Cellular concrete is a concrete where the coarse aggregates have been replaced with air bubbles. The uses of air in concrete is nothing new. Air entrainment is now standard practice to improve both durability and workability. For this purpose the amount of air entrained is normally less than 7 percent by volume; for cellular concrete the voids may occupy anything from 25 to 80 percent of the total volume. Cellular concrete has some unique properties. The thermal conductivity of cellular concrete is proportional to density - the lighter, the better insulation. This means that a 10 inch wall of 40 pounds of concrete will have the same insulating value as a brick wall three times as thick. The thermal expansion of cellular concrete is negligible and water resistance of cellular concrete is high due to the uniform nature of the cells and the fact that they are not interconnected. Cellular concretes are special materials highly suitable for insulation of piping and conduit, above and below ground, and as infilling for ducts. Boilers and tanks can also be insulated with cellular concrete, as well as cold storage and conventional buildings.