CHARACTERISTICS OF GOOD BRICKS

CHARACTERISTICS OF GOOD BRICKS

The following are the characteristics of a standard brick:

§  Brick should be uniform in color, size and shape.

§  They should be sound and compact.

§  They should be free from cracks and other flaws such as a bubble, stone nodules etc.

§  They should not absorb more than 1/5 of their own weight of water when immerged in water for 24 hours.

§  The compressive strength of bricks should be in the range of 5000 to 8000 psi.

§  The percentage of soluble salts (sulphates of ca, Mg, Na, and K) should not exceed 2.5% in burnt bricks.

§  They should be neither over burnt nor under burnt.

§  They weight should generally 6 lbs. per brick and the weight per cu.ft. Should not be less than 125 lbs.

§  They should have lower thermal conductivity.

§  They should be non-inflammable and in combustible.

§  Brick should not change in volume when wetted.(aziz,1995).

2.4 STANDARD SIZES OF BRICK

In Bangladesh according to P.W.D. specification, each brick should measure 9.5"x4.50"x2.75".this is the standard size of bricks in our country. There are others sizes brick also. But this size is most economical, because  when bricks are put in any construction with mortar the size becomes 10"x5"x3" (approximately) the size of walls which are constructed by bricks in our country are 3", 5", 10", 15", 20",25" and 30" so his size of bricks can be used safely without any breakage, hence, this standard size, is most in engineering, constructions in our 9.5"x4.5"x2.75" country (aziz,1995).

2.5 CLASSIFICATION OF THE BRICKS

2.5.1 Classification of bricks in Bangladesh

According to the PWD well burn brick classified into the following categories:

§  First class brick.

§  Second class brick.

§  Third class brick.

§  Picked jhama brick.

§  Jhama brick.

§  Brick bats.

§  Jhama bats.(aziz,1995)

2.5.1.1 First class brick

These first class bricks are table molded 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.

2.5.1.2 Second class brick

The second class bricks are ground molded 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.

2.5.1.3 Third class brick

These bricks are ground molded 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.

2.5.2 Uses of Bricks

1. As a Structural Unit

Since the clay bricks or burnt bricks are strong, hard, durable, resistive to abrasion and fire, therefore, they are used as a structural material in different structures

§  Buildings.

§  Bridges.

§  Foundations.

§  Arches

§  Pavement (Footpath, Streets).

2. As an Aesthetic Unit/Surface Finish

Bricks can be used in different colors, sizes and orientations to get different surface designs. As an aesthetic material bricks can be used-

§  In Pavements.

§  As Facing Brick.

§  For Architectural Purposes.