Determination of oxidation rates of air‐blown asphalts by infra‐red spectroscopy

Oxidation rates for eight air‐blown asphalts were determined by measuring the change in infrared absorption at 5.88 μ with time of exposure to the radiant energy of a carbon arc. While all the asphalts oxidised at different rates, those from the same geographical areas had similar rates; those from different areas varied considerably. The pattern of oxidation was generally the same for each of the eight asphalts, in that there was an induction period followed by a steady oxidation rate until near the failure point, beyond which time the oxidation rate accelerated until film failure as denoted by asphalt film cracking. An inverse relationship was found between the rate of oxidation and the accelerated weathering durability of each asphalt.