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Cutback Bitumen

Cutback Bitumen (Liquid Bitumen) is Bitumen that is dissolved in a solvent. Typical solvents include Naphtha, gasoline and kerosene, white spirit etc. The type of solvent controls the curing time while the amount determines the viscosity of the Cutback Bitumen.

Cutbacks are divided into three classifications, Rapid-Curing (RC), Medium-Curing (MC) and Slow-Curing (SC) depending on the solvent used. They are further defined by a number which indicates the minimum kinematic viscosity (fluidity) of the cutback.

Intended Use

Cutback Bitumens are used in asphalt Pavement Construction and Maintenance.

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.

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.

Slow-Curing (SC) Specification

* If the ductility at 25o C is less than 100, the material will be acceptable if its ductility at 15o C is more than 100

GRADE SC-70 SC-250 SC-800 SC-3000 Test Method
Property Min Max Min Max Min Max Min Max
Flash Point,(°C) 65 80 90 105 ASTM D3143
Kinematic Viscosity at 60°C,(mm2/s) 70 140 250 500 800 1600 3000 6000 ASTM D2170

 

Distillation Test: Total Distillate to 360 °C, (% by volume) 10

 

 

30

 

4

 

20

 

2

 

12

 

 

5

 

ASTM 402
Distillation Residue: Kinematic Viscosity @ 60 °C, (mm 2 /s) 400 7000 800 10000 2000 16000 4000 35000 ASTM D2170
Residue of 100 penetration, (% by mass) 50 60 70 80 ASTM D243
Tests on Residue from Distillation
Ductility of 100 penetration residue at 25 °C, (cm)* 80 120 80 120 80 120 80 120 ASTM D5
Ductility @ 25 °C, (cm) 100 100 100 100 ASTM D113
Solubility in Trich- loroethylene (% by mass) 99.0 99.0 99.0 99.0 ASTM D2042
Water, % by volume 0.2 0.2 0.2 0.2 ASTM D95

Medium-Curing (MC) Specification

*If the ductility at 25o C is less than 100, the material will be acceptable if its ductility at 15o C is more than 100.

GRADE MC-30 MC-70 MC-250 MC-800 MC-3000 Test Method
Property Min Max Min Max Min Max Min Max Min Max
Flash Point,(°C) 38 38 65 65 65 ASTM D3143
Kinematic Viscosity at 60°C,(mm2/s) 30 60 70 140 250 500 800 1600 3000 6000 ASTM D2170

 

Distillation Test, (% of Total Distillate to 360 C)

to 225 °C

to 260 °C

to 315 °C

 

 

 

 

40

75

 

 

 

 

25

70

93

 

 

 

 

20

65

 

 

 

 

20

60

90

 

 

 

 

15

60

 

 

 

 

10

55

87

 

 

 

 

45

 

 

 

 

35

80

 

 

 

 

15

 

 

 

 

15

75

 

 

 

 

 

 

ASTM 402

Residue from Distillation to 360 °C, Volume % by difference 50 55 65 75 80
Tests on Residue from distillation
Penetration @ 25o C, 100 g, 5 s, (0.1 mm) 120 250 120 250 120 250 120 250 120 250 ASTM D5
Ductility @ 25o C, (cm) 100 100 100 100 100 ASTM D113
Solubility in Trich- loroethylene (% by mass) 99.0 99.0 99.0 99.0 99.0 ASTM D2042
Water, % by volume 0.2 0.2 0.2 0.2 0.2 ASTM D95

Rapid-Curing (RC) Specification

*If the ductility at 25o C is less than 100, the material will be acceptable if its ductility at 15o C is more than 100.

GRADE RC-30 RC-70 RC-250 RC-800 RC-3000 Test Method
Property Min Max Min Max Min Max Min Max Min Max
Flash Point,(°C) 27 27 27 ASTM D3143
Kinematic Viscosity at 60°C,(mm2/s) 30 60 70 140 250 500 800 1600 3000 6000 ASTM D2170

 

Distillation Test, (% of Total Distillate to 360 C)

to 190 °C

to 225 °C

to 260 °C

to 315 °C

 

 

15

55

75

90

 

 

 

 

10

50

70

85

 

 

 

 

 

35

60

80

 

 

 

 

 

 

15

45

75

 

 

 

 

 

 

25

70

 

 

 

 

 

 

 

 

 

ASTM 402

Residue from Distillation to 360 °C, Volume % by difference 50 55 65 75 80

Tests on Residue from distillation

Penetration @ 25o C, 100 g, 5 s, (0.1 mm) 80 120 80 120 80 120 80 120 80 120 ASTM D5
Ductility @ 25o C, (cm) 100 100 100 100 100 ASTM D113
Solubility in Trich- loroethylene (% by mass) 99.0 99.0 99.0 99.0 99.0 ASTM D2042
Water, % by volume 0.2 0.2 0.2 0.2 0.2 ASTM D95
SLOW-CURING (SC) SPECIFICATION

 Slow-Curing (SC) Specification

MEDIUM-CURING (MC) SPECIFICATION

 Medium-Curing (MC) Specification

RAPID-CURING (RC) SPECIFICATION

 Rapid-Curing (RC) Specification