Bricks: Properties Composition and Composition of Good Quality of Bricks

Bricks are one of the building material which is used to construct the wall, foundation, etc. It is widely used at present in Reinforced concrete structures because of its good compressive strength, durability, low cost, and availability, etc. It is manufactured by molding clay in rectangular blocks of uniform size and kept for drying and in the end, burnt all the blocks.

Standard Size of Modular Bricks without mortar = 190 mm x 90 mm x 90 mm.

Size of Modular bricks with 10 mm thick mortar = 200 mm x 100 mm x 100 mm.

Properties/ Characteristics of Good quality Clay bricks

  • A good clay brick should have uniform Rectangular shape and size.
  • It shall be manufactured either hand or by machined.
  • All the arris should be straight edges.
  • It has to be well burnt.
  • Brick should have a uniform in deep red color that shows the uniformity in chemical composition.
  • It should be hard enough to resist the compressive load.
  • It should be free from holes, lumps, or grit.
  • The surface of the bricks should not be smooth because mortar will not stick to it.
  • It should be free from any kind of cracks.
  • Brick should have a uniform texture.
  • It should have surfaced so hard that cannot be scratched by the fingernail.
  • Good quality of bricks should have a metallic ring when one brick stuck against another brick.
  • It should not break when it falls from a height of about 1.5 m on the ground.
  • Water absorption of bricks shall be less than 20% of its dry weight when immersed in water for 24 hours.
  • The percentage of soluble salt should not exceed 2.5 percent in burnt bricks.

Composition or Ingredients of Clay Bricks

IngredientsComposition value in Percentage
Silica (SiO2)50-60
Alumina (Al2O3)20-30
Lime (CaO)Less than 10%.
Ferric oxide (Fe2O3)Less than 7%.
AlkalisLess than 10%.
Magnesia (MgO)Less than 1%.

Major ingredients of clay Bricks and its functions

Silica (SiO2)

Good quality of bricks contains 50-60% silica. The presence of Silica controls cracking, shrinkage, and warping of raw bricks. Aluminosilicate is formed when Silica (SiO2) reacts with Alumina (Al2O3). If the amount of silica is more than required then clay brick particles lose its cohesion between them. Due to the excess amount of silica, a brick becomes brittle in nature.

Alumina (Al2O3)

Alumina is one of the compositions of bricks which play majors role in terms of plasticity. Due to its plasticity property bricks can be molded into a rectangular shape.  If the amount of Alumina present in bricks is more than required, Crack occurs in bricks when clay gets dried.

Lime (CaO)

In brick, the amount of lime is less than 10%. Lime prevent the brick from shrinkage when it is under drying conditions. Excess amount of lime makes the brick melt and it may lose its shape and size.

Iron Oxide ((Fe2O3)

The main Function of Iron oxide is to provide red color to the bricks. The presence of oxygen on burning helps the brick to achieve the red color and due to the absence of oxygen, it will achieve dark brown or black color. If the amount of Iron oxide is more than required that makes the bricks dark blue. Iron oxide enhances the properties of impermeability, strength, durability, and hardness.

Magnesia (MgO)

The main function of magnesia is to provide yellow tint if it presents in small quantities. Magnesia content is less than 1% in brick. Due to the small quantity, magnesia decreases the amount of shrinkage after drying. If the amount of magnesia is more than required that causes the decay of brick.

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