Engineers 3D Print Strong Glass Bricks for Building Structures

What if building materials could be assembled and disassembled as easily as LEGO bricks? Such reconfigurable masonry would be disassembled at the end of a building’s lifespan and reassembled to form a new structure, in a sustainable cycle that could provide generations of buildings using the same physical building elements.

That’s the idea behind circular construction, which aims to reuse and repurpose a building’s materials whenever possible, to minimise the manufacture of new materials and reduce the construction industry’s “embodied carbon”, which refers to the greenhouse gas emissions associated with every process of constructing a building, from manufacturing to demolition.

Motivated by the ecological potential of circular construction, MIT engineers are now developing a new type of reconfigurable masonry made from 3D-printed recycled glass. Using custom glass 3D printing technology provided by MIT affiliate Evenline, the team has produced strong, multi-layered glass bricks, each shaped like a figure eight, designed to interlock, much like LEGO bricks.

In mechanical tests, a single glass brick withstood pressures similar to those of a concrete block. To demonstrate the structure, the researchers built a wall of interlocking glass bricks. They envision that the 3D-printable glass masonry could be reused multiple times as recyclable bricks for building facades and interior walls.

“Glass is a highly recyclable material,” says Kaitlyn Becker, an assistant professor of mechanical engineering at MIT. “We take glass and turn it into masonry that, at the end of its useful life, can be taken apart and reassembled to form a new structure, or can be put back into the printer and transformed into a completely different shape. All of this fits into our idea of ​​a sustainable, circular building material.”

“Glass as a structural material kind of breaks people’s brains,” says Michael Stern, a former MIT graduate student and researcher at MIT’s Media Lab and Lincoln Laboratory who is also the founder and director of Evenline. “We’re showing that this is an opportunity to push the boundaries of what’s been done in architecture.”

Becker and Stern, along with their colleagues, detail their glass brick design in a study published in the journal Glass Structures and EngineeringTheir MIT co-authors include lead author Daniel Massimino and Charlotte Folinus, as well as Ethan Townsend of Evenline.

Locking step

The inspiration for the new circular masonry design came in part from MIT’s glass lab, where Becker and Stern, then undergraduates, first learned the art and science of glassblowing.

“I found this material fascinating,” says Stern, who went on to design a 3-D printer that could print molten recycled glass, a project he began while a student in the mechanical engineering department. “I started thinking about how glass printing could find its place and enable interesting things, with construction being one possible avenue.”

In the meantime, Becker, who had accepted a professorship at MIT, began exploring the intersection between manufacturing and design, as well as ways to develop new processes that would enable innovative designs.

“I’m excited about expanding the possibilities for designing and manufacturing complex materials with interesting characteristics, such as glass and its optical properties and recyclability,” says Becker. “As long as it’s not contaminated, glass can be recycled almost infinitely.”

She and Stern teamed up to see if and how 3D-printable glass could be transformed into a structural masonry unit that’s as strong 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 printable molten form that the printer then deposits in layered patterns.

The team printed prototype glass bricks using soda-lime glass, which is typically used in a glassblowing studio. They incorporated two round pegs into each printed brick, similar to the studs on a LEGO brick. Like play blocks, the pegs allow the bricks to snap together and assemble to form larger structures.

Another material placed between the bricks prevents scratches or cracks between the glass surfaces, but can be removed if a brick structure needs to be disassembled and recycled, also allowing the bricks to be remelted in the printer and shaped into new forms. The team decided to give the blocks a figure eight shape.

“With the figure eight shape, we can constrain the bricks while assembling them into walls that have some curvature,” Massimino explains.

Stepping stones

The team printed glass bricks and tested their mechanical strength in an industrial hydraulic press that compressed the bricks until they began to fracture. The researchers found that the strongest bricks were able to withstand pressures comparable to those that concrete blocks can withstand. These strongest bricks were made primarily of printed glass, with a separately manufactured locking element that attached to the bottom of the brick.

These results suggest that the bulk of a masonry brick could be made of printed glass, with an interlocking element that could be printed, cast, or manufactured separately from a different material.

“Glass is a complicated material to work with,” Becker says. “The interlocking elements, made from a different material, have proven to be the most promising at this stage.”

The group is exploring whether a larger portion of a brick’s interlocking structure could be made from patterned glass, but they don’t see this as a barrier to scaling up the design. To demonstrate the potential of glass masonry, they built a curved wall of interlocking glass bricks. Next, they plan to build increasingly larger, freestanding glass structures.

“We’re getting a better understanding of the limitations of the material and how to adapt it,” Stern says. “We’re looking at building bleachers for buildings and want to start with a pavilion, a temporary structure that humans can interact with and then reconfigure into a second model. And you can imagine these blocks going through many lifetimes.”

This article is republished with kind permission from MIT News (web.mit.edu/newsoffice/), a popular site covering the latest research, innovation, and teaching at MIT.