Northwestern University engineers have developed a high-strength concrete using materials that are readily available on Mars. As a result, they potentially could be used to build shelter on future voyages to the red planet.

The concrete, developed by a team led by Gianluca Cusatis, associate professor of civil and environmental engineering, uses a Martian soil simulant created by the U.S. space agency NASA in place of gravel, and molten sulfur, which is abundant on Mars, in place of water.

After testing its mechanical properties, Cusastis found that the Martian concrete was more than two times stronger than typical sulfur-based concretes. After adjusting for gravity on Mars, its strength is equivalent to concrete used to build tall buildings on Earth.

Cusatis says that the concrete’s strength may be due to the small size of particles in the Martian soil as well as a little-understood chemical reaction between the soil and sulfur. His team also found that when the concrete breaks and is re-melted and re-casted, it becomes even stronger. This is likely due to the additional reduction of the particle sizes.

The Martian concrete (left) has smaller particles than conventional sulfur concrete. Image credit: Northwestern University.“Typical sulfur concrete uses sand, which is inert. It’s just filler,” Cusatis says. “In our Martian concrete, the sulfur is not just glue. It reacts with the minerals in the Martian soil. That completely changes the picture.”

While conventional concrete requires hours to develop full strength, Cusatis’ Martian concrete sets in 1-2 hours. For this reason, he says it may be a prime candidate for 3D printing. If 3D printers are sent to Mars, they could use local resources to print buildings made of concrete, which would be much more efficient and sustainable than sending materials from Earth.

Sulfur-based concrete is not a new idea. Highly corrosion-resistant, it is currently used in non-structural applications, such as pipes and landscaping. But because it is sensitive to heat and fire, it is rarely used for larger projects.

“You want buildings to be fire resistant, so that could be a vulnerability on Mars,” says Cusatis. “But for the first settlements, fire won’t be the problem. The problems will be having secure shelters and durable buildings that can survive meteorite impacts.”