ESTIMATION OF GYPSUM HEMIHYDRATE CONTENT ON RECLAIMED GYPSUMS DERIVED FROM WASTE PLASTERBOARDS BY HEATING METHODS

In order to utilize reclaimed gypsums derived from waste plasterboards as ground improvement materials, thermal behaviors of reclaimed gypsums and reagent gypsums are investigated in this paper. Furthermore, simple heating method of judging quality of reclaimed gypsums was examined to determine gypsum hemihydrate content. As the results, it was found that gypsum dihydrate is changed into gypsum hemihydrate under thermal condition of 90°C and gypsum hemihydrate is changed into anhydrite under that of 120°C with heating of 24 hours. And determining by calculating gypsum hemihydrate content and gypsum dihydrate content with the decrease in mass under the thermal condition of 90°C from 70°C, effectiveness of the estimation of gypsum hemihydrate content by using heating method was shown. Therefore comparing gypsum hemihydrate content determined by both methods of the heating method and the density measuring method, both results were in substantial agreement.