AASHTO T 85 and 84 methods. Testing the aggregate
in the natural moisture condition yielded results closer to
those of the oven-dried material, but the differences in
the test results were still statistically significant for some
materials. The vacuum drying method would be promising
if it was able to completely dry highly absorptive materials,
such as blast furnace slag and recycled concrete.
• For all coarse aggregates, the 10-minute vacuum soaking procedure
yielded Gsb and Gssd results that were not statistically
different from those measured using the 15-hour hydrostatic
soaking method. For all fine aggregates, the 10-minute vacuum
soaking procedure yielded all properties that were not
statistically different from those measured using the 15-hour
hydrostatic soaking method. Since the asphalt mix design
process requires only Gsb, aggregate samples can be vacuum
soaked for approximately 10 minutes according to the
vacuum saturation method described in AASHTO T 209.
This would replace the 15-hour soak required in AASHTO
T 85 and 84 and substantially reduce the testing time.