GB599736A - Improvements in or relating to the production of vesicular moulded articles from burnt clays or shales - Google Patents

Abstract

Vesicular products are obtained by burning chemically untreated argillaceous material, such as the shale obtained from the layers above coal seams, at least the final heating stage or a substantial proportion thereof being carried out while the material is confined in a mould. The whole heating process may be carried out while the material is in a mould, or the material may be first heated to just below the temperature at which vesiculation and expansion would occur and then filled into the mould and heated therein to expand it. The material may be ground and mixed with water to form a paste, may be rolled, pressed or extruded on its way to the mould in order to compact it, and may be compacted in the mould. The mould may be vibrated during filling and during the final heating stage. The final heating may be effected in an oxidizing atmosphere. A flux such as iron oxide, a siliceous material such as sand or powdered or fibrous glass, and a fibrous fireproof material such as asbestos may be added to the hot material prior to the vesiculation thereof. The mould walls may be lubricated with graphite to prevent sticking of the article thereto, or a mould wall or walls may be allowed to stick to the article to constitute part or all of the skin thereof. The mould walls may be of burnt brick-clay.