Bitumen is the heaviest, thickest form of petroleum. According to the U.S. Geological Survey, bitumen is further-distinguished as extra-heavy oil with a higher viscosity. Natural bitumen, also called tar sands or oil sands, shares the attributes of heavy oil but is yet more dense and viscous. Natural bitumen is oil having a viscosity greater than 10,000 cP. Natural bitumen and heavy oil differ from light oils by their high viscosity (resistance to flow) at reservoir temperatures, high density (low API gravity), and significant contents of nitrogen, oxygen, sulfur compounds, and heavy-metal contaminants. They resemble the residue from the refining of light oil. For naturally occurring bituminous sands used for petroleum production, see Oil sands.
The terms bitumen and asphalt are mostly interchangeable, except where asphalt is, used as an abbreviation for asphalt concrete.
The primary use (70%) of asphalt/bitumen is in road construction, where it is used as glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including the production of, roofing felt and for sealing flat roofs.
The terms, asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In American English, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside the United States, the product is often called bitumen. Geological terminology often prefers the term bitumen. Common usage often refers to various forms of asphalt/bitumen as “tar”, such as at the La Brea Tar Pits. Another archaic term for asphalt/bitumen is “pitch”.
The term “crude bitumen” sometimes specifies naturally occurring asphalt/bitumen. Its viscosity is similar to that of cold molasses, while the material obtained from the fractional distillation of crude oil boiling at 525 °C (977 °F), is sometimes referred to as “refined bitumen”.
