The penetration test of bitumen quantifies the hardness or softness of bitumen by measuring the depth of penetration of standard loaded needle in five seconds while maintaining bitumen sample temperature at 25°C. The more viscous the bitumen, the less distance needle is able to penetrate. Hence, the penetration value for viscous bitumen is less.
For instance, if the needle penetrates between 6 and 7 mm in 5 seconds, we will have 60/70 bitumen. The penetration is measured to specify the bitumen type in accordance with the climatic conditions of the area of bitumen consumption. The penetration depth is empirically (albeit only roughly) correlated with asphalt binder performance. Therefore, asphalt binders with high penetration numbers (called ‘’soft’’) are used for cold climates (like 85/100) while asphalt binders with low penetration numbers (called ‘’hard’’) are used for warm climates (like 40/50).
Viscosity Grade:
In the early 1960s, an improved asphalt grading system was developed that incorporated a rational scientific viscosity test. The testing bath temperature must be 60° +/- 0,3 °C, (average road surface temperature during sunshine) and 135°C (average temperature of bitumen when mixing asphalt). In hot climates, bitumen with low penetration and high viscosity is used (eg VG40), so it will not flow (deform) with the high ambient temperature., and bitumen with high penetration and low viscosity is used in cooler regions. it will not ‘’crack’’ under freezing temperatures (eg VG10).
Performance Grade:
PG system is a method of measuring asphalt binder performance. IN a Super-pave grading system, binders are classified according to their performance in extreme hot and cold temperatures and called Performance Grade Bitumen. The main purpose of grading and electing asphalt binder using the Performance Grade system is to ensure that the binder has the appropriate properties for environmental conditions in the field. Performance Grade asphalt binders are selected to meet expected climatic conditions as well as traffic speed and volume adjustment. Therefore, the Performance Grade system uses a common set of tests to measure the physical properties of the binder that can be directly related tot the field performance of the pavement at its service temperatures by engineering principles.
City NG is able to supply blow bitumen PG grades:
