Bricks are broadly classified into two broad categories as follows:
- Sun-dried bricks and
- Burnt bricks
Sun-dried bricks also called un-burnt or katcha bricks, and these are dried directly under the sun after the process of moulding. These bricks are of inferior quality and are used for the construction of temporary and cheap structures. Such bricks should not be used in areas exposed to heavy rains.
Burnt bricks are of superior quality, which are generally used for civil engineering constructions. These are discussed in depth below.
3.6.1 Quality Classification of Burnt Bricks
The classification of bricks under the following four categories on the basis of constituents, preparation and burning is called quality classification:
1. First-class Bricks
First-class bricks are table-moulded bricks and are burnt in kilns. These bricks should not have any defects like cracks, stones or lumps of clay. They should be of standard size and have uniform colour, sharp edges, even surfaces, correctly burnt and hard. These bricks are used for superior quality works and works of permanent nature.
2. Second-class Bricks
Second-class bricks are ground moulded and are burnt in kilns. In general, they have to satisfy the requirement – quality of first-class bricks. However, they may have a slightly irregular shape, rough uneven surfaces or may have slight cracks. These bricks are hard and are correctly burnt and used where the brick masonry is to be plastered.
3. Third-class Bricks
Third-class bricks are ground moulded and burnt in clamps. These bricks have irregular edges with less sharpness, uneven surfaces and are not hard enough. They give a dull sound when struck against each other. They are used for unimportant and temporary constructions.
4. Fourth-class Bricks
Fourth-class bricks are either over burnt or under burnt with irregular shapes, edges and surfaces. These are used as aggregates for concrete in road, floor and foundation construction.
3.6.2 Indian Standard Classification of Burnt Bricks
As per the Indian Standard (IS: 3102 – 1971), bricks are classified according to their strength as given in Table 3.1.
Table 3.1 Classification of bricks
Source: IS: 3102–1971.
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