| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a treating method which does not cause the change of color of obtained cements and the lowering of fluidity of concrete using the cements when gypsum board waste material is recycled as gypsum dihydrate for preparing cements such as portland cement. SOLUTION: The gypsum board waste material is deprived of paper, thereafter, is subjected to heating treatment at a temperature which is >= decomposition temperature of a surface active agent included in the gypsum board waste material and is <=400 deg.C, subsequently, is subjected to hydration treatment as need, thereby, is made to be gypsum dihydrate and, for example, the portland cement can be produced by mixing the gypsum dihydrate with cement clinker and crushing the same.</p> |
