A large amount of waste is produced by preparation plants. The properties of the waste vary depending on the mineralogical contents of the mother rock in which the coal is embedded. The waste quality depends on the method of mining and cleaning. The waste mainly consists of clays, quartz, carbonaceous materials, mica, pyrites, and so on. About 80% of coal-ash is now utilized and the remainder is disposed of at disposal sites. However, the life span of disposal sites is limited, and it is difficult to find new disposal sites. It is therefore requested that the percentage of utilized flyash be increased in all applicable fields in Japan. Thus, it is very desirable that cement supplemented with flyash be used as injection material for natural/artificial openings. With this perspective in mind, we attempt to clarify how much the size and shape of the flyash affects the properties of the injection mixture by way of an injection test.
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