Asfalto (material bituminoso)

The dark, brownish-black bituminous resin that is found in natural deposits or is produced as a byproduct of oil refineries. It has consistencies varying from viscous liquid to glassy solid. It is composed of aliphatic, alicyclic, and polycyclic aromatic hydrocarbons. It is soluble in oils and waxes and can act as a plasticizer or a strengthener, depending on the hardness of the variety. Natural asphalt, which is believed to have been formed during an early stage in the breakdown of organic marine deposits into petroleum, characteristically contains minerals, while residual petroleum asphalt does not. Asphalt has been used since the 3rd millennium BCE for waterproofing; it is also used for road paving, roof coating, joint sealing, and a waterproof barrier in sandy soils. Ancient sources for asphalt were Egypt, the north end of the Dead Sea, the Is river northwest of Babylon, and the Greek island of Zante.