GB374455A - Improvements in or relating to plaster and cement mixes and to methods of applying the same - Google Patents

Abstract

A plaster-cement mix which sets with a glossy surface consists of 5-95 per cent hydrated lime, or portland, white or aluminous cement with 95-5 per cent plaster of the accelerated anhydrite type with or without fillers such as sand or pigments. If applied to absorbent backings, the backing is preferably first rendered non-absorbent, e.g. by spraying with water or applying an aqueous bitumen emulsion. Hygroscopic agents such as calcium chloride or glycerol may also be added to the wet mix. When spraying, the mixture is preferably ground to pass through a 200 mesh sieve or may contain about 50 per cent of a relatively coarse filler such as sand. In an example 90 parts of ground anhydrite (catalysed with 1 per cent of potassium sulphate) and 10 parts of white cement and, if desired, pigment, is gauged with 35 per cent of water and sprayed on a cement-sand coating previously applied to a brick wall, which may be pretreated with a thin film of aqueous bitumen emulsion. In another example a mix is poured or sprayed into porous tile moulds the base of which is kept moist by standing in 1/8 in. of water. The moulds in this case may be made of the same material as the mixture which is sprayed into them. Specifications 236,695, 262,224, 317,672, [all in Class 22, Cements &c.], and 374,440 are referred to.