The cost of building a building has become very high these days. But if you want to build a concrete building, there is another material that can make it cheaper: mud.
Researchers at MIT have developed a way to use lightly treated sludge, such as soil from construction sites, as a “form” for pouring concrete. The technique employs 3D printing and could replace the more costly method of building complex wooden forms for concrete structures.
“What we’ve shown is that we can essentially turn the ground we stand on, or waste soil from a construction site, into precise, intricate, flexible forms for custom concrete structures,” says Sandy Kaas, a doctoral student in the MIT School of Architecture who led the project.
This method makes concrete construction faster and more efficient, while reducing costs and carbon emissions.
“This initiative can have an immediate impact and does not require changing the nature of the construction industry,” said Kurth, who also serves as director of the Programmable Mud Initiative.
Kurth has co-authored a paper on the technique, “EarthWorks: Zero-Waste 3D Printed Earth Forms for Shape-Optimized Reinforced Concrete Structures,” recently published in the journal Construction and Building Materials . Kurth wrote the paper with nine other co-authors, including Natalie Pearl, Emily Wisseman, Tim Cousin, Latifa Al-Khayat, Vincent Jacqueau, Keith Lee, and Oliver Moldau, all students at MIT, and Mohammed Ismail of the University of Virginia.
The paper’s final two co-authors are Lawrence Sass, professor and chair of the Computation Group in the MIT Department of Architecture, and Caitlin Mueller, associate professor in the MIT Department of Architecture and Department of Civil and Environmental Engineering. Sass was Kurth’s graduate supervisor.
Build a building once, never build it twice
Constructing wooden forms for buildings is expensive and time-consuming, and there’s a saying in the industry that a concrete structure must be built twice: once to build the wooden forms and then a second time to pour the concrete into the forms.
Using soil for the formwork changes the process. It may seem like an unusual material compared to the strength of wooden formwork, but soil is strong enough to withstand poured concrete. The Earthworks method, as it is commonly known, introduces several additive materials, such as straw and a wax-like coating, into the soil material to prevent water from leaking through the concrete. Using large-scale 3D printing technology, researchers are able to take soil from the construction site and print it into the shape of the custom-designed formwork.
“What we’ve done is created a system that makes simple, large-scale 3D printing technology highly functional in materials,” Kurth said. “We’ve discovered a way to create an infinitely recyclable formwork. It’s just dirt.”
In addition to cost and ease of material sourcing, this method has at least two related benefits. The first is environmental: Concrete construction accounts for up to 8 percent of global carbon emissions, and this method supports significant reductions in emissions, both through formwork materials and the ease with which the finished concrete can be cast using only what is structurally necessary. Using a technique called shape optimization, developed for reinforced concrete in earlier work by Ismail and Muller, the carbon footprint of concrete structural frames can be reduced by more than 50 percent.
“Earthworks’ technology brings these complex, optimized structures closer to the construction site by offering a low-cost, low-carbon formwork technology that can be deployed anywhere in the world,” Mueller said.
“This is a technology that will enable much more material-efficient reinforced concrete buildings, which will have a direct impact on global carbon emissions,” Kurth added.
Overall, the EarthWorks method allows architects and engineers to create custom concrete shapes more easily due to the flexibility of the form materials. Casting concrete from earth instead of wood makes it easier to cast concrete in unusual shapes.
“The beauty here is that we can create a shape-optimized building component in the same time and energy it takes to create a rectangular building component,” Curth says.
Group Project
As Curth points out, the projects developed by the Programmable Mud team are highly collaborative. He highlighted the role of both Sass, a company at the forefront of using computing to aid affordable housing development, and Mueller, which is also employing new computing methods to evaluate innovative structural ideas in architecture.
“Concrete is an incredible material when used thoughtfully and efficiently, as its geometry suggests,” says Mueller, “but the minimalist shapes that emerge from the optimization process defy traditional construction logic. It’s exciting to develop technologies that break this assumed trade-off and show that performance-driven complexity can be achieved with low carbon emissions and low cost.”
While working on his doctorate at MIT, Kurth is also starting a company called FORMA Systems, through which he hopes to bring EarthWorks’ methods to the construction industry. The method would require builders to have large 3D printers on-site, but it would also save a lot on materials costs, he said.
Kaas envisions that in the more distant future, the method could be used not just to make formwork but also to create templates for, say, two-story homes built entirely out of earth. Of course, adobe construction is widely used in some parts of the world, including the U.S., but the idea here is to systematize the production of such homes and make it cheaper in the process.
In either case, Kurth said, the result is a new way to add soil to a construction site, either as a form for concrete or separately.
“Humans have been building with earth for almost as long as buildings have existed, but given the concrete construction needs of modern cities, this approach essentially decouples cost and complexity,” says Kaas. “We guarantee we can build more efficient buildings for less money.”
The project is supported by the Sidara Urban Research Seed Fund, administered by MIT’s Leventhal Center for Advanced Urbanism and lyndaLABS.
