16:30 〜 16:45
[MIS14-09] 水和セメント材料を月面で：ISSにおける宇宙工学アナログ実験
キーワード：水和セメント材料、普通ポルトランドセメントとアルミナセメント、脱水
1. Context
Artemis program has just started and is ready to build a moon base and house human being. The key to the success of the program is the presence of water in the polar region of the moon, which could be used to construct the concrete base. Using cement technology, we can create robust solid structures from in-situ materials such like regolith. JAXA has previously studied the feasibility of building blocks using moon regolith, alkali, and water [1]. Latest tests conducted on the International Space Station (ISS) has shown that low gravity conditions may enhance the prismatic large crystals of portlandite (Ca(OH) 2) and pores in C3S (alite) hydrated cement [2]. The environment in space, including sun-light and low-pressure, can also cause damage to the solidified cements. Our previous tests on OPC (ordinary Portland cement) and CAC (calcium aluminate cement) which were recognized to be “sun-burned” at the ISS revealed surface nano-foaming [3].
2. Analyses
We are now focusing on the degradation mechanism of hydrous cement on the moon. Our observations and analyses with TEM and X-ray CT suggest that the surface nano-foaming may have been caused by dehydration and elemental redistribution. Further, we proceeded quantitative micro-XRD analysis with Rietveld calculation on OPC disk in order to distinguish exposed “sun-burned” surface with from shaded part. This corresponds with enrichments of ettringite (AFt) and periclase (MgO), but portlandite and calcium silicate hydrate (C-S-H).
3. Discussion
A simple 1D simulation was applied with a calculation code of Phreeqc for both OPC and CAC pastes to test the mineralogical redistribution under the sun-light. Anhydrous phases of Al2O3 developed more in CAC than OPC early 10 years. The resultant data confirmed that OPC is more stable than CAC due to less dehydration as confirmed by simulation and analysis of the cement materials. This is reasonably explained by DTA analysis of Ca(OH)2, Mg(OH)2 and Al(OH)3 at ~400, ~350 and ~300 °C, respectively [e.g., 4, 5, 6]. If the moon base is build using these types of cements, dehydration will be the main issue but damage is expected to be minimal, only about 0.01 mm after 10 years.
References: [1] Satoh, H. et al., (2016) Proceedings of 60th Space Sciences and Technology Conference. [2] Neves, J.M. et al. (2019) Frontiers in Materials. Vol. 6, 1-12. [3] Satoh, H. et al. (2022) JpGU2022 abstract. [4] Vance, K. et al. (2015) Ind. Eng. Chem. Res., 54, 8908-8918. [5] Zhang, J. et al. (2010) J. Phys. Chem. C, 114, 24, 10768–10774. [6] Yang, X. et al. (2007) J. Colloid & Interface Science, 308, 395-404.
Artemis program has just started and is ready to build a moon base and house human being. The key to the success of the program is the presence of water in the polar region of the moon, which could be used to construct the concrete base. Using cement technology, we can create robust solid structures from in-situ materials such like regolith. JAXA has previously studied the feasibility of building blocks using moon regolith, alkali, and water [1]. Latest tests conducted on the International Space Station (ISS) has shown that low gravity conditions may enhance the prismatic large crystals of portlandite (Ca(OH) 2) and pores in C3S (alite) hydrated cement [2]. The environment in space, including sun-light and low-pressure, can also cause damage to the solidified cements. Our previous tests on OPC (ordinary Portland cement) and CAC (calcium aluminate cement) which were recognized to be “sun-burned” at the ISS revealed surface nano-foaming [3].
2. Analyses
We are now focusing on the degradation mechanism of hydrous cement on the moon. Our observations and analyses with TEM and X-ray CT suggest that the surface nano-foaming may have been caused by dehydration and elemental redistribution. Further, we proceeded quantitative micro-XRD analysis with Rietveld calculation on OPC disk in order to distinguish exposed “sun-burned” surface with from shaded part. This corresponds with enrichments of ettringite (AFt) and periclase (MgO), but portlandite and calcium silicate hydrate (C-S-H).
3. Discussion
A simple 1D simulation was applied with a calculation code of Phreeqc for both OPC and CAC pastes to test the mineralogical redistribution under the sun-light. Anhydrous phases of Al2O3 developed more in CAC than OPC early 10 years. The resultant data confirmed that OPC is more stable than CAC due to less dehydration as confirmed by simulation and analysis of the cement materials. This is reasonably explained by DTA analysis of Ca(OH)2, Mg(OH)2 and Al(OH)3 at ~400, ~350 and ~300 °C, respectively [e.g., 4, 5, 6]. If the moon base is build using these types of cements, dehydration will be the main issue but damage is expected to be minimal, only about 0.01 mm after 10 years.
References: [1] Satoh, H. et al., (2016) Proceedings of 60th Space Sciences and Technology Conference. [2] Neves, J.M. et al. (2019) Frontiers in Materials. Vol. 6, 1-12. [3] Satoh, H. et al. (2022) JpGU2022 abstract. [4] Vance, K. et al. (2015) Ind. Eng. Chem. Res., 54, 8908-8918. [5] Zhang, J. et al. (2010) J. Phys. Chem. C, 114, 24, 10768–10774. [6] Yang, X. et al. (2007) J. Colloid & Interface Science, 308, 395-404.