Classification of Bricks
The classification of bricks is as follows:
(i) unburnt or sun-dried bricks; and
(ii) burnt bricks.
The unburnt or sun-dried bricks are those bricks which are dried with the help of heat that is received from sun after the process of moulding. The unburnt bricks can only be used in the construction of simple temporary and cheap structures. Unburnt bricks should not be used at places exposed to heavy rains.
The bricks used in construction works are burnt bricks and they are classified into the following four categories:
(1) First class bricks
(2) Second class bricks
(3) Third class bricks
(4) Fourth class bricks.
(1) First class bricks:
These first class bricks are table moulded and of uniform shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. They comply with all the qualities of good bricks. These bricks are used for important work of permanent nature.
(2) Second class bricks:
The second class bricks are ground moulded and they are burnt in kilns. The surface of the second class bricks is slightly rough and shape is also slightly regular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brickwork is to be provided with a coat of plaster.
(3) Third class bricks:
These bricks are ground-moulded and they are burnt in clamps. These bricks are not very hard and they have rough surfaces with irregular and blunt edges. These bricks give dull sound when they are struck together. They are used for unimportant works, temporary structures and at places where rainfall is not heavy.
(4) Fourth class bricks:
These are overburnt bricks with irregular shape and dark colour. These bricks are used as aggregate for concrete in foundations, brick floors, surkhi, roads, etc. because of the fact that the overburnt bricks have a compact structure and hence they are sometimes found to be stronger than even the first class bricks. It is thus seen that the above classification of bricks is based on the of manufacturing or preparing bricks.