4 Component Parts Of Flexible & Rigid Road Pavements Structure and Their Function - Civil Engineering

Tuesday, 19 March 2019

4 Component Parts Of Flexible & Rigid Road Pavements Structure and Their Function

4 Component Parts Of Flexible & Rigid Road Pavements Structure

The following are the 4 component parts of road pavement:
1) Subgrade or formation.
2) Subbase course.
3) Base course.
4) Surface course or wearing course.
Component Parts Of Flexible & Rigid Road Pavements Structure
Component Parts Of Flexible & Rigid Road Pavements Structure

1) Subgrade or Formation

The finished and compacted surface of earth work on which a road pavement rests is called subgrade or formation. 

Functions of Subgrade

Function of subgrade are as follows:
  1. To provide adequate and uniform support to the road pavements.
  2. To bear ultimately the entire load of pavement including the traffic load transmitted through the pavement.

2) Subbase course

The layer of granular material such as burnt clinker, gravel or slag provided in between the subgrade and base course in a road pavement is called subbase course. In some place boulder stones or bricks are also used as a subbase course.

Function of Subbase Course

The function of subbase course are:
  1. To improve the bearing capacity of the subgrade.
  2. To provide additional help to the base and surface course in distributing the load.
  3. To prevent undesirable entry of fine grained soils from subgrade to base course.
  4. To minimize the damaging effect of frost action.
  5. To improve the drainage.

3) Base Course

The layer of broken stones or brick provided over the subbase course or immediately over the subgrade in the absence of subbase, in a road pavement is called base course.

Function of Base Course

Function of base course are as follows:
  1. To act as the foundation of the road pavement and to transfer the traffic load safely to the subbase and subgrade .
  2. To withstand high shearing stresses due to impact of traffic.
  3. To prevent undesirable entry of subgrade soil in the pavement when the base course is constructed directly over the subgrade.

4) Surface Course or Wearing Course

The top most layer of the road pavement directly exposed to the traffic is called surface course or wearing course. 
In flexible pavement, normally a bituminous surface is used as wearing course. 
In Rigid Pavement, the cement concrete layer acts like a base course as well as wearing course.

Function of Surface or Wearing Course 

Function of surface or wearing course are as follows:
  1. To provide a smooth and uniform rigid surface.
  2. To resist the abrasive forces of traffic.
  3. To prevent dust nuisance.
  4. To act as a structural part of the pavement.
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