AAC blocks: Advantages and Disadvantages

Current housing and construction practices rely heavily on the use of conventional red bricks. However, the current building industry is attempting to permanently replace red bricks with concrete blocks. Concrete blocks have been gaining popularity as a building material because of its many benefits. One can save the environment and save money on the cost of creating his or her dream home by using this eco-friendly building material. Building with concrete blocks has simplified and sped up the process of constructing homes. Concrete blocks serve a wide variety of building needs, and as such, there are many varieties available. Concrete blocks come in a wide variety of densities and strengths, but AAC blocks, also known as lightweight blocks, are especially useful for constructing sturdy buildings while keeping their overall weight down. So, when it comes to non-load-bearing construction, AAC blocks are preferred over traditional alternatives. In Bangladesh, people are beginning to see that AAC blocks may be used instead of more expensive and less environmentally friendly materials without sacrificing quality.

AAC Blocks: An Affordable Greener Alternative 

AAC blocks, or Autoclaved Aerated Concrete, are a modern type of building material. Raw materials such as quartz sand, calcined gypsum, lime, portland cement, water, and aluminum powder are combined to form AAC blocks, which are then precast as foam concrete for sustainable construction. Aluminum interacts with cement, lime, and fly ash in a calculated ratio to produce this. The robust cell structure of AAC is the result of hydrogen gas escaping and creating millions of small air cells.  The air content of this particular sort of concrete block is around 80%. Curing it in an autoclave at high temperature and pressure is how it gets its special strength after the first mixing and shaping. AAC lightweight blocks are permeable, non-toxic, and recyclable due to their density of 550–650 kg/m3. Concrete is molded and cut into masonry blocks or planks and panels in the facility where it’s made. Blocks made with AAC material are in great demand because of their excellent performance and longevity, as well as their high strength, load-bearing, and thermal insulation capabilities.

In 1920, a Swedish architect came up with the idea for AAC Block. He was looking for an alternative to wood that had similar properties to wood, like good thermal insulation, a solid structure, and being easy to work with, but without the problems of being flammable, rotting, and being damaged by termites. AAC works effectively in high-rise structures and can withstand wide temperature fluctuations. As a result of its reduced density, AAC-built structures may use less steel and concrete for their framework. Because there are fewer seams between AAC blocks, less mortar is required during installation. The exact sizes of AAC imply less rendering material is needed. AAC manufacturers make blocks of varying sizes and strengths. However, they are often 8-9 times larger than a standard red clay brick while still having superior compressive strength and weighing only a fraction of what a standard brick would. Buildings, both indoors and out, may benefit from the versatility of AAC blocks. AAC may be utilized in structures dealing with extreme heat since it retains less heat. In addition to saving time and money, this method of construction also removes the need for additional insulating materials.

Advantages of AAC Blocks

• Affordability and Sustainability 

Manufacturing AAC blocks results in minimal byproducts since they use only natural, non-toxic components. Moreover, recycling and conversion to aggregate can be done for some of the wastes and residues produced, making it an eco-friendly choice. Its non-biodegradable composition ensures the structure’s long life and resistance to moisture-related damage. Due to its low weight, low energy consumption, and ease of installation, AAC blocks need less manpower overall and thus save money.

• Lightweight and Earthquake Resistance

An AAC Block has a density of 550-650 kg/m3, or roughly a third that of a traditional red brick. Due to its uniquely crafted cellular structure, AAC blocks are 30% lighter than concrete while being 3–4 times lighter than bricks. So with this smaller dead load, it’s possible to construct higher structures. The foundation and construction investment costs are minimized by around 27% and the total project cost is reduced by 5% due to the lower effective dead load. To a certain extent, a building’s susceptibility to earthquake damage is directly related to its weight. Due to its lightweight nature, AAC blocks mitigate the effects of natural disasters like earthquakes and high winds.

• Thermal Insulation and Fire Resistance

One of the most significant advantages of AAC blocks is their ability to insulate against heat transfer. They are equipped with many minuscule air vents all over their structures. As a result, it functions quite well as an insulator. So, throughout the winter months, the interior stays warm and cozy, while during the warmer months, the room stays cool and serene. As a consequence, AAC blocks drastically cut down on monthly costs for air conditioning. In addition, these blocks can withstand temperatures of up to 1,200 degrees Celsius for up to six hours without catching fire, which is far higher than the fire resistance of other common construction materials. This means it is also beneficial for preventing fires from happening.

