Weathering of Asphalts as Characterized by Infrared Multiple Internal Reflection Spectra

Identification and prediction of durability and weathering properties of paving asphalts are problems faced by highway material engineers. Correlation between accelerated laboratory durability tests and asphalt field performance is established on four asphalts. Double beam multiple internal reflection spectra are obtained for both laboratory-aged and field samples up to 48 months. Rheological properties and chemical analyses are also made. The kinetic model for weathering is found to be Δy = T/(a + bT) where Δy is the property change, T is the weathering time, and a and b are constants. Weathering of asphalts is characterized by changes in absorption at wavelengths of 5.88 µm and is correlated with chemical changes and aging index defined by viscosity change.