History of viscosity grade bitumens :
It was in the early 1690s that a modified grading system was developed that had some scientific criteria, which, unlike experiments, did not have an experimental form of diffusion and was based on viscosity experiments used to determine the properties of bitumen. Was taken. Most researchers believe that the viscosity characteristic can be more representative of the properties of bitumen than the other two characteristics (SP and Pen).
A so-called grade of refined bitumen is obtained by aerating the vacuum baton of the distillation tower and is divided according to their viscosity. Viscosity is a basic property of bitumen that determines the material at a certain temperature or a What is the behavior of the temperature range? The basic unit of viscosity is Pascals (Pa.s). In the classification based on the viscosity of bitumens according to the absolute viscosity at 60 ° C or kinematic viscosity at 135 ° C, classification and specific technical criteria have been determined for each of them. Absolute viscosity is expressed in terms of pouza and kinematic viscosity is expressed in terms of Santi Stokes. Classification and specifications of pure bitumen are reported in AASHTO-M226 and ASTM-D3381 standards.