Abstract: To address the critical strategic need for sustainable and permanent habitat construction in global lunar base development, this study adopted the concept of in-situ resource utilization on the Moon. Using a simulant with a composition similar to that of Chang’e-6 lunar regolith as the foundational raw material, lunar regolith-based geopolymers (LRG) were synthesized via a solid sodium silicate–activated “one-part” process. A systematic investigation was conducted into the evolution of mechanical performance under the Moon’s extreme surface temperatures (–178 to 113 ℃). The study focused on how key elemental ratios in the regolith (Ca/Si and Al/Si) affected the compressive strength of LRG. Furthermore, leveraging the advanced analytical techniques such as scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and nitrogen adsorption–desorption (NAD) tests, this study elucidated the microstructural evolution mechanisms of LRG under the combined effects of thermal cycling and elemental composition. The results showed that increasing Ca/Si (0.26–0.35, Al/Si=0.34) enhanced the compressive strength of LRG but concurrently heightened its susceptibility to cryogenic conditions; increasing Al/Si (0.34–0.58, Ca/Si=0.26) led to a rise-then-fall trend in strength, while cryogenic sensitivity initially decreased and subsequently increased. Notably, when Ca/Si was set at 0.35 and Al/Si at 0.58, the compressive strength of LRG reached 52.25 MPa and remained relatively robust even after cryogenic exposure. Further analysis indicated that strength degradation under cryogenic exposure arose from a combination of internal and external factors: internally, pore-structure deterioration due to collapse of the gel network; externally, pore-water freezing-induced cryo-suction and gel incompatibility collectively contributing to pore expansion. Degradation in high-calcium systems was attributed to the synergistic effects of internal and external factors, whereas in low-calcium systems it was predominantly governed by external factors. Moreover, this study proposed that the optimal construction window for lunar building operations entailed completing mixing and casting within approximately 100 hours prior to the onset of the high-temperature phase of the lunar daytime. This work not only clarified the regulation mechanism governing LRG mechanical performance via the synergistic interplay of Ca/Al/Si but also unveiled the cryogenic degradation patterns across diverse elemental compositions, thereby providing an important theoretical basis and technical support for the efficient utilization of lunar in-situ resources and economically sustainable extraterrestrial construction.

Key words: lunar regolith simulant, geopolymer, lunar temperature variation, cryogenic degradation mechanism, mechanical property