In this study, the author announces the results of the experiment which is carried out to investigate the elevated temperature properties of the CO
2 sand. Followings are the summary of the results obtained.
1) Above the temperatures of 500°C, the hot strengths of CO
2 sand decrease greatly down to less than 1kg/cm
2, and the amount of deformation is also great. But, no obvious change in hot strengths can be observed by the change of gassing time.
2) Contrary to the above mentioned result, the retained strengths of the CO
2 sand specimens immersed in temperatures higher than 500°C show great increase and this seems to be the main cause of poor collopsibility of CO
2 sand.
3) Expansion-contraction curve of the CO
2 sand during certain range of soaking time, say, from 30 seconds to 2 minute and a half, shows linear relation irrespective of soaking temperatures (600°C∼1400°C).
4) To increase elevated temperature strength and to decrease retained strength of the CO
2 sand, about 2 per cent of additives such as coal-tar-pitch, gilsonite and asphalt emulsion are recommended. Such additives in such additional amount do not seem to give bad influences on expansion contraction characteristics of the CO
2 sand.
5) Bentonite or clay addition is not preferable in view of decreasing hot strength, while increasing green and retained strengths of the CO
2 sand.
6) The addition of wood flour, cereal or resin binders also seems unpreferable because it gives poor hot strength while increasing deformation of the CO
2 sand.
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