Description
Cutback Bitumen ( Liquid Bitumen )is a Bitumen that is dissolved in a solvent. Typical solvents include Naptha, gasoline kerosene, white spirit, etc. The type of solvent controls the curing time while the amount determines the viscosity of the Cutback Bitumen.
The advantage Cutbacks have over Emulsions is a much higher residual Bitumen percent, typically over 80% compared with over 40-65% for Bitumen emulsions. The result is more Bitumen left on the roadway after curing, for the same volume of binder applied.
Cutback Classification
Cutbacks are divided into two classifications, Rapid-Curing (RC) and Medium-Curing (MC) depending on the solvent used. They are further defined by a number that indicates the minimum kinematic viscosity (fluidity) of the cutback.
Grades & Properties
| Grade | Curing Speed | Viscosity | Penetration of Residue |
|---|---|---|---|
| MC 30 | Medium | 30-60 | 120- 150 |
| MC 70 | Medium | 70-140 | 120- 150 |
| MC 250 | Medium | 250- 500 | 120- 150 |
| MC 800 | Medium | 800- 1600 | 120- 150 |
| MC 3000 | Medium | 3000- 6000 | 120- 150 |
| RC 70 | Rapid | 70-140 | 80- 120 |
| RC 250 | Rapid | 250-500 | 80- 120 |
| RC 800 | Rapid | 800- 1600 | 80- 120 |
| RC 3000 | Rapid | 3000- 6000 | 80- 120 |
*Kinematic Viscosity at 140 degrees F ( 60 degrees C), in Centistokes, Penetration of Residue at 77 degrees F (25 degrees C), 100 grams, 5 seconds
.Application
Cutback bitumen suitable for primer sealing can also be used in the manufacture of pre-mix asphalt, which is used in patch repairs. Cutback bitumen is used extensively in sprayed sealing applications, particularly in cooler weather where it provides improved initial stone retention due to its lower viscosity. Typically, a single application of the appropriate cutback bitumen is sprayed onto the primed pavement on which aggregate is laid.
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