Fly Ash Bricks: Properties, Advantages, Disadvantages

Fly Ash Brick
Fly Ash Bricks: Properties, Advantages, Disadvantages 4

Fly ash bricks are a building material, especially masonry units that are utilized in the construction of buildings. They are supposed to be a part of good and affordable building materials.

Fly ash is a waste product of a power generating plant that is reused in concrete by partial replacement of cement. It is also used for making bricks and is called Fly Ash Brick.

Fly Ash Bricks are used as the alternative material for burnt clay bricks for masonry works. The raw material used in the fly ash brick such as fly ash, sand/stone, and ordinary Portland cement. The test conducted to test fly ash brick includes a compressive strength test, Water Absorption Test, and Efflorescence Test.

They contain class C or class F fly ash and water. Fly ash brick is generally compressed at 28 MPa and cured for 24 hours in a 66°C steam bath, then stiffened with an air-entrainment agent, the bricks can last for more than 100 freeze-thaw cycles.

Owing to the huge concentration of calcium oxide in class C fly ash, the brick is interpreted as “self-cementing”. The manufacturing method of fly ash bricks saves energy, decreases mercury pollution in the environment, and often costs 20% less than conventional clay brick manufacturing.

Fly ash brick is considered good and inexpensive building material including class C, fly ash, and water.

Fly ash brick is environmentally friendly and manufactured by hydraulic pressure machines. They are 28% lighter than ordinary clay bricks and have a compressive strength greater than 40Mpa than ordinary bricks.

They are economical and eliminate the need for plaster, it can decrease high construction costs and soil erosion.

Read More: 30+ Types of Bricks Used in Construction

Fly Ash Bricks Properties

The following are properties of fly ash bricks,

  • Appearance: The bricks have a satisfactory cement color, which is uniform in shade and smooth, but does not need plastering for building works
  • Thermal Conductivity: They do not absorb heat and give extreme light reflection.
  • Sound Insulation: It gives an adequate degree of sound insulation.
  • Fire And Vermin Resistance: They have adequate fire resistance, it has no difficulty with vermin attacks.
  • Durability And Moisture Content: These blocks are highly durable, the absorption of moisture is 6–12%, which decreases the humidity of the walls.
  • Toxicity And Stability: When mixed with lime, fly ash turns into a non-toxic commodity thus has potential as a good building material.

Fly Ash Brick Size

The following are standard sizes of fly ash bricks,

For Modular Size,
Length is 190± 4mm
Width is 90±2 mm
Height is 90±2 mm and 40±2 mm

Fly Ash Bricks Sizes
Fly Ash Bricks: Properties, Advantages, Disadvantages 5

For Non-Modular Size
Length is 230± 4mm
Width is 110±2 mm
Height is 70±2 mm and 30±2 mm

IS Code for fly ash bricks is IS 13757 (1993): Burnt clay fly ash building bricks-Specification

Manufacturing of Fly Ash Bricks

Manufacturing of Fly ash bricks process is done by using a manually operated machine. The following points were followed in the manufacturing of compacted fly ash bricks

1. Fly ash and sand (fly ash bricks mixing ratio is 0.35 fly ash and 0.65 sand, by weight) were mixed in a dry state. Required quantities of lime and gypsum were added to the dry mixture.

Both these procedures were carried out in a mechanical mixer (for 5 minutes) extremely that a uniform mixture of fly, ash-sand-stabilizer was collected.

Fly Ash Bricks Manufacturing Process
Fly Ash Bricks: Properties, Advantages, Disadvantages 6

2. A Uniformed combination of fly ash-sand-stabilizer was spread into a thin layer (100 mm thickness).

The required quantity of water (10% for FAL10 and FALG10 bricks, and 12% for FAL17 and FALG17 bricks) was sprinkled and mixed manually with the relief of a spade in order to assure that moisture is uniformly allocated in the mixture.

3. Known amount of the raw mixture was weighed and poured into the machine mold. indicates the filled mould prepared for compaction.

After closing the lid the compaction is accomplished through the movement of a piston connected to the toggle lever

4. After the compaction stroke the lid is opened and the brick is ejected out and protected in a stack for curing.

The stack of fly ash bricks was coated with wet gunny cloth and water is sprinkled three to four times every day such that the whole stack is moist.

The bricks were cured for 28 days and then were enabled to dry in the open atmosphere for four weeks and then utilized for testing.

Fly Ash Bricks Machine Price List

Fly ash bricks manufacturing machines are also available in markets which enables large quantity production in a short period of time.

Fly ash brick machines are of two types 1) Automatic and 2) Manual Operation machines.

