Rapid Curing Cut Back Bitumen (RC) is one of the types of cut-back bitumen widely used in the road construction and building industries. This type of bitumen is produced by mixing pure bitumen with light solvents such as naphtha (gasoline) and hardens quickly due to the rapid evaporation of these solvents. This characteristic makes it particularly suitable for projects requiring fast curing and surface preparation.
In this article from Faraz Oil, we thoroughly examine Rapid Curing Cut Back Bitumen, its various grades, and their technical characteristics.
What is Cut Back Bitumen?
Cut-back bitumen is a type of bitumen produced by mixing regular bitumen with petroleum solvents. These solvents include materials like gasoline, naphtha, or kerosene, which mix with the bitumen and reduce its viscosity. In other words, this process turns bitumen into a more fluid and easily flowing material that can be applied at lower temperatures. Due to its combination with petroleum solvents, cut-back bitumen can be used on various surfaces and under conditions requiring faster performance and more uniform coating.
The reduction of bitumen viscosity through petroleum solvents works by the solvent entering the bitumen’s structure and dispersing its molecules behavior to a significant extent. As a result, the bitumen becomes a more fluid solvent, which can be easily spread on different surfaces. Ultimately, as the solvent gradually evaporates, the original bitumen remains as a solid or semi-solid substance, creating a stronger bond with the surface.
Types of Cut Back Bitumen
Cut-back bitumen comes in different types based on the solvent used and the degree of dilution to suit a variety of applications. The diverse needs of road construction, waterproofing, and surface coatings necessitate bitumen usage under different conditions, with varying solvent evaporation speeds, penetration rates, and adhesion capabilities. Thus, different types of cut-back bitumen with varying viscosities are manufactured to meet various environmental and project-specific needs. This diversity allows for optimal bitumen selection tailored to project conditions.
SC Bitumen
Slow Curing (SC) cut-back bitumen is produced by dissolving 85/100 bitumen in heavy solvents such as diesel or other fuels. These solvents evaporate slowly, leading to the gradual hardening of the bitumen. This type of bitumen is available in four grades: SC70, SC250, SC800, and SC3000.
SC cut-back bitumen is typically used in road construction, waterproofing, and industrial applications. Its unique feature compared to regular bitumen is its gradual hardening due to slow solvent evaporation, enhancing performance and long-term durability in various environmental conditions. Additionally, the choice of bitumen type is made based on project requirements, weather conditions, and surface characteristics.
MC Bitumen
Medium Curing (MC) cut-back bitumen is produced by dissolving bitumen in kerosene, which evaporates more slowly than gasoline. This type of bitumen is categorized into five main grades with viscosities ranging from 3-4 to 6000 at 60 degrees Celsius. In this process, 85/100 bitumen is typically mixed with kerosene to produce various grades of medium-curing bitumen, such as MC30, MC70, MC250, MC800, and MC3000.
MC bitumen is used for specific applications such as priming, layering, and light asphalt applications. Its controlled solvent evaporation and high penetration characteristics make it particularly useful for bonding asphalt layers. MC bitumen viscosity can be adjusted based on the intended application, and each type (from MC30 to MC3000) is tailored for varying curing times and hardness needs in different road construction, surface repairs, and protective layers.
Rapid Curing Bitumen
Rapid Curing (RC) liquid bitumen, identified by the RC abbreviation, is produced using light solvents like naphtha. Once applied to a project, the solvent quickly evaporates, leaving behind pure bitumen that retains its original properties.
RC cut-back bitumen can be made using pure bitumen with a specific penetration grade or performance grade (PG). This type of bitumen is black and manufactured in accordance with ASTM D2028m standards. Additionally, RC bitumen grades are categorized by viscosity, measured in centistokes, and include RC70, RC250, RC800, and RC3000, adhering to these standards.
Advantages of Rapid Curing Bitumen
- Fast Drying: Rapid solvent evaporation allows for quick setting, making it ideal for fast-paced projects.
- High Penetration Ability: Its liquid nature allows it to penetrate underlying layers easily, enhancing adhesion.
- Flexibility and Durability: RC bitumen can adapt to various environmental conditions, enhancing the longevity and durability of surfaces.
Rapid Curing Bitumen Grades Characteristics
Each RC bitumen grade has specific viscosity and behavior tailored for particular applications and environmental conditions.
RC-800
This grade offers excellent stability under various weather conditions, making it suitable for heavier asphalt layers and surface repairs.
- Viscosity: High viscosity suitable for heavier applications and projects requiring more stabilization time, enhancing adhesion.
- Flash Point: High flash point ensures safety during handling and transportation, preventing rapid ignition risks.
- Distillation Test: The solvent evaporates quickly, leaving a significant amount of bitumen for improved resistance and adhesion.
- Ductility: Suitable ductility to withstand stress and temperature changes without breaking.
RC-70
Typically used for thin surface coatings and surface preparation.
- Viscosity: Lower viscosity than higher grades, facilitating faster flow and spreading.
- Flash Point: Lower than higher grades, making it faster to evaporate.
- Distillation Test: Rapid solvent evaporation ensures good initial adhesion.
- Ductility: High flexibility, making it suitable for thinner layers and quick-setting surfaces.
Rapid Curing-250
Used for medium-level projects like layering and coatings.
- Viscosity: Medium viscosity, offering a balance between adhesion and flow.
- Flash Point: Moderate flash point, ensuring balanced safety and evaporation speed.
- Distillation Test: Leaves a significant amount of pure bitumen for good surface adhesion.
- Ductility: Maintains flexibility against temperature changes and stress.
RC-3000
This grade is used for heavy-duty and thick layers, often in high-stability conditions.
- Viscosity: Highest viscosity among RC grades, making it ideal for heavy-duty applications.
- Flash Point: High flash point ensures greater safety.
- Distillation Test: Slow solvent evaporation leaves a large amount of bitumen for high adhesion.
- Ductility: Lower ductility but offers strong stabilization for demanding projects.
Packaging of Rapid Curing Bitumen
RC bitumen is primarily packaged in barrels, which differ from regular 60/70 bitumen barrels by being thicker and more robust to accommodate its volatile nature. This packaging preserves quality and stability.
Additionally, RC bitumen can be transported in bulk and in Intermediate Bulk Bitumen Containers (IBC). This form of packaging is ideal for large-scale industrial projects and allows for efficient transport and storage.
Challenges and Limitations of Rapid Curing Bitumen
Despite its advantages, RC bitumen faces challenges, primarily due to the use of flammable solvents like gasoline and naphtha, posing safety risks. In cold and humid conditions, solvent evaporation may slow down, prolonging the curing process.
Conclusion
In this article from Faraz Oil Bitumen Refinery , we discussed how RC cut-back bitumen plays a key role in road construction and surface coating due to its unique properties. Selecting the appropriate grade based on project conditions and needs can improve performance and surface durability. By adhering to safety principles and understanding each grade’s characteristics, RC bitumen can be effectively used in construction and road projects.