Learn : Bricks,Classification,Characteristics and its uses. (i)Sun-dried or Kacha bricks,(ii)Burns or Pucca bricks.(a)First class bricks (b)Second class bricks(c)Third class or pilla bricks, (d)Overburnt or Jhama bricks,Classification as per ISI. bricks as per ISI : 1077-1976,TABLE : Classes of Common Burnt Clay Bricks
BRICKS
Bricks are blocks of tampered clay moulded to suitable shapes and sizes while it is still in plastic condition, dried in the sun and burnt, if desired so as to make them more strong, hard and durable.
Common building brick is not only one of the oldest but also the most extensively used material of construction. Popularity of bricks as a material of construction is because of their local and cheap availability, strength, durability, reliability and insulating property against heat and sound.
CLASSIFICATION
Bricks are broadly classified into two categories.
(1) Sun-dried bricks or kacha bricks or unburnt bricks, and
(2) Burnt bricks or pucca bricks.
While burnt bricks or pucca bricks are further classified as :
(a) First class bricks,
(b) Second class bricks,
(c) Third class bricks, and
(d) Overburnt bricks or Jhama bricks.
Characteristics and uses.
Below are discussed the characteristics and uses of each one of them:
(i) Sun-dried or Kacha bricks.
These bricks after moulding have been dried in the sun, and are used in the construction of temporary and cheap structures. These types of bricks should not be used at places exposed to heavy rains.
(ii) Burns or Pucca bricks.
There are four types of bricks.
(a) First class bricks
Characteristics.
(i) These are sound well burnt bricks of a uniform colour.
(ii) All the faces are uniform and smooth. All the edges are sharp.
(iii) These are free from cracks or flaws.
(iv) A broken surface shows a uniform compact texture.
(v) Scratch with figner nails leaves no mark.
(vi) These do not absorb more than 15% of their weight of water when kept immersed for 24 hours.
(vii) Two first class bricks when struck with each other give a sharp metallic ringing sound.
(viii) These are free from nodules of free lime.
(ix) These may have only slight presence of efflorescence.
Uses.
(i) Used for all sound work of a permanent character.
(ii) Used in the face work of structure not to be plastered but only pointed.
(iii) Used in flooring and in reinforced brickwork.
(b) Second class bricks
Characteristics.
These are as hard and well burnt bricks as the first class bricks but may be somewhat irregular in shape or size and may have a slightly rough surface. Other qualities are the same as those of first class bricks.
Uses.
(i) Used in unimportant situations or at places where the masonry is to be plastered.
(ii) Used as brick ballast in R.C.C. work and in Lime Concrete.
(c) Third class or pilla bricks
Characteristics.
(i) These are a little underburnt bricks.
(ii) These are soft.
(iii) These have lighter colour.
(iv) These emit a dull sound when struck against each other.
(d) Overburnt or Jhama bricks
Characteristics.
These are overburnt bricks that being near the fire in the kiln get fused and loose their shape.
Uses.
(i) Used for constructing inferior structures.
(ii) Used in the foundations of structures.
(iii) Used as aggregate for concrete.
(iv) Used as road metal.
Classification as per ISI : 1077-1976
common burnt clay bricks are classified on the basis of their average compressive strength as shwon in Table
Each class of bricks is further subdivided into two sub-classes A and B based on tolerances and shapes e.g. brick of classification 100 is further sub-classified as 100A and 100B and so on. Bricks of sub-class A shall have smooth faces, sharp edges and corners and uniformity in colour whereas bricks of sub-class B may be slightly distortec or may have slightly rounded edges subject to the condition that these distortions do not cause any difficulty in laying of uniform courses.
TABLE : Classes of Common Burnt Clay Bricks
| Class designation | Average compressive strength | |
| Not less than kg/cm3 | Less than kg/cm3 | |
| 350 | 350 | 400 |
| 300 | 300 | 350 |
| 250 | 250 | 300 |
| 200 | 200 | 250 |
| 175 | 175 | 200 |
| 150 | 150 | 175 |
| 125 | 125 | 150 |
| 100 | 100 | 125 |
| 75 | 75 | 100 |
| 50 | 50 | 75 |
| 35 | 35 | 50 |