Asphalt /ˈæsfɔːlt/ ( listen) or /ˈæsʃfɛlt/, also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch. Until the 20th century, the term asphaltum was also used.
The primary use of asphalt is in road construction, where it is used as the glue or binder mixed with aggregate particles to create asphalt concrete. Its other main uses are for bituminous waterproofing products, including 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. Natural deposits terminology also sometimes uses the word bitumen, such as at the La Brea Tar Pits.
Naturally occurring asphalt is sometimes specified by the term "crude Bitumen"; its viscosity is similar to that of cold molasses. whilst the material obtained from the fractional distillation of crude oil (boiling at 525 °C (977 °F)) is sometimes referred to as "refined bitumen".