Paved roads

• 8.1.

  Introduction

• 8.2.

  Distress features and their relationship to geosynthetics

• 8.3.

  Geosynthetic functions

• 8.4.

  History and experimental evidence for base reinforcement

• 8.5.

  Summary of critical design variables for base reinforcement

• 8.6.

  Design solutions and approaches for base reinforcement

• 8.7.

  Summary of main points

• 8.8.

  Some common questions and their answers

• References

Geosynthetics are used in paved roads to provide reinforcement, separation, drainage and filtration. Common geosynthetics used include geotextiles, geogrids, geonets and geocomposites. Geosynthetics help control the development of common pavement distress features such as rutting and cracking. This is accomplished by structural reinforcement of the base aggregate layer, controlling infiltration into moisture-susceptible layers, and preventing contamination of structural layers by the migration of fines from underlying soils. These functions help preserve and in some cases enhance the structural integrity of the constructed pavement layers. In this chapter, the functions listed above are described and illustrated for paved roads. Guidelines for the selection and use of geosynthetics for paved road reinforcement are presented. These guidelines currently rely upon the use of a traffic benefit ratio or a base-course reduction ratio. These parameters are dependent on the geosynthetic used and the design specific roadway materials and layer thickness. The ratios are currently determined by constructing test sections incorporating these conditions. New methods incorporating mechanistic-empirical design principles are currently under development and are discussed.