Energy dissipation in asphalt mixtures observed in different cyclic stress-controlled fatigue tests

Abstract

During cyclic fatigue testing of hot mix asphalt (HMA) under stress control, a continuous change of the strain amplitude is observed in each loading cycle either under pure tensile or under tensile-compressive stress conditions. Depending on the type of the applied load and on the specific viscoelastic behavior of the HMA this strain change can dramatically vary in association with a change in various mechanical properties. In order to study the variation of mechanical properties during cyclic fatigue tests under stress control an experimental program was performed using an approach based on dissipated energy. This study considers the following stress-controlled fatigue tests: indirect tensile test, uniaxial tension test and uniaxial tension-compression test. The hysteresis loops are drawn, and the dissipated energy is calculated. Based on the similar number of loading repetitions at failure, the tests are comparatively analyzed, and the changes in mechanical properties are identified. As a result, the tension-compression test shows low permanent deformation and high variation of dissipated energy which can be attributed to a distinct change in the material’s mechanical properties. On the other hand, the uniaxial tension test and indirect tensile test exhibit high accumulation of permanent deformation with very few changes in mechanical properties during cyclic excitation. Based on these results the uniaxial tension test and the indirect tensile test in stress control are not well-suited for fatigue analysis since failure most likely occurs by accumulation of permanent deformation.