In the design field of pavement rehabilitation, one finds a prominent absence of uniformity in the principles of calculation, a lack of clarity as to testing methods, and a confusion of basic physical concepts. These sometimes lead to significant contradictions in the practical output results, between one design method and another. An example of this is the essential question of the consideration given to the residual value of the pavement structure, depending on the volume of past traffic, i.e., in determining the residual or remaining life (RL), as the difference between the expected life span of a given pavement on its "birthday" (i.e., the total life of the pavement from its "birth" to its "death"), and the life span already used by the traffic which passed over the pavement from the day it was opened to the day under discussion. Another formulation of this essential question is: does the future life span of a pavement from a given point in time, depend on the volume of traffic already passed (i.e., a pavement whose future behavior is `unaffected' by its "past memory") or, in other words , at every point in time the pavement is characterized by new material data which may be seen as initial material data "created" as they are for the given point in time, rather than arising from previous stresses. In this context, it should be emphasized that the RL parameter constitutes an important measure which makes it possible to determine the bearing capacity of the pavement or, alternatively, the extent of rehabilitation required. The question is how to establish such a parameter in practice, and what is the relationship of this parameter to the pavement's bearing capacity level. The present work discusses these issues by looking into (a) the relationship between the pavement surface state and the RL parameter, (b) the relationship between the pavement's structural state and the RL parameter, (c) the relationship between the functional pavement state and the RL parameter, (d) the effects of asphalt fatique on the residual life span, and (e) the effects of the total structural deterioration on the residual life span. Finally, the work also presents the new AASHTO guidelines on this matter and their practical recommendations to include the residual life span parameter within the design process of flexible pavement rehabilitation.
Abstract