Asphalt cement grade of bitumen is one of the main categories of viscosity grade bitumen. AC grade is followed by a number which indicates the viscosity at 60o C. The viscosity grading system is more comprehensive compared to the penetration grading system. Viscosity is the conversion of fluidity. It’s a general concept for the texture of substances.
Chemically speaking, viscosity is applied as a consistency measurement. Viscosity test is conducted at 60 c (the maximum pavement temperature). Good to know that the measurement unit of viscosity grading system is Poise.
Here are six asphalt cement (AC) viscosity grades: AC-2.5 (which is the softest grade), AC-5, AC-20, AC-30, and AC-40(which is the hardest grade). As a brief explanation, AC-2.5 is asphalt cement with a target viscosity of 250 poises at 60c. (250 are divided by 100).
As mentioned above, for other grades, the divided number for each grade stands for the target viscosity poises.
Low viscosity grades are AC-2.5 and AC-5. They are recommended for cold climate whereas other grades AC10 to AC40 are suitable for hot climate.
| Property | Viscosity | |||
|---|---|---|---|---|
| AC-10 | AC-20 | AC-30 | AC-40 | |
| Dynamic viscosity @60°c (poise) | 1000+200 | 2000+400 | 3000+600 | 4000+800 |
| Kinematic Viscosity @135°c(Min, Cst ) | 250 | 300 | 350 | 400 |
| Penetration ,25°c,100g 5s,min | 80 | 60 | 50 | 40 |
| Flash Point °C | 220 | 230 | 230 | 230 |
| Solubility in trichloroethylene (min %) | 99.0 | 99.0 | 99.0 | 99.0 |
| Test on residue from thin film oven test viscosity @60°,max,poise | 5000 | 10000 | 15000 | 20000 |
| Ductility ,25°c,5cm/min/cm | 75 | 50 | 40 | 25 |
| Spot Test | ||||
| Naphtha solvent | Negative | |||
| Naphtha -xylene solvent ,xylene percentage | Negative | |||
| Heptane-xylene solvent ,xylene percentage | Negative |