Classification of Bricks :
Conventionally , the Bricks are classified in the following two types :
- Sun dried or Katcha Bricks :
- Burnt or Pucca bricks :
Sun Dried or Katcha bricks :
The bricks dried only in the sun after their moulding are called sun dried or Katcha Bricks.These should not be used at places exposed to heavy rains.
Uses : These are suitable for constructing temporary houses,enclosures etc. in rural area.
Burnt or Pucca Bricks :
These brick burnt in a clamp or klin,after moulding and drying are called burnt or pucca bricks.
These are hard,strong and durable.
Uses : These are generally in permanent works.
These further classified into the following four types :
FIRST CLASS BRICKS :
CHARACTERISTICS :
(i) Well burnt having even surface , perfectly rectangular shape & free from saline deposits.
(ii) When two bricks are struck against each other a ringing- sound is produced.
(iii) Its compressive strength shall not be less than 140kg/cm2 and its absorption after 24 hours, immersion shall not exceed 20 percent.
(iv) It should show a uniform appearance,colour , texture and structure when seen on fracturing.
(v) They shall be clean,smooth & free from cracks,chips,grits,holes , nodules of lime or kankar etc.
(vi) They shall not show any sign of efforescence on surface when dried in the shade.
(vii) They shall not absorb water more than 20% by weight after 24 hours immersion in cold water.
(viii) They shall have a minimum crushing strength of 105kg/sq.cm.
Uses : Every kind of masonry work, flooring etc. Where strength and durability is desired. They are also used for face work,reinforced brick work and as ballast for base concrete work in floors.
SECOND CLASS BRICKS :
CHARACTERISTICS :
- Well burnt, even slight over burning is accepted.
- Metallic-ringing sound is also a must in this case as well.
- In shape, rectangular, but slight irregularity is permitted. Surface may be slightly uneven.
- Compressive strength shall not be less than 70kg/cm2 and absorption value between 20-22 percent.
- Slight difference in structure on fractured surface is admissible.
- They have fine , compact ,uniform texture.
- They may have slightly chips , flaws or surface cracks but shall be free from lime & kankar nodules.
- They are not so hard & strong.
- They shall have a minimum crushing strength of 70 kg/sq.cm.
- They shall not absorb water more than 22% by weight after 24 hours immersion in cold water.
- They shall not show any sign of efflorescence on surface either in wet or in dry state.
Uses : These used in unimportant situations where bricks are hidden from front views as in the case of interior walls. They are never used in reinforcement brick work or face works of building.
THIRD CLASS BRICKS :
CHARACTERISTICS :
- Poorly and unevenly burnt, that is, may be over burnt or under burnt.
- On striking a dull thud (rather than metallic sound) is produce.
- Appearance, shape and size are also non- uniform and irregular.
- Compressive strength lies between 35- 70 kg/cm2 and absorption between 22-25 percent.
- Yellowish in colour & may be distorted and have round edges.
- They are soft & weak in strength.
- They shall not absorb water more than 25% by weight after 24 hours immersion in cold water.
Uses : These used in inferior and temporary buildings & in place not subjected to heavy rains . They are sometimes used for scaffolding and centring in the construction of building.
JHAMA OR FOURTH CLASS / OVER BURNT BRICKS :
CHARACTERISTICS :
- Irregular in shape and dark in colour, which is due to over burning.
- Quite strong in compressive strength, generally above 150kg/cm2 and low in porosity and absorption.
- They shall be over burnt , vitrified & distorted bricks.
- They shall be dark in colour.
- They shall be irregular in shape & size and may be available in the form of lumps.
- They shall be hard & strong.
- Produce metallic sound when struck with one another.
Uses : They are used as aggregates for making base for concrete to be used in foundations, floors etc. and as road metal for soling coats.
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