Types of binder
Three types of binder can be identified:
- natural binders (natural bitumen or asphalt rock);
- bitumes, obtained by refining and processing crude oil;
- tars (obtained by retorting coal).
Hydrocarbon binders is mainly composed of assemblies of carbon and hydrogen atoms.
Other binders that are derived from bitumen (bitumen emulsions, flux of cutback bitumens) are less viscous than the base bitumen which means they can be used at lower temperatures.
At the present time, almost all of the upper layers in pavements are made from bitumens and aggregate.