AAC BLOCK MANUFACTURING PLANT

AAC blocks are light weight Aerated Autoclave Concrete Block. It is manufactured through a reaction of aluminium powder and a proportionate blend of lime, cement, and fly ash or sand. Autoclaved aerated concrete (AAC) is a lightweight cellular concrete that has been used for more than 80 years. Currently, however, no good recycling options for AAC from construction and waste exist. During this process, the hydrogen gas escapes create lots (billions) of tiny air cells, applying AAC with a strong cellular structure. The hydrogen gas or bubbles cause the concrete to expand to roughly thrice times its original volume, further strengthened by high pressure steam curing. The product thus formed is not only light weight concrete but also has higher compressive strength. AAC is a masonry material that is lightweight, easy to construct, and economical to transport. AAC is one of the materials which can cope up with the shortage of building raw materials and can produce a light weight, energy efficient and environmentally friendly concrete. This study deals with the manufacturing process of the autoclaved aerated concrete blocks.

Autoclave aerated concrete blocks are also known as Auto clavedlight weight concrete(ALC) Autoclaved Aerated Concrete (AAC) is one of the eco – friendly and certified green building materials.AAC was perfected in the mid of 1920s by the Swedish architect. It has become one of the most used building materials in Europe and is rapidly growing in many other countries around the world. Basically, AAC is a mixture of cement, fly ash, sand, water, and aluminum powder. When the materials are proportionally weighed, AAC is using no aggregate larger than sand. Here, Aluminum powder reacts with calcium hydroxide and water to form H2. The hydrogen gas foams and doubles the volume of the raw mix creating gas bubbles shown. At the end of the foaming process, the hydrogen escapes into the atmosphere and is replaced by air. When the airs are removed from the material, it is solid but still soft. It is then cut into blocks and placed in a cylindrical chamber for 11-12 hours.

During this steam pressure hardening process, when the temperature reaches 190°C (374°F) and the pressure reaches to a maximum limit of 12 bar, sand reacts with calcium hydroxide to form calcium silicate hydrate, which gives AAC its high strength and light weight properties, solid but soft in nature. After the autoclaving process, the material is ready for immediate use on the construction site. It has become one of the most used building materials in Europe and is rapidly growing in many other countries around the world. The characteristic of AAC is helpful in green housings and saves fertile lands and a solution for fly ash disposal.

Autoclaved aerated concrete is a versatile lightweight construction material and usually used as blocks. Compared with normal (ie: “dense” concrete) aircrete has a low density and excellent insulation properties.

The low density is achieved by the formation of air voids to produce a cellular structure. These voids are typically 1mm-5mm across and give the material its characteristic appearance. Blocks typically have strengths ranging from 3-9 Nmm-2 (when tested in accordance with BS EN 771-1:2000). Densities range from about 460 to 750 kg m-3; for comparison, medium density concrete blocks have a typical density range of 1350-1500 kg m-3 and dense concrete blocks a range of 2300-2500 kg m-3.