Fly ash bricks are manufactured from industrial wastes such as fly ash, cement, sand/stone dust. Fly ash bricks are nowadays used in worldwide with gaining its popularity over clay bricks. The various advantages and disadvantages of fly ash bricks are as below:
Advantages Of Fly Ash Bricks:
The appearance of fly ash bricks is very attractive due to its pleasing color like cement, uniform size, and smooth finish. Due to uniform size, mortar required for walls and plastering reduces almost by 40-50%. Plaster of paris(Gypsum plaster), putty can be applied directly without a baking coat of plaster. These bricks are free from cracks, wrap age, organic matter, pebbles and nodules of free lime.
The compressive strength of fly ash bricks is very high (9-10 N/mm2). Due to high strength no breakages/wastages during transport and handling. The lower thickness of joints and plaster reduces cracking in plaster. These bricks do not cause any extra load for the design of structures and provide better earthquake resistance. It improves the strength over time and offers greater strength to the building.
3. Thermal Properties:
The thermal conductivity of fly ash bricks is 0.90 – 1.05 W/m2. They absorb less heat. The pozzolanic reaction between fly ash and lime produces less heat. It keeps your building cooler in summer, hence most suitable for Indian climates.
Fly ash bricks are highly durable and less permeable. The lower permeability can efficiently reduce the effect of efflorescence on bricks. These bricks are less porous, absorb less water and reduce dampness on the walls. It is also highly resistant to attack by mild acid, water, and sulfate.
5. Sound Insulation:
Construction with fly ash bricks provides decent sound insulation to the building.
6. Fire Resistance:
Fly ash bricks are highly fire-resistant.
Fly ash bricks are environmentally friendly as they are made of waste materials that come from combustion of coal in thermal power plants. There is no pollution or environmental damage, considered as a white category product.
Fly ash bricks have easy workability and absorb less water. They do not require soaking in water for 24 hours. The sprinkling of water before use is enough. The construction technique is same as clay brick construction and does not require any extra training for the masons.
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.
The same number of fly ash bricks will cover more areas than clay bricks. Consumption of mortar is also low. Requires less labour. The cost of fly ash bricks is approximately 30% lower than clay bricks.
Fly ash bricks are lightweight, so it is suitable for multi-storey structures. Less weight means less stress on the building. These bricks can be used 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 high- rise buildings.
Disadvantages Of Fly Ash Bricks:
1. Not all fly ash is suitable for construction, those are produced in power plants usually compatible with concrete, while others may need beneficiation. It is very important to use only high-quality fly ash to prevent negative effects on the structure.
2. If not made properly, it has no strength and not suitable for construction. Poor quality bricks have negative impact on concrete. It can increase permeability, resulting in damages to the structure.
3. Bonding with concrete is lower due to the smooth finish.
4. Limitation in size. Only modular size bricks can be produced. The larger size will have more breakages.
5. It is only suitable for subtropical areas, or where the climate is warm because fly ash bricks do not absorb heat. But in winter season it is not helpful.