What Is Road Pavement?
Road pavement is a hard surface covered with concrete or asphalt. The surface of the pavement is made of durable material. The purpose of a pavement is to carry vehicle or foot traffic.
Road pavement should have adequate skid resistance, proper ride quality. It should also have favorable light-reflecting characteristics and low noise pollution etc.
Pavements are used in various places as roads, runways, parking areas, etc. Land transport is used for most transportation in the world. This is why pavements should be properly designed for construction. And it should be strong and durable for his life.
The number of vehicles, speed of vehicles, climatic conditions, and other factors should be taken into consideration while designing the pavement.
The Function of Road Pavement
The main function of a pavement is to survive without being distorted by loads applied by heavy vehicles such as heavy trucks or aircraft. Water is harmful to the pavement. Water damages its surface by chemical reaction with the pavement. Adequate drainage is provided when constructing the pavement.
The primary function of the pavement is to transmit the vehicle load to the sub-base and the underlying soil. Modern, flexible pavements are composed of sand and gravel or crushed stone. This material is well compacted with binder materials such as bitumen, tar or tar, or bitumen oil. In addition, the pavement has plasticity-like properties to absorb shocks.
Ideal Road Pavement Requirement
An ideal pavement should have the following requirements,
- The pavement should be designed to be strong enough to withstand all types of stress.
- The pavement should be thick enough to distribute the wheel load stress to a safe value on sub-grade soils.
- The surface of the pavement should be such that enough friction is generated to prevent the vehicle from slipping.
- Noise from vehicles moving on the surface of the pavement should be minimum.
- The surface of the pavement should be such that the road users get comfort at high speed on a smooth surface.
- The surface of the pavement acts as an impermeable surface. So as to provide safety to sub-grade soils.
- The surface of the pavement is designed for long life with low maintenance costs.
- The surface of the pavement should be dustproof so that there is no safety hazard for traffic.
Types of Pavement
- Flexible Pavement
- Rigid Pavement
1. Flexible Pavement
This type of pavement is designed to distribute the wheel load of the vehicle over a wide area. In which stress decreases due to the depth of pavement.
The advantage of the stress distribution characteristic is that the flexible pavement has many layers. Due to this characteristic, the design of flexible pavement is done by multi-layered construction.
Flexible pavement is based on the best quality of the top layer, which is able to withstand maximum compressive stress.
Low-quality materials can be used in the flexible pavement due to low stress intensity in lower layers. Bituminous material is used in the composition of flexible pavement.
Flexible pavement has a granular structure of layers, which transmits vertical or compressed stress to the lower layers. Because they are in contact with each other or its layer is fully compacted.
In flexible pavement, a strong compacted granular structure is formed using strong graded aggregates, which divides the compressed stress into a wider area. Which helps create a flexible pavement layer. This load transfer capacity of this layer depends on its mixed design and material factors.
Typical Layers of Flexible Pavement
The layers of flexible pavement consist of different layers. Its layer includes seal coat, surface course, tech coat, binder course, prime coat, base course, sub-base course, compacted sub-grade, and natural sub-grade.
1. Seal Coat
The seal coat is applied to the surface as a thin layer of flexible pavement. The seal coat layer is applied to the surface of the pavements to provide water-proof and skid resistance.
2. Tack Coat
Tack coat is the only application of asphalt. The use of a track coat provides proper bonding between the two layers of pavement. This application should be thin so that it covers the entire surface of the pavement evenly. This coat is set very quickly between two layers.
3. Prime Coat
Prime Coat is an application of viscous bitumen to apply on absorbent surfaces such as granular material. After prime coat, a binder layer is placed on it. Thus the prime coat acts to provide a bond between the two layers. The prime coat is applied at a lower level, which removes voids and helps to create a water-tight surface for the surface of pavements.
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4. Surface Course
These surfaces are in direct contact with traffic loads and usually use the best quality materials. This type of layer is made of dense grade asphalt concrete (AC).
5. Binder Course
This layer provides the amount of asphalt concrete composition by layer. The main purpose of this type of layer is to distribute the load coming to the base course. It does not require as much quality as the surface course.
6. Base Course
The base course is provided below the surface of the binder course. The base coarse helps in load distribution. And contributes to sub-surface drainage. The base coarse can be made of crushed stone, crushed slag, and frozen material.
7. Sub-Base Course
Sub-base courses are offered at this level below the base course. This level serves to support the structural level, improve drainage, etc. The sub-base course acts as a filler between the sub-grade and the base course.
8. Sub-Grade
This layer should be compacted to the desired density. This layer is a layer of natural clay prepared above the soil, which is designed to transfer stress from the upper layers.
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2. Rigid Pavements
Rigid pavements have sufficient flexural strength to transfer the stress generated on the surface by the wheel load.
This type of pavement is formed directly on a compacted subgrade or on a single layer of stable material. Only one layer is constructed between concrete and sub-grade. This level is commonly called the base or sub-base course.
In rigid pavement, the traffic load of vehicles is transferred by concrete slab action.
The design of rigid pavement should be analyzed using plate theory rather than layer theory. It is assumed to be covered by an elastic plate on a viscous foundation.
In plate theory, it is assumed that the road slabs act as a medium thick plate for pavement. In which the plain remains before loading on the surface. And the plane remains after loading on the surface—pavement slabs experience wheel loads, temperature variations, and the resulting tensile, flexural stress, etc.
This semi-rigid pavement material has low resistance to load impact and abrasion resistance. The course of flexible pavement surface is used during the construction of these pavements.
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Difference Between Rigid Pavement and Flexible Pavement
| Sr No | Flexible Pavement | Rigid Pavement |
| 1 | Flexible pavement is formed by a series of layers with the highest quality material close to the pavement | A layer of rigid pavement is formed as a Portland cement concrete slab base |
| 2 | This type of pavement reflects distortions of the subgrade on the surface and its lower layers. | This type of pavement is capable of performing in areas of local failures and inadequate support. |
| 3 | The stability of a flexible pavement depends on the interlock, subtle friction, and synchronization of the material in its layers. | The strength of rigid pavement is provided only by the pavement slab. |
| 4 | The design of this type of pavement depends heavily on the strength of the subgrade | The strength of this type of pavement depends on the flexural strength of the concrete |
| 5 | This type of pavement works by distributing the load through the component layers. | This type of pavement is able to distribute the load over a wide area of the subgrade due to the high modulus of hardness and elasticity of the concrete. |
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