GYPSUM BINDER PREPARATION METHOD Russian patent published in 2003 - IPC

FIELD: manufacture of building materials. SUBSTANCE: gypsum- containing citric acid production waste, namely citrogypsum, is concentrated in presence of polyacrylamide. To concentrate pulp is added 1:2 mixture of copper and sodium sulfates in amounts 1.2-1.5 kg/cu. m. Pulp is subjected to recrystallization in autoclave to give calcium sulfate semihydrate, which is simultaneously dried and then ground. Samples manufactured using proposed material are characterized by bending strength 4.7- 5.4 MPa, compression strength 11.4-12.5 MPa, initial setting time 19-25 min, final set 27-48 min. EFFECT: improved performance characteristics. 1 dwg, 1 tbl, 6 ex