Durability Characteristics of Asphaltic Materials: Fid-Bau Portal

Durability Characteristics of Asphaltic Materials

R. P. Lottman / A. M. Rao

The conclusions are: (1) The constant-power calculated viscosities of the oven aged asphalts increased more rapidly with increasing oven temperature than with oven time; (2) The aging index values of the asphalt differed at a given viscosity test temperature and for a given asphalt and aging, the aging index increased with decreasing test temperature; (3) Using viscosity-shear plots, the asphalts were shown to have different degrees of non-Newtonian characteristics. Generally, non-Newtonianism increased as aging increased and as test temperature decreased; (4) The percent asphaltene content increased with oven aging, being highest for the most non-Newtonian asphalt and lowest for the least non-Newtonian asphalt; (5) As aging increased, the change in intrinsic viscosity of aged asphalt solutions in benzene increased. Excepting asphaltenes from the least non-Newtonian asphalt, the asphaltene intrinsic viscosity increased at a greater rate beyond a 'critical degree' of aging for each asphalt, indicating that the asphaltenes increase in size weight rapidly above some aging severity; (6) Molecular weights of asphaltenes were determined indirectly by calculations using Staudinger's equation with the intrinsic data. Due to the equation, molecular weights increased with aging in the same manner as intrinsic viscosity did, weights ranged from 900 to 1400 grams per mole; (7) Limited glass transition temperature data were obtained. It was found that by using the glass transition temperatures and log viscosity versus reciprical temperature plots obtained for the asphalt, plots of the unaged and aged asphalt samples could be shifted by use of the Williams-Landel-Ferry equation to a 'reference' plot. (Author)