A. Classification based on method of
manufacturing
Bricks can
broadly be categorized into two types as follows on the basis of how its
manufactured:
1.
Unburnt or sun-dried bricks
2.
Burnt bricks
1.
Unburnt
bricks or sun-dried bricks
Unburnt
bricks or sun-dried bricks are the types which are dried with the help of heat
received from sun after the process of moulding. These bricks can only be used
in the construction of temporary and cheap structures. Such bricks should not
be used at places exposed to heavy rains.
2.
Burnt
Bricks
Burnt bricks
are prepared by burning the brick-mould in the kiln inside the factory. These
are the most commonly used bricks for construction works. They can be further
classified into following four categories:
2.1. First class bricks
These bricks are table-moulded and of standard 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 superior work of permanent nature.
1.
Type
|
1.
Class 1
|
2.
Feature
|
2.
Table molded.
|
3.
Shape & Size
|
3.
Standard and uniform (rectangular).
|
4.
Surface & Edges
|
4.
Sharp, smooth, square and straight.
|
5.
Color
|
5.
Uniform red or brown.
|
6.
Maximum Water Absorbing
|
6.
15% of its self-weight when submerged in water for 24 hours.
|
7.
Crushing Strength
|
7.
105 kg/cm2
|
8.
Making Process
|
8.
Burnt in kilns.
|
9.
Use
|
9.
Permanent and superior work.
|
2.2. Second class brick
These bricks are ground-moulded and they are burnt in kilns. The
surface of these bricks is somewhat rough and shape is also slightly irregular.
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.
1.
Type
|
1.
Class 2
|
2.
Feature
|
2.
Table molded.
|
3.
Shape & Size
|
3.
Irregular
|
4.
Surface & Edges
|
4.
Rough, uneven faces, may consist of hairline cracks.
|
5.
Color
|
5.
Uniform color.
|
6.
Maximum Water Absorbing
|
6.
22% of its self-weight when submerged in water for 24 hours.
|
7.
Crushing Strength
|
7.
70 kg/cm2
|
8.
Making Process
|
8.
Burnt in kilns and sometimes may be slightly over burnt.
|
9.
Use
|
9.
Used in internal walls. (Plaster or coating is required.
|
2.3. Third class bricks
These bricks are ground-moulded and they are moulded in kilns.
These bricks are not hard and they have rough surfaces with irregular and
distorted edges. These bricks give dull sound when struck together. They are
used for unimportant and temporary structures and at places where rainfall is
not heavy.
1.
Type
|
1.
Class 3
|
2.
Feature
|
2.
Ground molded.
|
3.
Shape & Size
|
3.
Non-uniform
|
4.
Surface & Edges
|
4.
Irregular and distorted edges.
|
5.
Color
|
5.
Non-uniform and dark.
|
6.
Maximum Water Absorbing
|
6.
25% of its self-weight when submerged in water for 24 hours.
|
7.
Crushing Strength
|
7.
30 kg/cm2
|
8.
Making Process
|
8.
Burnt in kilns and may be overburnt or underburnt
|
9.
Use
|
9.
Used in temporary structures.
|
2.4. Fourth class bricks
These are over-burnt type of brick with irregular shape and dark
colour. These bricks are used as aggregate for concrete in foundations, floors,
roads, etc. because of the fact that the over-burnt bricks have a compact
structure and hence they are sometimes found to be stronger than even the first
class bricks.
B.
Classification based on shape
The ordinary
bricks are rectangular solids. But sometimes the bricks are given different
shapes to make them suitable for particular type of construction. Here we have
enlisted different types of bricks available with various shapes:
1. Bullnose brick
A brick moulded with a rounded
angle is termed as a bullnose. This type of brick is used for a rounded quoin.
A connection which is formed when a wall takes a turn is known as quoin. The
centre of the curved position is situated on the long centre-line of brick.
2. Channel bricks
These types
of bricks are moulded to the shape of a gutter or a channel and they are often
glazed. These bricks are used to function as drains.
3.
Coping
bricks
These bricks
are made to suit the thickness of walls on which coping is to be provided. Such
bricks take various forms such as chamfered, half round or saddle-back.
4. Cownose bricks
A brick
moulded with a double bullnose on end is known as a cownose.
5. Curved sector bricks
These bricks
are in the form of curved sector and they are used in the construction of
circular brick masonry pillar, brick chimneys, etc.
6. Hollow bricks
These are
also known as the cellular or cavity bricks. Such bricks have wall thickness of
about 20mm to 25mm. They are prepared from special homogeneous clay. They are
light in weight about one-third the weight of the ordinary brick of the same
size. These types of bricks can be laid almost about four times as fast as the
ordinary bricks and thus the use of such bricks leads to speedy construction.
They also reduce the transmission of heat, sound and damp. They are used in the
construction of partitioning.
7. Paving bricks
These bricks
are prepared from clay containing a higher percentage of iron. The excess iron
vitrifies the bricks at a low temperature. Such bricks resist better the
abrasive action of traffic. The paving bricks may be plain or chequered. These
bricks are extensively used for garden walks, street pavements, stable floors,
etc. These types of bricks also render the floor less slippery.
8. Perforated bricks
These bricks
contain cylindrical holes throughout their thickness. These bricks are light in
weight and they require less quantity of clay for their preparation. The drying
and burning of these bricks are also easy. If perforated bricks of large size
are used, it will result in the increase of output of mason. The perorated
bricks are used in the construction of panels for lightweight structures and
multi-storeyed framed structures. They may be circular, square rectangular or
any other regular shape in cross-section. The distance between the side of
brick and edge of perforation should not be less than 15mm. The distance
between the edges of successive perforations should preferably be not less than
10mm. The water absorption after immersion for 24 hours in water should not
exceed 15 percent by weight. The compressive strength of perforated bricks
should not be less than 7 N/mm2 on gross area.
9. Purpose-made bricks
In order to
achieve certain purpose, these types of bricks are made. The splay or cant
bricks are made for jambs of doors and windows. The arch bricks are made of
wedge shape to keep mortar joint of uniform thickness. The ornamental bricks
are prepared for corbels, cornices, etc. Similarly, engineering bricks are
prepared for constructions where high durability, compression strength and
adequate resistance to sudden shocks are required. These types of bricks are
usually more costly than the ordinary bricks. But they grant safe, clean and
quick construction. Hence, their cost is justified by their excellent
performance in situation for which they are purposely prepared.
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