In the 1970s, US introduced the Viscosity grading system as a solution to construction problems to offer high temperature performance. Unlike penetration grading system, the viscosity test, carries out at 60° ± 0,3 °C (the average road surface temperature during summer) and 135 °C (the average bitumen temperature for mixing asphalt). The viscosity measurements at two temperature provides users with an accurate asphalt mixing and temperature values for construction. Lower viscosity grades with higher penetration are used for cold regions to tackle cracking issues, while in hot climates, higher viscosity grades with lower penetration are employed to overcome deformation.
The viscosity binders can be employed for a wide variety of temperatures. A temperature of 60 °C for rutting, 25 °C for ravelling or fatigue problems or 135 °C for construction activities.
| Property | VG-10 | VG-20 | VG-30 | VG-40 | Test Method |
|---|---|---|---|---|---|
| Dynamic viscosity @60°c (poise) | 1000+200 | 2000+400 | 3000+600 | 4000+800 | |
| Kinematic Viscosity @135°c(Min, Cst ) | 250 | 300 | 350 | 400 | IS 1206 (Part3) |
| Penetration ,25°c,100g 5s,min | 80 | 60 | 45 | 35 | IS 1203 |
| Flash Point °C | 220 | 220 | 220 | 220 | IS 1448 [P:69 |
| Softening point °C | 40 | 45 | 47 | 50 | IS 1205 |
| Solubility in trichloroethylene (min %) | 99.0 | 99.0 | 99.0 | 99.0 | IS 1216 |
| Test on residue from thin film oven test | - | - | - | - | - |
| Ductility ,25°c,5cm/min/cm | 75 | 50 | 40 | 25 | IS 1208 |
| Viscosity ratio @60°C Max | 4.0 | 4.0 | 4.0 | 4.0 | IS 1206 (Part2) |