16:30 〜 16:45
[MIS12-10] 軌道上宇宙空間に晒された水和セメント物質の風化
キーワード：セメント系材料、宇宙風化、高分解能透過電子顕微鏡
Context: Cement technology based on production of bonding phase such as calcium silicate hydrate (CSH) supporting our civilization is now stepping into the new frontier, space. Previously, NASA conducted the test program for the novel utilization of cementitious material to build the moon base [1]. Recently, JAXA studied the geopolymer technology with less water using in-situ raw materials on the moon [2]. The International Space Station (ISS) 'Kibo' module provides us Exposed Experiment Handrail Attachment Mechanism: ExHAM to examine whether the conventional cement is feasible or not. Here, we conducted space exposure test for approximately 12 months from May 26, 2015 till June 13, 2016 at ISS [3].
Microanalyses of cements can for the first time serve the information about space weathering of hydrous materials.
Methods: Typical two cements were selected and launched: (1) ordinary portland cement (OPC); (2) calcium aluminate cement (CAC). Their major bonding materials are CSH and calcium aluminate (CAH), respectively along with portlandite (calcium hydroxide, CH). After 12 months exposure, these specimens were returned to the laboratory on ground to be evaluated with microanalyses, X-ray CT, FESEM and HRTEM.
Results: Returned samples showed 1-3 wt.% of a little weight loss and 8% of thickness decrease. In contrast to these minor changes, surface of these disk specimens vividly remained color change before and after the test. Microscopic observation on disks detected round-shaped “sunburn” surrounded by shaded rim under punched metal plate. So, we proceeded HRTEM observation (Hitachi HF5000) focusing on the exposed and masked surfaces. Results confirmed that the interface of exposed area accompanies foaming and more on OPC than CAC. Especially, exposed OPC developed deep foaming over 1 um. Elemental distribution across the interfaces displayed no significant change at OPC but small enrichments of Ca and alkalis at CAC.
Discussion: Feasible test of cement pastes served us a simple information about endurance under orbital space condition. Since the CAC can mostly endure but OPC suffered from space-weathering tends to be foamed and dried, the mechanism of bubble formation at the exposed interface can be explained by water-escape triggered by sunlight receiving. However, 12 months weathering made small damage of only 1 um deep. This fact suggests that terrestrial building technology with water fluid may be applicable in the moon environment.
Acknowledgements: We gratefully acknowledge technical supports of Hitachi High-Technologies.
References: [1] Ishikawa et al. (1992) NASA. Johnson Space Center, The Second Conference on Lunar Bases and Space Activities of the 21st Century, Volume 2, 489-491.; [2] Satoh et al. (2016) Proceedings of 60th Space Sciences and Technology Conference (in Japanese).[3] Sakon et al. (2018) The Japan Society for Aeronautical and Space Sciences, Volume 66, 381-387 (in Japanese).
Microanalyses of cements can for the first time serve the information about space weathering of hydrous materials.
Methods: Typical two cements were selected and launched: (1) ordinary portland cement (OPC); (2) calcium aluminate cement (CAC). Their major bonding materials are CSH and calcium aluminate (CAH), respectively along with portlandite (calcium hydroxide, CH). After 12 months exposure, these specimens were returned to the laboratory on ground to be evaluated with microanalyses, X-ray CT, FESEM and HRTEM.
Results: Returned samples showed 1-3 wt.% of a little weight loss and 8% of thickness decrease. In contrast to these minor changes, surface of these disk specimens vividly remained color change before and after the test. Microscopic observation on disks detected round-shaped “sunburn” surrounded by shaded rim under punched metal plate. So, we proceeded HRTEM observation (Hitachi HF5000) focusing on the exposed and masked surfaces. Results confirmed that the interface of exposed area accompanies foaming and more on OPC than CAC. Especially, exposed OPC developed deep foaming over 1 um. Elemental distribution across the interfaces displayed no significant change at OPC but small enrichments of Ca and alkalis at CAC.
Discussion: Feasible test of cement pastes served us a simple information about endurance under orbital space condition. Since the CAC can mostly endure but OPC suffered from space-weathering tends to be foamed and dried, the mechanism of bubble formation at the exposed interface can be explained by water-escape triggered by sunlight receiving. However, 12 months weathering made small damage of only 1 um deep. This fact suggests that terrestrial building technology with water fluid may be applicable in the moon environment.
Acknowledgements: We gratefully acknowledge technical supports of Hitachi High-Technologies.
References: [1] Ishikawa et al. (1992) NASA. Johnson Space Center, The Second Conference on Lunar Bases and Space Activities of the 21st Century, Volume 2, 489-491.; [2] Satoh et al. (2016) Proceedings of 60th Space Sciences and Technology Conference (in Japanese).[3] Sakon et al. (2018) The Japan Society for Aeronautical and Space Sciences, Volume 66, 381-387 (in Japanese).