Hot mix asphalt design follows AASHTO R 35 (Superpave volumetric mix design). Design gyrations (Ndes) based on traffic level: <3M ESALs: 75 gyrations, 3-30M: 100, >30M: 125. Volumetric criteria: VMA minimum per aggregate NMAS, VFA 65-78% for high traffic, air voids 4.0% at Ndes. VDOT additional requirements: TSR ≥80% (AASHTO T 283), Hamburg wheel track ≤12.5mm at 20,000 passes for PG 76-22 mixes.
References: AASHTO current edition, VA Standard Specifications, FHWA Technical Advisories, and applicable federal regulations (23 CFR). Contractors shall maintain current copies of all referenced standards on the project site.
Source: VDOT Materials Testing Manual, 2024 Edition. Pages 15–16 of 25.