Bitumen is produced from selected crude oils through a process of Fractional Distilation.
The crude oil is heated to temperatures of between 300 and 350 degrees Celsius and fed into a distillation column allowing the lightest fractions of the crude to separate, through vaporization, from the heavier fractions, which remain liquid.
The higher boiling point fractions are then drawn-off via a heat exchanger and enter a vacuum distillation column. This process produces a "short residue" that is used to manufacture several grades of bitumen. The pressure and temperature conditions within the vacuum process will determine the hardness of the short residue, and. The short residue may be further modified by 'air blowing' in which air is passed through the residue at temperatures of 250 - 300 degrees Celsius.
These are Penetration or Paving Grades of bitumen used in road surfacing, and some industrial applications
Additional processing yileds other grades of bitumen products and their applications are
Oxidized Bitumen - produced by more vigorous air blowing; they are more 'rubber like' and less temperature susceptible than the paving grades. Used in roofing, waterproofing, electrical products, and many others.
Hard Grade Bitumen - harder paving grades and are used in making paints and enamels etc
Cutback Bitumen - Blends of penetration bitumen with Solvent such as kerosene used in spraying and some mixing applications
Emulsion - Stabilized Suspensions of bitumen in Water. used largely in road surfacing applications
Polymer Modified Bitumen - Mixtures of selected bitumen with polymers such as Thermoplastics or Elastomer used in many applications