Reusable bricks made from 3D-printed glass could cut construction emissions

Engineers at MIT have developed interlocking bricks made from recycled glass that could be re-used at the end of a building's lifecycle.

It's part of a movement known as circular construction, which advocates for the reuse of building materials and for new structures to be designed in such a way that the components can be reconfigured in future. It aims to reduce the construction industry's carbon footprint, which adds up at every stage from construction through to demolition. 

The engineers used a custom 3D glass printing technology developed by Evenline, an MIT spinoff, to develop strong multilayered glass bricks in the shape of a figure of eight. They're designed to interlock like LEGO bricks, and withstood similar pressures to concrete blocks in mechanical testing. The researchers say the glass masonry could be used (and re-used) for facades and internal walls. 

“Glass is a highly recyclable material,” says 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.”

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

“I found the material fascinating,” says Stern, who 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.”

The team used soda-lime glass that is typically used in a glassblowing studio, and incorporated round pegs similar to the studs on a LEGO brick. “With the figure-eight shape, we can constrain the bricks while also assembling them into walls that have some curvature,” says Daniel Massimino of MIT, lead author of the research paper. 

In tests with an industrial hydraulic press, the researchers found the strongest bricks were those made from printed glass with a separate interlocking feature attached to the bottom of the brick made from a different material. “Glass is a complicated material to work with,” Becker says. “The interlocking elements, made from a different material, showed the most promise at this stage.”

“We have more understanding of what the material’s limits are, and how to scale,” Stern says. “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.”