Viscosity Grade Bitumen is a standard grade Bitumen usually used as a Paving Grade Bitumen suitable for road construction and for the production of asphalt pavements with superior properties. This grade of Bitumen is mainly used in the manufacture of hot mix asphalt for bases and wearing courses, and possesses characteristics and qualities unique sand quite different from other agents. They achieve very flexible and tenacious connections with other materials due mainly to viscoelastic response of bitumen, which behavior depends on how fast charges are applied.
Viscosity Grade bitumens are specified by the methods described in ASTM Standard D3381-09 and AASHTO M226. Viscosity Graded specifications covers bitumen (asphalt) graded by Viscosity at 60 °C .
Viscosity grade bitumens have a thermoplastic property which causes the material to soften at high temperatures and to harden at lower temperatures. This unique temperature/ viscosity relationship is important when determining the performance parameters such as the adhesion, rheology, durability and application temperatures of bitumen. In the Viscosity Graded Bitumen specifications further special emphasizes is placed on the Bitumen ductility.