| 摘要 |
<p>A particulate calcium sulfate hemihydrate-rich composition is prepared by selecting large lumps of mined gypsum, grinding the same so at least 50% by weight passes a 325 mesh (0.045 mm.) sieve, calcining the material at atmospheric pressure to a normal consistency not greater than about 54, and regrinding the particulate material to a particle size distribution in which at least about 75% by weight passes a 325 mesh (0.045 mm.) sieve, the latter material exhibiting a normal consistency of not greater than about 53. The resulting material may be mixed with portland cement, a defoaming agent and other materials as de sired, and the mixture may then be combined with sand and water and violently agitated to provide a pumpable, freely pourable slurry which, when poured upon a subfloor, hardens in a layer to provide a strong, crack-resistent floor underlayment.</p> |
