Apr 01, 1996 Abstract. Dry grinding of gypsum (CaSO 4 2H 2 O) with hydrated minerals, such as talc, kaolinite or montmorillonite as an additive was conducted in a planetary ball mill in order to investigate the transformation of gypsum into its hemihydrate form ( CaSO 4 1 2 H 2 O ). This transformation of gypsum is accelarated by grinding and by the presence of hydrated minerals
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