Relative Compaction from Field Density and Proctor Maximum
The pass/fail an earthwork inspector reads at every test point.
Example
You enter
- Field wet density (pcf) 128
- Field moisture content (%) 12
- Proctor maximum dry density (pcf) 120
- Required relative compaction (%) 95
You get
- Field dry density 114.3 pcf
- Relative compaction 95.2
Details, formula, and sources
RC = (field dry density / Proctor max) x 100, with the field dry density backed out of the nuclear-gauge wet density and moisture, gamma_d = gamma_wet/(1 + w). 128 pcf wet at 12% against a 120 pcf Proctor gives 114.3 pcf dry -> 95.2%, passing a 95% structural-fill spec; the same wet density at 16% moisture fails at 91.9% - the moisture reading is as important as the density, why over-wet fill is rejected. Enter the Proctor maximum (D698 / D1557). A QC aid; the geotechnical spec governs.
gd_field = wet / (1 + w/100); RC = gd_field / max x 100; pass when RC >= spec.
The relative-compaction relation RC = (gamma_d,field / gamma_d,max) x 100 with the moisture-back-out of field dry density and the ASTM D698/D1557 Proctor basis, a standard earthwork-QC result, by name.
The relative-compaction relation is a public earthwork-QC result; the ASTM D698/D1557 Proctor tests define the maximum dry density.
Estimate. AHJ and licensed professional govern.
Field names used by the API: wet_pcf, w_pct, max_pcf, spec_pct, gd_field, rc_pct
- Relative compaction field dry density as a percentage of the lab Proctor maximum dry densityearthwork QC practice
- Moisture back-out gamma_d,field = gamma_wet / (1 + w) from the nuclear-gauge or sand-cone readingfield density testing
- Proctor basis maximum dry density from ASTM D698 (standard) or D1557 (modified)ASTM D698 / D1557