Technical information

2-8
Table 2.2.1: HMA design parameters for mixes 1 to 4 (Timm and Priest, 2006).
Property Units Mix 1 Mix 2 Mix 3 Mix 4
Binder Grade - 76-22 67-22
Compactive Effort, gyrations 80
Mixing Temperature ºF (ºC) 345 (174) 325 (163)
Effective Binder Content percent 6.13 4.27 6.13 4.27
Dust to Binder Ratio - 0.88 1.10 0.88 1.10
Bulk Unit Weight of Compacted Pills
pcf
(kg/m³)
147.8
(2370)
153.6
(2463)
147.8
(2370)
153.6
(2463)
Air Void Content percent 4.3
Voids in Mineral Aggregate percent 17.9 14.5 17.9 14.5
Figure 2.2.5: Design gradation of different mix types used in the NCAT ‘structural
study’ (Timm and Priest, 2006).
Surveys of the as-built thicknesses were conducted during construction. These
focused on the pavement areas that included instrumentation. The average thicknesses
of individual lifts were as follows. For section N1, the bottom lift was 2.2 in. (56 mm)
thick, the intermediate was 2.1 in. (53 mm) thick, and the top lift was 0.6 in. (15 mm)
thick. For section N2, the bottom lift was 1.8 in. (46 mm) thick, the intermediate lift
was 2.0 in. (51 mm), and the top lift was 1.1 in. (28 mm) thick. Therefore, the average
total HMA thickness over the instrumented areas was 4.9 in. (124 mm) in both sections.
Cores taken after construction confirmed these results. It should be noted that the HMA