks.
“Glass as a structural material kind of breaks people’s brains a little bit.”
Michael Stern
In mechanical testing, it’s claimed, a single glass brick withstood pressures similar to that of a concrete block. As a structural demonstration, the researchers constructed a wall of interlocking glass bricks. They envision that 3D-printable glass masonry could be reused many times over as recyclable bricks for building facades and internal walls.
“Glass is a highly recyclable material,” said Kaitlyn Becker, assistant professor of mechanical engineering at MIT. “We’re taking glass and turning it into masonry that, at the end of a structure’s life, can be disassembled and reassembled into a new structure, or can be stuck back into the printer and turned into a completely different shape. All this builds into our idea of a sustainable, circular building material.”
Michael Stern, a former MIT graduate student and researcher in both MIT’s Media Lab and Lincoln Laboratory, is also founder and director of Evenline. He said: “Glass as a structural material kind of breaks people’s brains a little bit. We’re showing this is an opportunity to push the limits of what’s been done in architecture.”
Becker and Stern, with their colleagues, set out their glass brick design in a study published in the journal Glass Structures and Engineering. Their MIT co-authors include lead author Daniel Massimino and Charlotte Folinus, along with Ethan Townsend at Evenline.
Material fascination
The inspiration for the new circular masonry design arose partly in MIT’s Glass Lab, where Becker and Stern, then undergraduate students, first learned the art and science of blowing glass.
“I found the material fascinating,” Stern said. He later designed a 3D printer capable of printing molten recycled glass; a project he took on while studying in the mechanical engineering department.
“I started thinking of how glass printing can find its place and do interesting things, construction being one possible route,” he added.
Meanwhile, Becker, who accepted a faculty position at MIT, began exploring the intersection of manufacturing and design, and ways to develop new processes that enable innovative designs.
“I get excited about expanding design and manufacturing spaces for challenging materials with interesting characteristics, like glass and its optical properties and recyclability,” Becker said. “As long as it’s not contaminated, you can recycle glass almost infinitely.”
She and Stern teamed up to see whether and how 3D-printable glass could be made into a structural masonry unit as sturdy and stackable as traditional bricks.
For their new study, the team used the Glass 3D Printer 3 (G3DP3), the latest version of Evenline’s glass printer, which pairs with a furnace to melt crushed glass bottles into a molten, printable form that the printer then deposits in layered patterns.
The team printed prototype glass bricks using soda-lime glass that is typically used in a glass-blowing studio. They incorporated two round pegs onto each printed brick, similar to the studs on a Lego brick. Like the toy blocks, the pegs enable bricks to interlock and assemble into larger structures.
Another material placed between the bricks prevent scratches or cracks between glass surfaces but can be removed if a brick structure were to be dismantled and recycled, also allowing bricks to be remelted in the printer and formed into new shapes. The team decided to make the blocks into a figure-eight shape.
Massimino said:“With the figure-eight shape, we can constrain the bricks while also assembling them into walls that have some curvature.”
Brick by glass
The team printed glass bricks and tested their mechanical strength in an industrial hydraulic press that squeezed the bricks until they began to fracture. The researchers found that the strongest bricks were able to hold up to pressures that are comparable to what concrete blocks can withstand.
Those strongest bricks were made mostly from printed glass, with a separately manufactured interlocking feature that attached to the bottom of the brick. These results suggest that most of a masonry brick could be made from printed glass, with an interlocking feature that could be printed, cast, or separately manufactured from a different material.
“Glass is a complicated material to work with,” Becker said. “The interlocking elements, made from a different material, showed the most promise at this stage.”
The group is looking into whether more of a brick’s interlocking feature could be made from printed glass, but say they don’t see this as a “deal-breaker” in moving forward to scale up the design. To demonstrate glass masonry’s potential, they constructed a curved wall of interlocking glass bricks. Next, they aim to build progressively bigger, self-supporting glass structures.
“We have more understanding of what the material’s limits are, and how to scale,” Stern said. “We’re thinking of stepping stones to buildings, and want to start with something like a pavilion – a temporary structure that humans can interact with, and that you could then reconfigure into a second design. And you could imagine that these blocks could go through a lot of lives.”
Main image: A glass brick being printed with custom 3D glass printing technology. Courtesy of MIT. Image credit: Ethan Townsend
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