Subbase, Base, and Flexible (Asphalt) Pavement
Base and preparatory work
Aggregate base is accepted on gradation, plasticity, soundness, and abrasion resistance, then on compaction to the specified percentage of maximum density and on thickness and surface tolerance (often checked with a 10-ft straightedge). A prime coat is applied to an open granular base and allowed to cure; a tack coat goes between asphalt layers, is applied at a specified residual rate (commonly about 0.05–0.08 gal/sy), and must break before the next lift is placed.
Hot-mix asphalt
Know the mix design method (Marshall or Superpave), the volumetric targets (air voids, VMA, asphalt content), and the temperatures for production, delivery, placement, and rolling. Breakdown, intermediate, and finish rollers each have a job; rolling must finish before the mat cools below the specified temperature. Acceptance is typically density as a percent of maximum theoretical specific gravity (Gmm), commonly around 92 percent for mainline and slightly lower at longitudinal joints, verified by cores or a gauge. Thickness, smoothness (profilograph or IRI), and surface texture are separate acceptance items.
Traps
Do not confuse Gmm (maximum theoretical) with Gmb (bulk specific gravity of the compacted sample). Core thickness is measured on the core itself, not inferred from the screed. A cold longitudinal joint is the usual cause of low joint density and future cracking. Also watch yield questions that mix tons, square yards, and compacted thickness.
Worked example: a 24-ft wide, 500-ft long lift, 3 in compacted thick at 145 lb/ft³: volume = 24 × 500 × 0.25 = 3,000 ft³; weight = 3,000 × 145 = 435,000 lb ÷ 2,000 = 217.5 tons.