First and foremost, make sure that the pavement structure is adequate to take the anticipated traffic loads. Then we can now focus on the ‘toughness’ of the newly constructed wearing course.
If the binder used is penetration grade 60 - 70 (which normally is PG 64), it is considered appropriate for locations with average seven-day maximum pavement temperature around, say, 60 oC with normal traffic loads without having extraordinary high numbers of heavy vehicles or slow transient and standing load applications. If the design traffic is expected to be in the range of 10 - 30 million ESAL, or with significant slow moving heavy vehicles, then should consider using one performance grade higher i.e. PG 70. If the design traffic is expected to exceed 30 million ESAL, or with significant standing traffic (i.e. heavy vehicles stopping momentarily at a few junctions along the route), then should consider using two performance grade higher i.e. PG 76. The resistance to permanent deformation of the wearing course may be increased further by using asphalt mixtures with gap-graded aggregate which provide a stronger skeleton structure of the aggregate such as stone mastic asphalt (SMA).
