Properties of Bricks
Following are the essential qualities of good bricks:
- Color
- Shape
- Texture
- Soundness
- Hardness
- Strength
- Water Absorption
- Efflorescence
- Thermal Conductivity
- Sound Isolation
- Fire Resistance
(ii) Shape: The face of the bricks should be flat. They should have sharp and true right angles.
(iii) Size: Bricks should be of standard size as prescribed by the code.
(iv) Texture: They should be fine, dense and uniform in texture. They should not have cracks, cavities, loose grit and unburned lime.
(v) Soundness: When struck with a hammer or any other brick, it should produce a metallic sound.
(vi) Hardness: Scratching fingers should not affect the brick.
(vii) Strength: The crushing capacity of brick should not be less than 3.5 N/mm2. A field test for strength is that when dropped by 1.0 mm from a height of 0.9 m on a hard ground, the brick should not break into pieces.
(viii) Water Absorption: The water absorption by weight should not exceed 20% after the brick is immersed in water for 24 hours. For Class I works, this limit is 15 per cent.
(ix) Efflorescence: Bricks should not have white spots when soaked in water for 24 hours and then dried in shade. White spots are due to the presence of sulfates of calcium, magnesium and potassium. They keep the masonry in permanently moist and wet conditions.
(x) Thermal Conductivity: Bricks should have low thermal conductivity, so that the buildings built with them remain cool in summer and warm in winter.
(xi) Sound Insulation: Heavy bricks are poor insulators of sound whereas light weight and hollow bricks provide good sound insulation.
(xii) Fire Resistance: The fire resistance of bricks is generally good. In fact bricks are used to protect steel pillars from fire.