• Moisture Resistance and Pest Resistance

Moisture can cause extensive damage to a building. Low water absorption is guaranteed by the macro-pores found within AAC blocks. Open pores that create a capillary tube contribute to permeability, whereas in AAC blocks, the millions of closed air holes within vary in size from 2 to 4 millimeters,  efficiently blocking water permeability. These blocks have a permeability resistance that is around 85% greater than that of walls made of clay bricks. In this way, they offer superior protection against moisture. In addition, because AAC blocks are made from inorganic substances, they are resistant to the infestation of common pests like termites and rats.

• Acoustic Insulation

AAC blocks provide a high level of sound insulation because of their lightweight and porous construction. Since the AAC block’s inside is studded with so many small air holes, it negates noise and echoes very well. A great material for use in the building of walls in auditoriums, hospitals, offices, and schools as it provides sound attenuation of around 40-50 dB and filters out all severe sounds and disturbances.

• Better Return on Investment

Substantial turnaround on invested capital as a result of a reduction in construction time and related expenses (such as cement, steel, construction supervision fees, water, and lumber needed for centering and shuttering). The surface of AAC Blocks is smooth and uniform thanks to their wire cutting. Because of this, the cost of plastering interior walls may be avoided by having them immediately put and painted.  When used in large construction projects, they can cut transportation and handling expenses by 30–40%. Incredibly user-friendly and straightforward to set up. Shortens construction time by over 20%. When compared to traditional red bricks, AAC blocks use far less mortar when being joined together, resulting in significant savings.

Disadvantages of AAC Blocks

• Not Suitable for Load-Bearing

Because of the hundreds of air holes inherent to its structure, AAC blocks are very lightweight. Therefore, AAC Block may only be utilized in framed or partitioned constructions where it does not have to support any weight. Therefore, they can’t be utilized in structural walls. Load-bearing walls should ideally be constructed with dense, solid blocks.

• Brittle in Nature

The AAC blocks are more fragile than regular brick because of the porosity inside the substance. They require more attention during installation than clay bricks to prevent cracking. It is necessary to use wood-suitable drill bits or hammer for longer, thinner screws due to the blocks’ brittleness while assembling cabinets and hanging wall decorations.

• Prone to Cracks

Cracking is a common problem after installing AAC blocks, which is why they are sometimes avoided. This may be prevented by weakening the mortar’s strength and ensuring that the blocks are dry before, during, and after the installation process.

• Plastering issue

As a result of the smooth texture of the AAC block’s surface, plaster may have difficulty adhering to certain surfaces. It is essential that during the production process, enough precautions be taken to prevent the surfaces of the AAC blocks from becoming too smooth.

• Unfamiliarity among Contractors

A great number of contractors are unfamiliar with AAC blocks, and those that are aware of them lack the qualified labor necessary to work with AAC blocks. There are even those who are reluctant to work with modern forms of material like AAC blocks. Because the mortar used for AAC is thinner in comparison to traditional cement-based mortar, they frequently need to hire specialized laborers in order to get the job done.

Summary

AAC blocks, also known as lightweight blocks, are advantageous because their porous structure makes them resistant to fire and high temperatures while still being lightweight, eco-friendly, and sustainable. However, their brittleness, load-bearing limitations, susceptibility to cracks, etc., limit their usefulness in a variety of construction contexts. Yet, it has the potential to become a widely used building material because of its exceptional workability, flexibility, and durability in contemporary contexts.

F.A.Q.

How can you fix a cracked wall made of AAC blocks?

Ans. To repair cracks in AAC block walls and plaster, use a crack filler mortar designed specifically for this purpose.

Should you plaster over AAC blocks?

Ans. The surface of AAC blocks is flat and wire-cut. Plastering is unnecessary for interior walls for this reason. It’s now possible to paint or patch the walls immediately. Plastering the outside, however, is necessary.

Is it better to use AAC blocks than bricks?

Ans. When compared to bricks, AAC blocks are superior because they are eco-friendly, lightweight, strong, uniform in size and shape, simple to install, and inexpensive to build with. This is in contrast to the fact that the production of bricks contributes to pollution by releasing harmful gasses into the atmosphere.

Why do AAC blocks get cracks?

Ans. Deflection of the beam, uneven positioning of AAC blocks, the structural movement induced by thermal expansion, or change in moisture content is all potential causes of cracking in concrete blocks during installation.

Can I tile over AAC concrete blocks?

Ans. The answer is yes. You may tile over AAC blocks with thin-set adhesive.