MASS FOR MANUFACTURING BUILDING PARTS AND METHOD OF PREPARING THEREOF Russian patent published in 1997 - IPC

FIELD: manufacture of building materials. SUBSTANCE: invention relates to manufacturing building parts based on magnesia- gypsum cement, in particular, those based on sodium monochromatic production waste (rejected sludges) and may be applied at enterprises producing building materials or at chrome area works. Goal of invention is to reutilize reject sludges from chromate production and simultaneously to manufacture, on their basis, building materials as well as to widen their application area conditioned by absence of toxicity in mass, to increase quality of produce, and to reduce its cost. Mass is composed of (in wt %): chromate production sludge, 46.0-61.0; sulfuric acid, 11.0-21.5; organic filler, 4.0-10.0; and water, the balance. Chromate sludge in quantity 20-50% based on its initial weight is mixed with water in such proportion as to provide solids to liquid weight ratio 1: (1-3). Then sulfuric acid is added to provide sludge/acid weight ratio within the range 0.9 to 1.65. Reaction mixture is agitated for 20-60 min at 80-90 C, whereupon, to prepared magnesia-gypsum binder, organic filler and remaining amount of sludge are added. Resultant mass is dried to humidity content 5- 15%, molded, and hardened. To prevent reverse process of transferring chromium(III) from water-insoluble state into chromium(IV), mass may be supplemented with sulfur-containing reducing agent (sulfur, sodium sulfide, sulfite or thiosulfate) in quantity 0.1-0.5% based on sludge weight. EFFECT: improved quality and reduced cost due to utilizing waste. 8 cl, 2 tbl