What Is AAC Block?
The full form of AAC block is autoclaved aerated concrete. For producing concrete masonry units like blocks it is a precast, lightweight form of concrete building materials. The composition of AAC blocks is calcined gypsum, quartz sand, lime, cement, aluminum powder, and water.
In an autoclave, AAC blocks are cured under pressure and heat. The AAC blocks are generally providing to the structure, insulation, mold, and fire resistance. In this AAC block, many products are including that’s are wall panels, blocks, roof and floor panels, lintels, and cladding panels.
The AAC blocks we can use in the interior or exterior walls on both sides of the structure. After that, the walls may be coated or painted with a plaster or stucco compound. To guard against the element the AAC products are covered with a siding material such as vinyl siding or veneer brick.
The AAC material can be sanded, routed, and cut to the required size on the construction site the tools with the carbon steel cutters for their easy and quick installation.
When AAC Was First Developed?
As seek for alternate building materials with properties like wood in 1924 the AAC was developing by a Swedish architect. Wood has good qualities like firm structure, and thermal insulation and allows smooth working with it.
As a good side of the wood, there have some bad sides that are decay, combustibility, and termite damage. Also, the wood is fire and termite-resistant, so the AAC has all these properties of wood.
Advantages & Disadvantages of Using AAC Blocks
Advantages of Using AAC Blocks
There are have been many advantages of using AAC blocks that are w-
- The advantage of using AAC blocks is, from the traditional bricks, the AAC blocks are three to four-time lighter, so it is cheaper and more suitable to transport.
- From standard masonry blocks, the AAC block’s weight is approximately 50% less. It is her advantage of AAC blocks.
- For this above reason, the dead load of the construction will be decrease and the structure make lighter. So nowadays it is widely used in construction.
- With these AAC blocks, we can easily work and design the structure as required to the work. It is another advantage of AAC blocks.
- The common advantage of AAC blocks is, in this type of AAC blocks easily can cut to install hydro sanitary, ducts, or pipes after complete the structure.
- The advantage of using AAC blocks is, by reducing the number of joints in wall masonry, reduce the construction time by 20% from traditional bricks.
- As it is lighter so the blocks provide more comfortable and faster construction.
- The AAC blocks have minimum wastages less than 5%, so it is more preferable in construction.
- Another advantage of AAC blocks is, due to the thermal mass of blocks and tiny air pores these blocks allow excellent thermal insulation.
- For the above reason, it reduces the air conditioning and heating cost of the building.
- Up to 1600 degrees Celsius, the AAC blocks are fire-resistance and non-combustible. It is another advantage of AAC blocks.
- Depends upon the thickness of the blocks this type of block can resist fire for up to 2 to 6 hours.
- Another advantage of AAC blocks is, due to the surface accuracy of the blocks the requirement of plaster of AAC blocks is less than of the traditional bricks.
- In this AAC block, the water requirement for curing is less than from the traditional bricks.
Disadvantage of Using AAC Blocks
As the above advantage, the AAC blocks has some disadvantage that’s are below-
- The disadvantage of AAC blocks is; they can be used only for partition walls because they are non-load-bearing material.
- after installation, n the AAC blocks are well known for cracks that are the disadvantage of AAC blocks.
- While transporting and handling the AAC blocks require more care than clay brick.
- In the AAC blocks, the cost per unit is high to the traditional bricks.
- Another disadvantage of AAC block is, it has brittle nature.
- In these AAC blocks, we can’t use a hammer because it can be a break.
- The disadvantage of AAC blocks is, for the work the expert labor should be required.
Properties of AAC Blocks
The properties of AAC blocks are below-
- The density of oven-dry of AAC blocks is 552 to 650 kg/cum.
- As per code 2185, the compressive strength of AAC blocks is 35 to 40 kg/cm2.
- As per inch of thickness, the thermal resistance of AAC blocks is 0.8 to 1.25.
Technical Comparison of Blocks
|AAC Block||Concrete Block||
|Size||(600x200x100-300) mm||(400x200x100-200) mm||(230x115x75) mm|
|Compressive Strength||30 – 50/Kg/3Cm2||40 – 50/Kg/Cm2||25 – 30/Kg/Cm2|
|Dry Density||600-650/Kg/Cum||1800 Kg/Cum||1950 Kg/Cum|
|Fire Resistance||4-6/Hour Depending On Thickness||42 Hours||2Hours|
|Thermal Conductivity w/(Km)||0.25||0.51||0.81|
|Sound Reduction Index(DB)||60 For 200 mm thick wall||–||40 For 230 mm Thick Wall|
Here, the manufacturing process are as follows.
- The manufacturing process of the AAC blocks is a pre-cast product that’s used in construction.
- The AAC blocks are a mixture of gypsum, cement, pulverized fly ash, water, lime, and aluminum powder poured into a mold.
- When we add the aluminum powder into the mixture its reacts with fly ash and lime resulting in the formation of millions of microscopic hydrogen bubbles.
- After that, the times of its original volume the hydrogen subsequently evaporates leaving a high closed shale aerated concrete and the hydrogen Bubbles cause the concrete to expand to roughly double.
- After that, the AAC blocks are steam and pressure cured in an autoclave for 8 to 12 hours and finally, the aerated concrete is cut into blocks.
- It is the full process of manufacturing AAC blocks in the construction.
- The laying process of AAC Block shall have flowed as per IS 6041 of 1985 and IS 1905 of 1987.
- Only a few differences are there Opening and odd angles should be cut with a handsaw in AAC blocks otherwise it is almost smith lar to the brick masonry laying process.
- The vertical joint in AAC blocks shall not be in a straight line.
- In the AAC blocks, a minimum of 250 mm over the bottom course overlapping of block structure should be provided.
- In the AAC blocks the bond beams we can use for heavy-duty fixture attachment it should be placed at the top of the wall.
- In case of cement sand traditional motor, the thickness of the joint should be kept at 10 mm.
- Sometimes 3 to 5 mm thick motor is required if we are using dry mix mortar for AAC blocks.
Some Precautions Should Be Needed When We Laying AAC Blocks That’s Are Below
- Where beams and columns are not used there Avoid using AAC blocks for the load-bearing structure.
- do not use the rich motor with 1:4 as this will shrink, in AAC blocks the Mortar mix should be 1:6. If we used rich thenar then cause cracks in the walls the better results to result in AAC blocks the Portland pozzolana cement should be used.
- In AAC blocks after every three-metered-meter length is necessary to provide stiffener.
Why Do AAC Blocks Get Cracks? and Its Prevention
Due to Dry Shrinkage
- After manufacturing, AAC blocks It also need to dry for 10 to 15 day to obliterate contraction and expansion and its require 28 days curing.
- Due to expansion and cont, action there are more chances of cracks If manufacturers do not follow the process and deliver material early on the construction site.
- while dropping from a low height the AAC blocks may break easily having to have voids because the AAC blocks are brittle material.
Due to the Use of Cement Mortar
To avoid the development of cracks we should always use adhesive. For the installation of AAC blocks, we can use cement mortar as well as an adhesive.