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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.

In most USA asphalt construction projects the goal of compacting a hot-mix asphalt (HMA) layer is to achieve the optimum density which is 92% of the maximum specific gravity (Gmm) of the asphalt mixture. However, this level of density is not always achieved. This paper evaluates the effect of field compaction deficiencies on the HMA durability through laboratory testing. HMA samples were collected from construction sites in the United States. A series of laboratory tests were conducted to compare the performance of HMA mixtures at their actual in-place density as well as the desired density of 92% of Gmm. The statistical analysis on the results showed that the performance of the pavements could significantly improve by eliminating the deficiencies in their in-place densities. Moreover, the compactibility of the mixtures was investigated using the compaction data from the Superpave gyratory compactor. Compaction characteristics of the mixtures were compared to a control mixture, and the results showed that the shortage in the binder content of the mixtures could be a major factor which may have caused the density deficiencies. Furthermore, the effect of higher-than-optimum binder content was evaluated on the compactibility of the control mixture.