Perlite insulating concrete consists of a mixture of expanded perlite, Portland cement, water and an air entraining agent. The dry concrete weighs from 20 to 50 pounds per cubic foot, depending on the mix design selected. It is mixed in place, using the same equipment required for handling ordinary concrete, including transit mix trucks. Some of the specific advantages of perlite insulating concrete responsible for its continued acceptance in the construction field are the following: insulation, strength and rigidity, fire safety, and permanence. Insulation is probably of first importance. Loose perlite, because of its sealed dead air cells, is one of the best heat insulators known. A mix of one cubic foot of cement to six cubic feet of perlite aggregate provides both excellent strength and insulation value. Strength and rigidity of the roof deck are also greatly increased. Where metal lath, paper backed wire mesh, or bulb tees and formboards are used, the perlite concrete combines the functions of roof deck slab and insulation. The fire safety of perlite concrete is unsurpassed by most roof insulating materials of equivalent thickness. Perlite concrete is incombustible. When used as insulation over a corrugated steel deck, perlite concrete gives the system more than a 1 hour fire rating. Finally, permanence of perlite insulating concrete is another important factor. Perlite concrete is not subject to rot, mildew, or damage by water. In fact, its strength increases with age. Perlite concrete is also being used as a floor fill in multiple story buildings, in insulating concrete blocks and tilt-up panels, and as exterior insulating walls sprayed on the back of metal panel facings. It can also be used as non-load bearing fill in bridges, tunnels, and other types of construction.