AC in accordance to American standards

In American standards, as in European standards, ACs are also designated by the maximum aggregate size. Mixture and gradation limits specified by ASTM 3515 (2010) and control points, shown in boldface, specified by Superpave mix methodology (Asphalt Institute SP-2 2001) for dense AC are given in Table 5.4. It is stated that ASTM 3515 (2010) has been withdrawn in 2009 and has not been replaced. However, to the author s opinion, ASTM 3515 (2010) gradation limits are still helpful to determine the gradation envelope of dense AC until a replacement comes out. 

The control limits determined by Superpave mix methodology work in the same principle as the general requirements of CEN EN 13108-1 (2008). 

The criterion of restricted zone is obligatory and it is recommended that the target mix gradation should pass outside the restricted zone. 

The restricted zone prevents a gradation from following the maximum density line in fine aggregate sieves. Gradations that follow the maximum density line often have inadequate VMA to allow room for sufficient binder for durability. These gradations are typically sensitive to asphalt content, which may easily become plastic with even minor variations in binder content (Asphalt Institute MS-2). 

Sources Adapted from ASTM D 3515, Standard specification for hot-mixed, hot-laid bituminous paving mixtures, West Conshohocken, Pennsylvania, US ASTM International, 2010 and Asphalt Institute, Superpave mix design, Superpave Series No. 2 (SP-2), 3rd Edition, Lexington, USA Asphalt Institute, 2001. 

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