MECHANOCHEMICAL CAPILLARY REACTIONS IN PARTLY DEHYDRATED GYPSUM AND ALUMINUM HYDROXIDE INTERGROUND POWDER MIXTURES

Authors activate gypsum and alumina (or gypsum-hemihydrate + alumina) mixtures by intensive grinding in a water-cooled planetary mill and me asure water vapour adsorption, heat of solution, phase composition (by XRD) and activation energy of eliminated water (by thermal methods) o f activated and non-activated samples. Thermal treatment of mechanical ly activated samples results in a much more intensive formation of cry stalline products, thus e.g. the amount of calcium sulfoaluminate afte r a 2 hr/1200 degrees C heat treatment of the gypsum + Al(OH)(3) sampl e is much higher in activated samples. Based on these model experiment s, authors conclude that gels are formed during mechanical activation, due to chemisorption and mechanochemical capillary reactions, which, in turn, act as crystallization nuclei, greatly affecting thermal reac tions. Copyright (C) 1996 Elsevier Science Ltd