Typical Road Structure Cross Section
1. Soil Subgrade:
It is the natural ground on which the road is built which serves as a working plate form for the construction of upper pavement layers generally natural gravel. however in circumstance where the material is not suitable eg. clay, sand etc suitable material should be excavated from elsewhere to replace.
2. Sub Base Course:
This is laid on the subgrade. It is usually not provided on subgrade of good quality. This layer is also generally gravel material. It should be clean and free from organic matter and should be able to be compacted by roller, to form stable sub-base.
3. Base Course:
It is the layer immediately under the wearing surface, base course lies close under the pavement surface subjected to severe loading. The material used must be of extremely of high quality and its construction must be done carefully.
4. Surface Course/Wearing Course:
The top layers of pavement which is in direct contact with the wheel of the vehicle. Usually constructed of material in which bitumen is used as binder materials.
