ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 360

VTM t = VTM determined from the volumetric analysis

percent effective binder
dust-to-binder ratio
aggregate passing 0.075mm sieve

P be,est = adjusted

D/B est = adjusted

P D = percent

In Equation 9.17, the air voids are assumed to be 4.0%, the target air
void content for a Superpave mix design.
The adjusted results of the design aggregate structure evaluation are
compared to the Superpave mix-design criteria, as shown in Table 9.10.
The design aggregate blend is the one whose adjusted volumetric para-
meters meet all of the criteria. In the event that more than one of the blends
meets all of the criteria, the designer can use discretion for the selection of
the blend. A pair of samples is compacted at the adjusted binder content for
the selected aggregate blend. The average percent of maximum theoretical
specific gravity is determined and compared to the design criteria. If suc-
cessful, the procedure continues with the determination of the design binder
content. If unsuccessful, the design process is started over with the selection
of another blend of aggregates.

Sample Problem 9.4

Select a 19-mm Superpave design aggregate structure based on the following data:

Blend

Data 1 2 3

G mb 2.457 2.441 2.477

G mm 2.598 2.558 2.664

G b 1.025 1.025 1.025

P b 1 % 2 5.9 5.7 6.2

P s 1 % 2 94.1 94.3 93.8

P d 1 % 2 4.5 4.5 4.5

G sb 2.692 2.688 2.665

h ini 1 mm 2 125 131 125

1 2

h des mm 115 118 115

Solution
In this problem, the lab data were entered into an Excel spreadsheet and the appropri-
ate equations were entered, producing the results shown in the accompanying table.
The steps in the calculation are shown for the first blend only; the reader can verify the
calculations for the other blends