Which term is defined by excluding permeable and impermeable voids to determine the true volume of solids?

Which term is defined by excluding permeable and impermeable voids to determine the true volume of solids?

• A. Absolute Specific Gravity
• B. Apparent or Mass Specific Gravity
• C. Porosity
• D. Water Permeability

Answer: (A)

Understanding how density is defined relative to a reference volume helps here. To get the density of just the solid material itself, you must use the true volume of the solid—excluding all void spaces, whether open or closed. Using that true volume, the ratio of the material’s mass to its solid volume gives the absolute (true) specific gravity. This value reflects how dense the material would be if it had no pores at all. Porosity describes how much of the volume is void, which is a different property and relates to the void volume itself. Apparent or mass specific gravity uses a bulk volume that includes pores, so it blends solid and void volumes, leading to a lower apparent density for porous materials. Water permeability is about how easily water can flow through a material, not about the solid’s volume. Therefore, the term defined by excluding permeable and impermeable voids to determine the true volume of solids is the absolute specific gravity.

Understanding how density is defined relative to a reference volume helps here. To get the density of just the solid material itself, you must use the true volume of the solid—excluding all void spaces, whether open or closed. Using that true volume, the ratio of the material’s mass to its solid volume gives the absolute (true) specific gravity. This value reflects how dense the material would be if it had no pores at all. Porosity describes how much of the volume is void, which is a different property and relates to the void volume itself. Apparent or mass specific gravity uses a bulk volume that includes pores, so it blends solid and void volumes, leading to a lower apparent density for porous materials. Water permeability is about how easily water can flow through a material, not about the solid’s volume. Therefore, the term defined by excluding permeable and impermeable voids to determine the true volume of solids is the absolute specific gravity.