(9b) Composition-Property Relationships of BP-1 Lunar Regolith Binders for in-Situ Resource Utilization As Geopolymers & Planetopolymers

In situ resource utilization (ISRU) is required for long-term human habitation on the Moon and Mars, with the need to construct environmental protection and critical infrastructure foremost^1. Analogous to terrestrial construction materials formed from aluminosilicates, i.e., geopolymers, binders formed from lunar aluminosilicate regolith (planetopolymers) are necessary to create construction materials for lunar landing pads and habitats. The work presented here builds on a previous lateral study across multiple regolith simulants to focus on Black Point-1 (BP-1) lunar regolith simulant and study the effect of binder composition, i.e., compositional variations in solids weight percent of lunar regolith simulant, activating solution silicon and sodium content, and activating solution water content on seven-day compressive strength, strain to fail, and secant modulus, resulting in varying binder properties. Decreasing water content had a positive effect on compressive strength and secant modulus of planetopolymers formed at ambient-earth conditions, reaching maximum compressive strength at 75 wt% BP-1. Above a compositional limit of Si/H₂O=0.6, differences in chemical coordination cause variations in compressive strength with the elemental composition of the binder. At high solids in formulation, nonmonotonic behavior in compressive strength was observed with varying silicon and aluminum content, emphasizing the need for a mechanistic understanding of the relationship between composition and structure for optimization of material properties. This study provides a robust set of data for a widely available lunar regolith simulant that can guide further development of processing strategies for lunar ISRU.

¹ Comparison of lunar and Martian regolith simulant-based geopolymer cements formed by alkali-activation for in-situ resource utilization: J. N. Mills, M. Katzarova and N. J. Wagner Advances in Space Research 2022 Vol. 69 Issue 1 Pages 761-777