GB381155A - Improvements in or relating to the manufacture of building blocks and other pre-formed moulded articles - Google Patents

Abstract

381,155. Porous plaster compositions; moulds ; composite blocks. LEFEBURE, V., Willett Building, Sloane Square, and IMPERIAL CHEMICAL INDUSTRIES, Ltd., Millbank, both in London. June 23, 1931, Nos. 18179/31 and 238/32. [Classes 22, 70, and 87 (ii).] A porous or cellular building block or other article is formed of a plaster consisting of mineral anhydrite which has been given a set by the incorporation of accelerators such as alkali metal salts, certain metal sulphates, or mixtures thereof, especially the accelerators of Specifications 236,695 and 317,672, [both in Class 22. Cements &c.]. Up to 20 per cent of plaster of Paris or other calcium sulphate plaster of hemi-hydrated type may also be included. Fillers or pigments may or may not be included. The porous or cellular structure may be obtained by the use of a gas-producing agent such as aluminium sulphate. In making the blocks a large sheet or block of the material may be moulded and guillotined while wet into blocks of the desired size, or cut with a saw when set ; or partitions (which may be faced with neat or decorated plaster) may be inserted in the mould before or after filling in the material ; or the plastic material may be applied in layers, each layer being allowed to expand but not to set before the next is applied ; or a block or sheet may be built up in a mould by continuous application of wet plastic and gas-producing agent ; or a layer of wet normal plaster may be sprayed or poured into a mould followed by a spray of a gas-producing agent, the process being repeated until the desired thickness has been attained-if necessary with pauses between successive layers. The mould shown in the Figure may be used, which comprises sides 2, 3 fixed on a truck 1 by wedges 4 fitting into hooks 5 fixed to the base and engaging recesses in the walls 2, 3. The inner faces of the walls are slotted to receive end walls 8, 9, and partitions 10. The whole is held together by clamping bars 6, 7. The block &c. may be faced with neat non-cellular plaster and/or with fibrous material (such as cellulose-pulp board) or fabric (such as canvas). The block &c. may also be coated with the glossy plaster of Specification 374,455, or waterproofed by an aqueous emulsion of bitumen with or without subsequent application of the glossy plaster. The block &c. may also be waterproofed by means of a soluble salt of a higher fatty acid as described in Specification 380,821. Specification 337,926, [Class 22, Cements &c.], also is referred to.