| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which enables utilization of gypsum in a gypsum plaster board waste material, as a dihydrate gypsum source in the production of portland cement, in a >=25 wt.% substitution ratio of the gypsum in the waste material for dihydrate gypsum conventionally used in the cement, such as flue gas desulfurization gypsum, on the basis of the conventionally required amount of the dihydrate gypsum, and therefore solution of such a problem that conventionally, when gypsum in a gypsum plaster board waste material is utilized as a dihydrate gypsum source in the production of portland cement, a reduction in mortar strength (JIS) is recognized and 25% substitution of gypsum in the waste material for dihydrate gypsum in the cement is considered as the upper limit of utilization of gypsum in the gypsum plaster board waste material. SOLUTION: This method comprises preparing dihydrate gypsum containing >=25 wt.% of gypsum separated from a gypsum plaster board waste material so that the resulting gypsum has a <=2.5 wt.% paper content, measuring the respective amounts of cement clinker and this dihydrate gypsum so that the resulting mixture of them has a 1.6-3.0 wt.% SO3 content, and mixing the measured amounts of the cement clinker and dihydrate gypsum and grinding the mixture, under such conditions that the cement product temperature at the outlet of a grinder used, is 100-180 deg.C.
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