What Is AAC Block?
AAC or autoclaved aerated concrete block is a new building product in the construction industry. They are made from the common materials cement, sand, lime/gypsum, water, and aluminium powder.
After mixing and molding, it is then cured in an autoclave under heat and high pressure to achieve its desired strength and other unique properties. AAc blocks are porous, non-toxic, recyclable, renewable, and reusable.
This type of concrete block contains 80 percent air. In the factory where it is produced, the concrete is molded and cut into precisely dimensioned masonry blocks or formed as larger planks and panels.
AAC blocks are lightweight, precast green building materials used in residential, commercial, and industrial construction.
AAC blocks are gaining popularity day by day and replacing the traditional use of red bricks due to their various advantages.
Advantages Of AAC Blocks
AAC blocks are 3 to 4 times lighter than conventional red bricks, therefore, easier and cheaper to transport. Usage reduces the overall 60% dead load of a building, thereby allowing the construction of high-rise buildings. They are normally 9-12 kg in weight depending upon moisture conditions.
AAC blocks are superior in terms of strength, they have a compressive strength of 3 – 4 N/mm2 (As per IS:2185 part III). The high-strength blocks give higher stability to the building structure.
These blocks are highly durable. Structures made with these blocks have a long life because they are not affected by harsh climates or extreme weather changes.
4. Material Consumption
By reducing the dead load, they also gradually decrease the use of steel reinforcement and concrete in the structure. Jointing AAC bricks are economical as they require less mortar when compared to red bricks.
5. Easy Workability & Design Flexibility
These blocks are available in custom sizes. They can be easily cut, drilled, nailed, milled, and grooved to meet individual requirements.
Excellent size/weight ratio. On average, AAC blocks are 8 to 9 times the size of red bricks. Hydro-sanitary and electrical fittings, such as pipes or ducts, can be installed after the completion of main construction.
6. Thermal Insulation
Great thermal insulation due to tiny air pores and thermal mass present in blocks. Reduces air conditioning costs by keeping your room cooler in summer and warm in winter.
7. Fire Resistant
Excellent fire-resistant material (up to 1600° C) due to their unique cellular structure. Non-combustible and can withstand 6 hours of direct heat exposure.
8. Sound Insulation
Its unique porous structure provides excellent sound insulation/sound absorption of 42 dB.
9. Earthquake Resistant
Lightweight AAC blocks reduce the dead load of a structure hence providing excellent resistance to earthquake forces.
10. Water Resistant
The microscopic structure of the block prevents capillary action making it impervious to water. Its water barrier properties can be further enhanced by adding silicone-based additives.
11. Termite/Pest Resistant
The use of inorganic material and smooth finishes inherently prevents pests and fungal growth.
12. Great Ventilation
AAC blocks contain air pockets inside which reduces the humidity inside the building. AAC absorbs moisture and releases humidity providing great ventilation in the room.
13. Usable Area
More carpet area is available due to less thickness of the block.
14. Faster Construction
Easy to handle and easy to install. It sets and hardens quickly. Larger and lightweight blocks make construction easier and faster. Reduces construction time by almost 20%.
Lightweight blocks save energy, reduce transportation, and handling costs by 30-40% for large constructions.
Reduces overall construction cost by almost 2.5% as it requires less steel reinforcement and other building materials like cement, sand, and aggregates.
16. Less Maintenance
Requires less maintenance.
AAC Blocks are preferred for tall buildings because it considerably reduces the total dead load of the building.
18. Eco-friendly & Sustainable
Eco-friendly and recyclable. AAC blocks are made of non-toxic elements. The manufacturing process does not release harmful gases.
Disadvantages Of AAC
1. The presence of voids makes them extremely brittle in nature which means they can break easily. They need to be handled more carefully to avoid breakage and wastage.
2. Get cracks easily after installation. As the surface is very smooth, plastering doesn’t stick very to it and hence plaster starts to crack in a few months
3. These blocks often show inconsistency in quality and color.
4. You just can’t hammer to fix furniture in the AAC blocks wall, you need to use a drill bit and a raw plug.
5. The interior finishes require low vapor permeability and exterior finishes require high permeability in case of high humidity environments.
6. Unfinished exterior walls may require exterior cladding to protect them from extreme weather conditions.
7. The cost of AAC unit is comparatively higher than a conventional concrete block.
Size Of AAC Blocks:
The AAC Blocks are accurate in size because it is manufactured in factory by wire cut technology. The different sizes of these blocks are listed below.
|Dimension of AAC Blocks(L x H x B)||Weight of a AAC Block||No. of AAC Blocks in 1 Cubic Meter|
|600*200*075 MM||6/7 KGS (Approx)||111 Pcs (Approx)|
|600*200*100 MM||8/9 KGS (Approx)||83 Pcs (Approx)|
|600*200*125 MM||10/11 KGS (Approx)||66 Pcs (Approx|
|600*200*150 MM||12/13 KGS (Approx)||55 Pcs (Approx)|
|600*200*175 MM||14/15 KGS (Approx)||47 Pcs (Approx)|
|600*200*200 MM||16/17 KGS (Approx)||41 Pcs (Approx)|
|600*200*225 MM||18/19 KGS (Approx)||37 Pcs (Approx)|
|600*200*250 MM||20/21 KGS (Approx)||33 Pcs (Approx)|
|Density Oven Dry||550-650 kg/m3|
|Compressive strength||3.5-4 N/mm2 (MPa)|
|Shear Strength||0.6 N/m2|
|Modulus of Elasticity||2040 Mpa|
|Variation in dimensions||+/-1mm|
|Thermal Conductivity “K”||0.16 – 0.18 W/(K-m)|
|Fire Resistant||4 Hrs (for 200 mm wall)|
|Sound Absorption||42 DB|
Uses Of AAC Blocks
AAC is can be used for both interior and exterior wall construction. It can also be used for both load-bearing and non-load-bearing walls. Due to its high workability and flexibility standards, AAC blocks are widely used across the construction
- High rise buildings,
- Residential buildings,
- Office/Industrial buildings,
- Hospitals, Medical, Clinics,
- Hotels, Motels, and Restaurants,
- School/college buildings,
- Cold Storages,
- Auditorium & Theaters,
- Retail and Warehouse,
- Firewalls and sound walls.
Why AAC Blocks Get Cracks?
There could be many reasons for developing cracks in aac blocks. I am listing them below.
Brittleness: These blocks are extremely brittle in nature, and easily break even after dropping from a low height.
Shrinkage Cracks: If manufacturers deliver the products early on-site for use without following the post-manufacturing process then there are more chances of developing cracks due to expansion and contraction.
Improper Curing: If the blocks are not cured properly cracks may occur in the walls.
Use of very fine sand: Using very fine quality sand in the concrete mix also creates cracks in the wall. To avoid this we can use adhesive for installation.
Vibration & Hammering: Continuous vibration or frequent hammering for nailing may also be a reason for cracks in a wall.
Poor Workmanship: Poor workmanship or construction with unskilled labours often leads to cracking in aac block walls.
AAC Blocks Price
The aac blocks price varies depending upon size. In India, the price of 600 mm x 100 mm x 250 mm is 50 to 60 rupees (per unit).