AC Grade Bitumen
Asphalt Cement (AC) grade bitumen is one of the most widely used categories of viscosity-graded bitumen. According to the classification by AASHTO (American Association of State Highway Officials), viscosity-based bitumen is divided into two main groups:
- AC (Asphalt Cement) Grade Bitumen
- AR (Aged Residue) Grade Bitumen
Each AC grade represents a specific viscosity level, enabling its application in various climatic conditions and under different traffic loads. As a result, AC bitumen is a suitable option for road construction projects requiring a stable and temperature-resistant binder.
Difference Between AC and AR Grade Bitumen
Although AC and AR grades may appear similar, the meaning of the numbers following each grade is different.
- In AC grade bitumen, the number represents the absolute viscosity measured at 60°C.
- In AR grade bitumen, the number indicates the viscosity at 60°C after the Thin Film Oven Test (TFOT), which simulates ageing conditions.
What are AC-10, AC-20, and AC-30 Grades?
The most commonly used AC grades are AC-10, AC-20, and AC-30—often referred to as AC10 asphalt, AC20 asphalt, and AC30 asphalt.
The AC classification is based on absolute viscosity at 60°C, expressed in 100 poises. For example:
- AC10 means the viscosity equals 10 × 100 = 1000 poise (100 Pa.s).
AC10 Asphalt – Properties and Applications
Bitumen AC-10, also known as AC10 asphalt, is a low-viscosity AC grade with relatively high penetration and ductility characteristics. This grade is widely used in areas with cooler climates or in the construction of light-traffic roads, where greater flexibility is required.
Below are the standard specifications for AC10 bitumen:
| Bitumen AC10 Specification | ||||
|---|---|---|---|---|
| Specification | Test Method | Unit | Value | |
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | 1000±200 | |
| Viscosity, @ 135 ◦C | ASTM D2170 | CST | Min 150 | |
| Flash Point (Cleveland Open Cup) | ASTM D92 | ◦C | Min 219 | |
| Solubility in Trichloroethylene | ASTM D2042 | %WT | Min 99 | |
| Penetration, 100g, 5s, @ 25 ◦C | ASTM D5 | 0.1mm | Min 70 | |
| Thin-Film Oven Test (TFOT) | ||||
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | Max 5000 | |
| Ductility, 5 cm/min, @ 25 ◦C | ASTM D113 | cm | Min 50 | |
AC20 Asphalt – Properties and Applications
Bitumen AC 20 is suitable for moderate temperature and traffic load. It is harder than AC 10 and softer than AC 30.
Below are the standard specifications for AC20 bitumen:
| Bitumen AC20 Specification | |||
|---|---|---|---|
| Specification | Test Method | Unit | Value |
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | 2000±400 |
| Viscosity, @ 135 ◦C | ASTM D2170 | CST | Min 210 |
| Flash Point (Cleveland Open Cup) | ASTM D92 | ◦C | Min 232 |
| Solubility in Trichloroethylene | ASTM D2042 | %WT | Min 99 |
| Penetration, 100g, 5s, @ 25 ◦C | ASTM D5 | 0.1mm | Min 40 |
| Thin-Film Oven Test (TFOT) | |||
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | Max 10000 |
| Ductility, 5 cm/min, @ 25 ◦C | ASTM D113 | cm | Min 20 |
AC30 Asphalt – Properties and Applications
Bitumen AC 30 is a hard type of AC bitumen. It has a high viscosity and a low penetration value. Bitumen AC 30 is recommended for high temperature areas with heavy traffic loads.
Below are the standard specifications for AC30 bitumen:
| Bitumen AC30 Specification | |||
|---|---|---|---|
| Specification | Test Method | Unit | Value |
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | 3000±600 |
| Viscosity, @ 135 ◦C | ASTM D2170 | CST | Min 250 |
| Flash Point (Cleveland Open Cup) | ASTM D92 | ◦C | Min 232 |
| Solubility in Trichloroethylene | ASTM D2042 | %WT | Min 99 |
| Penetration, 100g, 5s, @ 25 ◦C | ASTM D5 | 0.1mm | Min 30 |
| Thin-Film Oven Test (TFOT) | |||
| Viscosity, @ 60 ◦C | ASTM D2171 | Poise (10*Pa.s) | Max 15000 |
| Ductility, 5 cm/min, @ 25 ◦C | ASTM D113 | cm | Min 15 |