Bitumen Types

Bitumen Types:

Penetration grade bitumen:

Penetration Grade Bitumen is a standard bitumen usually used as a Paving Grade Bitumen essential for road construction and some industrial applications.

The penetration grading system was developed in the early 1900s to characterize the consistency of semi-solid asphalts. Penetration rate bitumen is graded based on penetration and softening point tests. Bitumen with lower penetration grade is used in the regions with warm climate while higher penetration grade is used for cold climates.

GD-2801E1 Asphalt Penetration test apparatus

GD-2806G Asphalt softening point test apparatus

Viscosity grade bitumen:

With the increased use of designed dense mixes,increased traffic volume and loading,higher road users’ expectations and changes in crude quality,new test method was felt essential lately. Hence new standards such as absolute viscosity at 60°C and 135°C were developed.

Bitumen is graded based on absolute viscosity at 60ºC or kinematic viscosity at 135ºC. 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.

According to viscosity (degree of fluidity) grading,higher the grade,stiffer the Bitumen. Tests are conducted at 60˚C and 135˚C,which represent the temperature of road surface during summer (hot climate) and mixing temperature respectively.

GDJ-1F Absolute viscosity Test Instrument

GD-265E Kinematic Viscometer

Performance Grade Bitumen:

Performance Grade bitumen (PG) is graded based on its performance at different temperatures. In Super pave grading system,binders are classified according to their performance in extreme hot and cold temperatures and called as performance grading (PG) bitumen. The main purpose of grading and selecting asphalt binder using the PG system is to make certain that the binder has the appropriate properties for environmental conditions in the field. PG asphalt binders are selected to meet expected climatic conditions as well as traffic speed and volume adjustments. It is one of the most important changes introduced in Super pave that acceptance limits are the same but have to be met at specific pavement temperature and traffic conditions.

The Long-Term Pavement Performance has given a certain algorithm to calculate the temperature of the pavement based on the temperature of the air above. From this,the highest and the lowest temperatures of the pavement are calculated and the bitumen that performs well in that temperature range is selected. A wider PG range means higher resistance and more favorable specifications.

PAV : performance grade bitumen

BBR:Bituminous Mixtures Bending Beam Rheometer

DSR:Dynamic shear rheometer