Rigid Pavements are those which possess noteworthy flexural strength or flexural rigidity. The rigid pavements are generally made of Portland Cement Concrete (CC) and are therefore called ‘CC Pavements’. Plain cement concrete pavements slabs made of specified strength characteristics are laid, with or without steel reinforcement at the joints.
The most common material used for the design and construction of rigid pavements is high-quality plain cement concrete meant for the pavement, generally called ‘Pavement Quality Concrete’ (PQC). The CC pavement slabs made of PQC are generally expected to sustain up to 45kg/cm2 of flexural stresses.
Objective of Rigid Pavements
In the case of Rigid Pavements, the design is essentially based on the flexural strength of the CC pavement slab that is considered in the design and the stresses that are likely to develop due to:
1. The application of the anticipated wheel loads
2. The climate variables in the region
The CC pavement is to be designed so as to sustain the expected wheel loads during the design life. Therefore it is necessary to carry out axle load distribution studies and to determine the design wheel load based on the spectrum of wheel loads on the road. The CC pavement has to withstand the fatigue caused by the repeated application of the loads exceeding the design wheel load during the design life.
Advantage of Rigid Pavements
- CC pavements do not get deteriorated under wet weather conditions and when exposed to stagnant water.
- CC pavements of major roads are generally designed and constructed for 30 year period and therefore the service life could be 30 years or even more. The routine and periodic maintenance costs are very low as the maintenance of joints only are required.
- The life cycle cost of CC pavements is much lower than that of flexible pavements.
- The total thickness of CC pavement and the number of hard aggregates required is lower than flexible pavements, particularly for the construction of highways passing through weak soils and carrying heavy traffic loads.
- Good night visibility even under wet weather conditions..
Disadvantage of Rigid Pavements
- The design of CC pavement is to be carried out for a life of 30 years or more in order to reduce the life cycle cost.
- The ‘design wheel load’ for the design of CC pavement is not equal to the standard wheel load.
- It is not possible to restore a failed or badly cracked CC pavement.
- The surface of the CC pavement is likely to become too smooth and slippery during the long service life and re-texturing of the CC pavement is difficult or too expensive.
- Generally, a long curing period of 28 days is required before opening to traffic. This may be a drawback for the construction of CC pavements on busy urban roads.
Components of Rigid Pavements
- Compacted Soil Subgrade at the bottom or lowest layer
- Granular Sub-base (GSB) course and drainage layer
- BAse Course
- CC/PQC Pavement slab
Affecting Factors of Rigid Pavements
- Wheel Load
- Temperature variations at the location of the road
- Types of joints and their spacing
- Subgrade and the other supporting layers below the CC pavement slab
- Drainage characteristics
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