Pavement : Difference between Flexible and Rigid Pavements

A pavement or road is a structure consisting of superimposed layers of processed materials above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads to the sub-grade. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, and low noise pollution. The ultimate aim is to ensure that the transmitted stresses due to wheel load are sufficiently reduced, so that they will not exceed bearing capacity of the sub-grade.

Flexible Pavement

Types of Pavements

Two types of pavements are generally recognized as serving this purpose, namely flexible pavements and rigid pavements. This chapter gives an overview of pavement types, layers, and their functions, and pavement failures. Improper design of pavements leads to early failure of pavements acting the riding quality.

1. Flexible pavement
2. Rigid pavements

Flexible pavement

These pavements reflect the deformation of sub grade and the subsequent layers to the surface. These pavements reflect the deformation of sub grade and the subsequent layers to the surface. Flexible, usually asphalt, is laid with no reinforcement or with a specialized fabric reinforcement that permits limited flow or repositioning of the roadbed under ground changes.

Rigid pavement

The rigid characteristic of the pavement are associated with rigidity or flexural strength or slab action so the load is distributed over a wide area of sub grade soil. The rigid characteristic of the pavement are associated with rigidity or flexural strength or slab action so the load is distributed over a wide area of sub grade soil. Rigid pavement is laid in slabs with steel reinforcement.

Difference between flexible pavements and rigid pavements

Flexible Pavements 1. Deformation in the sub grade is transferred to the upper layers 2. Design is based on load distributing characteristics of the component layers 3. Have low flexural strength 4. Load is transferred by grain to grain contact 5. Have low completion cost but repairing cost is high 6. Have low life span 7. Surfacing cannot be laid directly on the sub grade but a sub base is needed 8. No thermal stresses are induced as the pavement have the ability to contract and expand freely 9. That is why expansion joints are not needed 10. Strength of the road is highly dependent on the strength of the sub grade 11. Rolling of the surfacing is needed 12. Road can be used for traffic within 24 hours 13. Force of friction is less Deformation in the sub grade is not transferred to the upper layers.

Rigid Pavements 1. Deformation in the sub grade is not transferred to subsequent layers 2. Design is based on flexural strength or slab action 3. Have high flexural strength 4. No such phenomenon of grain to grain load transfer exists 5. Have low repairing cost but completion cost is high 6. Life span is more as compare to flexible 7. Surfacing can be directly laid on the sub grade 8. Thermal stresses are more vulnerable to be induced as the ability to contract and expand is very less in concrete 9. That why expansion joints are needed 10. Strength of the road is less dependent on the strength of the sub grade 11. Rolling of the surfacing in not needed 12. Road cannot be used until 14 days of curing 13. Force of friction is high