Fly ash Bricks

Fly ash bricks are manufactured by mixing water, Quarry Dust / River Sand, cement, fly ash and Stone aggregates less than 6mm in Size.

Normally the required actual cement volume will be replaced with 10% to 20% fly ash.

They are considered good and inexpensive building materials, including Class C, fly ash and water.

Fly ash bricks are environmentally friendly, manufactured by hydraulic pressure machines.

They are 28% lighter than normal clay bricks and have a compressive strength greater than 40Mpa than normal bricks.


They are inexpensive and eliminate the need for plastering due to fine finish, it can reduce high construction costs and soil erosion.

Properties of Flyash bricks:

Appearance: The bricks have a pleasing cement colour, which is uniform in shade and smooth but does not require plastering for building works.

Thermal conductivity: they do not absorb heat, reflect it and give maximum light reflection.

Sound Insulation: It provides an acceptable degree of sound insulation.

Fire and Vermin Resistance: They have good fire ratings, it has no problem with vermin attacks.

Durability and moisture content: These blocks are highly durable, the absorption of water is 6–12%, which reduces the humidity of the walls.

Toxicity and Stability: When mixed with lime, fly ash turns into a non-toxic product; it can thus have potential as a good building material.

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Advantages of Fly ash Bricks:

  1. They are light in weight, so are very suitable for multi-storey buildings because as the height of the buildings increases, the stress and strain on the foundation and structure increases and due to the lighter bricks, this stress and strain are decreases manifold.
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  3. Fly ash bricks absorb less heat and are better than clay bricks, for Indian climate.
  4. Due to the high strength, there is practically no breakdown during transport and use.
  5. The leakage of water through bricks is reduced due to less water penetration.
  6. Gypsum plaster (plaster of Paris) can be directly applied on these bricks without a backing coat of lime plaster.
  7. These bricks do not require to soak in water for 24 hours, a sprinkling of water before use is sufficient.
  8. Less mortar is required during construction, further, for the operation of the machine requires less labour.
  9. The compressive strength is very high and they are less porous.
  10. They absorb less water and save costs.
  11. It is environmentally friendly and therefore allows your business to take a step towards sustainable development.
  12. No fossil fuels are required for the production of fly ash brick and hence no emission of greenhouse gases.
  13. The production of clay bricks damages the top-soil and prevents fly ash in the process of manufacturing bricks, there is no solid loss.
  14. Flyash bricks are stronger, more uniform and denser than clay bricks; while their mortar consumption is low, their dissipation is only 1% against clay bricks which is around 10%.

Disadvantages of Fly ash Bricks:

  1. Poor quality often has a negative impact on concrete, it can increase permeability, thus damaging the building.
  2. Some fly ash, which originates in a power plant, is usually suitable for concrete; thus it is very important to use only high-quality fly ash to prevent negative effects on the structure of the building.
  3. The strength of mechanical bonding is weak but can be corrected using marble waste.
  4. There will be more wear and tear in the range of size.

Fly ash bricks manufacturing process:

Fly ash bricks manufacturing process

Application of Fly ash Bricks:

  • In low- and medium-sized structures, load-bearing exterior walls.
  • On load-bearing internal walls.
  • High load-bearing exterior or interior walls in high-size buildings.

Frequently Asked Questions:

How are fly ash bricks made?

Step 1: Fly ash reacts with lime in the presence of moisture to form calcium silicate hydrate which is the binder material.
Step 2: The raw mixture is moulded into a moulding press/machine, pressed under the pressure of bricks.
Step 3: The bricks are then taken out of the moulding machine and dried in the air under the sun and kept for 1 day.

What is the cost of fly ash bricks?

Fly ash brick costs around Rs 3.50-4, clay brick costs around Rs 5-5.50 per brick in India.

Which brick is better fly ash or normal brick?

Fly ash bricks are made from waste materials that come from the combustion of coal in thermal power plants, which is the main reason that makes fly ash bricks much better than clay bricks.

Are fly ash bricks safe?

Fly ash bricks emit radon gas, but at only 50% emitted from concrete; thus, it is safe to use.


Mechanical properties were found to be enhanced in fly ash bricks as compared to clay bricks.

Compressive strength and flexural strength of fly ash brick were 54.21% and 56% higher than clay bricks.


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