Classification Of Bricks
Classification of bricks is done on various bases which are as follows:-
Based on Field Practice
First Class Bricks
- They are thoroughly burnt.
- They are of deep red, cherry or copper colour.
- They should have a uniform texture.
- They should be free from flaws, cracks and stones.
- Their surface should be smooth and rectangular.
- They should have parallel, sharp and straight edges and square corners.
- The fractured surface of the brick should not show lumps of lime.
- When the scratch is made by a fingernail, no impression should be left on the brick.
- When two first-class bricks are struck against each other, a metallic or ringing sound should be heard.
- When immersed in cold water for 24 hours, water absorption should be 12-15 % of the brick's dry weight.
- The crushing strength should not be less than 10 N/mm2. This limit varies with different Government organizations around the country.
- Uses:- In pointing, exposed face work in masonry structures, flooring and reinforced brickwork.
Second Class Bricks
- They are supposed to have the characteristics as that of first-class bricks(mentioned above)except for these three characteristics which are as follows:-
- They can have small cracks and distortion.
- They can have a higher water absorption of about 16-20% of the brick's dry weight.
- Their crushing strength should not be less than 7 N/mm2.
- Uses:- In all important or unimportant masonry works and centring of reinforced brick and reinforced cement concrete(RCC) structures.
Third Class Bricks
- They are underburnt.
- They are soft and light-coloured.
- When two third-class bricks are struck against each other, a dull sound is heard.
- They have water absorption of about 25 % of the brick's dry weight.
- Uses:- In building temporary structures.
Fourth Class Bricks
- They are overburnt.
- They are badly distorted in shape and size.
- They are brittle in nature.
- Uses:- Their ballast is used in foundation and floors in lime concrete and road metal.
Based on Use
- It is a general multi-purpose unit manufactured economically.
- It is manufactured without special reference to the appearance.
- These bricks may vary greatly in strength and durability.
- Uses:- In filling, backing and in walls where appearance is of no importance.
- It has a good appearance either of colour or texture or both.
- These bricks are durable under severe exposure.
- Uses:- In fronts of building walls where appearance is of importance.
- These bricks are strong, impermeable, smooth, table moulded and hard.
- These bricks conform to defined limits of absorption and strength.
- Uses:- In all load-bearing structures.
Based on Finish
- It has a textured surface manufactured by sprinkling sand on the inner surfaces of the mould.
- It has a mechanically textured finish which varies in the pattern.
Based on Manufacture
- These bricks are hand moulded.
- Machine-made bricks are further divided into three types of bricks:-
- Wire-cut Bricks:- Bricks cut from clay extruded in a column and cut off into brick sizes by wires.
- Pressed Bricks:- Bricks are manufactured from plastic or semi-dry clay and pressed into moulds.
- Moulded Bricks:-Bricks are moulded by machines imitating hand mixing.
Based on Burning
- These are underburnt bricks obtained from the outer portion of the kiln.
- These are well-burnt bricks obtained from the central portion of the kiln.
- These are overburnt bricks obtained from the inner portion of the kiln.
Based on Types
- These bricks can have small holes which don't exceed 25 % of the volume of the brick.
- These bricks can have frogs which don't exceed 20 % of the volume of the brick.
- These bricks can have small holes which don't exceed 20 % of the volume of the brick.
- These bricks can have holes(which need not be small) which exceed 25 % of the volume of the brick.
- These bricks have holes(closed at one end) which exceed 20 % of the volume.
Based On Strength
- The Bureau of Indian Standards has classified the bricks on the basis of compressive strength which is as follows:-
|Image From Book By S.K. Duggal|
Each class of bricks mentioned above is further divided into subclasses A and B based on tolerances and shape.