Asphalt cement grade of bitumen is one of the main categories of viscosity grade bitumen.

With AC grading, asphalt binder is specified by properties it possesses before it undergoes HMA making process. Asphalt binder samples Viscosity of standard bitumen measured at 60 ºC (the maximum pavement temperature). Good to know that the measurement unit of the viscosity grading system is Poise (cm-g-s = dyne-second/cm2). The viscosity grading is done on both original (as-supplied) asphalt binder called AC grading and aged residue binder called AR grading. The AC grading is related to absolute viscosity at 60 c in 100 poises.

Here are six asphalt cement (AC) viscosity grades: AC-2.5 (the softest grade), AC-5 (viscosity is 500 ± 100 poise at 60° C (140° F)), AC-10, AC-20, AC-30, and AC-40 (the hardest grade (viscosity is 4000 ± 800 poise at 60° C (140° F))). As a brief explanation, AC-2.5 is asphalt cement with a target viscosity of 250 poises at 60c. (250 are divided by 100).

As mentioned above, for other grades, the divided number for each stands for the target viscosity poises.