[S-CG53] 岩石・鉱物・資源

[SCG53-P01] Mechanochemical activation of Martian soil simulants and their application to construction materials

*亀田 純¹ (1.岡山大学惑星物質研究所)

キーワード：火星模擬土、メカノケミカル粉砕、コンクリート

The utilisation of local resources will be essential for future migration to Mars. This study examines the effective use of Martian regolith as a construction material, which will be important for in situ resource utilisation (ISRU) in the early stages of migration. Several processing methods have been studied to use extraterrestrial regolith as a construction material, including firing and combustion synthesis, the simplest of which is the cold-pressing method. Generally, in these regoliths, the hydrous clay minerals and the water in the green body act as a binder to develop the strength of the cold-pressed material. In fact, the binder effect of smectite minerals has been confirmed in cold-pressing experiments using Martian soil simulants (Ishikawa et al. 1992; Boyd 1989). On the other hand, it has recently been reported that non-fired ceramics can be obtained in powder systems without clay minerals by inter-particle bonding through mechanical activation of silica powder (Nakashima et al., 2018). Such a method could be an effective processing method for sourcing suitable construction materials from Martian soils with diverse mineral compositions. In this study, three Mars soil simulants, MGS-1 (Cannon et al., 2019), MGS-1C (MGS-1 with smectite) and MGS-1S (MGS-1 with gypsum), were mechanically processed in a ball mill and strength tests on their pellets were conducted. The powders were processed by ball milling for a specified time under ambient conditions, and then compressed in a uniaxial press for 10 seconds at 10 MPa to produce pellets (12 mm diameter and 8 mm height). The uniaxial compressive strengths of the pellets were higher in the as-supplied powders, in the order MGS-1C, MGS-1S and MGS-1. The high strength seen in MGS-1C may be due to the binder effect of the clay. An increase in strength was observed in all samples with increasing grinding time, but no significant changes were observed after approximately one hour grinding. The strength increase in MGS-1 without hydrous minerals (up to a factor of approximately 10) may be due to activation of the particle surfaces, which may have promoted inter-particle bonding. In the grinded samples, a significant increase in strength was observed in MGS-1S, with the strength attained being about 1.5 times higher than in MGS-1C. XRD analysis of the post-processes samples confirmed the amorphisation of gypsum and subsequent formation of a dehydrated phase (bassanite). The behaviour of dehydrated water from grinded gypsum may have promoted the agglomeration of fine particles into a high-strength material.

Reference Cannon et al. 2019, Icarus 317, 470–478. Ishikawa et al. 1992, Eng. Constr. Oper. space-III, 1335–46. Boyd et al. 1989 The Case for Mars III. Nakashima et al. 2018, Advanced Powder Technology 29, 1900–1903.