Can 3D Printing With Local Soils Offer a Low-Carbon Alternative to Concrete? Part 2

Without the need for long-distance transportation or carbon-intensive production techniques, one research lab is experimenting with local soils that may offer a greener path forward
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Illustration by Rae Scarfó

If you think of chemists and literary types as different species, you must not know Professor Sarbajit Banerjee. As a teenager, he was “very much into magical realism” and found “Gabriel García Márquez, Salman Rushdie and those sorts of folks very inspiring.” It wasn’t until late in high school that he discovered a love of chemistry.  

“It’s very third-perception oriented. It’s symmetry oriented,” Banerjee said. “Those are the parts I enjoy most about chemistry—which are, you know, also reflected in architecture.” 

In his lab at Texas A&M University, and as Built initially profiled in Part 1 of this two-part series, Banerjee and his interdisciplinary team are exploring “the intersection of materials chemistry, construction science and civil engineering.” The team is finding “a lot of opportunity for new materials that can bring new function to buildings.”  

Giving adobe a millennial reboot 

Among the lab’s priorities is finding an alternative to concrete that can be sourced and disposed of or recycled more sustainably. “You know, if concrete were a country, it would be in the top five CO2 emitters in the world,” Banerjee said. And he sees additive manufacturing, with its capability of creating previously inaccessible complex forms, as a key to bringing that alternative to market.  

The lab’s research focuses on using “backyard clays”—material sourced from the immediate vicinity of the building site—that have been put through a process called geo-polymerization to cross-link particles and create load-bearing composites. It’s an idea that takes us backward and forward in time simultaneously by drawing on ancient adobe structures for inspiration but also asking how chemistry can reboot that building material, give it properties and capacities similar to those of concrete and make it 3D printable. 

The additive manufacturing component of this unfolding solution presents its own challenges. “When you print the material, you want to be able to come back and do a second pass,” Banerjee said. “The material has to be ready to hold the shape and form while you put that next layer down. “You have to be able to come up with material that sets or cures. It doesn’t cure so fast that it clogs up your nozzle, but it sets fast enough that you can put the next layer down and keep building.”  

Clay, code, compliance 

The use of additive manufacturing also introduces new requirements in terms of code compliance, testing, quality control and repeatability. “It’s relatively easy to do stuff that’s architectural, but not structural,” Banerjee said. “An arch, a façade, a mantelpiece. It becomes much more difficult when you’re talking about load-bearing beams and such, especially the larger the structure gets. Then there’s not just a technical challenge. There’s a regulatory challenge.”  

The research has the potential to be put into play in starkly different places, from the Moon to Qatar, where there is interest in exploring the viability of building from sand. “We’re trying to see how far we can extend this,” Banerjee said. “I think generally speaking, if there’s clay particles, if there’s minerals, we’re going to be able to come up with some sort of formulation that will allow us to cross-link them together and hold them together. I don’t know yet that we can build in every environment. But, hopefully, we have a toolkit that we can start understanding what needs to be done in different sorts of sets of environments.” 

A stronger climate change toolkit 

The team is also considering how this new approach to creating construction materials could help buildings to withstand the impact of climate change.  

As Texans, the members of Banerjee’s team have ample experience with hurricanes and are familiar with how quickly drywall develops mold after flooding. For solutions, the team again is looking to the past as well as the future, this time to ancient Rome, where it was common to construct water-resistant limestone-based buildings. With that in mind, Banerjee’s team is considering how lime elements could be integrated into composite materials. “That’s going to require an entirely different mindset of resilience,” Banerjee said. “And that’s something we are very interested in.” 

Banerjee sees these developments getting to market in as little as five to 10 years, and he said that companies have already expressed interest in using the materials his team is developing. Given that relatively short time horizon, what do architects, engineers and construction professionals need to learn to prepare for the shift?  

“It’s not going to be business as usual,” but instead will reflect the impact of “a whole lot of new chemistries that are going to come into play,” Banerjee said. “I think the whole field of architecture will ultimately end up having to get a much deeper understanding of materials science.” 

Is building with clay poised for a comeback?