Cutback Bitumens (liquid Bitumens) are Bitumens that are dissolved in a petroleum solvent (cutter). Typical solvents include naptha (gasoline) and kerosene. The type of solvent controls the curing time of the cutback and thus when it will obtain its ultimate strength. Rapid curing cutbacks use naptha (gasoline) while medium curing cutbacks use kerosene. The amount of cutter affects the viscosity of the cutback Bitumen. The higher the cutter content, the lower the viscosity and the more fluid it will be.
The advantage cutbacks have over emulsions is a much higher residual Bitumen percent, typically over 80 percent. This compares with just over 65 percent for Bitumen emulsions. The result is more Bitumen cement 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 which indicates the minimum kinematic viscosity (fluidity) of the cutback. The lower the number, the more fluid the cutback is.
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 deg F ( 60 deg C), in Centistokes , Penetration of Residue at 77 deg F (25 deg C) , 100 grams, 5 seconds.
Detailed Specifications
Medium Curing Cut Back Bitumen MC30
Properties Range Standard
Kinemalic 1 viscosity at 60°C, eSt 30 /60 ASTM D2170 Flash Point (Tag Open-Cup),°C 38 / - ASTM D1310 Distillate test : Distillate, percent by Volume of total Distillate to 360°C To 190°C - / 15 ASTM D402 To 225°C 20 / 60 ASTM D402 To 260°C 50 / 90 ASTM D402 To 316°C 80 / 100 ASTM D402 Residue from distillation to 360°C, percent volume by different Test on residue from distillation 50 / - Penetration at 25°C,100g, 5 sec. Ductility 3 at 25°C, cm 120 / 250 ASTM D402 / ASTM D5 Solubility in trichloroethylene, 100 / - ASTM D402 / ASTM D113 Water, percent volume 99.0 / - ASTM D402 / ASTM D2024 Water, percent volume - / 0.2 ASTM D95
Medium Curing Cut Back Bitumen MC70
Properties Range Standard
Kinemalic 1 viscosity at 60°C, eSt 70 /140 ASTM D2170 Flash Point (Tag Open-Cup),°C 38 / - ASTM D1310 Distillate test : Distillate, percent by Volume of total Distillate to 360°C To 190°C - / 10 ASTM D402 To 225°C 20 / 55 ASTM D402 To 260°C 40 / 80 ASTM D402 To 316°C 75 / 95 ASTM D402 Residue from distillation to 360°C, percent volume by different Test on residue from distillation 55 / - Penetration at 25°C,100g, 5 sec. Ductility 3 at 25°C, cm 120 / 250 ASTM D402 / ASTM D5 Solubility in trichloroethylene, 100 / - ASTM D402 / ASTM D113 Water, percent volume 99.0 / - ASTM D402 / ASTM D2024 Water, percent volume - / 0.2 ASTM D95
Medium Curing Cutback MC3000
Properties Min Max Kinematic viscosity at 600C (140 0F), centistrokes, 3000 6000 Flash point (Tag. Open Cup), [0C (0F)] 66(150) … Water percent … 0.2 Distillation test: Distillate percentage by volume of total distillates to 260 0C (500 0F) 0 15 Distillate percentage by volume of total distillates to 316 0C (600 0F) 15 75 Residue from distillation to 360 0C (680 0F) percent volume by difference 80 … Test on residue from distillation: Viscosity at 600C, (1400F), P or 300 1200 Penetration, 100g, 5sec, at 250C (770F), [dmm] 120 250 Ductility, 5cm/min, at 250C (770F), cm or 100 … Ductility at 15.50C (600F), cm (See “Note 1”) 100 … Solubility in Trichloroethylene, percent by weight, [%] 99 … Spot test: (see ‘’Note’’) Standard naphtha Negative Negative Naphtha-xylene solvent, percent xylene Negative Negative Heptane-xylene solvent, percent xylene Negative Negative
Sampling and Testing Standards for Cut Back Bitumen
Type o f T e s t Standards AASHTO ASTM Sampling T40 D140 Kinematic Viscosity T201 D2170 Flash point T79 D1310 Water T55 D95 Distillation T78 D402 Penetration T49 D5 Ductility T51 D113 Solubility in trichloroethylene T44 D2042 Spot test T102
