Type of Pavement

In near future, the cost of bitumen will go on increasing. So, various alternates to construct the roads are to be explored. Though concrete roads are one of the good alternates, but still their use is limited. This paper discusses the merits and demerits of all types of pavements construction and proposes their optimum use.

Dr Praveen Kumar, Professor, Transportation Engineering Group, Civil Engineering Department, IIT Roorkee. Ankit Gupta, IIT Roorkee.

Introduction

Development of a country depends on the connectivity of various places with adequate road network. Roads are the major channel of transportation for carrying goods and passengers. They play a significant role in improving the socio-economic standards of a region. Roads constitute the most important mode of communication in areas where railways have not developed much and form the basic infra structure for the development and economic growth of the country. The benefits from the investment in road sector are indirect, long-term and not immediately visible. Roads are important assets for any nation. However, merely creating these assets is not enough, it has to be planned carefully and a pavement which is not designed properly deteriorates fast. India is a large country having huge resource of materials. If these local materials are used properly, the cost of construction can be reduced. There are various type of pavements which differ in their suitability in different environments. Each type of pavement has it’s own merits and demerits. Despite a large number of seminars and conference, still in India, 98% roads are having flexible pavements. A lot of research has been made on use of Waste materials but the role of these materials is still limited. So there is need to take a holistic approach and mark the areas where these are most suitable.

Types of Pavements

There are various type of pavements depending upon the materials used. A briefs description of all types is given here.

Flexible Pavements
Bitumen has been widely used in the construction of flexible pavements for a long time. This is the most convenient and simple type of construction. The cost of construction of single lane bituminous pavement varies from 20 to 30 lakhs per km in plain areas. In some applications, however, the performance of conventional bitumen may not be considered satisfactory because of the following reasons:

1. In summer season, due to high temperature, the bitumen becomes soft resulting in bleeding, rutting and segregation finally leading to failure of pavement.
2. In Winter season, due to low temperature, the bitumen becomes brittle resulting in cracking, raveling and unevenness which makes the pavement unsuitable for use.
3. In rainy season, water enters the pavement resulting into pot holes and sometimes total removal of bituminous layer.
4. In hilly areas, due to sub zero temperature, the freeze thaw and heave cycle takes place. Due to freezing and melting of ice in bituminous voids, volume expansion and contraction occur. This leads to pavements failure.
5. The cost of bitumen has been rising continuously. In near future, there will be scarcity of bitumen and it will be impossible to procure bitumen at very high costs.

Recently, a large number investigations have demonstrated that bitumen properties (eg. viscoelsticity and temperature susceptibility) can be improved using an additive or a chemical reaction modification.