When the term highway pavement is used, most people think of the moderate to thick systems on which their vehicles travel on intermediate- or high-type roadways. These pavement systems are typically constructed of bituminous concrete or portland cement concrete. This is not to say that low-volume roads do not have a pavement system; however, in case of low-volume roads, the pavement system usually consists of unbound aggregates, sod, soil materials, or at the most very thin or moderate applications of a binding material. It is the high-type pavement systems to which the comments in this paper will be addressed specifically.
These high-type pavements serve two primary functions. On the one hand, these pavements are the wearing surface upon which the tires of the vehicles travel. Because of high stresses at the tire-pavement interface, the surfacing materials must be extremely stable. The hard, bound surface provides a dust-free and smooth-riding surface. Secondly, the pavement system provides a means of transferring the total load of the vehicle to the supporting subgrade or earth foundation. The design of such a pavement system is thus a structural problem very similar to the design of bridges or office buildings
