| 摘要 |
PROBLEM TO BE SOLVED: To provide a lightweight material having a small particle size irrespective of having a low absolute dry density, and to provide an ultra lightweight article having a large particle size. SOLUTION: The lightweight material is produced by using at least expansible shale and/or expanded clay as a raw material, the raw material being fed into a rotary kiln. This lightweight material comprises a reddish-brown surface layer part and a black inner layer part, and the volume ratio of the surface layer part/ä(surface layer part)+(inner layer part)} is 0.4 or less. Such a lightweight material can be obtained by firing the raw material in a rotary kiln, wherein the residence time while the raw material temperature is from 500 to 1,000°C is set to 10 minutes or less, and the raw material residence time while the raw material temperature is 1,050°C or higher is set to 2 minutes or more. COPYRIGHT: (C)2009,JPO&INPIT
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