A Fundamental Study of the Ryukyu Coral Limestone

• Published in: Journal of the Ceramic Association, Japan Vol. 64; no. 729; pp. 211 - 217
• Main Authors: SHIMADA, Kinji, KOMAKI, Takashi
• Format: Journal Article
• Language: Japanese
• Published: The Ceramic Society of Japan 01.10.1956
• ISSN: 0009-0255; 1884-2127
• DOI: 10.2109/jcersj1950.64.729_211

Coral limestone resourses are very abundant in the Amami Islands, though very little have ever been reported on them. The object of this paper is to describe the results of the writers' works on the fundamental properties of three kinds of the “Ryukyu Coral limestone”, namely those produced in Amami-Oshima, Okinoerabu-shima, and Yoron-shima. Chemical analysis, determination of specific gravity, various thermal tests, X-ray analysis etc. were conducted on these coral limestones and compared with that produced in Shiraishi, Kumamoto prefecture. Moreover, differential thermal analysis, X-ray analysis, slaking test and sedimentation test were made on these coral limestones calcined at various temperatures, with the following results. (1) The Ryukyu coral limestones are mainly composed of calcite with the following physical properties and chemical compositions: true density 2.68-2.74, porosity 6.31-23.41%, water absorption 2.51-11.81%, CaO 52.30-54.65%, MgO 0.37-1.62%, Al2O3+Fe2O3 0.37-1.78%. (2) From differential thermal analysis and powder X-ray diffraction, the decomposition of these coral limestone begins from about 700°C and comes to end at about 900°C. (3) When burnt to 1000°C, the coefficient of maximum expansion of all three coral limestones was 0.7-2.3%, while that of Kumamoto limestone showed a lower value, 0.6%. (4) The effect of calcing temperature on the slaking velocity has been observed both on the powder and on the block samples of the coral limestones. The results show that the calcination at 900°C is suitable for the powder specimens, while that at 1000°C is desirable for the block specimens.