PROBLEM TO BE SOLVED: To make the calcining for manufacturing a lightweight aggregate unnecessary and to reduce a manufacturing cost therefor.;SOLUTION: A softened specified material is extruded into a tubular form under pressure and the extruded tubular material is cut and is formed so as to close the opening of the end part of the tubular material. The lightweight aggregate formed thereby has a hollow shape and so it is not necessary to use the material having small specific gravity. Further, the manufacture of the lightweight aggregate does not require the calcining and gets along with the extrusion forming of the material. Therefore, the lightweight aggregate can be continuously manufactured by the use of inexpensive equipment and can be mass-manufactured at a low cost.;COPYRIGHT: (C)2004,JPO
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