Lunar regolith can allow the synthesis of cement materials with near-zero water consumption

With the continuous development of science and technology and the human understanding of the moon, many scientists have planned the creation of a space station on the moon using lunar building materials. Environmental factors mainly include large temperature differentials, and the presence of a hard vacuum on the surface of the moon is a huge challenge for the performance of lunar building materials. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Additionally, they meet most of the requirements for use in the lunar environment. Here, we present a potential lunar cement material that was fabricated using volcanic ash and sodium hydroxide solution as activator, based on geopolymer technology. The compressive strengths of the volcanic ash geopolymer specimens processed for 24 h under vacuum conditions and 30 freeze-thaw cycles in liquid nitrogen are 45.53 and 44.95 MPa, respectively. Additionally, 98.61% of water could be recycled, in consistence with the water recycling-simulated lunar environment in the lab. Although volcanic ash is not equivalent to the lunar soil, we speculate that the alkali activation of lunar soil could be very close to that of volcanic ash because of their similar chemical and mineralogical composition. In summary, this study provides a feasible approach for the development of near-zero water consumption lunar cement materials based on geopolymer technology.