Performance Grade Bitumen Advantages

1.  Common tests are conducted at a single test temperature which is 25°C in penetration and 60°C in viscosity test, which means that they cannot give any details about how the bitumen would behave in low or high temperatures. Superpave grading indicates a working temperature range of binder and therefore, helps with choosing the best type according to the condition each project demands.

2. Empirical methods such as viscosity and penetration grading systems were developed based on old experiences and can be applicable if those conditions still exist. But,climatic and current traffic conditions are rapidly changing and past experiences can no longer be defining criteria. In the PG system, it is possible to use actual traffic volumeand vehicle speed which represents the duration of loads are applied.

3. Because of the visco-elastic properties of bitumen, the rate of load application and temperature have a great effect on its behavior. Although the behavior of bitumen in lower loading rates corresponds to that of higher temperatures, none of the other grading systems doesn’t take the rate of load into account except for Superpave. While Superpave can be easily used for both unmodified and modified bitumen, conventional methods areused only for unmodified bitumen types.

4. Conventional methods ignore the long-term aging of binders and its behavior. But Superpave takes both long-term aging using with the pressure aging vessel (PAV) and short-term aging using the rolling thin film oven test (RTFOT) into account.

5. Bitumen properties indicated at different temperatures contribute to resistance to the distresses in a different level. Bitumen contributing in a better rutting resistance is measured at maximum pavement temperatures and which leads to a more elastic and stiffer binder. Bitumen contributing to fatigue resistance is the most crucial at average pavement temperatures and it requires asofter bitumen while it still favors an elastic binder. Bitumen contribution to thermal cracking is sensitive atminimum pavement temperatures and it demands a less elastic and soft bitumen.

Specification