Preparation and evaluation of geopolymer based on BH-2 lunar regolith simulant under lunar surface temperature and vacuum condition

The construction of a lunar base and habitation on the moon has always been of great significance to utilizing lunar resources and deep space exploration. In this paper, a new type of lunar regolith simulant denoted as BH-2 of similar compositions and particle size distribution with real one was developed and used for geopolymer synthesis under simulated lunar surface temperature and vacuum conditions. The geopolymer products were characterized by compressive strength test, Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscope coupled, and Si-29 magic angle spinning-nuclear magnetic resonance (Si-29 MAS-NMR). The results showed that BH-2 lunar regolith simulant could be used to synthesize geopolymer. And the 72-h compressive strength of the geopolymer cured at the temperature of group C, corresponding to the 324-384 h of one lunar day, could reach 38.2 MPa, which was advantageous in the early stages of lunar construction because no additional curing equipment is required. The pores originated from lunar regolith simulant and caused by incomplete geo-polymerization resulted in decreased compressive strength of the resulting geopolymer. Vacuum conditions on the moon favored the preparation of lunar geopolymers due to the lack of carbon dioxide weakening the efflorescence effect. This study benefits to lunar base construction with in-situ resource.