NICET CMT Asphalt cheat sheet

Asphalt Construction Materials Testing

• Asphalt binder grades follow the Performance Grade (PG) system: PG 64-22 means average 7-day maximum pavement temperature 64 °C and minimum pavement temperature -22 °C.

• Superpave mix design selects aggregate structure, then binder content at 4% air voids; the design binder content is chosen at the air void content corresponding to Ndesign gyrations.

• Volumetric formulas: VMA = Vbe + Va (bulk volume of voids in mineral aggregate); VFA = 100 × Va / VMA; Gmm = (Gsb + Pb·Gb relationship via Gmm = (Pmm)/(100/Gmm) − ... ) - practical form: Gmm = 100 / (Ps/Gse + Pb/Gb).

• Percent absorbed binder: Pba = 100 × (Gse − Gsb) / (Gsb × Gse) × Gb. Effective binder content Pbe = Pb − (Pba/100) × Ps.

• Dust-to-effective-binder ratio = P200 / Pbe (asphalt ratio); typical Superpave range is 0.6 to 1.2 by mass.

• Maximum theoretical specific gravity Gmm is measured per AASHTO T 209; bulk specific gravity of compacted specimens Gmm-basis uses AASHTO T 166 (saturated surface dry).

• Percent compaction in the field = (field Gmm-basis density / laboratory Gmm) × 100; typical acceptance is 92–93% of Gmm for dense-graded mixes.

• Marshall method: 50 or 75 blows per face; stability and flow measured at 60 °C; design binder content at 4% air voids with VMA/VFA criteria.

• Moisture sensitivity: AASHTO T 283 (TSR) requires tensile strength ratio ≥ 0.80; antistrip additives or hydrated lime are used when TSR fails.