ABSTRACT
The stresses induced by the loads are high at the surface but reduce with depth. Thus, the surfacing material must be of high quality, but at greater depths below the surface, economies can be achieved by using materials of lower strength. Fatigue cracking arises from the fact that under repeated applications of tensile stress/strain, a bituminous material will eventually fracture. The higher the level of stress and strain applied, the smaller the number of load applications before cracking occurs. A number of laboratory tests have been developed to assess the fatigue characteristics of bituminous materials. Roads deteriorate in a number of ways, but broadly there are two forms of failure – functional and structural. Functional failure is usually associated with the road surface through deterioration with time. The term ‘critical’ means that failure is imminent but the road still has sufficient structural capability to support strengthening and to provide an extended life from the strengthened road.
