Definition or Meaning of Road Pavement

A layered structure supported by the sub-grade soil to form the carriageway of the road is called a road pavement.

Purpose of a Road Pavement

• The main purpose is to carry heavy wheel loads of vehicular traffic.
• To distribute the vehicular load over a large area of the underlying sub-grade soil.
• Generally to provide a smooth road pavement surface.
• To prevent ill effects of weathering agencies on sub-grade soil.

Requirements of a Good Road Pavement

• Generally road pavement should be suitable to all type of traffic.
• They should be easy to construct and cheap in budget.
• It should be durable and strong.
• They should not develop corrugation.
• It should provide good visibility at night.
• Riding a bike or driving a vehicle must be safe and comfortable on the pavements.
• Maintenance cost should be low.

Component Parts of Road Pavement Structure

• Sub-grade or Formation
• Sub-base
• Base Course or Foundation Course
• Base Coat or Intermediate Course
• Wearing Course

1. Sub-grade :

Definition : The finished and compacted earthwork on which a road pavement rests is called as sub-grade or formation.

Functions of Sub-grade:

• To provide support to the pavements.
• Sub-grade carries entire load of pavement including the traffic.

2. Sub-base :

Definition : A layer of granular material provided in between the sub-grade and the base course in a road pavement is called sub-base.

Functions of Sub-base :

• It improves the bearing capacity of sub-grade.
• It improves drainage and keep check on capillary rise of subsoil water.

3. Base Course :

Definition : A layer of boulders or bricks provided in double layer over the sub-base or immediately over the sub-grade in the absence of sub-base in a pavement is called base course.

Functions of Base Course:

• To withstand high shearing stresses develop due to the impact of traffic on the wearing course.
• To act as foundation to the pavement, which transfers load over the pavement surface to the sub-base and sub-grade lying underneath.

4. Base Coat :

Definition : The layer of hard stones provided in between the base course and the wearing course in a road pavement is called base coat or bearing course or intermediate coat.

Functions of Base Coat :

• Generally to transmit the load over the large area of the base course.
• To act as layer of transmission material.

5. Wearing Course :

Definition : The top most layer of pavement directly exposed to traffic is called as wearing course or surfacing.

Functions of Wearing Course :

• The main function of wearing course is to provide impervious layers so that entry of water to the base course can be prevented.
• Moreover the entire traffic load is safely distributed over the base course.
• It acts as impervious layer, thus avoids the entry of water to the base course.

Types of Road Pavement

• Flexible Pavement
• Rigid Pavement

Flexible Pavement :

Definition : The pavement which can change their shape to some extent without rupture are known as flexible pavement.

The common examples of flexible pavements are all bituminous pavements, gravel pavements, water bound macadam pavement etc.

In India, the flexible pavement are favored mainly for the following reasons :-

(a) It is cheap and easy in construction
(b) Locally available material can be easily used for the construction of road pavement
(c) Require less supervision.

Rigid Road Pavements :

Definition : The pavement which cannot change their shape without rupture are known as rigid pavement. Some of the common example of rigid pavement is cement concrete pavement.