How is density defined for the concrete in this context?

• A. Net weight of concrete (lb) divided by Volume of concrete (ft^3)
• B. Volume of concrete (ft^3) divided by Net weight of concrete (lb)
• C. Mass of concrete (kg) divided by Volume of concrete (m^3)
• D. Net weight of concrete (lb) divided by Area of concrete (ft^2)

Answer: (A)

Density is how much matter is in a given volume, and in field practice with US customary units that’s expressed as weight per volume. So for concrete, you take the net weight and divide by the volume to get pounds per cubic foot. This matches how density is typically reported (weight per volume) rather than using mass per volume or any per-area measure. The other formulations would give an inverse density, a mass-based density in different units, or a weight-per-area value, which isn’t density.