AAC Blocks - Advantages, Disadvantages, Price & Specification

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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

1. Lightweight

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.

2. Strength

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.

3. Durability

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%.

15. Cost-Effective

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.

17. Applicability

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
600200075 MM	6/7 KGS (Approx)	111 Pcs (Approx)
600200100 MM	8/9 KGS (Approx)	83 Pcs (Approx)
600200125 MM	10/11 KGS (Approx)	66 Pcs (Approx
600200150 MM	12/13 KGS (Approx)	55 Pcs (Approx)
600200175 MM	14/15 KGS (Approx)	47 Pcs (Approx)
600200200 MM	16/17 KGS (Approx)	41 Pcs (Approx)
600200225 MM	18/19 KGS (Approx)	37 Pcs (Approx)
600200250 MM	20/21 KGS (Approx)	33 Pcs (Approx)

Technical Specification

Parameters	Specification
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)
Water Absorption	8%
Drying Shrinkage	0.04%
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 labors 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).