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Gradation & SIze
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Percent retained or percent passing each sieve size by mass and material finer than the 0.075 (No. 200) sieve.
Superpave mix design specifies aggregate gradation control points for mixes of NMAS 0.375 inch (9.5 mm), 0.5 inch (12.5 mm), 0.75 inch (19.0 mm), 1.0 inch (25.0 mm) and 1.5 inch (37.5 mm). Figure 10 shows just one of these sizes in a pile at a fully fractionated aggregate quarry.
See the Gradation Control Point Table
See the Gradation Control Point Graph
There is no standard gradation and size for Superpave mix design. Generally, gradation and size will meet gradation control points defined in the Superpave mix design specification (AASHTO M 323). However, many state and local agencies specify their own gradation control points, which can differ from standard Superpave gradation control points.
Although gradation and size will vary by a HMA's intended use, location and material availability, a majority of Superpave HMA mixes are 0.5 inch (12.5 mm) or 0.75 inch (19.0 mm) NMAS dense graded mixtures.
Pavement designed for heavy loading such as airports (Figure 11), industrial facilities (Figure 12) and port facilities (Figure 13) will often use a larger NMAS (usually ≥ 0.75 inch (19.0 mm)). These pavements require special care in order to be designed and constructed correctly.
A HMA base layer is sometimes constructed with larger NMAS; usually ≥ 19.0 mm (0.75 inch).
Gradation may be reported as either a percentage retained or percentage passing each sieve size.
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| Where: | Msieve | = | cumulative mass retained on a sieve |
| Mtotal | = | total original sample mass | |
