Air-entrained Concrete:
The cement concrete, prepared through mixing aluminium in it, is known as air entrained or cellular or aerated or gas or foamed concrete.
Subsequent are the categories of air entrained concrete:
Gas Concrete
It is obtained by mixing finely divided aluminium powder in cement matrix. A chemical reaction takes place with hydroxide or alkali or calcium. It liberates hydrogen which forms the bubbles. Hydrogen peroxide can also be used which generates oxygen.
Foamed Concrete
It is produced by adding foaming agent to the mix. It introduces and stabilizes air bubbles during mixing at high speed.
Air entrained concrete may not contain the aggregate. Powdered zinc can also be used in this concrete. Depending upon density, strength and thermal conductivity also vary. Mixes have densities between 480 kg/m3 to 1120 kg/m3. Cellular concrete has a high thermal shrinkage and moisture movement. These can be minimized by high pressure steam curing. It also increases the compressive strength of concrete. Cellular concrete offers better fire resistance than ordinary concrete. It has good resistance to frost. Cellular concrete is mostly suited for partitions for heat insulation purposes due to its low thermal conductivity and for fire proofing.