Differences Between Concrete and Asphalt Pavement
Historically, pavements have been divided into two broad categories, rigid and flexible. These classical definitions, in some cases, are an over-simplification. However, the terms rigid and flexible provide a good description of how the pavements react to loads and the environment.
The flexible pavement is an asphalt pavement. It generally consists of a relatively thin wearing surface of asphalt built over a base course and subbase course. Base and subbase courses are usually gravel or stone. These layers rest upon a compacted subgrade (compacted soil). In contrast, rigid pavements are made up of portland cement concrete and may or may not have a base course between the pavement and subgrade.
The essential difference between the two types of pavements, flexible and rigid, is the manner in which they distribute the load over the subgrade. Rigid pavement, because of concrete’s rigidity and stiffness, tends to distribute the load over a relatively wide area of subgrade. The concrete slab itself supplies a major portion of a rigid pavement's structural capacity. Flexible pavement, inherently built with weaker and less stiff material, does not spread loads as well as concrete. Therefore flexible pavements usually require more layers and greater thickness for optimally transmitting load to the subgrade.
The major factor considered in the design of rigid pavements is the structural strength of the concrete. For this reason, minor variations in subgrade strength have little influence upon the structural capacity of the pavement. The major factor considered in the design of flexible pavements is the combined strength of the layers.
One further practical distinction between concrete pavement and asphalt pavement is that concrete pavement provides opportunities to reinforce, texture, color and otherwise enhance a pavement, that is not possible with asphalt. These opportunities allow concrete to be made exceedingly strong, long lasting, safe, quiet, and architecturally beautiful. Concrete pavements on average outlast asphalt pavements by 10-15 years before needing rehabilitation.
