Bitumen

Aslt also known as bitumen is a sticky, black and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as a pitch.

Until the 20th century, the term asltum was also used. The word is derived from the Greek 'asltos' which in turn was borrowed from an Eastern word.

The primary use of aslt/bitumen is in road construction, where it is used as the glue or binder mixed with aggregate particles to create aslt concrete. Its other main uses are for bituminous waterproofing products, including production of roofing felt and for sealing flat roofs.

The terms aslt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance. In English, aslt is the carefully refined residue from the distillation process of selected crude oils. This product is often called bitumen. Geologists often prefer the term bitumen. Common usage often refers to various forms of aslt/bitumen as "tar".