AAC blocks, also known as Autoclaved Aerated Concrete blocks, are a type of lightweight and durable building material. They are made from a mixture of cement, sand, lime, and water, which is then mixed with an expanding agent and poured into a mold.
The expanding agent causes the mixture to rise and form tiny air pockets, resulting in a lightweight, cellular structure.
After pouring, the mixture is cut into blocks of various sizes and then cured in an autoclave under high pressure and temperature. This process results in a strong, lightweight, and durable building material that is ideal for walls, floors, and roofs.
Composition of AAC blocks
- Cement – 50 to 60%
- Fly Ash – 20 to 30%
- Lime – 5 to 10%
- Gypsum – 2 to 3%
- Aluminum Powder/Paste – 0.2 to 0.3%
- Water – 25 to 30%
Cement
This is a binding agent that is used to hold together the other materials in the AAC block. It is typically made from limestone, clay, shale, and other minerals that are heated to high temperatures and then ground into a fine powder.
The most commonly used cement in AAC blocks is Portland cement.
Fly Ash
This is a fine, powdery material that is a byproduct of coal combustion in thermal power plants. It is typically used as a replacement for sand in the AAC block mixture.
Fly ash is a lightweight material that contributes to the insulating properties of the AAC block.
Lime
This is another binding agent that is used in AAC blocks. It is a calcium-containing compound that is produced by heating limestone in a kiln.
Lime is added to the AAC block mixture to improve its workability and enhance the strength and durability of the finished product.
Gypsum
This is a mineral that is added to the AAC block mixture to regulate the setting time of the cement. It helps to control the rate at which the mixture hardens and ensures that the finished blocks are strong and durable.
Aluminum Powder/Paste
This is added to the AAC block mixture as a foaming agent. When it reacts with the other materials in the mixture and with water, it produces hydrogen gas, which creates tiny air pockets within the mixture, resulting in a lightweight and cellular structure.
Water
It is used to form a slurry with the other materials in the AAC block mixture. It is necessary to create a workable mixture that can be poured into molds and then autoclaved to form the finished blocks.
The water also reacts with the other materials to form a strong and durable finished product.
Manufacturing process of AAC Block
AAC blocks are manufactured through a process that involves mixing the raw materials, pouring the mixture into a mold, and then curing it in a high-pressure autoclave chamber.
The raw materials used to make blocks include fly ash, cement, lime, gypsum, and aluminum powder. These materials are mixed in the right proportions to create a homogenous mixture.
Once the mixture is ready, it is poured into a mold and left to cure for several hours. During this time, a chemical reaction between the aluminum powder and the other materials causes the mixture to expand and harden, forming a solid block.
After curing, the block is removed from the mold and cut and shaped to the desired size. The block is then placed in an autoclave chamber, where it is exposed to high temperature and pressure for a specific period of time. This process further strengthens the AAC block and ensures its durability.
Finally, these blocks are packaged and transported to the construction site for use in building projects.
AAC block size
AAC blocks are available in a range of sizes to suit various construction needs. Generally, they can be found in lengths ranging from 600mm to 625mm, widths from 200mm to 400mm, and thicknesses that range from 75mm to 250mm.
These sizes can vary slightly depending on the manufacturer and specific application, but they provide flexibility to accommodate different construction requirements.
Whether it’s for walls, floors, or roofs, these blocks are versatile building materials that can be tailored to meet the needs of various construction projects.
Here is the list of some common AAC block sizes available in the market:
- 600mm x 200mm x 75mm
- 600mm x 200mm x 100mm
- 600mm x 200mm x 125mm
- 600mm x 200mm x 150mm
- 600mm x 200mm x 175mm
- 600mm x 200mm x 200mm
- 625mm x 240mm x 75mm
- 625mm x 240mm x 100mm
- 625mm x 240mm x 125mm
- 625mm x 240mm x 150mm
- 625mm x 240mm x 175mm
- 625mm x 240mm x 200mm
AAC block price
The price of AAC blocks in India can vary depending on several factors such as the location of the supplier, quantity purchased, brand, and quality.
However, on average, the price of AAC blocks in India can range from Rs. 2000 to Rs. 3500 per cubic meter (including GST).
