Page 61 - Lecture Notes DCC3113

4.1.1 About the flexible pavement

Flexible Pavements are constructed from bituminous or unbound material and the stress is
transmitted to the sub-grade through the lateral distribution of the applied load with depth.

The FOUR (4) layers of flexible pavement structure
• Sub-grade soil or simply sub-grade
• Sub-base
• Road Base
• Surface layer

Tack Coat Wearing Course
Surface Course
Prime Coat Binder Course

Base Course

Sub Base Course

Subgrade

Figure 4-3: Cross – section of a Flexible Pavement

The function of Flexible Pavement

 To provide a level/flat surface for a more comfortable and safe journey
 To receive and distribute the load of the vehicle to the ground layers
 To protect the sub-grade layers from damage due to exposure of climate change.

The different between flexible pavement and rigid pavement

Table 4-1: The different between flexible pavement and rigid pavement

Flexible pavement Rigid pavement

In flexible pavement, load distribution is based on Rigid pavement most of the load carries by slabs itself.
layered system.

Due to layered system in flexible pavement, structural Rigid pavement, most of the structural capacity
capacity depends on the characteristics of all layers. depends on the characteristics of slab only, because
of low bearing capacity of underlying layers.
In flexible pavements, intensity of load decreases as A rigid pavement, due to minor capacity of underlying
the depth increases or as the load moves to the further layers maximum load intensity reduces in the top most
underlying layers. layers and that is slab.
Flexible pavement has very low modulus of elasticity Modulus of elasticity of rigid pavement is very high,
(less strength). because of high strength and more loads bearing
capacity than as compared to flexible pavements.
In flexible pavements, underlying layers play very Rigid pavements, little function of underlying layers.
important role. Therefore, more roles are playing only Maximum role is playing by the top layer (that is slab)
underlying layers. by itself. Therefore, little influence on sub layers.

54