Viscosity Grade (VG) Bitumen
Introduction
Viscosity grade (VG) bitumen is a type of bitumen obtained by air blowing the vacuum bottom residue of the distillation tower. It is classified based on its viscosity (or flowability). VG bitumen is widely used in road construction, waterproofing, building construction, and the production of liquid bitumen. VG30 bitumen is particularly suitable for moderate climates.
Classification and Specifications
VG bitumens are classified and specified based on their absolute viscosity at 60°C or kinematic viscosity at 135°C. Specific technical criteria are defined for each grade. Absolute viscosity is expressed in Poise (Pa.s) and kinematic viscosity in centiStokes (cSt). The classification and specifications of pure bitumen are reported in standards AASHTO-M226 and ASTM-D3381.
Bitumen Viscosity
Viscosity is a fundamental property of bitumen that characterizes the behavior of the material at a specific temperature or temperature range. The main unit of viscosity is Pascal-second (Pa.s).
Absolute or dynamic viscosity of bitumen, measured in Pa.s, is the shear stress applied to the sample (in Pa) divided by the shear rate (1 Pa = 10 Poise). The absolute viscosity of bitumen can be measured using a sliding plate viscometer.
Viscosity can also be expressed in m²/s or the more common mm²/s, where 1 mm²/s is equal to 1 cSt. These units are related to kinematic viscosity.
Kinematic viscosity is measured using a capillary tube viscometer. The following equation can be used to relate kinematic viscosity to dynamic viscosity:
VG Bitumen Grades
The higher the temperature, the softer the bitumen. In the VG grade, the viscosity test is measured at 60°C and 135°C, which correspond to the summer road surface temperature and the asphalt mixing temperature, respectively.
The penetration degree at 25°C, which is the average annual temperature of the asphalt pavement, is also specified in this bitumen standard.
VG bitumen grades are classified based on the results of the viscosity test. This category of bitumen, which has widespread applications in regions like India, will soon replace penetration grade bitumen in these areas.
VG Bitumen Grades:
- VG-10 bitumen
- VG-20 bitumen
- VG-30 bitumen
VG-40 bitumen
| Specification | Test Method | ||||
| VG 40 | VG 30 | VG 20 | VG 10 | ||
| Absolute Viscosity at 60°C, Poises | Min. 3200 | Min. 2400 | Min. 1600 | Min. 800 | IS 1206 (Part 2) |
| Kinematic Viscosity at 135°C, cSt | Min. 400 | Min. 350 | Min. 300 | Min. 250 | IS 1206 (Part 3) |
| Flash Point (Cleveland Open Cup), °C | Min. 220 | Min. 220 | Min. 220 | Min. 220 | IS 1209 |
| Solubility in trichloroethylene, % | Min. 99 | Min. 99 | Min. 99 | Min. 99 | IS 1206 |
| Softening Point (R&B), °C | Min. 50 | Min. 47 | Min. 45 | Min. 40 | IS 1205 |
| Penetration @ 25°C(100g, 5 sec.),0.1 mm | 40 – 60 | 50 – 70 | 60 – 80 | 80 -100 | IS 1203 |
| i) Viscosity ratio at 60°C | Max. 4.0 | Max. 4.0 | Max. 4.0 | Max. 4.0 | IS 1206 (Part 2) |
| ii) Ductility at 25°C, cm, after thin film oven test | Min. 25 | Min. 40 | Min. 50 | Min. 75 | IS 1208 |
| Specific Gravity @ 27/27 °C | Min. 0.99 | Min. 0.99 | Min. 0.99 | Min. 0.99 | IS 1202 |
Bitumen Cutback: Types and Applications
Introduction
Bitumen is a hydrocarbon material with a black to dark brown color that is soluble in carbon disulfide and carbon tetrachloride. Bitumen consists of various compounds such as naphthalene, polycyclic aromatic compounds, polar aromatic compounds like phenol, saturated hydrocarbons, and heterocyclic compounds. It comes in different types, including:
- Petroleum bitumen
- Oxidized bitumen
- Natural bitumen
- Emulsified bitumen
- And more
Bitumen Cutback Definition
Bitumen cutback is a type of bitumen that has been dissolved in a petroleum solvent. It is classified into three main categories:
1. Rapid Curing (RC)
RC stands for Rapid Curing. This type of cutback bitumen is made using light solvents such as gasoline and naphtha. It can be further divided into four types: RC-70, RC-250, RC-800, and RC-3000.
It’s worth noting that the higher the solvent content in the bitumen, the more fluid the resulting material will be. Therefore, RC-70 is the most fluid and RC-3000 is the stiffest type of cutback bitumen.
2. Medium Curing (MC)
MC stands for Medium Curing. This type of cutback bitumen is made using medium-heavy solvents such as kerosene. The solvent in MC bitumen evaporates more slowly than in gasoline and naphtha.
MC bitumen is also classified into five types based on its kinematic viscosity and centiStokes:
- MC30
- MC70
- MC250
- MC800
- MC3000
The lower the solvent content, the more fluid the bitumen will be. These bitumens are produced according to the ASTM D2027m-13 standard and are used in various industries.
3. Slow Curing (SC)
SC stands for Slow Curing. This type of cutback bitumen is made using heavy solvents such as diesel, fuel oil, or black oil. Under normal conditions, these solvents do not evaporate but rather undergo molecular changes.
SC bitumen can also be classified into four main types based on solvent content, kinematic viscosity, and centiStokes. The higher the solvent content, the more fluid the resulting bitumen will be.
- SC70
- SC250
- SC800
- SC3000
Main Applications of Bitumen Cutback
As mentioned earlier, different solvents are used to produce each type of cutback bitumen. Each solvent has its own unique physical and chemical properties, making it suitable for different applications and locations.
The main applications of bitumen cutback include:
- Use in protective asphalt
- Tack coat and single coat surface dressing
- Dust suppression, dust binding, and mulching
- Use in single and multiple layer asphalt
- Continuous grading and immediate and non-immediate pothole repair
- Sand seal, mastic seal, and water-resistant seal with aggregate materials
- Stone-free fog seal and prime coat penetration seal on low-porosity surfaces
- And more
Bitumen Emulsion vs. Bitumen Cutback
Bitumen cutback and bitumen emulsion are similar in appearance, which is why they are often confused with each other. However, the main difference between them is the type of solvent they use.
As mentioned earlier, bitumen cutback is produced using petroleum solvents. In contrast, bitumen emulsion is produced using water as a solvent. This leads to significant differences between the two products.
Some of the key differences between bitumen cutback and bitumen emulsion include:
- Bitumen emulsion is less expensive than bitumen cutback.
- Bitumen emulsion is less resistant to freezing and cold weather.
- Bitumen emulsion is less flammable than bitumen cutback.
- Bitumen emulsion is more environmentally friendly.
- Bitumen emulsion is easier and less expensive to use than bitumen cutback.
- Bitumen emulsion can be used in wet and humid conditions, unlike bitumen cutback.
- Bitumen emulsion has a limited shelf life, while bitumen cutback has a longer shelf life and does not require circulation.
Bitumen Cutback Price
The price of bitumen cutback is influenced by various factors, making it impossible to provide a specific price. However, some of the key factors that affect the final price include:
- Application of bitumen
- Manufacturer
- Supply and demand
- Currency exchange rates and fluctuations
- Type of bitumen and its technical specifications
- Physical and chemical properties of bitumen
- And more
Conclusion
Bitumen cutback is a type of bitumen that is produced using petroleum solvents. It is classified into three main categories based on the