Specification Of Clay Bricks

To specify a particular brick it is necessary to define certain key criteria, which relate to form, durability and appearance. The British Standard BS 3921: 1985 gives a performance specification based on size, frost resistance, soluble-salt content, compressive strength and visual appearance. The European Standard BS EN 771-1: 2003 requires an extensive minimum description for masonry units including, the European Standard number and date (e.g. BS EN 771-1: 2003), the type of unit (e.g. high density -HD), dimensions and tolerances from mean value, configuration (e.g. a solid or frogged brick), com-pressive strength and freeze/thaw resistance. Also, depending upon the particular end use, additional description may be required. This may, as appropriate, include dry density, dimensional tolerance range, water absorption, thermal properties, active soluble salts content, moisture movement, reaction to fire and vapour permeability.

Within the building industry the classification usually also includes some traditional descriptions:

• place of origin and particular name (e.g. Staffordshire smooth blue);

• clay composition (e.g. Gault, Weald or Lower Oxford Clay, Etruria Marl, Keuper Marl [Mercian Mudstones] or shale);

• variety - typical use (e.g. Class A engineering, common or facing);

• type - form and manufacturing process (e.g. solid, frogged, wire cut);

• appearance - colour and surface texture (e.g. coral red rustic).

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