Asphalt is a dark brown complex mixture composed of hydrocarbons with different molecular weight and their non-metallic derivatives. It is a kind of high viscosity organic liquid. It mostly exists in the form of liquid or semi-solid petroleum. Its surface is black and soluble in carbon disulfide and carbon tetrachloride. Asphalt is a kind of waterproof, moisture-proof and anticorrosive organic cementing material. Asphalt can be divided into three types: coal tar pitch, petroleum asphalt and natural asphalt: coal tar pitch is the byproduct of coking. Petroleum asphalt is the residue of crude oil distillation. Natural asphalt is stored underground, and some form ore beds or accumulate on the surface of the crust. Asphalt is mainly used in coatings, plastics, rubber and other industries, as well as pavement.