Advanced spectroscopic investigation of lunar highland simulant (LHS-1) geopolymer for in-situ resource utilization

In situ resource utilization (ISRU) is essential for sustainable lunar infrastructure, where geopolymers provide a promising pathway to reduce dependence on Earth-supplied materials. This study evaluates Lunar Highland Simulant-1 (LHS-1) as a geopolymer precursor, comparing as-received and screened fractions activated with sodium hydroxide. While the general effects of alkali concentration on geopolymerization are established, the spectroscopic characteristics and mineralogical effects of LHS-1 remain insufficiently understood and are systematically investigated here. Screening reduced the median particle size by about 33 percent, increasing surface area and reactivity. Multi-technique spectroscopic analyses (FT-IR, NMR, XPS, Raman) confirmed enhanced aluminosilicate network formation in screened and high-alkali systems, accompanied by the development of crystalline sodalite and garronite phases. Mechanical testing showed that compressive strength improved by 42 to 44 percent with screening, achieving up to 29.7 MPa in the 10 M mixture after screening. Thermal and microstructural evaluations (TGA, MIP, calorimetry) further demonstrated greater N-A-S-H gel formation, refined pore structure, and accelerated reaction kinetics. These findings provide new information into the geopolymerization characteristics of LHS-1, providing a laboratory-scale reference for ISRU material screening.