#According to viscosity (degree of fluidity) grading, higher the grade, stiffer the Bitumen. Furthermore VG Grade Bitumen can be done on original (as-supplied) asphalt binder samples ( AC grading). Also aged residue samples (AR grading). AR viscosity test is based on viscosity of aged residue from rolling thin film oven test. With AC grading, asphalt binder is specify by properties it possesses before it undergoes HMA making flow.