For volumetric determinations, which gravity measure is acceptable to use for RAS?

• A. Bulk gravity
• B. Apparent gravity
• C. Specific gravity of water
• D. Effective gravity

Answer: (D)

For volumetric determinations, you need the gravity measure that reflects the in-place density of the material, including any binder and moisture filling the pore spaces. That measure is effective gravity. It accounts for how much of the voids are actually occupied by asphalt binder and absorbed water in the RAS, giving you accurate weight-to-volume conversions for mix calculations.

Using bulk gravity would treat all voids as part of the volume, without considering how binder and moisture fill those spaces, which can misrepresent the true volume. Apparent gravity looks at the density of the solids without accounting for the pore-filling fluids, so it also fails to match the actual material in place. The specific gravity of water is just a reference standard and does not describe the density of the asphalt–aggregate system itself.