Aerated concrete (also known as autoclaved aerated concrete or AAC) is a lightweight building material made from cement, lime, sand, and water, in which millions of tiny air bubbles are created by adding a foaming agent (aluminium paste), giving the material its characteristic cellular structure.
Composition and production
Aerated concrete is produced by combining a mixture of finely ground quartz sand, cement, lime, and water with a small amount of aluminium paste. The aluminium reacts with the lime to form hydrogen gas, which creates millions of microscopic air bubbles throughout the mixture.
After rising, the raw mass is cut into the desired shapes and then autoclaved: the material is steam-cured under high pressure and temperature (approximately 190 degrees Celsius). This autoclaving process gives aerated concrete its final strength and dimensional stability.
The result is a material with very low density (400-700 kg/m3) compared to ordinary concrete (approximately 2400 kg/m3). The trapped air cells provide excellent thermal insulation properties.
Properties
- Lightweight: four to six times lighter than normal concrete
- Thermal insulation: good insulation value due to trapped air cells
- Fire resistance: non-combustible and resistant to high temperatures
- Workability: easy to saw, drill, and mill with standard tools
- Dimensional stability: minimal shrinkage after autoclaving
- Sound insulation: moderate, less effective than heavier materials
Application
Aerated concrete is widely used in both residential and commercial construction. The material is available as blocks, panels, and lintels. AAC blocks are commonly used for internal and external walls. Reinforced aerated concrete panels serve as floor and roof elements. Due to its low weight, aerated concrete is particularly suitable for adding storeys to existing structures and for situations where the load-bearing structure has limited capacity. It is one of the most popular masonry materials in Europe and continues to grow in use worldwide.
Related terms
- Autoclaved aerated concrete (AAC)
- Lightweight concrete
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