Following are fly ash bricks machine price or fly ash bricks making machine cost is given below,

Operation Types Minimum Price Maximum Price
Automatic Rs 1550000/Unit Rs 2500000/Unit
Automatic Rs 610000/Unit Rs 1975000/Unit
Manual Rs 150000/Unit Rs 750000/Unit
Semi-Automatic Rs 270000/Unit Rs 1600000/Unit

Read More: 7 Brick Test to Decide Quality of Bricks

Fly Ash Brick Advantage and Disadvantage

Fly Ash Bricks Advantages

The following advantages of fly ash bricks used in construction,

1. Appearance

The Appearance of the fly ash brick is impressive due to its satisfying colors like cement, uniform size, and smooth finish. Due to uniform size, mortar mandatory for walls and plastering was reduced nearly by 40- 50%.

of Paris (Gypsum plaster), putty can be applied rapidly without a baking coat of plaster. These bricks are independent of the cracks, wrap age, organic matter, pebbles, and nodules of the free lime.

2. Strength

The compressive strength of the fly ash brick is relatively high (9-10 N/mm2). Due to high strength no breakages/wastages during conveyance and handling.

The less thickness of joints and plaster reduces cracking in plaster. These bricks do not result in any extra load for the design of structures and give better earthquake resistance.

It enhances strength over time and offers incredible strength to the building.

3. Thermal Properties

The thermal conductivity of fly ash bricks is nearly 0.90 – 1.05 W/m2. They absorb less heat. The pozzolanic effect between the fly ash and lime generates less heat.

It protects your building cooler in summer, therefore most suitable for Indian climates.

3. Durability

These bricks are highly durable and less permeable. The lower permeability can efficiently lessen the effect of efflorescence on bricks.

The fly ash bricks are lessened porous, consume less water, and decrease dampness on the walls. It is also highly resistant to attack by mild acid, water, and sulfate.

4. Sound Insulation

The Construction with the fly ash bricks provides decent sound insulation to the building.

5. Fire Resistance

The fly ash bricks are highly fire-resistant compared to the normal clay bricks.

6. Sustainability

The Fly ash bricks are environmentally friendly as they are prepared of waste materials that reach from the combustion of coal in power plants.

There is no pollution or environmental damage, deemed as a white-category product.

7. Buildability

The fly ash bricks have easy workability and consume less water. Unlike clay bricks, they do not impose draining in water for 24 hours. The sprinkling of water before use is sufficient.

The construction procedure is similar to clay brick construction and does not need any extra training for the masons.

8. Availability

These bricks are commonly available closer to thermal power plants. However, finding dealers in all main cities and towns wouldn’t be a difficulty.

9. Cost

A similar number of fly ash bricks will enclose more areas than clay bricks. Consumption of mortar is also low. It Requires less labor. The cost is almost 30% lower than clay bricks.

10. Applicability

Due to their lightweight, these bricks are desirable for multi-story structures. Less weight indicates less stress on the building.

These bricks can be utilized in load-bearing external walls in low/mid structures, non-load-bearing inner walls in low/mid structures, and non-load-bearing inter-outer walls in high-rise buildings.

Disadvantages of Fly Ash Bricks

The following are the fly ash bricks disadvantages,

  • Not all fly ash bricks are convenient for construction, those are manufactured in power plants usually similar to concrete, while others may desire beneficiation. It is relatively important to use only high-quality fly ash to avoid negative impacts on the structure.
  • If bricks are not prepared properly, it has no strength and is not suitable for construction. Poor-quality bricks have an adverse impact on concrete. It can increase permeability, occurring in damage to the structure.
  • Bonding with the concrete is lower due to the brick’s smooth surface.
  • Restriction in size. Only modular-size bricks can be manufactured. The bigger size brick will have more breakages.
  • Fly ash bricks are only applicable for subtropical areas, or where the atmosphere is warm because fly ash bricks do not consume heat. But in the winter season, it is not effective.

Raw Materials Used In Fly Ash Bricks

Material Mass
1. Fly ash 60%
2. Sand / Stone dust 30%
3. Ordinary Portland cement/(Lime + Gypsum) 10%

The total formula of material is 100%

The strength of fly ash brick produced with the above configurations ranges between 7.5 MPa and 10 MPa. The Fly ash bricks are tougher and lighter than clay bricks.

The fly ash bricks have main ingredients such as fly ash, water, quicklime or lime sludge, cement, aluminum powder, and gypsum. Auto craving raises the hardness of the block by stimulating quick curing of the cement. Gypsum conducts as a long-term strength gainer.

Utilizing the fly ash bricks in the buildings decreases the dead load, permitting one to save around 30 to 35% of structural steel, and concrete.

Commercial processes fall into two sectors; the lime route, and the cement (Ordinary Portland Cement) path where the latter is utilized as a source of lime.

