Bitumen is a black or dark-colored (solid, semi-solid, viscous), amorphous, cementitious material that can be found in different forms, such us rock asphalt, natural bitumen, tar and bitumen derived from oil, which is referred to as petroleum bitumen.
Currently most of the roads globally are paved with bitumen. Today the world’s demand for bitumen accounts for more than 100 million tons per year which is approximately 700 million barrels of bitumen consumed annually.
Petroleum bitumen is typically referred to as bitumen or asphalt. In Europe for instance bitumen means the liquid binder. In North America, on the other hand the liquid binder is referred to as asphalt, or asphalt cement.
In general the term “bituminous materials” is used to denote substances in which bitumen is present or from which it can be derived. Bituminous substances comprise of primarily bitumens and tars.
Bitumen occurs in nature in several forms: hard one - easily crumbled bitumen in rock asphalt and softer, more viscous material which is present in tar sands and asphalt 'lakes'. Another way in which bitumen can be obtained is through petroleum processing in this manner the bitumen is essentially the residue yielded through a distillation process of petroleum. Although bitumen can be found in natural form, the world currently relies for all purposes on petroleum. The material has been produced in this way for over a hundred years.
Tars on the other hand do occur in nature. Tars derive as condensates from the processing of coal (at very high temperatures), petroleum, oil-shale, wood or other organic materials. Pitch is produced when a tar is partially distilled so that the volatile components have evaporated.
Often coal tar is confused with bitumen however they are two entirely chemically different products and should not be mistaken.