Apparent specific gravity is the ratio of the mass in air of a unit volume of the impermeable portion of aggregate ( does not include the permeable pores in aggregate ) to the mass in air of an equal volume of gas-free distilled water at a stated temperature.

• A. Depends on temperature
• B. True
• C. False
• D. Only for liquids

Answer: (C)

Apparent specific gravity compares how much mass a given unit volume of aggregate has in air to the mass of the same volume of water, using the entire unit volume of the aggregate (including the pore spaces). In air, the permeable pores are filled with air, which adds essentially no weight, so the measurement reflects the solid material per the full volume, not just the impermeable portion. Saying that the ratio uses only the impermeable portion would be mixing in a concept closer to the true density of the solid materials, not the apparent density of a porous aggregate. The use of gas-free distilled water in the denominator is to have a precise reference density at the stated temperature, but the key point is that the numerator does not exclude the permeable pores; it uses the whole unit volume.