Effect of Aging on Rheological, Chemical, and Thermodynamic Properties of Asphalt Components

Many molecular structures are found in asphalts; however, the commonly used classification separates asphalt into asphaltenes and maltenes (Saturates, Aromatics and Resins). Rheology of asphalts depends on the combination of the different constitutive fractions and greatly depends on the degree of association of asphaltenes and the relative quantity of other substances present in the system to stabilize those associations. Asphalts are subjected to an aging process during mixing, laydown and service life that also affects their rheology. The objective of this study was to evaluate the effect of aging on rheological, chemical and thermodynamic properties of the asphalt binder main components: asphaltenes and maltenes. An AC-30 asphalt binder and its individual components were aged using the Rolling Thin Film Oven (RTFO) and the Pressure Aging Vessel (PAV), and were analyzed using a Dynamic Shear Rheometer (DSR). A Iatroscan thin film chromatography and a Polarized Light Microscopy analysis were also used for characterization purposes. A Thermogravimetric analysis (TGA), a Differential Scanning Calorimetry Analysis (DSC) and a Fourier Transform Infrared Spectroscopy (FTIR) analysis of the asphalt binder and its components were performed before and after aging. The results indicated that the thermal stability of the asphalt binder can be attributed mostly to the higher stability and lower susceptibility to oxidation of the asphaltenes at normal handling temperatures for paving operations. Overall, there is clear evidence that aging of the asphalt binder components has an effect on the morphology of the asphalt binder.