Asphalt

Asphalt is a thick, black-brown, viscous hydrocarbon that occurs naturally and as a byproduct of petroleum refining.   Pitch and bitumen are variations of asphalt with different viscosities (resistance to flow).   At higher temperatures, asphalt become less viscous and flows; that is, it is a liquid.   Natural asphalt was known and widely used by the ancients, who used it for waterproofing ship joints, homes, barns, baskets, clothing, cisterns, etc.   Since the production of asphalt is cheap, it is widely used commercially for road paving, roof coating, joint sealing and as a waterproof barrier to maintain water levels for crops in sandy soils.

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