Viscosity Grade Bitumen
Bitumen is produced from heavier components of crude oil which is also called the “residue” of distillation process. It’s composed of complex hydrocarbons and contains elements such as calcium, iron, sulfur, and oxygen. There is also a kind of naturally occurring bitumen which is the remaining of migrated crude oil with very huge molecules of hydrocarbon.
Alike other petroleum products, bitumen is characterized by bulk physical properties. There are different standards that define the behavior of bitumen in different conditions.
Recent standard method of classification of bitumen is to categorize it based on its viscosity. Bitumen is graded based on absolute viscosity at 60 ºC or kinematic viscosity at 135 ºC. The SI physical unit of dynamic viscosity is Poise and kinematic viscosity is expressed in Centi-Stokes. Pure bitumen has been graded based on AASHTO-M226 and ASTM-D3381 standards.
Viscosity graded bitumen is used in road and motorway construction. This method of classification is more recent than penetration grading. The main advantage of this grading system is that viscosity is a fundamental engineering parameter. Also, temperature sensitiveness can be better determined because viscosity is measured at three different temperatures while penetration only is measured at 25°C (77°F).
Two major methods are implemented in viscosity grading, Grading based on Original Asphalt (AC) and Grading based on Aged Residue (AR). Below are the tables of AC and AR grades based on AASHTO-M226 and ASTM-D3381 standards.
Technical Specifications of Pure Bitumen Based on Viscosity at 60 oC (AASHTO-M226)
| Viscosity | Test | |||||
| AC-40 | AC-30 | AC-20 | AC-10 | AC-5 | AC-2/5 | |
| 4000±800 | 3000±600 | 2000±400 | 1000±200 | 500±100 | 250±50 | Viscosity at 60C-P |
| 400 | 350 | 300 | 250 | 175 | 125 | Viscosity at 135 C |
| 40 | 50 | 60 | 80 | 140 | 220 | Penetration at 25C,100 grams, 5seconds/min |
| 232 | 232 | 232 | 219 | 177 | 163 | Flash point, Cleveland open cup-min |
| 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | Solubility in trichloroethylene |
| Test on the residue of thin bitumen layer | ||||||
| 0.5 | 0.5 | 0.5 | 0.5 | 1.0 | – | Heating loss |
| 16000 | 12000 | 8000 | 4000 | 2000 | 1000 | Viscosity at 60C-P |
| 25 | 40 | 50 | 75 | 100 | 100* | Ductility at 25C,(cm)-min |
| Stain Test | ||||||
| Negative | Naphtha Solvent | |||||
| Negative | Naphta-Xylene Solvent,Xylene Percentage | |||||
| Negative | Naphta-Xylene Solvent,Xylene Percentage | |||||
*If the ductility is less than 100 at 25 oC, the material will be accepted if its ductility at 15.6 oC is more than 100 cm at a pull rate of 5 cm/min.
Technical Specifications of Pure Bitumen Based on Viscosity at 60 oC (AASHTO-M226)
| Viscosity | Test | ||||
| AR-160 | AR-80 | AR-40 | AR-20 | AR-10 | |
| 16000±4000 | 8000±2000 | 4000±1000 | 2000±500 | 1000±250 | Viscosity at 60 C-P |
| 550 | 400 | 275 | 200 | 140 | Viscosity at 135C,min |
| 20 | 20 | 25 | 40 | 65 | Penetration at 25C,100 grams, 5 seconds/min |
| 52 | 50 | 45 | 40 | – | Percentage of penetration in primary bitumen at 25/min |
| 75 | 75 | 75 | 100** | 100** | Ductility at 25C,(cm)-min |
| Test on Primary Bitumen | |||||
| 238 | 232 | 227 | 219 | 205 | Flash point, Cleveland open cup |
| 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | Solubility in trichloroethylene |
*AASHTO T240 may be used but as a comparing method.
** If the ductility is less than 100 at 25 oC, the material will be accepted if its ductility at 15.6 oC is more than 100 cm at a pull rate of 5 cm/min.
Technical Specifications of Pure Bitumen Based on Viscosity at 60 oC (ASTM-D3381)
| Viscosity | Test | ||||||
| AC-40 | AC-30 | AC-20 | AC-10 | AC-5 | AC-2/5 | ||
| 4000±800 | 3000±600 | 2000±400 | 1000±200 | 500±100 | 250±50 | Viscosity at 60 C-P | |
| 400 | 350 | 300 | 250 | 175 | 125 | Viscosity at 135 C,min | |
| 40 | 50 | 60 | 80 | 140 | 220 | Penetration at 25C-min | |
| 232 | 232 | 232 | 219 | 177 | 163 | Flash point, Cleveland open cup-min | |
| 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | Solubility in trichloroethylene | |
| Test on the remained bitumen | |||||||
| 20000 | 15000 | 10000 | 5000 | 2500 | 1250 | Viscosity at 60C,max | |
| 10 | 20 | 50 | 75 | 100 | 100* | Ductility at 25C, 5cm/min | |
* If the ductility is less than 100 at 25 oC, the material will be accepted if its ductility at 15.6 oC is more than 100 cm at a pull rate of 5 cm/min.
Technical Specifications of Pure Bitumen Based on Viscosity at 60 oC (ASTM-D3381)
| Viscosity | Test | ||||
| AR-16000 | AR-8000 | AR-4000 | AR-2000 | AR-1000 | |
| 16000±4000 | 8000±2000 | 4000±1000 | 2000±500 | 1000±250 | Viscosity at 60C |
| 550 | 400 | 275 | 200 | 140 | Viscosity at 135C,min |
| 20 | 20 | 25 | 40 | 65 | Penetration at 25C,100 grams, 5 seconds/min |
| 52 | 50 | 45 | 40 | – | Percentage of penetration in primary bitumen at 25-min |
| 75 | 75 | 75 | 100** | 100* | Ductility at 25C,(cm)-min |
| Test on Primary Bitumen | |||||
| 238 | 232 | 227 | 219 | 205 | Flash point, Cleveland open cup-min |
| 99.0 | 99.0 | 99.0 | 99.0 | 99.0 | Solubility in trichloroethylene |
* Thin-film oven test may be used but the rolling thin-film oven test shall be the referee method.
**If ductility is less than 100 at 25 oC, material will be accepted if ductility at 15/6 oC is 100cm min. at a pull rate of 5 cm/min.