GB1339275A - Foamed mastic composition and method of preparing same - Google Patents

Abstract

1339275 Foamed magnesia cement BLOUNT BROS CORP 2 Dec 1970 57219/70 Heading C3N [Also in Division E1] A method for the preparation and application of a foamed magnesia cement comprises: (a) preforming an aqueous foam by aerating a solution of foaming agent in water; (b) mixing magnesium oxide, magnesium sulphate and/or magnesium chloride in an aqueous slurry; (c) adding the preformed foam to said slurry to provide a pumpable and sprayable foamed cement; (d) pumping the thus foamed cement to the point of application; (e) spraying the foamed cement upon a suitable substrate to form a layer thereon; and (f) allowing said sprayed layer to dry and become converted into a foamed magnesia cement. The foaming agent, which may be a hydrolyzated protein surfactant, may be used in 4 to 15% by weight solution in water, suitably aerated in a foam generator with air under pressure between 50 and 150 p.s.i.g., and the preformed foam added to the slurry to comprise generally between 0À1 and 5% by dry weight of foaming agent to dry weight of the cement. A filler may be used in the aqueous slurry, especially an inorganic filler including a fibrous constituent, or a hydrous filler. Asbestos, mica, vermiculite, shale, granulated shell, and calcined calcium sulphate are specified. Fibrous fillers enhance the cohesion of the cement; the specified fillers either retain water in their natural mineral condition or absorb water from the slurry, so that when the cement is subjected to high temperatures, e.g. during a fire, water is evolved and heat absorbed, enhancing the fire retardant properties of the cement. Suitably, the slurry contains 10 to 90% by weight of filler material based on the total weight of the dry solids and 20 to 400% by weight of water based on the total weight of the dry solids. A preferred slurry consists of 8 to 18 parts by weight of magnesia, 10 to 16 parts by weight of magnesium salt, 82 to 66 parts by weight of fibrous filler material, and 166 to 234 parts by weight of water. The foamed cement so made suitably has a wet density of 8 to 30 pounds per cubic foot, contains 20 to 400% by weight of water based on the total weight of the dry solids, has a pH of 6 to 9, and may be sprayed from an applicator at 40 to 125 p.s.i.g. A porous fire retardant and sound insulating layer may be formed by spraying the cement on to a metal substrate, followed by air-drying, and structural building elements in general may be sprayed with the cement.