AAC Blocks Manufacturing Process – Raw Material Preparation

AAC Blocks Manufacturing Process

Step 1 – Raw Material Preparation

AAC blocks manufacturing process starts with raw material preparation. List of raw materials and relevant details are mentioned below.

Fly ash or sand

Key ingredient for manufacturing Autoclaved Aerated Concrete (AAC) blocks is silica rich material like fly ash, pond ash or sand. Most of the AAC companies in India use fly ash to manufacture AAC blocks. Fly ash is mixed with water to form fly ash slurry. Slurry thus formed is mixed with other ingredients like lime powder, cement, gypsum and aluminium powder in quantities consistent with the recipe. Alternately sand can also be used to manufacture AAC blocks. A ‘wet’ ball mill finely grinds sand with water converting it into sand slurry. Sand slurry is mixed with other ingredients just like fly ash slurry.

AAC blocks manufacturing process - Feeding ash into slurry tank

A worker feeding pond ash into slurry tank for AAC blocks manufacturing process.

Limestone powder

Lime powder required for AAC production is obtained either by crushing limestone to fine powder at AAC factory or by directly purchasing it in powder form from a vendor. Although purchasing lime powder might be little costly, many manufacturers opt for it rather than investing in lime crushing equipment like ball mill, jaw crusher, bucket elevators, etc. Lime powder is stored in silos fabricated from mild steel (MS) or built using brick and mortar depending of individual preferences.

AAC blocks manufacturing - AAC blocks manufacturing process

Crusher for grinding lime stone. Notice the bag filter next to it

Cement

53-grade Ordinary Portland Cement (OPC) from reputed manufacturer is required for manufacturing AAC blocks. Cement supplied by ‘mini plants’ is not recommended due to drastic variations in quality over different batches. Some AAC factories might plan their captive cement processing units as such an unit can produce cement as well as process lime. Such factories can opt for ‘major plant’ clinker and manufacture their own cement for AAC production. Cement is usually stored in silos.

AAC blocks manufacturing process - Autoclave and raw material silos

AAC blocks manufacturing process set up – Storage silos for cement, lime powder and gypsum are visible behind autoclaves

Gypsum

Gypsum is easily available in the market and is used in powder form. It is stored in silos.

Aluminium powder/paste

Aluminium powder/paste is easily available from various manufacturers. As very small quantity of Aluminium powder/paste is required to be added to the mixture, it is usually weighed manually and added to the mixing unit.

AAC blocks manufacturing process (…contd…)

AAC Blocks Manufacturing Process Step 2 – Dosing and Mixing

AAC Blocks Manufacturing Process Step 3 – Casting, Rising and Pre-curing

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