ASPHALT BINDERS AND ASPHALT MIXTURES - Materials for Civil and Construction Engineers - page 346

T ABLE 9.6 Aged-Residue Grading System of Asphalt Cement

Viscosity

Absolute Kinematic* Flash Point* @

Grades (poises) (cSt) Penetration* °C (°F)

AR-1000 1000 ; 250 140 65 205 (400)

AR-2000 2000 ; 500 200 40 219 (425)

AR-4000 4000 ; 1000 275 25 227 (440)

AR-8000 8000 ; 2000 400 20 232 (450)

AR-16000 16000 ; 4000 550 20 238 (460)

*Specification is for the minimum acceptable values
Flash point specification is for the asphalt cement before rolling thin-film oven conditioning.
All other specifications are for samples that have been conditioned.

@

■ Asphalt Cutbacks

Three types of cutbacks are produced, depending on the hardness of the
residue and the type of solvent used. Rapid-curing cutbacks are produced by
dissolving hard residue in a highly volatile solvent, such as gasoline.
Medium-curing cutbacks use medium hardness residue and a less volatile
solvent, such as kerosene. Slow-curing cutbacks are produced by either di-
luting soft residue in nonvolatile or low-volatility fuel oil or by simply stop-
ping the refining process before all of the fuel oil is removed from the stock.
Curing the cutback refers to the evaporation of the solvent from the as-
phalt residue. Rapid-curing (RC) cutbacks cure in about 5 to 10 minutes, while
medium-curing (MC) cutbacks cure in a few days. Slow-curing (SC) cutbacks
cure in a few months. In addition to the three types, cutbacks have several
grades defined by the kinematic viscosity at 60°C (140°F). Grades of 30, 70,
250, 800, and 3000 are manufactured, with higher grades indicating higher
viscosities. Thus, cutback asphalts are designated by letters (RC, MC, or SC),
representing the type, followed by a number that represents the grade. For ex-
ample, MC-800 is a medium-curing cutback with a grade of 800. The different
grades of cutback are produced by varying the amounts and types of solvent
and base asphalt. The specifications of cutbacks are standardized by ASTM
D2026, D2027, and D2028.

9.7.2

■ 9.7.3 Asphalt Emulsions

Asphalt emulsions are produced in a variety of combinations of the elec-
tric charge of the emulsifying agent, the rate the emulsion sets (brakes), the
viscosity of the emulsion, and the hardness of the asphalt cement. Both