A series of categories of minimum binder contents in SMA mixes, denoted Bmin, is detailed in the standard. However, maximum binder contents are not defined; therefore an appropriate category of Bmin should be matched with each SMA specification.
The categories given in the standard have been adopted for a reference density of an aggregate mix equal to 2.650 Mg/m3. For aggregate mixtures with other densities, the required lower limit of the binder content should be modified using the factor a
2.650 a =
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Pa
FIGURE 14.2 The position of boundary points of SMA 11S gradation envelopes according to EN 13108-5 and German final gradation limits for this mixture according to TL Asphalt- StB 07. |
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a
a
FIGURE 14.5 The position of overall limits to a target composition of SMA 14 according to EN 13108-5 and British final gradation limits for this mixture according to BS PD 6691:2007.
where pa is the particle density of the aggregate mix in megagrams per cubic meter, according to EN 1097-6.
The binder content determined for an SMA mixture should be the sum of all possible sources of binder in it, which includes the following:
• Added binder
• Binder from the RAP (when added)
• Natural asphalt (when added)
Available categories of the minimum binder content in SMA (to be chosen in an NAD or a contract specification) range from 5.0 to 7.6% in 0.2% increments (i. e., Bmin= 5.0, 5.2, 5.4, 5.6 …).[76]
