Cutback Bitumen Drum Packing
DESCRIPTION OF CUTBACK BITUMEN
Cutback Bitumen ( Liquid Bitumen ) is Bitumen that is dissolved in a solvent . Typical solvents include Naptha, gasoline and 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% compares with over 40-65% for Bitumen emulsions. The result I The ability to reshape is a great advantage the cutbacks have over the common penetration grade bitumen. It also requires less heat to liquefy which makes cutback grades easier to use at lower temperatures. more Bitumen left on the roadway after curing, for the same volume of binder applied. The benefit Cutbacks offer compared to Emulsions, is a much higher residual Bitumen percentage, usually over 80% while the rate for emulsions is around 40-65%. As a result, for the same volume of binder applied, more Bitumen is left on the roadway after curing. 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.
CUTBACK CLASSIFICATION
Cutbacks are divided into two classifications, Rapid-Curing (RC) and Medium-Curing (MC), and slow-curing ( SC) depending on the solvent used. They are further defined by a number that indicates the minimum kinematic viscosity (fluidity) of the cutback.
- slow-curing ( SC) often called “road oils,” are usually a residual material produced from the fractional distillation of certain crude petroleums. Traditionally any kind of aromatic, naphthenic, and paraffinic oils are used. Slow Curing liquid bitumen materials can be prepared by blending bitumen with an oily petroleum fraction.
- Medium-Curing (MC) is a blend of Bitumen with lighter hydrocarbons such as kerosene.
- Rapid-Curing (RC) products are prepared with light, rapidly evaporating diluents such as naphtha or gasoline.
As a solvent required to produce a cutback asphalt, it is possible to use not only the above described petroleum type solvent but also a coal type solvent or may be a mixture of various solvents and an additive in order to further improve the performance of final products (e.g. antistripping effect). Each of these three types of liquid asphaltic materials is produced in six standard grades. The prefix of each grade denotes the type: SC for Slow Curing, MC for Medium Curing, and RC for Rapid Curing. The suffix, or grade number, denotes the consistency range of the material. In each type, grade 0 is the most liquid, grade 5 the most viscous, with the intermediate grades ranging in consistency in an orderly progression. At room temperature, the consistency of grade 0 materials resembles that of heavy cream while grade 5 materials have the consistency of heavy molasses in cold weather. These products “cure” by the evaporation of the petroleum diluent. Formerly the advantage of application of cutback asphalt mixtures is a difference in the reduced paving temperature. However in these days cutback asphalt are used mostly as prime coat and/or tack coat.When cutback asphalts are used as a prime coat, the cutback asphalt is sprayed to the surface of untreated sub grade or base layers in order to fill the surface voids and protect the subbase from water penetration; stabilize the fines and preserve the subbase material and/or promote bonding to the subsequent pavement layers. When used as a tack coat, the cutback asphalt is applied between hot mix asphalt pavement lifts to promote adequate bonding. This cutback promoted adequate bonding between construction lifts and especially between the existing road surface and an overlay is critical in order for the completed pavement structure to behave as a single unit and provide adequate strength. If adjacent layers do not bond to one another they essentially behave as multiple independent thin layers, none of which are designed to accommodate the anticipated traffic imposed bending stresses. Inadequate bonding between layers can result in delamination (debonding) followed by longitudinal wheel path cracking, fatigue cracking, potholes, and other distresses such as rutting that greatly reduce pavement life.
ADVANTAGE OF CUTBACK BITUMEN
The advantage Cutbacks have over Emulsions is a much higher residual Bitumen percent, typically over 80% compares 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.
APPLICATION OF CUTBACK BITUMEN IN PAVEMENT CONTRUCTION AND MAINTENANCE
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. Cutback bitumens suitable for priming 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 cool for an effective priming operation, or where traffic is likely to upset a primed surface before the final seal can be sprayed, a primer seal can be used to give adequate protection of the pavement for periods of up to 6 to 12 months. Cutback bitumens suitable for primer sealing can also be used in the manufacture of pre-mix asphalt, which is used in patch repairs.
SPRAY SEALING: Cutback bitumens are used extensively in sprayed sealing applications, particularly in cooler weather 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.
