The role of an aggregate base course layer in a flexible pavement system is to distribute loads to a stress level that can be sustained by the underlying subgrade. When a pavement is analyzed as a layered, isotropic elastic system, it is not uncommon to see tensile stresses at the bottom of the base course layer upon application of a wheel load. Tensile stresses cannot be sustained by unbound granular materials since they have little or no tensile strength. Because these tensile stresses are generally known to be either unrealistic or overpredicted, using such an analysis can lead to pavement designs that have lower
total permanent deformation or rutting (unconservative) and higher fatigue cracking prediction in the asphalt layer (overconservative).