In the lime path, the configuration is fly ash (50%), slaked lime (30%), and anhydrous gypsum (20%), to which 3 to 4 times of stone dust, sand, or any inert filling material can be added.

In the cement route, the composition is fly ash (76%), Ordinary Portland cement (20%), and anhydrite (4%), to which 3 to 4 times of filling materials can be added.

Uses Of Fly Ash Bricks

The following are the fly ash bricks used in construction,

  • Fly ash bricks are generally used in low and medium-sized structures, with load-bearing exterior walls.
  • On load-bearing structure internal walls.
  • Fly ash bricks can be used in the building industry.
  • Brick is used in high load-bearing exterior or interior walls in high-rise buildings.
  • Fly ash bricks are used as an alternative material for burnt clay bricks which is one of the most important building materials obtained for the construction of housing and buildings. The fly ash building bricks are inefficient in all types of brick masonry works and can replace the conventional burnt clay bricks in almost all applications.
  • Fly ash bricks are used in multistory structures, factories, house construction, high-rise buildings, power plants, and warehouses.

Fly Ash Bricks Price

Fly ash bricks price is comparatively lower than red bricks price. The fly ash Bricks price list is given as per size of bricks,

Fly ash Bricks 230x110x75mm

M5+ Grade Fly Ash Bricks Price ₹4.40/-
M7.5+ Grade Fly Ash Bricks Price ₹4.90/-
M10+ Grade Fly Ash Bricks Price ₹5.40/-

Read More: Fly Ash Bricks vs Red Bricks – Which is Better?

Difference Between Fly Ash Bricks vs Red Bricks

Following are key comparison points for Fly ash bricks vs red bricks,

Sr. No.Red BricksFly Ash Bricks
1Clay bricks are unequal in shape as most clay bricks are made manually.Uniform in shape and smooth in finish as the manufacturing is accomplished using machinery.
2The colour of fly ash brick is similar to the brick manufacturing conducted using machinery in controlled conditions.Fly ash bricks are minor porous
3As the surface finish is not flat or straight, plastering is necessary.As the surface is flat and joints are thinner, no plastering is needed in normal cases.
4Clay brick is Heavier in weight.Fly ash brick is lighter as the major configuration is fly ash.
5Clay bricks are more porous compared to fly ash bricks.The expense of these bricks is almost 30%lower than clay bricks.
6The cost of clay brick is greater than fly ash brick.This is composed by using by-products of Thermal Power Plants. Which preserves the environment from occurring pollution.
7Proceeding with the use of clay bricks in the construction industry will lead to a large loss of fertile topsoil. This could be aThis is composed by using by-products of Thermal Power Plant. Which preserves the environment from occurring pollution.


In conclusion, fly ash brick has emerged as a sustainable alternative to conventional clay bricks, offering numerous advantages for the construction industry and the environment.

This brick is made from the by product of coal combustion known as fly ash, that would otherwise end up in landfills, by utilizing fly ash this bricks help in reducing environmental pollution and conserving natural resources.

Fly ash bricks possess several desirable properties such as durability, thermal insulation and high strength. They are lighter in weight compared to clay bricks, which reduces the load on structures and lowers transportation costs.

Moreover, the production process of fly ash bricks consumes less energy and emits fewer greenhouse gases, contributing to a greener and more sustainable construction sector, with their cost-effectiveness. Eco-friendliness and superior performance, fly ash bricks have popularity in the construction industry.

Their adoption promotes sustainable development by reducing the carbon footprint and conserving natural resources, as we move towards a more environmentally conscious future, fly ash bricks present a promising solution for constructing durable and environmentally friendly buildings.


What is hydraulic cement?

Hydraulic cement is a type of cement that sets and hardens through a chemical reaction with water. It is called “hydraulic” because it has the ability to set even when submerged in water.

How does hydraulic cement work?

Hydraulic cement contains compounds that react with water, producing chemical bonds that lead to the hardening of the material. This reaction results in the formation of calcium silicate hydrates, contributing to the strength and durability of the cement.

What are the primary uses of hydraulic cement?

Hydraulic cement finds various applications in construction and repair projects. It is commonly used for sealing and repairing cracks in concrete structures, waterproofing basements and foundations, anchoring bolts and posts, and creating watertight seals in concrete joints.

What are the advantages of using hydraulic cement?

Some advantages of hydraulic cement include its ability to set and harden even in the presence of water, its excellent durability and resistance to water penetration, strong adhesion to concrete and other surfaces, and its relatively fast setting time, allowing for quick repairs.

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2 thoughts on “Fly Ash Bricks: Properties, Advantages, Disadvantages”

  1. can we use fly ash bricks for retaining wall with soil elevation difference being 8 feet

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