Calcium aluminate cements
June 3, 2009 by blogtopia
Filed under Definitions
Calcium aluminate cements are cements consisting predominantly of hydraulic calcium aluminates. Alternative names are "aluminous cement", "high-alumina cement" and "ciment fondu". They are used in a number of small-scale, specialist applications.
The method of making cement from limestone and low-silica bauxite was patented in France in 1908 by Bied of the Pavin de Lafarge Company. The initial development was as a result of the search for a cement offering sulfate resistance. The cement was called "Ciment Fondu". Subsequently, its other special properties were discovered, and these guaranteed its future in niche applications.
The main active constituent of calcium aluminate cements is monocalcium aluminate (CaAl2O4). It usually contains other calcium aluminates as well as a number of less reactive phases deriving from impurities in the raw materials. Rather a wide range of compositions is encountered, depending on the application and the purity of aluminium source used.
The cement is made by fusing together a mixture of a calcium-bearing material (normally limestone) and an aluminium-bearing material (normally bauxite for general purposes, or refined alumina for white and refractory cements). The liquified mixture cools to a basalt-like clinker which is ground alone to produce the finished product. Because complete melting usually takes place, raw materials in lump-form can be used.
Source: Wikipedia
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