Calcium sulphate alpha-mono:hydrate mfr. by autoclaving di:hydrate - mouldings obtd. from powder have controlled porosity, fully converted crystals are controlled from acicular to squat columnar

摘要

Mouldings of fine gypsum dihydrate contg. 15-60 vol.% porosity and over 5 vol.% air in pores are heated with water in autoclave at 110-180 deg.C under controlled pressure to recrystallise to alpha-hemihydrate. Mouldings are pref. placed in autoclave at room temp. so that water condensed on surface isdrawn into pores by capillary action; also part of water pref. arises from dihydrate -at least 50 vol.% of porosity pref. contains air. Mouldings are pref. formed at 14N/mm2 in presence of 3-20 wt.% physically bonded water. Growth controlling additives are pref. mixed with dihydrate and are pref. fine brown coal, peat, wood, humic acid, timber prods. or mixt. thereof. Portion of dihydrate pref. is obtd. from gas desulphurisation plant in power station fired on brown coal.