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Types of pavements

Pavement and their Types

Road is rigid surface constructed between two places that is used for transportation.so people can travel form one place to another using motor, bike, truck etc. based on rigidity roads are divided into two types of roads which are given below:

  • Flexible roads
  • Rigid roads

Types of Pavement

Flexible Roads:

Flexible roads consist of four layers and require proper maintenance or it will crumble due to heavy load traffic. All type of roads are flexible roads except concrete roads 

  • Sub Grade:
  • Sub Base:
  • Base course
  • Surface course

Sub Grade:

Sub grade is the first structural part of road or you can say it’s the lowest part of the road. This part is usually laid on the surface level of earth or sometimes the earth soil is excavated and replace with the new soil of having great soil bearing capacity. If the earth beneath the sub grade have low soil composition then using this material for the road will not make the road great it will crumble under heavy load that is why the sub grade is replace with good soil having good soil composition, and bearing capacity. Sub grade material must have good drainage good characteristic. All road load is transmitted to the sub grade if this part fail the whole road fails the strength of sub grade load bearing is measured by California Bearing Ratio (CBR) test. Its level must be kept above flood level up to 60 cm (2 feet).  

Function of Sub Grade:
  • Subgrade support the all the loads it is the foundation of road
  • It transmits the load through grain to grain contact

Sub Base:

In construction of road the sub base layer is laid upon sub grade. Its material is batter then sub grade. Usually it is constructed form, local gravel stones. Upon sub base lays base course. If sub grade is strong then there is no need for sub base but if sub grade is of poor quality then sub base is provided. The thickness of the sub base layer is kept between 15 to 7.5 cm (3 to 6 inch). For concrete road the thickness of sub base is kept 15 cm (6 inch).

Functions of Sub Base:
  • Sub base block rise capillary action or water rising.

Base Course:

This layer of road is constructed on sub base or sub grade. This is usually a mixture of crushed stones and binders. This layer transmitted the traffic load to sub base or sub grade. For concrete road this layer is made of concrete slab. The thickness of this layer depends on the thickness of sub grade and on the traffic volume.

Functions of Base Course:
  • Base course stop the deformation of surface course because of its sufficient density
  • It Supports the surface course
Materials:
  • In Upper Base, the high quality materials is used if the intensity of load is high or increases.
  • In Lower Base, the high quality materials is used if the intensity of load is not high or decrease.

Surface Course:

 It’s the upper most layer of the road it is also called wearing course. Its main function is to stop rain water or water coming from any other source into the lower layers of road. However, it also keeps the surface of road smooth and also resists abrasive friction of the traffic.  In flexible road asphalt concrete is used for surface course.

Functions of Surface Course:
  • Surface course stop the penetration of water in to the pavement
  • Binder Course join or bond the surface Course with the Base of road.
  • Surface Course allow a smooth riding
  • Surface coarse used to Saves the lower surfaces from abrasion and also protect the moving vehicles from effects of weathering.
Material:
  • Surface course is construct from bituminous materials.
  • In construction of flexible pavement asphalt concrete is used

Except for these roads the topper most layer is called the surface course of the road examples are

  • Earthen roads
  • Gravel roads
  • Moorum roads
  • Water bound macadam roads
  • Bituminous roads
  • Concrete roads

Rigid Roads:

Rigid roads consist of three layers they are non-flexible roads concrete roads are the best example of the rigid roads

  • Sub grade
  • Base course
  • Surface course

Sub Grade:

Sub grade of rigid road is same as flexible road in rigid road it is the first structural part of road and lowest part of the road. Sub grade is actually rest on the surface level of land. sometimes the soil of earth is excavated and replace with the new soil of having great soil bearing capacity. If the soil composition or bearing capacity below the sub grade is low, then the materials of road using in construction. it will collapse because of heavy load that’s why the sub grade is replace with good soil having good soil composition, and bearing capacity. Sub grade material must have good drainage, good characteristic. All road load is transmitted to the sub grade if this part fail the whole road fails the strength of sub grade load bearing is measured by California Bearing Ratio (CBR) test. Its level must be kept above flood level up to 60 cm (2 feet).  

Function of Sub Grade:
  • Subgrade support the all the loads it is the foundation of road
  • It transmits the load through grain to grain contact

Base Course:

Base course of rigid road is also same as flexible road This layer of road is constructed on sub grade. Typically, base course is a mixture of crushed stones and binders. This layer transmitted the traffic load to sub base or sub grade. For concrete road this layer is made of concrete slab. The thickness of this layer depends on the thickness of sub grade and on the traffic volume.

Functions of Base:
  • Base course stop the deformation of surface course because of its sufficient density
  • It Supports the surface course
Material:
  • In Upper Base, the high quality material is used if the intensity of load is high or increases.
  • In Lower Base, the high quality material is used if the intensity of load is not high or decrease.

Surface Course:

 In rigid road reinforced cement concrete (RCC) is used. It’s the upper most layer of the road it is also called wearing course. Its main function is to stop rain water or water coming from any other source into the lower layers of road. However, it also keeps the surface of road smooth and also resists abrasive friction of the traffic.

Functions of Surfacing Course:
  • Surface course stop the penetration of water in to the pavement
  • Binder Course join or bond the surface Course with the Base of road.
  • Surface Course allow a smooth riding
  • Surface coarse used to Saves the lower surfaces from abrasion and also protect the moving vehicles from effects of weathering.
Material:
  • For the construction of Rigid Pavements Reinforced Cement Concrete (RCC) is used

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