| 摘要 |
<p>Prodn. of a homogeneous mixt. of hemihydrate and gypsum in the form of compacted elements of fine particles of hemihydrate is described in which the hemihydrate is brought to a certain free water content, the mixt. is compacted into an agglomeralut without addition of binders, and the pieces are ground. Specifically, the hemihydrate produced as filter cake with 10-30 wt.% free water, is dried to the "state of production" (sic) and then made alkaline by addn. of 1-4 wt.% CaO to absorb water of crystallisation, 2.0-4.6 wt.% free water is then added and the mixt. is stored for at least 5 h. for this to react forming some gypsum. The mixt is granulated to 0-16 mm and the mixt. adjusted to the following particle size compsn.:- 10-40% 0.2 mm; 20-45% 0.2-1 mm; 15-40% 1-3.15 mm, 5-30% 3.15-16 mm so as to obtain a granular homogeneous mixt. formed of 68-90% hemihydrate and 5-25% gypsum, with an initial setting time of 12 min. Used in coal mining, esp. for construction of barrages for cutting faces and pit props etc. to be formed in situ., and for filling and consolidation of spent workings. The mixt. produced will set on addition of water; it can be transported dry, pneumatically, without forming dusts. It has an improved strength on hardening while having a short setting time.</p> |
