N design, the gyration count at which a Superpave specimen is evaluated for volumetric properties. Common levels are 50 for low-volume roads, 75 for medium traffic, 100 for heavier routes and 125 for the busiest highways, and the mix is designed to hit 4.0 percent air voids at that count. Specs also check density at Ninitial, and sometimes Nmax, to catch tender mixes and mixes that would keep densifying under traffic.
County's Ndes is 50, so the mix will be richer and easier to roll than the 100-gyration interstate stuff.
Lower Ndes means more binder at the same 4 percent voids, which is why low-traffic mixes tend to be more durable and easier to compact.
Also heard as
- N design
- design gyrations
Related terms
Gyratory compactor
The lab machine that compacts mix specimens by pressing and tilting them in a rotating mold.
Superpave
The performance-based system for grading binders and designing asphalt mixes around climate and traffic.
Air voids
The small pockets of air between binder-coated aggregate in compacted mix, given as a percent of total volume.
Puck
Lab slang for a compacted cylindrical mix specimen, especially one made in the gyratory compactor.