Heavy oil is a general term for unconventional petroleum in the petrochemical industry. It includes heavy oil, high viscosity oil, natural asphalt, oil sands, and oil shale. Heavy oil is generally inactive at normal temperature and can only be extracted from the earth's crust by heating or dilution. In the narrow sense, heavy oil refers primarily to heavy oil. It is the remainder of crude oil after extraction of light oil such as gasoline and diesel oil. Its main characteristics are large molecular weight and high viscosity. It is mainly composed of long-chain hydrocarbons with more than 20 carbon atoms. Compound composition.

Asphalt is divided into natural asphalt, petroleum asphalt and coal tar asphalt. Coal tar pitch is a by-product left after coking, that is, a black, difficult-to-evaporate substance remaining in the distillation kettle after the coal tar is distilled; petroleum pitch is a residue left after the crude oil is distilled and refined, and it is a shiny black sticky Natural bitumen exists in nature itself, and it is mainly stored in the ground, exists as a ore layer or accumulates on the surface of the earth's crust.

Asphalt is a widely used engineering material, and it is known that it is most commonly used in engineering construction, such as road construction. Asphalt and gravel are evenly mixed together and the road paved after compaction is what we usually call the asphalt road.

In fact, the use of asphalt by human beings has a long history. Archaeological studies have found that humans have already used natural asphalt for a long time. At that time, people used weapons to paint bitumen to paint weapons and things. Especially in the two river basin areas, natural asphalt is widely used because of its satisfactory content. The Sumerians there were coated with natural asphalt on the outside of vessels and boats for corrosion resistance. In addition, they also use natural asphalt as a binder in clay bricks to make them more durable.