AAC Blocks(Autoclaved Aerated Concrete) is an eco-friendly alternative to bricks and is a certified green building material which is lightweight, with sound insulation and water resistant properties, and a durable building blocks and 3 times lighter when compared to red bricks.


AAC Blocks – Manufacturing Process


Materials that are involved in the process

  1. Cement

Cement is one of the most important material in the preparation of AAC blocks. The most suitable form of is fine cement i.e cement of higher grade like OPC grade 53.

  1. Fly Ash

Fly ash is the base of AAC blocks. Fly ash is a waste industrial product obtained from thermal plants. The density of fly ash ranges from 400-1800 kg/m3. It is because of flyash that AAC blocks get properties like thermal insulation, fire resistance, and sound absorption. Class C flyash is usually used.

3. Limestone

Limestone is crushed to fine powder before using it as in ingredient in the process. You can directly purchase lime stone powder or crush it at the factory.

4. Aluminum Powder

Aluminium is required to introduce air bubbles in AAC blocks. This makes the AAC blocks to expand and also make them light. The raw material reacts with aluminium releasing hydrogen gas producing air bubbles in the block.


Step 1: Raw Material Preparation

The process starts with mixing of raw materials like flyash and water to form a slurry.åÊ This is later mixed with other raw materials like cement, gypsum and others.

Step 2: Dosing and Mixing

The ratio with which the materials need to be mixed is very important to maintain the quality of the final product. Hence based on the final product, this ratio is varied.

Aluminium is about 8% of the total dry materials but the water is about 60%of the total mixture.

  1. Fly ash is poured into a container till a desired weight is obtained.
  2. lime powder, cement, and gypsum are in their individual containers connected to a mixer.
  3. These are poured into a mixing drum in required proportions from the individual containers.
  4. After mixing for a certain time, it is poured into moulds of required sizes

Step 3: Casting, Rising and Curing

  1. The final products are poured into moulds. You can have any custom sized moulds based on your requirement.
  2. The moulds are coated with thin layer of oil so that the mixture does not stick to the mould.
  3. Aluminium, calcium hydroxide and water mix to release hydrogen gas. This leads to the formation of tiny bubbles which cause the slurry mix to expand.
  4. The mixture in mould expands up to three times their original size. The bubble is about 2- 5mm in size. The mixture is called green cake.
  5. When the rising of mixture in moulds is over, green-cake is allowed to settle and cure. It takes about 4 hours to rise.
  6. The mixture is then autoclaved in a large pressure vessel with steam at high pressure. The pressure typically reaches 800KPa to 1200Kpa with a temperature of 180å¡C.


Step 4: Demoulding and Cutting

  1. Once the required strength is achieved, the mixture is removed from moulds and cut as per requirements.
  2. Standard market sizes available are
    600 x 200 x 100, 600 x 200 x 150, 600 x 200 x 200.