Characterization of rutting potential of large-stone asphalt mixes in Kentucky

Large-stone mixes are becoming a popular means for reducing rutting in flexible pavements. Heavy concentration of aggregate interlock in large-stone mixes allows for efficient dissipation of compressive and shear stresses that are otherwise known to be responsible for rutting and shoving in flexible pavements. Mix design procedures and laboratory testing for characterization of rutting potential of large-stone asphalt mixes (LSAMs) in Kentucky are documented. A series of large-stone aggregate gradations was studied. In cooperation with the Kentucky Department of Highways and representatives of the asphalt industry, a promising aggregate gradation was selected. On the basis of the findings of this study, several test sections were constructed on coal-haul corridors throughout Kentucky. At this time, these LSAM sections have been in service for less than 1 year; therefore, any conclusion on the performance is premature. However, performance-oriented laboratory test results indicate that higher levels of structural capacity and rutting resistance, as compared with conventional hot mix asphalt, can be achieved by using LSAMs in flexible pavements.