PURPOSE: To obtain a high hardness foamed artificial lightweight aggregate excellent in crwsh strength by sintering a granulated article of a raw material composed of a fired coal ash (coal ash), a fin glass powder (glass powder) and a plastic clay.

CONSTITUTION: The artificial lightweight aggregate is formed by sintering a lump obtained by granulating the coal ash and the glass powder by the tackiness power of the plastic clay. In the sintering process, a liquid phase grows from the softened glass and is gasified by the reaction of an oxygen supplying component in the glass powder and moisture adsorbed on the surface of the glass powder and the fusion of the coal ash with the clay is accelerated. And simultaneously the lightweight aggregate uniform in the diameter of pores, rich in homogeneous and high in mechanical strength is obtained by foaming with a gas generated by the thermal decomposition of the structural components.