Clay bricks shrinkage

Clays or shales that may be utilized ia the manufacture of bricks, tiles, and other heavy clay products exist ia every state ia the United States. (See Building materials, survey). Some blending of materials is often necessary to control shrinkage of the product, and the economics of manufacture are governed by the demands of fuel, labor, transportation costs, and the market. 

Clays composed of mixtures of clay minerals having from 20—50% of unsorted fine-grain nonclay materials are most satisfactory. Large amounts of iron, alkaHes, and alkaline earths, either in the clay minerals or as other constituents, cause too much shrinkage and greatiy reduce the vitrification range thus, a clay with a substantial amount of calcareous material is not desirable. Face bricks, which are of superior quaHty, are made from similar materials but it is even more desirable to avoid these detrimental components (see Building materials, survey). 

Form-sand, m. molding sand, -schwindung, /. shrinking, shrinkage, -stahl, m. structural steel profile steel, -stein, m. shaped brick (Lead) pipe stone, -stiiek, n. shaped part, -ton, m. molding clay. 

There is another variety of silica bricks called semi-silica bricks. The raw materials for these bricks are low-grade ganisters or artificial sand/clay mixtures. The properties are in between those of silica and firebricks. They are inexpensive with low after-shrinkage—an advantage over firebricks. Semi-silica bricks have better spalling resistance than silica bricks. Once the surface is glazed, they are not attacked by slag. They exist in a metastable state. Their structure can be visualized as a matrix of firebrick in which silica particles are embedded. 

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