| 摘要 |
<p>1466772 Casting and curing heated cementitious mix J N LOWE and B C GREBE 23 May 1975 [7 Aug 1974] 34831/74 Heading B5A [Also in Division C1] An article such as a building panel is cast from a mixture including calcined gypsum, cement and water with at least one of these components being heated before mixing so that the mixture has an initial temperature of from (70-130)‹ F., the article is removed from the mould, belt or other supporting device when its component mixture has set sufficiently to be self-supporting, and loss of heat and moisture from the article is then prevented or restricted for at least two hours. During this time, the temperature of the article rises to within the range (90-180)‹ F., and the article is kept in an atmosphere of 100% relative humidity. As described, some of the required water is passed through a heater 4 (Fig. 2(a)) into a mixer 1, and the dry components added, followed by the remaining heated water and all additives. The mixture is cast by a flexible pipe 6 into a horizontal preheated, PVC or plasticscoated timber mould 8, screeded, the supporting table 7 vibrated, and a heat insulating cover added. The calcined gypsum content sets and the temperature of the article starts to rise, whereafter the mould 8 is tilted to a vertical position and the self-supporting article is removed and held vertically on the floor by a crane engaging an eye 22 of embedded reinforcements 21. The mould 8 is returned to the horizontal for casting of a further article, while one face of the removed article is sprayed with liquid polyurethane. The crane then suspends the article in a heat and moisture insulated chamber 10 (Fig. 2(c)) having walls comprising polyethylene coated foamed polystyrene members 11, 15, which prevent moisture escape so that relative humidity in the chamber rises to 100%, while heat loss is minimised. When the cement content of the article has cured, a fan blows air over the article (with the chamber lid 15 removed) and suction is applied for drying. The chamber is then filled with CO 2 , and finally the unsprayed panel surface is coated with an acrylic resin emulsion. Materials.-(90-10)% of calcined gypsum, (10-90)% of Portland cement (sulphateresisting or rapid hardening), Pozzolana cement, sisal fibres, prestressing cables, foaming agent, a fluidizer (e.g. Gum Arabic), sodium citrate, potassium sulphate, acrylic resin emulsion, water, aggregate. The mould 8 can be contoured to simulate brickwork, and pigments or aggregate applied to its surface. Randomly mixed two-colour mixtures can be used.</p> |
