Comments on European and American composition methods of AC

Regarding the composition of ACs, the European standard for AC mixtures, CEN EN 13108-1 (2008), realising the weakness of the Marshall mix design, has broadened the 

As a consequence, it is now possible to specify the target AC using an empirical or a fundamental specification. Both are based on a combination of requirements for composition and constituent materials with performance-related requirements. The difference between the two specifications is that the fundamental specification provides more degrees of freedom than the empirical specification. 

Although the target mixture is now determined in Europe on performance-related requirements, European limit values have not yet been set. Until European limit values are set, each country specifies its own limit values. 

The American Superpave design methodology was developed bearing in mind the use of performance-related requirements. At present, the Superpave design selects the bitumen on the basis of performance-related specifications but the target asphalt mix is still determined on the basis of volumetric properties. 

Additionally, unlike the European specification CEN EN 13108-1 (2008), the compaction of the specimens under the Superpave design methodology is restricted to gyratory compaction only. This is a positive step since it simulates better the compaction carried out on site and eliminates variations on the mechanical properties of asphalt mixtures attributed to type of compaction. 

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