Slow Curing Cutbacks
Asphalt cutbacks use petroleum solvents for fluidifying asphalt cement. The solvents are called distillate, diluents or cutter stock. If the solvent used in making the cutback asphalt is highly volatile, it will evaporate quickly, while solvents of lower volatility evaporate more slowly. Based on the relative speed of the solvent fraction’s evaporation, cutback asphalts are divided into three types: rapid-curing (RC), medium-curing (MC) and slow-curing (SC).
Slow-curing (SC) cutback asphalt cement combines diluents of low volatility, typically in the heavy distillate range, with asphalt cement. Slow-curing cutback grades include SC-70, SC-250, SC-800, and SC-3000.
The degree of fluidity developed in each cutback’s case depends principally on the ratio of solvent to asphalt cement. To a minor degree, the liquidity of the cutback may be affected by the hardness of the base asphalt from which the cutback is made. The degree of fluidity results in several grades of cutback asphalt, some quite fluid at ambient temperatures and others somewhat more viscous. The more viscous grades may require a small amount of heating to make them fluid enough for construction operations.
Slow-curing (SC) cutback asphalts are often called road oils and are used primarily in road-mixing and dust suppressant applications. This term originated in earlier days when asphalt residual oil was used to give roads a low-cost, all-weather surface. Slow-curing cutback asphalts are also used for stockpile patching mixes, are plant-mixed with graded aggregates, and are used occasionally for priming granular surfaces.