FINE AGGREGATE ANGULARITY

摘要

Superpave aggregate qualifications include the fine aggregate angularity (FAA). The numerical value of the FAA is the voids in the mineral aggregate of the loosely packed fine aggregate. Higher and lower values of FAA represent fine aggregate with high and low frictional characteristics, respectively. The degree of friction depends on the aggregate particle shape and texture. Higher friction is associated with increased rutting resistance. Fine aggregate angularity levels used in the Superpave system are below 40, 40 to 45, and above 45. The higher values are specified for layers near the surface and for higher traffic levels. Past and current experience shows that there are fine aggregates below the specified levels in mixtures that are performing well. There are also aggregates above these levels in mixtures that are not performing as desired. A study has been conducted utilizing the PURWheel laboratory wheel track tester to develop performance-based data on mixtures with various fine aggregates. A single asphalt (PG 64-28) and 9.5-mm coarse aggregate were used in the study. The coarse aggregate was selected to emphasize the fine aggregate performance. Six fine aggregates were used with FAA ranging from 39 to 49. In addition, two of these aggregates were blended in various proportions to produce blends with FAA values of 43,45, and 46. Wheel track, compacted aggregate resistance, and Florida bearing tests were conducted. Test results indicated that the tests were successful in delineating potential performance of the mixtures tested.