Concrete Paving  With mounting stress on our transportation infrastructure, construction of concrete highways is a proven long-term infrastructure investment. The United States already recognizes the benefits of a concrete infrastructure and has incorporated concrete pavement into over 30% of its interstate highways. Concrete provides not only economic and environmental benefits, but also direct user benefits that offer a sustainable solution to infrastructure challenges.
One of the most well known advantages of concrete is its superior durability and longer structural life. This durability translates into less road delays due to construction and maintenance. A 1998 life cycle cost report by ERES Consultants Inc. indicates that the expected life of an asphalt road is 17 years compared to 34 years for concrete.
The report also indicates that asphalt highways require maintenance activities every three to five years and major rehabilitation becomes more and more frequent after the initial 17th year overlay. Concrete on the other hand, requires its first minor maintenance after 12 years and retexturing of the concrete surface at year 18, allowing roadway users to get to their destination with fewer delays.
Concrete pavement is a rigid structure and asphalt is a flexible structure. Historically, pavements have been divided into two broad categories, rigid and flexible. These traditional definitions, in some cases, are an over-simplification. However, the terms rigid and flexible provide a good description of how the pavements react to traffic loads and the environment.
Flexible asphalt pavement generally consists of a surface of asphalt built over a base course and sub-base course. Base and sub-base courses are usually gravel or stone. These layers rest upon a compacted sub-grade (compacted soil). In contrast, rigid highway pavements are made up of portland cement concrete and have only a base course between the pavement and sub-grade using approximately half as much granular material.
By virtue of its rigidity and stiffness, concrete pavements tend to distribute the load over a relatively wide area of sub-grade. 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 sub-grade.
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