Searching effective indicators of microstructural changes in bitumens during aging: A multi-technique approach

A study on the effect of artificial aging process applied to asphalt binders characterized by different degrees of penetration was carried out by performing rheological characterization, thermal analysis by means of differential scanning calorimetry and optical microscopy, X-Ray powder diffraction, FT-IR and Raman spectroscopy. The microstructural information such as dimension of unit cell (crystalline parameters) layer diameter, inter-layer distance, height of the unit cell, and the aromaticity were calculated and compared between unaged and aged asphaltenes. The parameter that quantifies the aromaticity proved to be a good indicator of the extent of aging to which the bituminous materials under study were subjected. It turned out that more rigid bitumens possess more polar fractions which can be oxidized by aging, therefore bringing to a more pronounced increase in rigidity upon aging.