GB588524A - An improved method of producing cellular concrete and the product thereby produced - Google Patents

Abstract

Cellular concrete is prepared by adding to the cement mix a foam which has been treated so that any chemical therein normally reactive to the ingredients of the cement mix has been rendered substantially inactive, so that the properties of the concrete are not affected. An ordinary concrete mix is prepared with sufficient water to produce a friable mass without rendering it flowable. A resin soap is prepared by boiling rosin with an aqueous solution of sodium or potassium hydroxide; alternatively, the resin soap may be partially or wholly replaced by a soluble oleate, palmitate, or stearate. To produce a firmer foam with smaller bubbles, there is added a mucilage prepared by soaking alkali-soluble casein in cold water and adding ammonia and stirring, about 3 per cent. of the weight of the casein of sodium penta-chlorophenate being added as a preservative if necessary. A solution in hot water of the soap or soap-caseinate mixture is prepared, the concentration varying from 0.5-20 per cent. and is beaten to produce a foam of the desired consistency and is then treated, with gentle agitation, with an agent which forms water-insoluble bubble pellicles and renders inactive towards the cement-mix ingredients any chemicals in the foam. Any soluble metal salts capable of replacing the basic constituents of the soap or caseinate compound may be employed, e.g., chromium salts, iron sulphate, lime water, or, preferably, aluminium sulphate or calcium chloride. Solutions of up to 10 per cent. concentration may be used. To increase the water-repellent properties, foam containing a higher percentage of soap, or ammonium, calcium, or aluminium stearate may be added. The foam is then allowed to drain; if necessary, it may first be sprayed or washed with warm water to remove any excess of the reaction products. The liquid which drains off may be pumped back over the foam or applied to another batch. Sufficient foam is added to the cement mix to produce the desired volume increase, e.g., from 2 to 6 times the original and the incorporation is effected slowly at first to prevent breaking-down of the bubbles, and, when they have become coated, more rapidly. Hardening and quick-setting agents such as sodium or potassium silicates may be added to the mix, but preferably the set concrete is treated with a solution of the silicate, to which colouring matter may be added, as by spraying, brushing, or immersion. To insure rapid impregnation, the concrete is immersed in the silicate solution in a chamber to which a vacuum is applied. The concrete should then be washed with water to remove any caustic soda produced by the reaction or residual sodium silicate.