Sub-base
A sub-base (also subbase) is a layer of crushed rock or similar material located above the subgrade, but beneath the base course of a road pavement.
The sub-base is often the main load-bearing layer of the pavement. Its role is to spread the load evenly over the subgrade. The materials used may be either unbound granular, or cement-bound. The quality of subbase is very important for the useful life of the road.
Location Within Pavement
