Effect of laboratory mixing and compaction temperatures on asphalt mixture volumetrics and dynamic modulus

Employment of conventional asphalt testing protocols for characterization of polymer-modified asphalts remains a challenge. NCHRP launched Project 9-39 to identify an approach to determine the mixing and compaction temperatures applicable to unmodified and modified asphalt binders. The Asphalt Institute, Lexington, Kentucky, in cooperation with FHWA, embarked on the research reported here to evaluate how mixture performance is affected by laboratory mixing and compaction temperatures. Samples were mixed and conditioned at various temperatures and conditioning durations with modified and unmodified binders. Volumetric analysis confirmed that slight changes in the mixing temperature did not change the results of volumetric testing. Compacted samples were tested to determine the dynamic modulus as an indication of pavement performance. A comprehensive statistical analysis was performed, and the overall results showed that the impact of the conditioning temperature and duration on the dynamic modulus was more significant than the influence of the mixing temperature. Further, for modified binders the significance of the impact of the mixing temperature seemed to be a function of the crude source of the binders.