Bitumen is the visco-elastic binder that gives bituminous mixtures their flexibility and durability. It is produced by distilling crude oil.
Bitumen is visco-elastic. Its properties are affected by temperature and the length of time a force is applied to it. Different grades of bitumen have differing visco-elastic resistance to deformation.
Bitumen can be dispersed in water to form a bitumen emulsion. The bitumen is distributed throughout the emulsion as very small particles that are held in suspension by electrostatic charges created by the addition of an emulsifier.
Full details are given in:
BS EN 12591 replaced most of: BS 3690-1, Bitumens for building and civil engineering
BS EN 13808 replaced most of: BS 434-1, Bitumen road emulsions (anionic and cationic). Specification for bitumen road emulsions