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The part of the road which is finished with a hard smooth surface is known as a pavement. It helps in making them durable and able to withstand traffic.
Types of road pavement
(a) Flexible pavements
The pavements which have a very low flexural strength and are flexible in their structural behaviour under the wheel loads are called flexible pavements. Because of the low flexural strength, the pavement deforms if the sub-grade deforms, in flexible pavments the vertical load of traffic is transmitted to the lower layers by grain to grain transfer. A well compacted granular structure forms a good flexible pavement layer.
The load transferring ability of the flexible pavement depends on the type of material and thickness of payment. The pavement thickness is so designed that the stress on the sub-grade soil is kept within its bearing capacity and the sub-grade is prevented from excessive deformations. In flexible pavement the sub-grade plays an important role as it carries the vehicle load transmitted through the pavement. The strength and smoothness of the pavement depend to a great extent on the deformation suffered by the sub-grade.
All bituminous pavements, Water Bound Macadam (W.B.M), gravel pavements etc., are the example of flexible pavements.
(b) Rigid pavements
Rigid pavements are those which possess a considerable flexural strength of flexural rigidity.
A Rijid payment derives its capacity to withstand loads from flexural strength. The rigid pavement has the slab action and is capable of transmitting the loads to a wider area. The Rigid pavment does not get deformed to the shape of the lower surface as it can bridge the minor variations of the lower layer.
Cement concrete pavement is the best example of the Rigid pavement.
(c) Semi-rigid pavement
Semi-rigid pavements represent an intermediate state between the Flexible and the Rigid pavement. The flexural strength of such type of pavment is much lower than the concrete slab, but it derives support by the lateral distribution of loads through the pavement depth as in flexible pavement.
Lean cement concrete, soil cement and lime-puzzolanic concrete construction are examples of semi-rigid pavements.
Book- Highway Engineering, Writer- A.K. Upadhyay