Contact Time Sun - Fri: 09:30 -06.00
Contact Email info@lightbrick.com.np

1st | 3rd Floor, Pashupati Vision Building, Pingalasthan, Gaushala, Kathmandu

PROCESS

The Aerated Autoclave concrete consists of mainly two process- Aeration and Autoclave

  •  The aeration process is due to reaction between quick lime and aluminum powder. In aeration process lime reacts with aluminum powder to produce Tricalcium Hydrate and Hydrogen. This leads to rising of the cake and makes the blocks truly lighter.
  •  Autoclave is the process of producing high pressure and high temperature steam curing in close vessels. Autoclave is a long vessel with a temperature of about 185 degree and pressure at about 700 Kpa. AAC blocks undergo autoclaving for about 14 to 18 hours. This provides required strength to the blocks.

Unlike most other concrete applications, AAC is produced using no aggregate larger than sand. Quartz sand, calcined gypsum, lime (mineral) and/or cement and water are used as a binding agent. Aluminum powder is used at a rate of 0.05%–0.08% by volume (depending on the pre-specified density). In some countries, like India and China, fly ash generated from thermal power plants and having 50-65% silica content is used as an aggregate.

When AAC is mixed and cast in forms, several chemical reactions take place that give AAC its light weight (20% of the weight of concrete) and thermal properties. Aluminum powder reacts with calcium hydroxide and water to form hydrogen. The hydrogen gas foams and doubles the volume of the raw mix creating gas bubbles up to 3mm (inch) in diameter. At the end of the foaming process, the hydrogen escapes into the atmosphere and is replaced by air.

When the forms are removed from the material, it is solid but still soft. It is then cut into either blocks or panels, and placed in an autoclave chamber for 12 hours. During this steam pressure hardening process, when the temperature reaches 190° Celsius (374° Fahrenheit) and the pressure reaches 8 to 12 bars, quartz sand reacts with calcium hydroxide to form calcium silica hydrate, which gives AAC its high strength and other unique properties. Because of the relatively low temperature used AAC blocks are not considered fired brick but a lightweight concrete masonry unit. After the autoclaving process, the material is ready for immediate use on the construction site. Depending on its density, up to 80% of the volume of an AAC block is air. AAC’s low density also accounts for its low structural compression strength. It can carry loads of up to 8 MPa (1,160 PSI), approximately 50% of the compressive strength of regular concrete.

Since 1980, there has been a worldwide increase in the use of AAC materials. New production plants are being built in Australia, Bahrain, China, Eastern Europe, India, Israel, and the USA. AAC is increasingly used by developers, architects, and home builders worldwide.

© 2018 AAC Light brick. Powered By Hamroinfosys