A STRUCTURE-RELATED MODEL TO DESCRIBE ASPHALT LINEAR VISCOELASTICITY

Viscoelastic properties of paving grade asphalt cements (AC) were meas ured on a Rheometrics RDA II. Thermal properties were studied with a M ettler TA 2000 B differential scanning calorimeter. A review of the li terature showed that most authors proposed that the time-temperature s uperposition principle applies to asphalt over the whole temperature r ange. 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. Asphal tenes are suspended in a colloidal manner within the AC matrix and are peptizided by the species called resins. Thus, a temperature dependen t solid fraction exists within a liquid (or glassy) matrix. This paper shows that the viscoelastic properties of asphalt are bimodal: they a re governed by both solid and continuous phases. (C) 1996 Society of R heology.