抄録
In the present paper were reported the results of various studies on utilization of byproduct gypsum material, which are called as “Gomi” and “Scale” and have the main compositions of NaCl and CaSO4 mixed with MgCI2, KCI, MgSO4, K2SO4, Na2SO4, etc. These gypsum containing byproducts were firstly washed with sea water or dilute brine to dissolve and exclude NaCI and other salts above mentioned. CaSO4 in these byproducts “Gomi” and “Scale” was proved to be of anhydrour form, which is called as soluble anhydrous gypsum, owing to the high boiling temperature in the concentrated brine solution. This soluble anhydous gypsum (CaSO4) changed easily to the crystal gypsum (CaSO4·2H2O), by treating with dilute NaCI solution, which is the dissolving solution to separate out NaCI, KCI, MgCI2, MgSO4, K2SO4, etc. above mentioned.
Crystalgpysum (CaSO4·H2O), thus obtained, was mixed homogeneously with calcined dolomite powder and slaked with proper amount water, and obtained special gypsum dolomite plaster (called by the present authors as “Gypster”), by the following equation. This special gypsum dolomitegypster (Gypster) was proved io be superior plastering material, x (CaSO4·2H2O)+(1-x)(CaO+ MgO)+y H2OxCaSO4·1/2H2O+(1-x)[Ca(OH)2+Mg(OH)2] by various testing methods of various plasters.
This purified crystal gypsum or its cr ude raw material “Gomi” or “Scale” was mixed with raw dolomite in proper proportion and this mixture was calcined at about 900°C and then slaked with water of proper amount to special gypsum dolomite plaster. This poduct was also proved to be useful as plastering material of superior quality.