If you want to purchase AAC blocks in smaller quantities or pieces, the price per block can range from Rs. 35 to Rs. 120 depending on the size and thickness.
It’s important to note that purchasing these blocks in smaller quantities can sometimes be more expensive due to handling and transportation costs.
Advantages of AAC block
These types of blocks offer several advantages over traditional building materials, some of which include:
1. Lightweight
These blocks are lightweight, which makes them easy to handle, transport, and install. They weigh approximately one-fifth of traditional concrete blocks, making them ideal for high-rise buildings and other structures where weight is a concern.
2. Thermal Insulation
These blocks have excellent thermal insulation properties, which means they can help to keep buildings cool in summer and warm in winter. This can lead to significant energy savings on heating and cooling costs.
3. Sound Insulation
These blocks also offer good sound insulation, which can help to reduce noise levels from external sources as well as between different rooms within a building.
4. Fire Resistant
These blocks are fire-resistant and can withstand high temperatures, making them ideal for use in buildings where fire safety is a concern.
5. Eco-Friendly
These blocks are made from natural materials and do not contain any toxic substances. They are also recyclable and can be reused in other construction projects.
6. Cost-Effective
Although the initial cost of AAC blocks may be slightly higher than traditional building materials, they offer long-term cost savings due to their energy efficiency and durability.
7. Pest Resistant
These blocks are not susceptible to pests such as termites and ants, which can be a problem with traditional building materials.
8. Easy to Work With
These blocks are easy to cut, shape, and install using standard tools, which reduces the need for specialized equipment and skilled labor. This can help to lower construction costs and improve productivity.
9. Uniform Quality
These blocks are produced in a controlled environment using modern manufacturing techniques, which ensures consistent quality and eliminates variations in size, shape, and strength.
10. Flexibility
These blocks can be easily modified to meet specific design requirements, such as creating curved or angled walls, adding decorative elements, or integrating electrical and plumbing systems.
11. Fast Installation
These blocks can be easily cut, drilled, and shaped on-site, which makes the installation process fast and efficient. This can help to reduce construction time and costs.
Disadvantages of AAC block
1. Delicate Surface
The surface of AAC blocks can be easily damaged during transportation, handling, or installation, which can result in cracks or breakage. Careful handling and installation are required to prevent surface damage.
2. Limited Availability
These blocks may not be widely available in all areas, which can make it difficult to source the material for construction projects.
3. Requires Special Mortar
These blocks require a special type of mortar or sealant that is designed to adhere to the porous surface of the block. This can increase the complexity and cost of the construction process.
4. Absorbent Material
These blocks are porous and can absorb water, which can lead to moisture problems if not properly sealed and maintained.
5. Limited Load-Bearing Capacity
While these types of blocks are strong, they have limited load-bearing capacity when compared to other construction materials, such as concrete or steel. This can limit their use in certain types of structures.
Uses of AAC Block
1. Walls
These are commonly used for building walls due to their high strength and durability.
They can be used for both load-bearing and non-load-bearing walls in residential, commercial, and industrial construction projects.
2. Floors and Roofs
These blocks can also be used for flooring and roofing systems, particularly in buildings where lightweight construction is required.
These blocks are ideal for upper floors and roofs due to their lightweight nature, which reduces the overall weight of the building.
FAQ
What are AAC blocks made of?
These blocks are made from a mixture of fly ash, cement, lime, gypsum, and aluminum powder.
How are AAC blocks manufactured?
These blocks are manufactured through a process of mixing the raw materials in a high-speed mixer and pouring the mixture into a mold. The mixture is then allowed to expand and harden in an autoclave chamber, which gives the block its unique cellular structure.
What are the advantages of using AAC blocks?
The advantages of using AAC blocks include their lightweight nature, high strength, durability, thermal and sound insulation properties, fire resistance, and eco-friendliness.
What are the different sizes of AAC blocks available in the market?
These blocks are available in various sizes, ranging from 600mm to 625mm in length, 200mm to 400mm in width, and thickness ranges from 75mm to 250mm.
Can AAC blocks be used for load-bearing walls?
Yes, these blocks can be used for load-bearing walls in construction projects.
Also read: Fly ash bricks, uses, advantages and disadvantages
