Structures are quite expensive these days. However, when concrete edifices are being erected, there is an alternative material that can lower their costs: clay.

Researchers at MIT have devised a technique to utilize lightly processed clay, including soil from construction sites, as the “formwork” molds into which concrete is poured. This method employs 3D printing and can replace the pricier technique of constructing intricate wooden formworks for concrete building.

“What we’ve demonstrated is that we can essentially utilize the ground beneath our feet, or surplus soil from a site, and convert it into precise, highly intricate, and adaptable formwork for tailored concrete structures,” states Sandy Curth, a doctoral candidate in MIT’s Department of Architecture who has been central to the project.

This strategy could facilitate faster and more efficient concrete-based constructions. It may also lead to reductions in expenses and carbon emissions.

“It has the potential for immediate influence and doesn’t necessitate altering the core of the construction industry,” Curth adds, who also serves as director of the Programmable Mud Initiative.

Curth has collaborated on several publications regarding the technique, most recently, “EarthWorks: Zero waste 3D printed earthen formwork for shape-optimized, reinforced concrete construction,” featured in the journal Construction and Building Materials. Curth co-authored this paper with nine collaborators, including Natalie Pearl, Emily Wissemann, Tim Cousin, Latifa Alkhayat, Vincent Jackow, Keith Lee, and Oliver Moldow, all from MIT; along with Mohamed Ismail from the University of Virginia.

The final two co-authors of this paper are Lawrence Sass, a professor and chair of the Computation Group in MIT’s Department of Architecture, and Caitlin Mueller, an associate professor at MIT in both the Department of Architecture and the Department of Civil and Environmental Engineering. Sass is Curth’s doctoral advisor.

Constructing a structure once, not twice

Creating wooden formwork for a building is pricey and labor-intensive. There’s a saying in the industry that concrete structures must be constructed two times — once with the wooden formwork, and then again with the concrete poured into these forms.

Utilizing soil for the formwork could revolutionize this process. While it may initially seem like an unusual material in comparison to the sturdiness of wooden formwork, soil is robust enough to support poured concrete. The EarthWorks technique, as it is known, incorporates some additive materials like straw and a wax-like covering for the soil to prevent moisture from seeping out of the concrete. By employing large-scale 3D printing, the researchers can take site soil and print it into customized formwork shapes.

Besides the financial savings and ease of obtaining materials, the technique provides at least two additional interconnected benefits. One is ecological: Concrete construction is responsible for up to 8 percent of global carbon emissions, and this method facilitates significant emissions reductions, both through the formwork material itself and the simplified shaping of the resulting concrete to utilize only what is structurally necessary. By employing a technique called shape optimization, developed for reinforced concrete in earlier research by Ismail and Mueller, it is feasible to decrease the carbon emissions of concrete structural frameworks by more than 50 percent.

“The EarthWorks method brings these intricate, optimized structures much closer to reality by providing a low-cost, low-carbon production technique for formwork that can be used globally,” says Mueller.

“It’s an enabling technology to make reinforced concrete buildings much more materially efficient, which has a direct impact on international carbon emissions,” Curth adds.

More broadly, the EarthWorks method allows architects and engineers to create tailored concrete forms more effortlessly, thanks to the adaptability of the formwork material. Creating concrete in an unconventional shape is easier when molding it with soil instead of wood.

“The exciting part is that we can produce shape-optimized building components in the same amount of time and energy it takes to create rectilinear building components,” Curth says.

Collaborative effort

As Curth points out, the projects initiated by the Programmable Mud team are highly synergistic. He emphasizes the contributions from both Sass, a pioneer in leveraging computation for developing affordable housing, and Mueller, whose research also utilizes novel computational methods to analyze innovative structural concepts in architecture.

“Concrete is an excellent material when utilized thoughtfully and efficiently, which is inherently related to how it is shaped,” Mueller remarks. “However, the minimal forms that result from optimization often conflict with traditional construction logic. It’s thrilling to advance a technique that overcomes this supposed tradeoff, demonstrating that performance-driven complexity can be achieved with low carbon emissions and low cost.”

While completing his doctoral studies at MIT, Curth has also established a company, FORMA Systems, through which he envisions bringing the EarthWorks method into the construction realm. Implementing this technique does require builders to have a large 3D printer on-site; however, they would also substantially cut down on material expenses, he asserts.

Looking ahead, Curth imagines a future where the technique could be utilized not just for formworks, but for constructing models for, say, two-story residential buildings made entirely of earth. Although some regions, including the U.S., already extensively employ adobe architecture, the aim would be to systematize the creation of such homes and make them affordable in the process.

In any case, Curth expresses that whether as formwork for concrete or on its own, we now have novel methods to incorporate soil into construction.

“Humanity has built with earth for as long as we have had structures, but given modern demands for urban concrete buildings, this approach essentially separates cost from complexity,” Curth states. “I assure you we can begin to construct higher-performance buildings for a lower price.”

The project was backed by the Sidara Urban Research Seed Fund managed by MIT’s Leventhal Center for Advanced Urbanism, along with contributions from lyndaLABS.