Evaluation of Long-Term Oven Aging of Asphalt Mixtures (AASHTO PP2-95) on Superpave Thermal Cracking Performance Predictions

Abstract

A study was conducted to determine the effects of long term oven aging of asphalt mixtures (AASHTO PP2-95) on the thermal cracking performance evaluation of mixtures using the SUPERPAVE Indirect Tensile Test (IDT). Asphalt mixtures were aged according to the procedures developed by the Strategic Highway Research Program (SHRP) and tested using the SUPERPAVE Indirect Tensile Test after short- and long-term oven aging. The results were used to make thermal cracking performance predictions using the Penn State Thermal Cracking Model, which is a part of the SUPERPAVE mixture analysis system. The analyses indicated that: 1) long-term oven aging of mixtures produced changes in mixture compliance that led to differences in thermal cracking performance predictions, 2) long-term oven aging can produce excessive aging which results in erroneous (unconservative) performance predictions and 3) the relative ranking of thermal cracking performance of short-term oven-aged mixtures is, for most cases, the same as that of long-term oven aged mixtures. In other words, the system distinguished between mixtures with significantly different performance levels regardless of whether the mixtures were tested after short-term oven aging or long-term oven aging. This finding implies that long-term oven aging may not be justified for mixture specification purposes when the SUPERPAVE low temperature performance evaluations are used.