Performance Grade Bitumen

Performance Grade (PG) bitumen is bitumen which is graded based on its performance at different temperatures. The Long-Term Pavement Performance (LTPP) has given certain algorithms 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.

Penetration grading and viscosity grading are somewhat limited in their ability to fully characterize asphalt binders for use in Hot Mix Asphalt (HMA) pavement. Therefore, as part of the Super pave research effort new binder tests and specifications were developed to more accurately and fully characterize asphalt binders for use in HMA pavements. These tests and specifications are specifically designed to address HMA pavement performance parameters such as rutting, fatigue cracking, and thermal cracking.

Super pave performance grading (PG) is based on the idea that an HMA asphalt binders properties should be related to the conditions under which it is used. For asphalt binders, this involves expected climatic conditions as well as aging considerations. Therefore, the PG system uses a common battery of tests (as the older penetration and viscosity grading systems do) but specifies that a particular asphalt binder must pass these tests at specific temperatures that are dependent upon the specific climatic conditions in the area of use. This concept is not new. The selection of penetration or viscosity graded asphalt binders follows the same logic but the relationships between asphalt binder properties and conditions of use are more complete and more precise with the Super pave PG system. Information on how to select a PG asphalt binder for a specific condition is contained in the super pave mix design method. The table below shows how the Super pave PG system addresses specific penetration, AC and AR grading system general limitations.