Lightweight granulate for mfg. concrete - is made by roasting clay or coal mine tailings mixed with pumice and gypsum

摘要

The mixt. is preheated in an oxidising atmos., and is then heated to its softening temp. The mixt. includes 5-20 vol.% (w.r.t. the clay) of the porous inorganic substance with a size below 2 mm. Heating is pref. to 550 degrees C., at a rate of is not 30 degrees C/min. The clay material used is pref. a non-expanding, or only slightly expanding clay, or a clay with a high m.pt. A weathered and/or milled slate may be used as the clay. The porous inorganic substance is pref. pumice with open pores. Used inmfr. of light expanded concrete, prestressed concrete, or for using waste from coal mines, e.g. washed tailings in concrete.