Numerical Investigation of Design Strategies to Achieve Long-Life Pavements

Increasing the HMA base thickness and modifying the HMA mixture properties to improve the resistance to fatigue cracking are among the most popular methods for achieving long-lasting pavements. Such methods are based on the idea of reducing the tensile strain at the bottom of the HMA layer below the Fatigue Endurance Limit (FEL), a level of strain below which no cumulative damage occurs to the HMA mixture. This study investigates the effectiveness of several design strategies involved in long-life, perpetual pavement design. A 3D Finite Element model of the pavement involving a linear viscoelastic constitutive model for HMA materials and non-uniform tire contact stresses is developed using ABAQUS 6.11. The effects of asphalt base course thickness and mixture type, rich binder layer, and aggregate subbase layer are examined. Four asphalt base course mixture types, namely dense graded, polymer modified, high modulus, and standard binder, are studied as a function of the asphalt base course thickness. The results underline a better performance of the high-modulus asphalt base, as compared to the other base course mixtures. The aggregate subbase layer on top of subgrade soil showed a relatively minor effect on the longitudinal and lateral strain response at the bottom of asphalt base course. The addition of a rich binder layer at the bottom of the asphalt base course showed a significant reduction in tensile strains. Tables are provided as a guideline to assess the different alternatives in design of long-life perpetual pavements.