Sand Lime Bricks or Calcium silicate bricks

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Sand Lime Bricks are made of sand and lime popularly known as sand lime bricks.

These bricks are used for various works in construction such as decorative work, masonry work and many other works in buildings.

Here we will learn about sand lime bricks, advantages and disadvantages of sand lime bricks.

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Introduction to sand lime bricks:

Sand lime bricks are popularly used in European, Australia and African nations.

In India, these bricks are used extensively in the state of Kerala, their use is often increasing.

Properties of sand lime bricks:

  • Very smooth and uniform finish, it has an attractive appearance.
  • They are dense, strong and tough.
  • They are porous therefore free from indigestion.
  • Also, uniform in size, shape, finish and no plastering is required.
  • When required, the amount of plaster is significantly less.
  • Essential materials are quite common in the event can be used as an alternative to clay bricks

Materials used for sand lime bricks:

The materials listed below are used to produce calcium silicate bricks.

Sand:

Calcium silicate bricks have a high amount of sand which is about 88 – 92%.

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The properties used for these bricks depend on the characteristics of the sand.

The sand used can be well classified, should not contain impurities such as natural substances, soluble salts and many others.

Finely divided clay may be present but is only up to 4% which helps to suppress the brick and provides an easy texture.

Lime:

The content of lime in calcium silicate bricks varies from 8 to 12%.

The lime used will be of good quality and high calcium lime.

Water:

Clean water should be used to prepare the calcium silicate bricks.

Seawater or water containing more than 0.25% soluble salts or organic matter are not suitable.

Pigment:

The pigment is commonly used to colour bricks, they are mixed in sand and lime, applied when mixing.

The total weight of the brick is 0.2 to 3% of the pigment volume.

Manufacturing process of calcium silicate bricks:

  • Within the first stage, an appropriate ratio of sand, lime, and pigment is mixed well with 3 to 5% water; the paste is obtained with a moldable density.
  • The mixture is moulded into bricks using a rotary tablet that uses the mechanical pressure to pressurize the bricks.
  • The pressing pressure varies from 31.5 to 63 N / mm2.
  • Within the final stage, the bricks are positioned in an autoclave.
  • The autoclave is nothing but a steel cylinder with tightly closed ends.
  • The autoclave has a diameter of 2 m and a length of about 20 m.
  • After placing the bricks in the closed chamber the saturated steam pressure is released which is about 0.85 to 1.6 N / mm2.
  • The temperature inside the chamber is increased and the reaction process begins.
  • The amount of calcium within the compound such as silica content and lime crystals in the sand is called calcium hypo silicate, this process is carried out for 6 to 12 hours.
  • Finally, the bricks obtained are transported to the site.

Advantages of calcium silicate bricks:

  1. The mortar required to provide plaster on calcium silicate bricks is very low.
  2. The colour and texture of those bricks are the same.
  3. The comparative strength of sand-lime bricks is about 10N/mm2, so they are suitable for multi-storey buildings.
  4. For construction in clay soils, these bricks are preferable.
  5. Efflorescence doesn’t arise within the case of sand lime bricks.
  6. Bricks, blocks and tiles can be made using calcium silicate.
  7. Sand lime bricks provide great comfort and accessibility for the architect to realize the specified size and design.
  8. These bricks have the precise shape and dimension with straight edges.
  9. The solar heating effect is lowered on exposed walls made of calcium silicate bricks.
  10. Coloured sand-lime bricks are not required to complete the wall therefore reduce prices.
  11. These bricks have great fire resistance and water repellent properties.
  12. Calcium silicate brick walls prevent noise from outdoors.
  13. The cost of construction is about 40% less of the total cost due to the following factors:
  • The dissipation of calcium silicate products can be very low.
  • Decrease quantities of mortar are needed.
  • The wall thickness will be lowered when using these bricks as a result of excessive compressive strength.

Disadvantages of calcium silicate bricks:

  1. These bricks are manufactured using a mechanized method only.
  2. They are unsuitable for foundations and paving because the presence of water can cause damage to bricks and poor resistance to abrasion.
  3. In some situations, calcium silicate bricks are not suitable.
  4. If the clay is available in insufficient quantities, clay bricks are extra economical than calcium silicate bricks.
  5. These are not suitable for laying foundations, as they cannot provide resistance to water for long intervals of time.
  6. They cannot even resist fire for long, they are not suitable for building furnaces, etc.
  7. The abrasion resistance of these bricks is very low, so they cannot be used as a pavement material.

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Conclusion:

Sand lime bricks is a product that uses lime instead of cement, it is usually a white brick made of lime and selected sand, cast in a mould and cured.

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