Asphalt(USi/sflt/orUK/sflt/,[1][2]occasionally/flt/), also known asbitumen(/btjumn,ba-/),[3][4]is a sticky, black and highlyviscousliquid or semi-solid form ofpetroleum. It may be found in natural deposits or may be a refined product; it is a substance classed as apitch. Until the 20th century, the termasphaltumwas also used.[5]The word is derived from the Greek 'asphaltos' which in turn was borrowed from an Eastern word.[6]The primary use (70%) of asphalt/bitumen is in road construction, where it is used as the glue or binder mixed withaggregateparticles to createasphalt concrete. Its other main uses are forbituminous waterproofingproducts, including production ofroofing feltand for sealing flat roofs.[7]The termsasphaltandbitumenare often used interchangeably to mean both natural and manufactured forms of the substance. InAmerican English, asphalt (or asphalt cement) is the carefully refined residue from thedistillationprocess of selected crude oils. Outside the United States, the product is often called bitumen. Geological terminology often prefers the termbitumen. Common usage often refers to various forms of asphalt/bitumen as "tar", such as at theLa Brea Tar Pits. Another term for asphalt/bitumen, now rather archaic, is "pitch".Naturally occurring asphalt/bitumen is sometimes specified by the term "crude bitumen". Its viscosity is similar to that of coldmolasses[8][9]while the material obtained from thefractional distillationofcrude oilboiling at 525C (977F) is sometimes referred to as "refined bitumen".Contents[hide] 1Composition 2Occurrence 3History 3.1Ancient times 3.2Early use in Europe 3.3Photography and art 3.4Early use in the United Kingdom 3.5Early use in the United States 4Modern use 4.1Rolled asphalt concrete 4.2Mastic asphalt 4.3Asphalt emulsion 4.4Other uses 5Production 5.1From oil sands 5.2Alternatives and bioasphalt 6Etymology 6.1Modern usage 7See also 8Notes 9References 10Sources 11External linksComposition[edit]See also:AsphalteneThe components of asphalt are classified into four classes of compounds: saturates,saturated hydrocarbons, the% saturates correlates with softening point of the material Naphthene aromatics, consisting of partially hydrogenatedpolycyclic aromatic compounds. Polar aromatics, consisting of highmolecular weightphenolsandcarboxylic acids Asphaltenes, consisting of high molecular weight phenols andheterocyclic compoundsThe naphthene aromatics and polar aromatics are typically the majority components. Additionally, most natural bitumens containorganosulfur compounds, resulting in an overall sulfur content of up to 4%. Nickel andvanadiumare found in the