Cutback Bitumen
Cutback bitumen consist of bitumen that has been diluted in solvent (cutter or flux) to make it more fluid for application. The fluidity of cutback bitumen depends on the degree of hardness of the bitumen and the proportion of diluent.
Cutbacks are classified according to the time it takes for them to cure, or become solid due to the evaporation of the diluent. Classifications are rapid curing (RC), medium curing (MC) or slow curing (SC). A cutback varies in behavior according to the type of cutter or flux used as the diluent with white spirit commonly used for RC grades, kerosene for MC and diesel for SC. A rapid-curing (RC) solvent will evaporate more quickly than a medium-curing (MC) solvent, which in turn will cure more rapidly than a slow-curing (SC) solvent.
The viscosity of the cutback bitumen is determined by the proportion of solvent added – the higher the proportion of solvent, the lower the viscosity of the cutback. “. When the solvent has evaporated, the binder reverts to the original penetration grade. The advantage of cutback bitumen is that they can be applied at lower temperatures than penetration grades because of their lower viscosities.
Lab Tests on Cutback Bitumen to Check Quality:
Among Cutback tests, the important of them is kinematic viscoustity and distillation test. Also there is a general requirement in the specification that cutback bitumens should be free of visible water, and will not foam when heated to application temperature. Flash point, a measure of the temperature to which a cutback bitumen can safely be heated under certain conditions, is usually monitored at the point of manufacture since certain precautions are necessary during transportation and application of the product.
Kinematic Viscosity at 60°C ; ASTM D-2170
Flash Point (top open cup) (°C); ASTM D-3143
Distillate, %volume of total distillate to at 360°C: ASTM D-402
Residue from Distillation to 360°C : ASTM D-402
Solubility in Trichloroethylene (%wt); ASTM D-2024
Water Content (%vol); ASTM D-95
| BITUMEN MC 30 | ||
| Characteristic | Value | Test Method |
|---|---|---|
| Kinematic Viscosity at 60°C (cSt) | 30-60 | ASTM D-2170 |
| Flash Point (top open cup)(°C) | 38 min | ASTM D-3143 |
| Distillate, %volume of total distillate to at 360°C: To 225°C To 260°C To 316°C |
25 max 40-70 75-93 |
ASTM D-402 |
| Residue from Distillation to 360°C (%Vol by difference) | 50 min | |
| Test on Residue from Distillation | ||
| Viscosity at 60°C | 30-120 | ASTM D-2170 |
| Penetration at 25°C (dmm) | 120-250 | ASTM D-5 |
| Ductility at 25°C (cm) | 100 min | ASTM D-113 |
| Solubility in Trichloroethylene (%wt) | 99 min | ASTM D-2042 |
| Water Content (%vol) | 0.2 max | ASTM D-95 |
| BITUMEN MC 70 | ||
| Characteristic | Value | Test Method |
|---|---|---|
| Kinematic Viscosity@ 60°C (cSt) | 70-140 | ASTM D-2170 |
| Flash Point (Top open cup)(°C) | 38 min | ASTM D-3143 |
| Distillate, %volume of total distillate to @ 360°C: to 225°C to 260°C to 316°C |
20 max 20-60 65-90 |
ASTM D-402 |
| Residue from Distillation to 360°C (%Vol by difference) | 55 min | ASTM D-402 |
| Test on Residue from Distillation | ||
| Viscosity@ 60°C (cSt) | 30-120 | ASTM D-2170 |
| Penetration @ 25°C (dmm) | 120-250 | ASTM D-5 |
| Ductility @ 25°C (cm) | 100 min | ASTM D-113 |
| Solubility in Trichloroethylene (%wt) | 99 min | ASTM D-2042 |
| Water Content (%vol) | 0.2 max | ASTM D-95 |
| BITUMEN MC 800 | ||
| Characteristic | Value | Test Method |
|---|---|---|
| Kinematic Viscosity@ 60°C (cSt) | 800-1600 | ASTM D-2170 |
| Flash Point (top open cup)(°C) | 66 min | ASTM D-3143 |
| Water Content (%vol) | 0.2 max | ASTM D-95 |
| Distillate, %volume of total distillate to @ 360°C: to 225°C to 260°C to 316°C |
— 0-35 45-80 |
ASTM D-402 |
| Residue from Distillation to 360°C (%Vol by difference) | 75 min | ASTM D-402 |
|
Test on Residue from Distillation |
||
| Penetration @ 25°C (dmm) | 120-250 | ASTM D-5 |
