Discover Civil may | Page 58

The Material Most people have never heard of Autoclaved Aerated Concrete, commonly known as AAC, as a building material. Yet it’s been around a long time. It was invented in Sweden in 1923 when their forests were substantially depleted. AAC is a superior alternative to red clay bricks manufactured using fly ash mixed with cement, lime, water and an aeration agent placed in an autoclaved chamber. The resultant building material comprising of millions of tiny air pores is set and cut into blocks of varying sizes. So what’s actually AAC stands for and what does it convey? According to Webster's Dictionary definitions: to autoclave is to use superheated steam under pressure, to aerate is to impregnate a substance with air, and concrete is a hard strong building material made by mixing a cementing material (as Portland cement) and a mineral aggregate (as sand and gravel) with sufficient water to cause the cement to set and bind the entire mass. It is possible to construct virtually an entire house from autoclaved aerated concrete, including walls, floors - using reinforced aircrete beams, ceilings and the roof. Autoclaved aerated concrete is easily cut to any required shape. Manufacturing If we look at its manufacturing it’s quite similar to baking a cake where baking soda act as a raising agent by releasing carbon dioxide when used in baking. Its main ingredients include sand, water, quicklime,