Types of Base Course

1. Granular Base Course:

A mixture of soil particles ranging in size from coarse to fine. Processing involve crushing oversized particles and screening where it is necessary to secure the desired grading. The requirements of a satisfactory soil aggregate surface are;

• Stability
• Resistance to abrasion
• Resistance to penetration of water
• Capillary properties to replace moisture lost by surface evaporation upon the addition of wearing course requirement change.
  

2. Macadam Base:

Successive layers of crushed rock mechanically locked by rolling and bonded by stone screening (rock duct, stone chips etc).

3. In-water bound Macadam:

The crushed stones are laid, shaped and compacted and then finer materials are added and washed into surface to provide a dense material.

4. Treated Bases:

Compose of mineral aggregate and additive to make them strong or more resistant to moisture. Among the treating agents is bitumen.