At Wintality Petroleum, we provide an advanced understanding of Viscosity Grading for asphalt binders, a crucial aspect of ensuring optimal performance in asphalt concrete (AC) pavements. Our approach encompasses both original (as-supplied) asphalt binder samples, known as AC grading, and aged residue samples, referred to as AR grading. This comprehensive grading system allows us to accurately characterize the properties of asphalt binders before and after the hot mix asphalt (HMA) manufacturing process.
Viscosity Grading Explained
AC Grading (As-Supplied)
AC grading evaluates the properties of asphalt binders in their original state, prior to any processing. This method provides valuable insights into how the binder will perform under typical conditions, including temperature fluctuations and traffic loads.
AR Grading (Aged Residue)
AR grading assesses the viscosity of aged residue obtained from the Rolling Thin Film Oven Test (RTFOT). This test simulates the aging process that asphalt binders undergo during HMA production and service life. The AR grading system aims to reflect how asphalt binders will behave in real-world pavement applications, making it a more representative measure for long-term performance.
Advantages and Disadvantages of Viscosity Grading
| Advantages | Disadvantages |
|---|---|
| Viscosity is a fundamental engineering parameter that provides a clearer understanding of binder performance. | The principal grading temperature (25°C or 77°F) may not accurately represent low-temperature rheology. |
| Testing at multiple temperatures correlates well with average pavement
temperatures and mixing conditions: - 25°C (77°F) – average pavement temperature - 60°C (140°F) – high pavement temperature - 135°C (275°F) – HMA mixing temperature |
Variability in thin film oven test residue viscosities can occur even within the same AC grade, leading to inconsistent performance post-construction. |
| Temperature susceptibility can be evaluated more effectively since viscosity is measured at different temperatures. | The testing process is generally more expensive and time-consuming compared to penetration testing. |
| Widely available testing equipment and standards facilitate consistent application across the industry. |
Viscosity Grades and Specifications
The viscosity grading system has evolved to include new nomenclature based on viscosity measurements at 60°C and 135°C. Below are the key standards for both AC and AR grading:
Asphalt Cement (AC) Grades
- AASHTO M 226
- AC-2.5
- AC-5
- AC-10
- AC-20
- AC-30
- AC-40
- ASTM D 3381
- AC-2.5
- AC-5
- AC-10
- AC-20
- AC-30
- AC-40
Aged Residue (AR) Grades
- AASHTO M 226
- AR-10
- AR-20
- AR-40
- AR-80
- AR-160
- ASTM D 3381
- AR-1000
- AR-2000
- AR-4000
- AR-8000
- AR-16000
Viscosity Grade Specifications (ASTM D3381)
| Property | Units | AC-10 | AC-20 | AC-30 | AC-40 | Test Methods |
|---|---|---|---|---|---|---|
| Viscosity, 140°F (60°C) | P | 1000±200 | 2000±400 | 3000±600 | 4000±800 | ASTM D-2171 |
| Viscosity, 275°F (135°C), Min | cSt | 150 | 210 | 250 | 300 | ASTM D-2171 |
| Penetration, 77°F (25°C), 100g, 5sec, Min | 0.1MM | 70 | 40 | 30 | 20 | ASTM D-5 |
| Flash point, Cleveland open cup, Min | °C | 219 | 232 | 232 | 232 | ASTM D-92 |
| Solubility in trichloroethylene, Min | %Wt | 99 | 99 | 99 | 99 | ASTM D-2042 |
Benefits of Viscosity Grading Over Penetration Grading
The transition from penetration grading to viscosity grading addresses several key issues:
- High Temperature Performance: By adopting viscosity-based specifications for high temperatures, we ensure better resistance to rutting and deformation.
- Compaction Issues: The requirement for minimum viscosity at mixing temperatures helps mitigate problems associated with tender asphalt mixtures during compaction.
- Streamlined Testing: With viscosity grading, we can reduce the total number of tests required without compromising quality, simplifying compliance with industry standards.
Conclusion
At Wintality Petroleum, our commitment to quality and innovation drives us to utilize advanced viscosity grading systems for our asphalt binders. By understanding both AC and AR properties, we are equipped to provide products that meet the rigorous demands of modern infrastructure projects. For further inquiries or to request a quote on our viscosity-grade bitumen products, please visit our Contact Us page. Wintality Petroleum is here to support your construction needs with expertise and high-quality materials tailored to your specifications.