Petroleum solvents are used to fluidize asphalt cement in asphalt cutbacks. Distillate, diluents, or cutter stock are the solvents. Solvents used to make cutback asphalt will evaporate quickly if they are highly volatile. Solvents with a lower volatility will evaporate at a slower pace.
Cutback asphalt cement with medium-curing properties (MC) is a mixture of medium diluents with intermediate volatility, typically in the range of kerosene boiling points, and asphalt cement. MC-30, MC-70, MC-250, MC-800, and MC-3000 are medium-curing cutback grades.
Each cutback's degree of fluidity is primarily determined by the ratio of solvent to asphalt cement. The hardness of the asphalt base from which the cutback is made can affect the liquidity of the cutback to a minor extent. 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.
Medium curing grades are designed to be mixed with aggregates. Due to the fact that these grades do not break immediately upon contact with aggregates, mixes utilizing medium-setting cutbacks can be worked for long periods of time and can therefore be stored cold.
Application of medium curing cutback bitumen
A cutback bitumen medium curing MC is simply a mixture of asphalt cement and petroleum solvent. Cutbacks are used because they reduce asphalt viscosity for applications requiring lower temperatures (tack coats, fog seals, slurry seals, stabilization material).
As with emulsified asphalts, after cutback asphalt is applied, the petroleum solvent evaporates, leaving behind asphalt cement residue. Asphalt that has been cut back is said to "cure" as the petroleum solvent evaporates. The use of cutback asphalt is decreasing due to environmental regulations.
Analysis of MC bitumen grades
Cutback asphalt is usually only used for patching materials in cold weather. Cutback MC bitumen is medium curing (MC) cutback asphalt and consists of penetration grade asphalt cement and a diluent or cutter of medium volatility. The diluent temporarily reduces the viscosity of the asphalt cement so that it can be handled and applied more easily. Petrochemical Trade Cutback MC bitumen meets ASTM D2127 (Medium-Curing Asphalt) or AASHTO M82 specifications.
* Roofing - As a waterproofing membrane and as an adhesive to stick chippings onto a flat, horizontal roof to minimize the effects of weathering from the sun.
* Damp-Proof Courses - Used as damp-proof membranes in concrete floors, particularly for small repairs or where extensions are keyed-in to existing structures.
