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ASTM International · Soils · Laboratory test
ASTM D854: Specific Gravity of Soil Solids by Water Pycnometer
Specific gravity of the soil solids themselves, measured in a water pycnometer — the value that void ratio, degree of saturation, and hydrometer calculations all depend on.
| Designation | ASTM D854 |
| Setting | Laboratory |
| Service line | Construction Materials Testing |
Testing is performed to the current edition of ASTM D854 referenced by your project specification. This page is a plain-language overview, not a substitute for the published standard.
What the ASTM D854 test measures
ASTM D854 measures the specific gravity of soil solids: the ratio of the density of the soil particles themselves to the density of water. A typical value for mineral soils is 2.65 to 2.75. The number rarely appears in a specification, but it underlies most of the calculations that do: void ratio, porosity, degree of saturation, the zero-air-voids line on a Proctor curve, and the particle diameters computed in a hydrometer test.
How the ASTM D854 test works, step by step
A known mass of dry soil is placed in a calibrated pycnometer flask with de-aired water. Entrapped air is removed by boiling or vacuum. The flask is filled to its calibration mark, brought to a known temperature, and weighed. Because the flask volume, water density, and total mass are known, the volume of the soil solids can be solved for and the specific gravity calculated. The test is normally run on the fraction passing the No. 4 sieve; coarser particles are tested per ASTM C127 and the results combined.
What the numbers mean
Values below about 2.60 suggest organic content, volcanic soils, or other low-density minerals. Values above 2.80 point to iron-rich or heavy mineral soils. A geotechnical engineer uses the result to compute phase relationships for settlement, permeability, and slope stability analyses, and a laboratory uses it to plot the zero-air-voids curve that checks whether a Proctor result is physically possible.
What can throw the result off
Incomplete de-airing is the dominant error and always lowers the result. Temperature differences between calibration and test, and soil that dissolves or reacts in water, such as gypsum-bearing soils, also matter. The method requires duplicate specimens agreeing within a set tolerance.
Common questions about ASTM D854
Why does a Proctor report show a zero-air-voids line?
It is the theoretical maximum dry unit weight at each moisture content when all air is driven out, computed from specific gravity. A compaction point plotting above it is a testing error.
Is 2.65 a safe assumption?
For clean quartz sands, usually. For clays, organics, and unusual geology it is not, and the difference shows up in every calculation that uses it.
How we help with ASTM D854 testing
We run specific gravity alongside Proctor, gradation, and hydrometer testing so the values a geotechnical engineer needs for phase relationships all come from the same sample.
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