Process by which compressed air is blown into vacuum bottom residue, typically at 230-260 C in a reactor. This process results in complex reactions (Such as dehydrogenation, polymerization, Oxidation) different grades for suited applications produced due to ratio of air blowing. 90 percent of the bitumen is used in the construction and maintenance of roads and the remaining 10 percent is used in the roofing and other (canals tunnels, pipe coating). Various types bitumen are as follows: Petroleum Bitumen: Mixture of hydrocarbons derived from petroleum. Black or brown it varies from viscous to solid, producing by air blowing process vacuum bottom (crude oil derivaties) Coal Tar: Coal tar is a black or dark brown a residue produced by the heat treatment of coal. It is solid at room temperature. Natural Bitumen: This bitumen is extracted from mines, which are used in many industries, including road construction, the paint industry, polish and insulation of tanks, tubes and molding. Although we have a lot of producers of bitumen but the two main refineries are Pasargad and Jay