Printability Analysis and Strength Enhancement of Extraterrestrial Geopolymers

Abstract This study investigates the printability and compressive strength development of extraterrestrial geopolymers produced from lunar [Lunar Highlands Simulant (LHS-1) and Lunar South Pole Simulant (LSP-2)] and Martian [Martian Global Simulant (MGS-1C)] regolith simulants, with emphasis on mixture design, curing procedure, particle size, and centrifugation. A systematic experimental program evaluated the effects of mixture design on setting behavior, extrusion-based printability, and mechanical performance. Results indicate that silica availability governs geopolymerization, with high-silica formulations achieving the highest cofmpressive strengths for lunar simulants (up to ∼ 52 MPa ), while medium-silica mixtures exhibited rapid setting that limited processability. Longer curing significantly enhanced strength development for lunar geopolymers but caused shrinkage-induced cracking in MGS-1C, demonstrating the need for material-specific curing protocols. Centrifugation produced only marginal strength gains under terrestrial gravity, indicating greater relevance for mixing under extraterrestrial conditions. Overall, optimized silica enrichment and curing strategies are critical for achieving mechanically robust and printable extraterrestrial geopolymers.