Two kinds of common dolomite plasters obtained from the market and one of gypsum plaster were mixed in several proportions, and these mixed special gypsum-dolomite plasters were tested on their various properties, i.e., (a) bending and compressive strengths, (b) shrinkage cracks, (c) hardness, (d) fineness, etc., which results were proved to be clearly superior than those of common simple dolomite plaster.
Nextly, samples of special mixed gypsum-dolomite plaster were obtained by adding dilute sulphuric acid solution to calcined dolomite powder. By this reaction of dilute sulphuric acid to calcined dolomite, the common dolomite plaster was obtained on the one side, and gypsum crystal was obtained simultaneously on the other side, which changed to hemi-hydrated gypsum plaster by the slaking temperature of calcined dolomite with dilute sulphuric acid solution above mentioned.
These special mixed gypsum-dolomite plasters were proved to be of superior quality by the comparative testings of common dolomite plaster. These studies are now being continued to prepare these special mixed gypsum-dolomite plasters from several dolomite samples obtained and collected from various places, i.e., Kuzuu, Nogami and Nabeyama in Tochigi Prefecture, Ibuki in Gifu Prefecture, Irino in Okayama Prefecture, etc., which results will be reported in the next papers.
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