抄録
Two ksinds of dolomite plasters,(a) three samples of cover coating dolomite plasters and (b) two samples of under coating dolomite plasters were tested without or with addition of 3, 5, 10 or 15% of gypsum plaster of calcined hemihydrate (CaSO4·1/2H2O) on their hardening shrinkage, strength, and shrinkage cracks. The addition of 10-15% of calcined gypsum plaster was determined to be decidedly effective to improve the properties of calcined dolomite plasters of both under and cover coating uses. The shrinkage and its cracks of simple dolomite plaster were completely diminished by the addition of 10-15% of calcined gypsum plaster. The degrees of whiteness of these plasters were measured and compared with the standard whiteness and determined that these simple plasters of gypsum plaster, cover coating dolomtie plaster and gypsum-dolomite plaster were superior to the stadard whiteness, but the under coating dolomite plaster was inferior to the standard whiteness. The surface hardness of ha rdened plasters of these simple dolomite plaster and gypsum-dolomite plaster is now being further studied from several points.
