| 摘要 |
<p>A method of making a cast article from a composition which contains a hydraulic binding agent comprising by weight from 90% to 10% calcined gypsum and from 10% to 90% Portland cement comprises mixing the composition with water to produce a fluid mixture, either the water or some at least of the components of the composition or both being heated so that the mixture has a temperature of from 70 DEG to 130 DEG F, and pouring the fluid mixture into a mould or other supporting device where the reaction of the calcined gypsum with the water causes the mixture to set and the heat of this reaction causes the temperature of the mixture to begin to rise. As soon as the mixture has set sufficiently to be self supporting, the set mixture, which forms the cast article, is removed from the mould or other supporting device and then the dissipation of both heat and moisture from the cast article is controlled so that the temperature of the article continues to rise to from 90 DEG to 180 DEG F. This temperature is maintained for a period of at least two hours to allow the moisture in the article to cure the cement. Preferably the dissipation of heat and moisture from the cast article is controlled by confining the cast article in a heat and moisture insulating jacket which maintains an atmosphere of 100% relative humidity around the article. After the temperature and moisture content has been maintained to cure the cement, the cast article is dried either by the application of a vacuum to a part at least of its surface or by causing air to flow over its surface while the article is still hot.</p> |
