AAC Block Full Form (Autoclaved Aerated Concrete)
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AAC stands for Autoclaved Aerated Concrete — a lightweight, precast building block made from fly ash, cement, lime and a small amount of aluminium powder, cured under steam pressure in an autoclave. The aluminium reacts to create millions of tiny air pockets, which is what makes AAC light and insulating.
What AAC blocks are made of
Fly ash (or sand), cement, lime, gypsum, water and aluminium powder are mixed and cast. The aluminium reacts with the lime to release hydrogen, foaming the mix; it is then cut to size and autoclaved (steam-cured at high pressure), which gives the final strength.
Why builders use AAC over red bricks
| Feature | AAC block | Red clay brick |
|---|---|---|
| Weight | Light (~1/3 of brick) | Heavy |
| Size | Large (fewer joints) | Small |
| Thermal insulation | Good (air pockets) | Lower |
| Mortar & plaster | Less | More |
| Structural dead load | Lower | Higher |
Because AAC is lighter and larger, a wall goes up faster with less mortar, and the reduced dead load can save a little on the structure. Its insulation keeps interiors cooler — useful in Indian summers.
Where AAC is used
AAC blocks are used mainly for non-load-bearing infill walls in RCC-framed buildings — the frame carries the load, the blocks fill the panels. A block-work house needs far fewer units and much less mortar and plaster than the brick figures in the thumb rules.
Frequently asked questions
What is the full form of AAC block? Autoclaved Aerated Concrete — a lightweight precast block foamed with aluminium powder and steam-cured under pressure.
What are AAC blocks made of? Fly ash or sand, cement, lime, gypsum and a little aluminium powder, mixed, cast, cut and autoclaved.
Are AAC blocks better than red bricks? For non-load-bearing walls in framed buildings, AAC is lighter, larger, better insulating and uses less mortar and plaster. Red bricks remain common and are load-bearing.
Can AAC blocks be used for load-bearing walls? They are mainly used as non-load-bearing infill in RCC frames; load-bearing use needs specific design and block grades.
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CivilSite Editorial Team✓ Engineer reviewed
Written and reviewed by practising civil engineers with 10+ years of Indian residential construction experience.