2.8.1 Nominal Mix Size
The nominal size of an asphalt mix is an indication of the maximum particle size present and is usually expressed as a convenient whole number above the largest sieve size to retain more than 0% and less than 10% of the aggregate material (AS 2150).
The selected nominal size of the mix will be determined by:
- location of asphalt course in the pavement
- proposed compacted thickness of the layer
- functional requirements of the asphalt layer.
Table 2.1 indicates typical nominal mix sizes for different applications.
|Application||Typical mix size|
Dense graded wearing course:
7 or 10 mm
10 or 14 mm
Generally 14 mm (also 10 mm)
14 or 20 mm
|Dense graded intermediate course||In general it is better to use the largest size practicable where the wearing course is dense graded asphalt. Where the asphalt surface is open graded asphalt, the largest size mix used in this application is typically 14 mm|
|Dense graded basecourse||Normally 20 mm. 28 mm may also be used depending on layer thickness and availability. 40 mm has been used in the past but now largely discontinued through difficulties associated with increased segregation in larger sized mixes and general unavailability|
|Dense graded corrective course||5, 7, 10, 14 or 20 mm|
|Stone mastic asphalt wearing course||7, 10 or 14 mm|
|Open graded wearing course||10 or 14 mm|
|Open graded basecourse (drainage layers)||14, 20 or 28 mm|
|Fine gap graded asphalt||Generally 10 mm (also 7 mm)|
10 mm (also 5, 7, 14 and 20 mm)
All sizes as appropriate