Viscoelastic Analysis of Flexible Pavements and Its Effects on Top-Down Cracking

Abstract

When employing linear elastic layer analysis, which is widely used for the structural analysis of flexible pavements, it is commonly observed that most critical tensile strains occur at the bottom of an asphalt layer. It is well known that an asphalt mixture is a viscoelastic material, so its response is time and rate dependent; therefore, the results from the elastic assumption may not be borne out in the response of the asphalt layer. This study utilized viscoelastic analysis to identify critical tensile strains and their time-dependent responses. It was found that tensile strains occurred at the bottom and at the top of an asphalt layer and grew because of the rheological behavior of an asphalt mixture. As load repetitions continued, the strain at the top showed a higher strain value than the strain value at the bottom. A sensitivity analysis performed on various design parameters indicated that the development of strains at the top and at the bottom is a function of the structural characteristics of pavement structures. Expected trends were observed and findings compared favorably to results of field-calibrated top-down cracking model predictions.