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Viscosity Grade

Viscosity grade bitumen 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. Viscosity Grade Bitumen (Asphalt) is a Bitumen grade mostly used as a Paving Grade and it’s suitable for road construction and for the asphalt pavements producing with premier attributes. VG Bitumen is usually used in the production of hot mix asphalt. Viscosity Grade bitumen is specified by ASTM Standard D3381 and AASHTO M226. VG Bitumen specifications cover by Viscosity at 60 ̊C (140 °F). Viscosity grading can be done on original (as-supplied) asphalt binder samples (called AC grading) or aged residue samples (called AR grading).

 The AC grading is based on absolute viscosity at 60 °C in units of 100 poises. Six asphalt cement viscosity grades were established as AC-2.5 (softest), AC-5, AC-10, AC-20, AC-30, AC-40 (hardest). AC-2.5 means asphalt cement with a target viscosity of 250 poises at 60˚C. Similarly, AC-5, AC-10, AC-20, AC-30, and AC-40 mean asphalt cement with target viscosity of 500, 1000, 2000, 3000, and 4000 poises, respectively. Low viscosity grades AC-2.5 and AC-5 are used in cold climate while high viscosity grades AC-10 to AC-40 are generally suitable for the hot climate. Common AR grades are AR-10, AR-20, AR-40, AR-80.