Autoclaved Aerated Concrete (AAC) – A New Green Building System

Autoclaved Aerated Concrete (AAC) | Efficient Building Systems | Green Material

Autoclaved Aerated Concrete (AAC) was developed in Sweden in the late 1920s and has been used successfully in a variety of applications in commercial, industrial and residential construction. AAC is a lightweight, high strength building material and is produced in a variety of forms from blocks, to structural floors and wall panels.

AAC is credited by LEED (Leadership in Energy and Environmental Design) and USGBC (US Green Building Council) as an “green” alternative to traditional construction materials. Indian Green Building Council (IGBC) recommends its use in India.

AAC consists of 80% of air. It is manufactured by combining silica in the form of sand or recycled flyash, cement, lime, water and an expansion agent – aluminium powder and paving it into a mold.

Autoclaved Aerated Concrete (AAC) – A New Green Building Material
Autoclaved Aerated Concrete (AAC) – A New Green Building Material

Structurally reinforced AAC products like lintels or roof panels, steel rebar or mesh are also placed in the mould.

When added to concrete, the aluminium powder reacts with the silica, resulting in the formation of millions of microscopic hydrogen bubbles. The hydrogen bubbles cause the concrete to expand to roughly five times its original volume.

The hydrogen evaporates and leaving a highly closed cell aerated concrete. It is then cut into blocks or panels which are then steam and pressure cured in an autoclaved. Using AAC is very advantageous because it is environmentally friendly qualifies as a ‘green’ building material from manufacturing to recycling.

All the waste material like trimmings, rejected units are all recycled and hence there is zero wastage. All the waste on the sites is crushed and safely used as a fill or buried shallow underground. Spread AAC dust on the lawn serves as a great lime supplement.

AAC is so lightweight, it weighs 1/5th of the weight of the standard concrete, which results in lower transportation costs, faster work-flow lower material handling costs etc. AAC is in ‘ready to build’ material, requiring no onsite curing time. It has unparalleled workability because it can be sown, drilled, nailed, screwed and milled with common hand tools. AAC openings are easily and alternately cut.

The accurate panels are finished with a very thin mortar joint producing a surface that requires minimum rendering. AAC possesses excellent structural integrity, resisting moisture penetration.

Additional weather and moisture resistance is achieved with a surface treatment such as stucco, plaster and paint or cladding such as bricks or other exterior materials.

AAC has outstanding durability qualities over traditional materials, like humidity, freeze/thaw cycles and chemical attack. AAC is non-combustible. It offers the greatest fire resistance than any building material.

The use of AAC eliminates the need for applying costly fire proofing materials. AAC has extraordinary thermal insulating qualities and because of its unique physical structure. AAC provides much greater thermal insulation than conventional masonry.

AAC is pest resistant because there are no voids for insects/pests to make homes. AAC cannot be penetrated by termites or insects and hence reduces the need of pesticides. AAC has shown to provide better sound insulation and absorption than any other solid building material under comparable conditions and so it is ideal for projects that require greater acoustic insulation such as apartments, hotels and entertainment halls. Walls, floors and roofs constructed with AAC reduce the transmission of sound 7dB greater than other building material of the same weight.

Its relatively low consumption of low materials, excellent durability, relative cost effectiveness and the ability to be recycled. AAC has been aptly called the ‘Superhero’ of building materials.

3 thoughts on “Autoclaved Aerated Concrete (AAC) – A New Green Building System”

  1. I would like to add that It has better capillary water absorption performance in comparison to clay brick because AAC had discontinuous pores. We can put a clay brick and AAC brick of same size in water and can see the performace. clay brick becomes completely wet and AAC brick remains approximately unaffected. There is no penetrain of water on AAC wall. IS Specification code for AAC is IS-2185 ( Part – 3 ) and water absorption test is not included as not required in case of AAC. So, AAC is excellent material.

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