Cutback Bitumen SC-70 is a slow-curing cutback asphalt produced by blending penetration grade bitumen with low-volatility petroleum distillates, typically gas oil. This formulation significantly reduces the viscosity of the base bitumen, allowing it to remain fluid at ambient temperatures while curing gradually through solvent evaporation.
SC-70 belongs to the Slow Curing (SC) category of cutback bitumen, commonly referred to as road oil, and is particularly suitable for prime coats, cold applications, and surface penetration where deeper absorption and longer working time are required.
Definition and Material Characteristics
Cutback Bitumen SC-70 is manufactured from petroleum grade bitumen derived from fractional and vacuum distillation of crude oil. The base bitumen is fluxed with less volatile distillates compared to rapid-curing grades, resulting in slower evaporation and extended curing time.
Key material characteristics include:
- Low to medium viscosity at ambient temperature
- Gradual curing behavior
- Deep penetration into granular base layers
- Strong bonding and waterproofing performance
- Thermoplastic behavior after curing
SC cutback asphalts such as SC-70 and SC-250 are chemically and physically similar to heavy refinery residual products like fuel oil No.6 (Bunker C).
Meaning of SC-70 Classification
The designation SC-70 indicates:
- SC (Slow Curing): Use of low-volatility distillates
- 70: Kinematic viscosity classification measured at 60°C
This viscosity range provides sufficient fluidity for cold application while allowing controlled penetration and bonding before curing.
Performance Characteristics
Cutback Bitumen SC-70 offers:
- Excellent penetration into non-asphalt base courses
- Reliable bonding of loose mineral particles
- Effective waterproofing and sealing of capillary voids
- Uniform coating of aggregates without heating
- Longer working time compared to RC and MC grades
Its slow curing nature makes it especially suitable for preparatory pavement treatments.
Applications of Cutback Bitumen SC-70
Typical applications of Cutback Bitumen SC-70 include:
- Prime coats on granular base and sub-base layers
- Cold-applied waterproofing treatments
- Patching and stockpile asphalt mixtures
- Surface sealing and dust suppression
- Preparation of pavement layers prior to surfacing
SC-70 is widely used where easy application, deep penetration, and extended curing time are required without the need for heating or thinning.
Safety, Handling, and Environmental Considerations
Due to the presence of petroleum distillates, proper safety procedures must be followed:
- Refer to the Safety Data Sheet (SDS) before use
- Store and apply at the lowest practical temperature
- Remove all ignition sources during application
- Avoid inhalation of vapors and contact with skin
- Use appropriate personal protective equipment (PPE)
- Prevent discharge into soil, stormwater, or sewer systems
Packing and Supply
Cutback Bitumen SC-70 is supplied in:
- New thick steel drums on pallets to prevent leakage
- Bulk bitutainers
- Bulk tanker trucks for large-scale projects
Packaging options are designed for safe transport and efficient on-site handling.
Technical Specification – Cutback Bitumen SC-70
Standards: ASTM / EN 15322:2009
| Property |
Min |
Max |
Test Method |
| Kinematic Viscosity @ 60°C, mm²/s |
70 |
140 |
ASTM D2170 |
| Flash Point (Cleveland Open Cup), °C |
60 |
— |
ASTM D92 |
| Distillation Test |
|
|
ASTM D402 |
| Total Distillate to 360°C, vol % |
— |
35 |
ASTM D402 |
| Solubility, % |
95 |
— |
ASTM D2024 |
| Kinematic Viscosity of Residue @ 60°C, mm²/s |
200 |
7000 |
ASTM D2170 |
| Asphalt Residue |
|
|
|
| Residue of 100 Penetration, % |
40 |
— |
ASTM D243 |
| Ductility of Residue @ 25°C, cm |
50 |
— |
ASTM D113 |
| Water Content, % |
— |
0.5 |
ASTM D95 |
Conclusion
Cutback Bitumen SC-70 is a slow-curing road oil designed for prime coats, cold applications, and surface preparation where deep penetration and controlled curing are essential. Its ease of application, waterproofing capability, and strong bonding performance make it a reliable solution for pavement construction and maintenance projects under a wide range of site conditions.
