An evaluation of an oxidative aging procedure for asphalt materials is described. Test results and the effectiveness of the aging device used are presented. The study was performed by Oregon State University and the Oregon Department of Transportation. This study involved laboratory tests on field core samples as well as laboratory mixture samples and asphalt cements used in three projects constructedin Oregon. The procedure selected for aging laboratory mixtures involved using a pressure oxidation bomb (POB), a sealed container in which asphalt mixtures or asphalt samples, or both, were subjected topure oxygen at 100 psi pressure at 60 deg C for periods of up to 5 days. Resilient modulus and fatigue tests were performed to measure the properties of cores and laboratory mixtures (before and after aging). The asphalt samples were aged on a Fraass plaque to achieve minimum disturbance of the sample, and the degree of aging was assessed by changes in the Fraass breaking temperature. The results of thisstudy showed that the POB was an effective means of producing measurable changes in both mixtures and asphalt samples. However, the mixture properties were substantially different from those measured forthe field core samples whereas the asphalt properties were similar.As evaluation parameters, the modulus ratio and Fraass breaking temperature are good indicators of the aging rate of mixtures and asphalt cement, respectively. The study also indicated that aging rate isa function of air voids in the mixture and asphalt properties.(A).
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