Damage theory applied to flexural fatigue tests on conventional and asphalt rubber hot mixes

Application of the Continuum Damage Theory (CDT) to evaluate the evolution of internal damage in Hot Mix Asphalt (HMA) is investigated in this paper. The CDT leads to the formulation of a characteristic curve relating normalized pseudo-stiffness and the internal damage variable, and this curve is supposed to be unique for each material. The uniqueness of the characteristic curve was investigated in this paper by performing fatigue tests in which prismatic samples of HMA were subjected to cyclic bending loads under strain controlled tests. Asphalt mixtures with dense, open and gap gradation using conventional and rubber modified binders were tested. The results of all the tests showed the existence of unique curves independent of loading mode, amplitude or frequency within the studied range. This property may be implemented in numerical codes to simulate the behavior of flexible pavements under a variety offield conditions, using a well formulated mechanistic approach.