Bitumen is a dark brown complex mixture composed of hydrocarbons with different molecular weight and their nonmetallic derivatives, which is a kind of organic liquid with high viscosity. Mostly in the form of liquid or semi-solid petroleum, black surface, soluble in carbon disulfide, carbon tetrachloride. Asphalt is a kind of organic cementitious material which is waterproof, moisture-proof and anticorrosive. Asphalt can be divided into coal tar pitch, petroleum asphalt and natural asphalt three kinds: among them, coal tar pitch is a by-product of coking. Petroleum pitch is the residue of crude oil after distillation. Natural bitumen is stored underground, forming seams or accumulating on the surface of the earth's crust. Asphalt is mainly used in coatings, plastics, rubber and other industries as well as pavement.