GB632164A - Method for the manufacture of aluminous cements, with special reference to white aluminous cement - Google Patents

Abstract

Aluminous cements are prepared from raw materials containing aluminium such as clay, shale, ashes, metallurgical slags and bauxites by firing with lime or limestone to produce a soluble calcium aluminate which is leached out with water or a weak solution of a salt, preferably an alkaline salt such as sodium carbonate, separating the solution from the insoluble residue and precipitating the aluminium, by injection of carbon dioxide or other methods, as a mixture of hydrated alumina and calcium carbonate or of hydrated alumina, lime and calcium carbonate, or as hydrated calcium aluminate; to this precipitate are added materials such as lime and aluminium silicate to bring the composition to that required for the final cement, and the resulting mixture burned to give a product which after grinding gives the desired cement. Particulars are given of the relationship between the quantities of lime required for the initial firing and the composition of the raw material. White aluminous cement may be prepared by this process from aluminous raw material free of iron, particularly bauxite. The residue after leaching out the calcium aluminate may be utilised to manufacture cements of the Portland cement type by making suitable additions to get the desired composition, and burning in a normal cement kiln.