Comparison between Flexible Pavement and rigid pavement in highway construction

Updated on 13 Feb 2017
Carriageway

A carriage way is defined as the width or portion of road which is used by the vehicular traffic for their movement. It is generally central portion of the total land width and the bituminous concrete is placed or paved as to provide good service for the users. Width of the carriage way depends on the number of the lanes in the road which again depends on the class of the highway. If it is higher level road then it will need more numbers of lanes and therefore the carriage way width will be more.

Pavement is an open, public way for the passage or transport of vehicles, people, and animals. Pavement is finished with a hard smooth surface. The smooth surface helped make them durable and able to withstand traffic and the environment. Road pavements decay over time due to the impact of traffic, particularly heavy vehicles and environmental factors such as weather, pollution. One of the primary functions of the pavement is load distribution.

Pavements are primarily to be used by vehicles and pedestrians. Storm water drainage and environmental conditions are a major concern in the designing of a pavement. The first of the constructed roads date back to 4000 BC and consisted of stone paved streets or timber roads. The roads of the earlier times depended solely on stone, gravel and sand for construction and water was used as a binding agent to level and give a finished look to the surface. All hard road pavements usually fall into two broad categories namely

Purpose of prime coat 

Flexible pavements are those which are surfaced with bituminous or asphalt materials. It’s flexible since the total pavement structure bends or deflects due to the traffic loads. Generally this type of pavement requires some sort of maintenance or restoration every 10 to 15 years.

A flexible pavement structure is typically composed of several layers of material. The layers consist better quality materials will lay on top where the intensity of stress from traffic loads is high and lower quality materials will lay at the bottom where the stress intensity is low. Flexible pavements can be analyzed as a multilayer system under loading. A typical flexible pavement structure consists of the surface course and underlying base and sub base courses. Each of these layers contributes to structural support and drainage.

When hot mix asphalt is used as the surface course, it is the stiffest and may contribute the most to pavement strength. The underlying layers are less rigid but are still important to pavement strength as well as drainage and frost protection. When a seal coat is used as the surface course, the base generally is the layer that contributes most to the structural stiffness. A typical structural design results in a series of layers that gradually decrease in material quality with depth.

A rigid pavement structure is composed of a hydraulic cement concrete surface course and concealed base and sub base courses. The surface course is the rigid layer and provides the majority of strength. The base or sub base layers are orders of magnitude less rigid than the PCC surface but still make important contributions to pavement drainage and frost protection and provide a working platform for construction equipment.

Rigid pavements are substantially harder than flexible pavements due to the high modulus of elasticity of the PCC – Plain Cement Concrete material, resulting in very low deflections under loading. The rigid pavements can be analyzed by the plate theory. Rigid pavements can have reinforcing steel, which is generally used to handle thermal stresses to reduce or eliminate joints and maintain tight crack widths.

 Comparison of Rigid and flexible pavement