Aircrete (aerated) blocks are the lightest of the family of concrete blocks and correspondingly have the highest insulation value, making them a popular choice for both internal walls and in foundations. They are available in a wide range of sizes, have a range of densities (typically 460 kg/m3 to 770 kg/m3), compressive strengths (2.9 to 9.0 N/mm2) and thermal conductivity values (typically grouped as 0.11, 0.15 and 0.19 W/mK) and can be constructed using conventional mortar or the thin-joint technique.
They are used in structural applications for low-rise construction, as components of curtain walling in higher buildings and for partitions. Aircrete blocks can perform a similar range of functions as aggregate blocks. The blocks are made from cement, lime, sand, fly ash (FA) and water. FA or ground sand is mixed with water to form slurry. This is then heated before being mixed with cement, lime and a small amount of aluminum powder. The aluminum reacts with the lime to form bubbles of hydrogen. As the mixture expands into a ‘cake’ the hydrogen is diffused and replaced by air. When the mixture is partially set, it is cut to block size and transferred to an autoclave where it is high pressure steam-cured to develop strength and the final properties which are fully achieved after autoclaving.