Viscoelastic properties of paving grade asphalt cements (AC) were measured on a Rheometrics RDA II. Thermal properties were studied with a Mettler TA 2000 B differential scanning calorimeter. A review of the literature showed that most authors proposed that the time-temperature superposition principle applies to asphalt over the whole temperature range. However, the results presented herein demonstrate that it indeed fails at high temperature, especially for high asphaltene content and high crystalline content materials. This paper focuses on the role of asphaltenes, which are, by definition, insoluble in n-heptane. Asphaltenes are suspended in a colloidal manner within the AC matrix and are peptizided by the species called resins. Thus, a temperature dependent solid fraction exists within a liquid (or glassy) matrix. This paper shows that the viscoelastic properties of asphalt are bimodal : they are governed by both solid and continuous phases.