| Ductility @ 25°C (cm) | 100 min | ASTM D-113 |
| Solubility in Trichloroethylene (%wt) | 99 min | ASTM D-2042 |
| BITUMEN MC 3000 | ||
| Characteristic | Value | Test Method |
|---|---|---|
| Kinematic Viscosity at 60 °C (cSt) | 3000-6000 | ASTM D-2170 |
| Flash Point (top open cup)(°C) | 66 min | ASTM D-3143 |
| Distillate, %Volume of Total Distillate to at 360°C: To 225°C To 260°C To 316°C |
— 0-15 15-75 |
ASTM D-402 |
| Residue from Distillation to 360°C (%Vol by difference) | 80 min | ASTM D-402 |
| Test on Residue from Distillation | ||
| Viscosity at 60°C | 30-120 | ASTM D-2170 |
| Penetration at 25°C (dmm) | 120-250 | ASTM D-5 |
| Ductility at 25°C (cm) | 100 min | ASTM D-113 |
| Solubility in Trichloroethylene (%wt) | 99 min | ASTM D-2042 |
| Water Content (%vol) | 0.2 max | ASTM D-95 |
Packing
- Drum 208 litr (0.8 mm Thickness )
Application of Cutback Bitumen
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Prime and Tack Coating
The process of priming involves applying a low viscosity binder to a prepared but usually unbound aggregate base. It is intended to be absorbed by the top layers of the base and provide a surface more easily ‘wetted’ by a subsequent bituminous covering. The primer will be able to carry traffic for a short time (although this practice is uncommon) and help control dust. Generally, primers are applied at rates between 0.5 and 1.4 L/m2. Priming-suitable cutback bitumen are also used for tack coats, which are applied to an underlying surface to help with the adhesion of subsequent asphalt layer. A typical application rate is between 0.2 and 0.4 L/m2.
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Prime Sealing
Where temperatures are too cold for an effective priming operation, or where traffic is likely to distress a primed surface before the final seal can be sprayed, a primer seal can be used to provide adequate protection of the pavement for periods of up to 6 to 12 months. Cutback bitumen suitable for primer sealing can also be used in the production of pre-mix asphalt, which is used in patch repairs.
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Spray Sealing
Cutback bitumen are used more usually in sprayed sealing applications, particularly in colder temperature where they provide improved initial stone retention due to their lower viscosity. Typically, a single application of the appropriate cutback bitumen is sprayed onto the primed pavement onto which aggregate is laid.
-
Prime and Tack Coating
The process of priming involves applying a low viscosity binder to a prepared but usually unbound aggregate base. It is intended to be absorbed by the top layers of the base and provide a surface more easily ‘wetted’ by a subsequent bituminous covering. The primer will be able to carry traffic for a short time (although this practice is uncommon) and help control dust. Generally, primers are applied at rates between 0.5 and 1.4 L/m2. Priming-suitable cutback bitumen are also used for tack coats, which are applied to an underlying surface to help with the adhesion of subsequent asphalt layer. A typical application rate is between 0.2 and 0.4 L/m2.
-
Prime Sealing
Where temperatures are too cold for an effective priming operation, or where traffic is likely to distress a primed surface before the final seal can be sprayed, a primer seal can be used to provide adequate protection of the pavement for periods of up to 6 to 12 months. Cutback bitumen suitable for primer sealing can also be used in the production of pre-mix asphalt, which is used in patch repairs.
-
Spray Sealing
Cutback bitumen are used more usually in sprayed sealing applications, particularly in colder temperature where they provide improved initial stone retention due to their lower viscosity. Typically, a single application of the appropriate cutback bitumen is sprayed onto the primed pavement onto which aggregate is laid.
