The construction industry is currently facing two major challenges: the demand for sustainable infrastructure and the need to repair deteriorating buildings, bridges, and roads. While concrete is the material of choice for many construction projects, it leaves a significant carbon footprint, resulting in new waste and high energy use. Researchers are now reporting progress in creating sustainable building material from local soil using a 3D printer to create a supporting structure. Scientists will present their results at a virtual meeting and exhibition of the American Chemical Society (ACS).

The environmental impact of the construction industry is of growing concern. Some researchers have turned to additive manufacturing, or building structures layer by layer, which is often done with a 3D printer. This progress has begun to transform the construction sector in terms of reducing waste, but the materials used in the process must also be sustainable.

Sarbajit Banerjee, PhD, Principal Investigator of the Project

For example, construction projects using concrete have demonstrated the potential for additive manufacturing of building structures quickly and cheaply. However, according to the International Energy Agency, concrete production accounts for approximately 7% of carbon dioxide emissions.

Historically, people have built from local materials such as adobe, but the switch to concrete has caused many environmental problems. The main idea of ​​the scientists was to turn back the clock and find a way to adapt materials “from our yards” as a potential replacement for concrete, the researchers explain.

The advantage of using local soil in construction is that materials do not need to be produced and transported to the construction site, which reduces both costs and environmental damage. It is also said that soil-based additive manufacturing could one day be used outside of Earth to create settlements on the Moon or even Mars.

Soil is usually classified by the layers of material it comprises, from the top organic layer where plants grow to the hard base of the earth’s crust. Beneath the original organic layer is clay, which gives the soil the plastic character that the researchers used in their project.

The researchers began by collecting soil samples from their colleague’s backyard and processing the material with a new environmentally friendly additive so that it binds together and can be easily extruded through a 3D printer. Because soils vary greatly by location, their goal was to have a chemical “toolbox” that could transform any type of soil into a printable building material.

The next step was to make sure that the mixture can withstand the load, which means that it will support the weight of the layers as well as other materials used in construction such as reinforcement and insulation. To help with this, the researchers strengthened the clay mixture by zipping up microscopic layers on its surface to prevent water absorption and expansion that could compromise the printed structure. Using this method, researchers have shown that the material can hold twice as much weight as an unmodified clay mixture.

The team then plans to improve the load-bearing capacity of the soil to expand their test structures and get as close as possible to replacing concrete. In addition, they are collecting data to understand if these 3D printed designs are as environmentally friendly as they think, especially in terms of carbon footprint and recyclability potential. Once they have a better understanding of the chemical composition, functionality, and construction possibilities using local soils, they plan to continue exploring the use of this technology outside of our planet.