Toward a Mechanistic Approach for Analysis and Design of Asphalt Pavements

Abstract

Most current analysis and design methodologies of asphalt pavements rely on experience and empirical relationships. These relationships were developed on the basis of results of laboratory tests and by monitoring the performance of actual pavements and sections in accelerated loading experiments. The empirical relationships are limited in accounting for the fundamental properties of the materials, loading configuration, distribution of loads, and variable environmental conditions. In spite of these limitations, fairly good pavements could be constructed until recently, primarily because the lack of appropriate models could be backed up by practical experience. Relying on experience is, however, not acceptable any more because of the rapidly changing conditions of the road network. First, the significant increase in the capital investment in road construction and the need for maintenance-free roads encouraged the design of improved pavement materials modified binders, aggregate treatment, layer stabilization, and new designs of asphalt mixes . In addition, economical and environmental factors have put more emphasis on the use of local and secondary recycled building materials. Advancing the material properties and the use of locally available materials should be accompanied by developing experimental and analytical approaches that can accurately determine the effect of these materials on the design of long-lasting pavements and life-cycle cost. Second, the number and loads of trucks have increased beyond expectation as a consequence of the need to increase road transport efficiency. Furthermore, the expected introduction of aramide-reinforced truck tires in combination with foreseeable changes in wheel configurations will result in extremely high wheel pressures. Recently, a significant change in design philosophy has occurred through the development of the empirical-mechanistic design guide. The mechanistic part refers to the use of layered elastic analysis and viscoelastic material properties in some parts of the guide to determine the pavement response. Empirical relationships are used to link the calculated pavement elastic response at critical points within the structure and damage mechanisms such as permanent deformation and cracking. The empiricalmechanistic design guide includes approaches to account for traffic distribution over time and for the influence of environmental conditions on material properties. Although the empirical-mechanistic approach is considered a major step, the constitutive material models in this approach are still considered to be oversimplified because they are not able to accurately determine all aspects of the inelastic triaxial and