Bituminous pavements are constructed in different layers such as base course, binder course and surface course. These layers are made of different materials and provides different functions to the bituminous pavements.
Different Layers in a Bituminous Pavement
1. Bituminous Base Course
Base course layer in a bituminous pavement consists of mineral aggregates such as gravel, stones and sands bonded together with bituminous materials. This layer is used as the foundation on which surface course or binder is placed.
2. Bituminous Binder Course
Binder course layer is an intermediate layer between base course and surface layer. It is the first layer in case of two-layer bituminous resurfacing. Bituminous binder course is made of bituminous-aggregate mixture, also called as levelling course.
3. Bituminous Concrete Layer
Bituminous concrete layer is a mixture of aggregates continuously graded from maximum size to minimum sizes (typically less than 25mm to 0.075mm aggregates). Sufficient bitumen is added to the mix so that the compacted concrete mix effectively impervious and has acceptable dissipative and elastic properties.