ASPHALT PAVEMENTS IN HIGHWAY AND TRANSPORTATION ENGINEERING:

Asphalt technology is used for pavements of high ways and urban roads, for junctions and interchanges, for bus and rail tracks, for multi-purpose traffic lanes, hard shoulders and median strips, cycle paths and footways, for traffic lanes in service areas etc.

               Pavements of traffic areas are built in form of asphalt surface courses, binder course and base courses to ensure high durability against stresses caused by traffic and weathering. The typical structure of asphalt pavement and their functional properties dipper according to design. The design and execution of highway and transportation areas is based on engineering requirements concerning load bearing capacity, stiffness against permanent deformation, frost resistance and evenness and the required profile of the pavement. Besides the pavement the highway construction also comprises the subgrade and the sub base influenced by static and dynamic traffic loads.

               This multi-layer system is stressed by load, time and temperature dependent shearing and bending forces and deformed in dependence of the stiffness of effective layers. The carriageway pavement must be designed and built for safe riding traffic under any load condition, whereby its stability shall not be at risk at any time. This design goal demands a constructive interaction of all effective layers and a low and uniform level of deformation. According to this principle the layers must have load distributing properties complying with the different possible types of loads and be able to mutually compensate overloads. These performance requirements depend on the stiffness of system, which in turn is depending on the strength and deformation characteristics of layers as well as the layer thicknesses including the thickness ratio of successive layers. This principle of the constructive interaction is met when the stiffness properties of the individual layers are adapted to each other in way that the system stiffness increases from the bottom upwards according to the course of stresses. The stiffness of the system changes because of permanent mechanical load applied by traffic in combination with local condition or seasonal climatic cycle. Particularly critical condition may arise during winter, when frost related non-uniform heaves occur or the stiffness of the sub-layers drops during thawing intervals. During summer, when warping stresses develop and the stiffness of the visco-elastoplastic deformable asphalt layers is reduced by high temperatures.