1. Asphalt

Origin

Although this material is ancient, it is still widely used for certain jobs. Asphalt, not to be confused with bitumen, is a naturally occurring fossil material. It is a rock impregnated with bitumen over the ages, and is found in certain countries.

Today, however, asphalt is most often synthetic, obtained from bitumen distilled from petroleum.

Bitumens are mixtures of varying composition of high molecular weight hydrocarbons, which may be chemically aliphatic, aromatic or naphthenic.

Bitumen fractionation

By using a light hydrocarbon in great excess as a selective solvent, bitumen can be split into two parts:

• the dissolved part (malthenes), which looks like a dark, viscous oil;

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