Researchers from the University of Delaware (USA) have created an alternative cement material that successfully withstood six months of exposure to extreme space conditions after being placed outside the International Space Station (ISS).
In some tests, samples returned to Earth demonstrated mechanical strength exceeding that of identical samples stored in terrestrial soil. These results confirm the feasibility of using this material for creating infrastructure on the Moon, as transporting cement from Earth is economically unviable.
According to scientists, the lunar soil itself—regolith, a layer of dust and rock fragments covering the satellite's surface—could be an alternative for constructing structures on the Moon's surface. Norman Wagner, a professor in the Department of Chemical Engineering at the University of Delaware, explained that 'regolith is essentially a silicate material similar to clay' and that it 'is one of the most common materials both on Earth and on the Moon, making it interesting for construction.'
Wagner's laboratory is developing geopolymers—a replacement for traditional cement—which bind clay materials through chemical reactions, eliminating the need for high-temperature production processes. The goal is to produce building materials using regolith with minimal additives, thereby reducing the demand for energy-intensive industrial processes. Researchers also believe this technology could contribute to enhancing the sustainability of civil construction on Earth.
To assess the behavior of geopolymers in space, the team sent thin plates made using commercial simulators of lunar and Martian regolith as part of NASA's MISSE-20 mission. For half a year, the samples remained attached to the exterior of the ISS, subjected to the hostile environment of low Earth orbit.
After returning to Earth, researchers found that the materials showed no signs of degradation. Moreover, in several cases, the samples demonstrated greater strength compared to equivalent materials that had been on Earth for the same period. This study was published in the journal Advances in Space Research.
In addition to surviving space conditions, future building materials for the Moon must be reliably manufactured directly on the lunar surface. To solve this problem, the team conducted a second study, published in the journal Acta Astronautica, utilizing artificial intelligence (AI).
The scientists developed a machine learning model that predicts the strength of geopolymers based on the characteristics of the regolith used and the method of material processing. According to the scientists, this approach accounts for the fact that different types of lunar clays may possess varying properties requiring specific manufacturing methods.
Another study by Wagner's laboratory examined the behavior of geopolymers during the mixing, pumping, and molding stages, prior to solidification. The researchers identified a transition point, known as the critical gel point, the moment when the material ceases to behave like a moldable paste and begins to form a solid structure. Experiments showed that mixing or shearing before this stage did not affect either the setting time or the final strength of the material. In the researchers' opinion, this means that future engineers can have greater freedom in manipulating and processing building materials on the Moon without compromising their quality. This work was published in a special issue of the Journal of Rheology dedicated to the behavior of materials beyond Earth.