SLOW CURING CUTBACK BITUMEN SPECIFIACATION
(ASTM D2026)
| Slow Curing (SC) | SC-70 | SC-250 | SC-800 | SC-3000 | Test Methods | ||||
| Property | Min | Max | Min | Max | Min | Max | Min | Max | |
| Kinematic viscosity at 60°C, mm2/s | 70 | 140 | 250 | 500 | 800 | 1600 | 3000 | 6000 | ASTM D-2170 |
| Flash point (Cleveland open cup), °C | 66 | - | 79 | - | 93 | - | 107 | - | ASTM D-92 |
| Distillation test: | ASTM D-402 | ||||||||
| Total distillate to 360°C, volume % | 10 | 30 | 4 | 20 | 2 | 12 | - | 5 | - |
| Solubility in trichloroethylene, % | 99.0 | - | 99.0 | - | 99.0 | - | 99.0 | - | ASTM D-2042 |
| Kinematic viscosity on distillation residue at 60°C, mm2/s | 400 | 7000 | 800 | 10000 | 2000 | 16000 | 4000 | 35000 | ASTM D-2170 |
| Asphalt residue: | ASTM D-243 | ||||||||
| - Residue of 100 penetration, % | 50 | - | 60 | - | 70 | - | 80 | - | ASTM D-5 |
| - Ductility of 100 penetration residue at 25°C, cm | 100 | - | 100 | - | 100 | - | 100 | - | ASTM D-113 |
| Water, % | - | 0.5 | - | 0.5 | - | 0.5 | - | 0.5 | ASTM D-95 |
MEDIUM CURING CUTBACK BITUMEN SPECIFICATION
(ASTM D2027 OR AASHTO M82-752008)
| Medium Curing (MC) | MC-30 | MC-70 | MC-250 | MC-800 | MC-3000 | Test Methods | |||||
| Property | Min | Max | Min | Max | Min | Max | Min | Max | |||
| Kinematic viscosity at 60°C, mm2/s | 30 | 60 | 70 | 140 | 250 | 500 | 800 | 1600 | 3000 | 6000 | ASTM D-2170 |
| Flash point (Cleveland open cup), °C | 38 | - | 38 | - | 66 | - | 66 | - | 66 | - | ASTM D-92 |
| Distillation test: Distillate, volume percent of total distillate to 360°C: | ASTM D-402 | ||||||||||
| to 225°C | - | 35 | - | 25 | - | 20 | - | - | - | - | - |
| to 260°C | 30 | 75 | 10 | 70 | 5 | 55 | - | 40 | - | 15 | |
| to 316°C | 75 | 95 | 65 | 93 | 60 | 90 | 45 | 85 | 15 | 75 | |
| Residue from distillation to 360°C, percent volume by difference | |||||||||||
| Tests on residue from distillation: | |||||||||||
| Viscosity at 60°C, Pa | 30 | 120 | 30 | 120 | 30 | 120 | 30 | 120 | 30 | 120 | |
| Ductility at 25°C, cm | 100 | - | 100 | - | 100 | - | 100 | - | 100 | - | |
| Solubility in trichloroethylene, % | 99.0 | - | 99.0 | - | 99.0 | - | 99.0 | - | 99.0 | - | ASTM D-4 |
| Water, % | - | 0.2 | - | 0.2 | - | 0.2 | - | 0.2 | - | 0.2 | ASTM D-95 |
RAPID CURING CUTBACK BITUMEN SPECIFICATION
(ASTM D2028 OR AASHTO M81-92 2008)
| Medium Curing (RC) | RC-70 | RC-250 | RC-800 | RC-3000 | Test Methods | ||||
| Property | Min | Max | Min | Max | Min | Max | Min | Max | |
| Kinematic viscosity at 60°C, mm2/s | 70 | 140 | 250 | 500 | 800 | 1600 | 3000 | 6000 | ASTM D-2170 |
| Flash point (Cleveland open cup), °C | - | - | 27 | - | 27 | - | 27 | - | ASTM D-92 |
| Distillation test: Distillate, volume percent of total distillate to 360°C: | ASTM D-402 | ||||||||
| to 190°C | 10 | - | - | - | - | - | - | - | - |
| to 225°C | 50 | - | 35 | - | 15 | - | - | - | |
| to 260°C | 70 | - | 60 | - | 45 | - | 25 | - | |
| to 316°C | 85 | - | 80 | - | 75 | - | 70 | - | |
| Residue from distillation to 360°C, percent volume by difference | 55 | - | 65 | - | 75 | - | 80 | - | |
| Tests on residue from distillation: | |||||||||
| Viscosity at 60°C, Pa | 60 | 240 | 60 | 240 | 60 | 240 | 60 | 240 | |
| Ductility at 25°C, cm | 100 | - | 100 | - | 100 | - | 100 | - | ASTM D-113 |
| Solubility in trichloroethylene, % | 99.0 | - | 99.0 | - | 99.0 | - | 99.0 | - | ASTM D-4 |
| Water, % | - | 0.2 | - | 0.2 | - | 0.2 | - | 0.2 | ASTM D-95 |
