What unit is used for density readings in this testing approach?

• A. pcf
• B. g/cm3
• C. kg/m3
• D. lb/ft3

Answer: (A)

In this testing approach, density readings are reported as pounds per cubic foot. That unit, abbreviated pcf, is the standard for field density measurements in US customary units and directly ties the measured density to the soil’s compacted state relative to its maximum dry density from Proctor tests. The nuclear density gauge and similar field methods typically yield a dry density in pcf, and engineers use that to determine percent relative compaction.

Metric density units like g/cm3 or kg/m3 aren’t the norm for FDOT field density readings, since the standard practice in these tests uses imperial units. While lb/ft3 expresses the same concept as pcf (weight per volume), pcf is the conventional form used in the context of FDOT earthwork testing and reporting.