Fly Ash Bricks

Fly Ash Bricks: Composition, Manufacture, Uses, Advantages & Disadvantages

Fly Ash Bricks is a building material prepared by utilizing class C or class F fly ash and water. Fly ash is a result of coal-fired power plants that are repeatedly utilized as an admixture in concrete to substitute a portion of Portland cement.

Fly ash bricks are utilized as an alternative to regular clay bricks and have more useful properties than clay bricks. Fly ash bricks are competitive in comparison to the normal clay bricks and provide enormous indirect benefits. The utilization of fly ash bricks outcome in the conservation of natural resources as well as the prevention of the environment.



  1. Composition of Fly Ash Bricks  

The important compositions of fly ash bricks are:

a. Fly ash

b. Cement

c. Sand

d. Water


In India 72% of power plants are coal-based. These power stations produce about 40 million tonnes of fly ash yearly. Fly ash includes Co2 ejected from thermal power plants, and industries utilizing coal as fuel radiates undesirable ash and smoke from which fly ash is made.

In entire power plants and industries, they divide the fly ash by utilizing the cyclone converter. This fly ash is then utilized as a raw material for the manufacture of bricks.



  2. Manufacturer of Fly Ash Bricks  

The process of manufacturing Ash bricks is as follows:

1. Mixing Fly ash with cement, sand & water.

2. Pouring mortar into the mold.

3. Drying in Atmospheric temperature & pressure.

4. Curing for 28 days.

5. Removing from the mold.

6. The fly ash brick is ready now.



  3. Comparison of Clay Bricks and Fly Ash Bricks  

The comparison between clay bricks and fly ash bricks is as follows:

Properties Red Bricks/Clay Bricks Fly Ash Bricks Remarks
Density 1600-1750 kg/m3 1700-1850 kg/m3 Higher load-bearing
Compressive strength 30-35 kg/cm2 90-100 kg/cm2 Higher load-bearing
Absorption 15-25% 10-14% Less dampness
Dimensional stability Very low tolerance High tolerance Saving in mortar up to 25%
Wastage during transit Up to 10% Less than 2% Saving in costs up to 8%
Plastering Thickness varies on both sides of the wall. Even on both sides Saving in plaster up to 15%.



Fly Ash Bricks



  4. Uses of Fly ash Bricks  

The fly ash bricks are used in the following places:

a. Multistorey structures

b. High-rise buildings

c. House construction

d. Factories

e. Warehouses

f. Power plants



  5. Advantages of Fly Ash Bricks  

The advantages of fly ash bricks are as follows:


1. Appearance

The formation of fly ash bricks is very pleasing due to their attractive color like cement, uniform size, and smooth finish. Due to uniform size, mortar needed for walls and plastering decreases nearly by 40-50%.

Plaster of Paris (Gypsum plaster), putty can be involved straight without a baking coat of plaster. These bricks don’t contain cracks, wrap age, organic matter, pebbles, and nodules of free lime.


2. Strength

The compressive strength of fly ash bricks is extremely high (9-10 N/mm2). Due to high strength no breakdown and cracks during moving and handling. The less thickness of joints and plaster decreases cracking in plaster.

These bricks do not generate any additional load for the design of structures and deliver more useful earthquake opposition. It enhances the strength over time and provides higher strength to the structure.


3. Thermal Properties

The thermal conductivity of fly ash bricks is around 0.90 – 1.05 W/m2. They soak negligible heat. The pozzolanic reaction between fly ash and lime ejects negligible heat. It maintains your building cooler in summer, hence most suited for hot climates.


4. Durability

These bricks are highly long-lasting and less permeable. Less permeability can highly decrease the effect of efflorescence on bricks. These bricks are negligibly permeable, absorb negligibly water, and decrease dampness on the walls. It is also greatly resistant to attack by mild acid, water, and sulfate.


5. Sound Insulation

The structure constructed with these bricks provides proper sound insulation to the structure.


6. Fire Resistance

These bricks are can withstand fire highly compared to regular clay bricks.


7. Sustainability

Fly ash bricks are environmentally friendly as they have manufactured waste materials that outcome from the discharge of coal in thermal power plants.

There is no pollution or environmental damage, considered a white category product.


8. Buildability

These bricks have uncomplicated workability and soak slighter water. Unlike clay bricks, they do not need soaking in water for 24 hours. The sprinkling of water before utilization is sufficient.

The construction technique is the same as clay brick construction and does not require any extra training for the masons.


9. Availability

These bricks are generally available closer to the thermal power plants. However, finding dealers in all major cities and towns wouldn’t be a problem.


10. Cost

The exact number of fly ash bricks will occupy large areas than that of clay bricks. The use of mortar is less. Need less labor. The cost is about 30% lower than clay bricks.


11. Applicability

Due to their lightweight, these bricks are appropriate for multi-story structures. Minor weight means negligible stress on the structure.

These bricks can be utilized in load-bearing external walls in low/mid structures, non-load bearing internal walls in low/mid structures, and non-load bearing internal or external walls in highrise buildings.



  6. Disadvantages of Fly ash Bricks  

The disadvantages of Fly ash bricks are as follows:

a. Slow Strength Gain.

b. Longer setting Times.

c. Poor Air Content Control

d. Seasonal Restrictions

e. Size Limitations

f. Attachment with concrete is less due to the smooth finish.



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