2000 Volume 7 Issue 288 Pages 460-466
The present work was made to investigate preparation of gypsum block from waste gypsum board specimen. The lining paper was perfectly separated from gypsum hemihydrate specimen which was dehydrated to formation ratio of above 45% as gypsum hemihydrate by heating the waste gypsum specimen (70 × 40 × 12.5 mm) at 200°C. The gypsum block was prepared by pilling up some gypum hemihydrate specimens which was sprayed with water or saturated solution of gypsum dihydrate. The compressive strength of hardened gypsum specimen was increased under conditions of formation ratio of 55% as gypsum hemihydrate, spraying with saturated solution of gypsum dihydrate and amount of hydration water (H2O/CaSO4·1/2H2O molar ratio) of about 3.0. The compressive strength of gypsum block prepared by hydrating after pilling up seven pieces of the gypsum hemihydrate specimen was 3.1 MPa by exerting load of 0.18 kg·cm-2. This finding was the same compared with that of stacked seven pieces of the waste gypsum specimen which was mechanically removed lining paper.
