Sustainability

Researcher Studies Potential for 3D-Printed “Dirt Houses”

Usually, a “dirt-cheap” house doesn’t inspire much confidence. But a civil engineering professor is looking into how 3D-printed soil and bacteria could potentially create a material that rivals concrete.

In April, University of Arkansas professor Michelle Bernhardt-Barry received a $500,000 National Science Foundation grant for her work with 3D printers. Bernhardt-Barry works with a binder jet printer, which prints using an adhesive and a powder medium to build shapes. The machine’s blade lays down a layer of powder medium, then the printer’s nozzle lays down adhesive in a predetermined pattern. The printer builds with alternating layers of adhesive and powder in a process that requires no heat.

Bernhardt-Barry has printed with a gypsum-based powder that is similar to sand, but not entirely waterproof. Recently, she revealed that her grant is being used to develop printing capabilities with sand and soil.

She is currently studying microbial-induced calcium carbonate precipitation (MICP), a bacterial process that causes calcium carbonate—a substance found in limestone—to precipitate from the soil. MICP has already been studied for its potential use in self-healing concrete, where appropriate bacteria and nutrients are embedded into the concrete, so that when they become exposed, they can precipitate calcium carbonate. Once this process perfected, users could potentially gather soil on-site and feed it through the printer to produce a better building material.

This is not the first project to use dirt as a 3D-printing medium. Barcelona’s Institute for Advanced Architecture of Catalonia (IAAC) is currently developing Pylos, a robot that prints with a material that’s 96 percent soil. But the IAAC’s project uses a traditional 3D printer, extruding wet material in layers, and doesn’t utilize bacteria in its development.

Bernhardt-Barry’s project will run for five years, from July 1 of this year through June 30, 2023. During that time, Bernhardt-Barry will employ two doctoral students to assist with her research. At the end of the project, the researchers will perform a life-cycle analysis to determine if the dirt-printed building material can last as long as materials like concrete.

Bernhardt-Barry hopes that her soil material can be used in remote places, where concrete is difficult to source but dirt is plentiful. She also believes it will be more environmentally friendly than concrete, which has a high carbon footprint. “I think the trick is figuring out the science part of it and sort of the shapes and the materials and so that it is cost-effective,” she told Talk Business. “That’s going to be the bigger piece. We can build anything, but it’s got to be cost-effective.”