Medium Curing Cutback Asphalt
Medium Curing Cutback Asphalt
Medium curing (MC) cutback asphalts are defined as those asphalt grades, which are prepared by using the medium volatile kerosene as the prime coat with boiling point ranges (MC-30, 70, 250, 800, 3000). The mix is done in a cold manner.
Cutback bitumen or asphalt is classified based on the curing as follows, 1) Slow, 2) medium and 3) rapid curing.
The degree of evaporation in the medium curing cutback asphalt is intermediate because the kerosene is intermediate volatile liquid as compared to the naphtha and diesel. The degree of liquidity depends on the proportion in which the kerosene is mixed in the asphalt cement.
The following specification for the medium curing cutback asphalt with its properties are as given below.
The medium curing cutback asphalt is used in the flexible pavements for surface dressing, prime coating, and tack coating. Evaporation of the solvents will be at a moderate rate. This grade is used with aggregates for ensuring better workability in the mix.
The degree of liquidity developed in each case depends principally on the proportion 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 ordinary 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.
The medium setting grades are designed for mixing with aggregates. Because these grades do not break immediately upon contact with aggregate, mixes using them can remain workable for extended periods of time and lend themselves to cold mix stockpiles.
Application of Cutback bitumen medium curing MC
A cutback bitumen medium curing MC is simply a combination of asphalt cement and petroleum solvent. Like emulsions, cutbacks are used because they reduce asphalt viscosity for lower temperature uses (tack coats, fog seals, slurry seals, stabilization material).
Similar to emulsified asphalts, after a cutback asphalt is applied the petroleum solvent evaporates leaving behind asphalt cement residue on the surface to which it was applied. Cutback asphalt is said to “cure” as the petroleum solvent evaporates away. The use of cutback asphalts is decreasing because of environmental regulations.
Petroleum cutback asphalt
Cutback asphalts contain volatile chemicals that evaporate into the atmosphere. Emulsified asphalts evaporate water into the atmosphere. Loss of high energy products. The petroleum solvents used require higher amounts of energy to manufacture and are expensive compared to the water and emulsifying agents used in emulsified asphalts. In many places, cutback asphalt use is restricted to patching materials for use in cold weather.
