ASTM D5550-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5550 − 14 D5550 − 23
Standard Test Method for
Specific Gravity of Soil Solids by Gas Pycnometer
This standard is issued under the fixed designation D5550; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers the determination of the specific gravity of soil solids by means of a gas pycnometer. Particle size
is limited by the dimensions of the test specimen container of the particular pycnometer being used.
1.2 Test Method D854 may be used instead of or in conjunction with this test method for performing specific gravity tests on soils.
Note that Test Method D854 does not require the specialized test apparatus needed by this test method. However, Test Method
D854 may not be used if the test specimen contains matter that can readily dissolve in water, whereas this test method does not
have that limitation.
1.3 All measuredobserved and calculated values shall conform to the guidelines for significant digits and rounding established in
Practice D6026.
1.3.1 For purposes of comparing a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall
be rounded to the nearest decimal or significant digits in the specified limits.
1.3.2 The procedures used to specify how data are collected/recorded and calculated in this standard are regarded as the industry
standard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do not
consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives;
and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations.
It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.
1.4 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical
conversions to inch-pound units, which are provided for information only and are not considered standard.
1.4.1 The converted inch-pound units use the gravitational system of gravitational system of inch-pound units is used when
dealing with inch-pound units. In this system, the pound (lbf) represents a unit of force (weight), while the unit for mass is slugs.
The converted slug unit is not given, unless dynamic (F = ma) calculations are involved.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.03 on Texture, Plasticity
and Density Characteristics of Soils.
Current edition approved Dec. 15, 2014Jan. 1, 2023. Published January 2015February 2023. Originally approved in 1994. Last previous edition approved in 20062014
as D5550 – 06. DOI: 10.1520/D5550-14.14. DOI: 10.1520/D5550-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5550 − 23
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D854 Test Methods for Specific Gravity of Soil Solids by Water Pycnometer
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4318 Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils
D4542 Test Methods for Pore Water Extraction and Determination of the Soluble Salt Content of Soils by Refractometer
D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and Construction
Materials Testing
D6026 Practice for Using Significant Digits and Data Records in Geotechnical Data
3. Terminology
3.1 Definitions:
3.1.1 For common definitions of common technical terms in this standard, refer to Terminology D653.
4. Summary of Test Method
4.1 This test method is used to determine the specific gravity of soil grains using a gas pycnometer. This test method also contains
equations for correcting the initial specific gravity value for dissolved matter within the pore fluid.
5. Significance and Use
5.1 The specific gravity value is used in many phase relation equations to determine relative volumes of particle, water, and gas
mixtures.
5.2 The term soil particle typically refers to a naturally occurring mineral grain that is not readily soluble in water. Therefore, the
specific gravity of soils that contain extraneous matter (such as cement, lime, and the like) or water-soluble material (such as salt)
must be corrected for the precipitate that forms on the test specimen after drying. If the precipitate has a specific gravity less than
the parent soil grains, the uncorrected test result will be too low. If the precipitate has a higher specific gravity, then the uncorrected
test value will be too high.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users
of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors;
Practice D3740 provides a means of evaluating some of those factors.
5.3 Heating during drying may diagenetically alter the structure of some clay minerals. Therefore caution should be exercised
if the mineral composition of a clay test specimen is going to be determined after drying. It is possible to dry the test specimen
at a lower temperature. However, the effect on water content and hence specific gravity should be investigated. In addition, some
materials other than clay may be affected by drying at 110°C, such as gypsum, soils containing organics, fly ash containing residual
coal, island sands. Test Method D2216 includes recommendations for drying gypsum using a lower temperature, such as 60°C.
NOTE 1—The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the
equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users
of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors;
Practice D3740 provides a means of evaluating some of those factors.
6. Apparatus
6.1 Pycnometer—The gas pycnometer shall be one of the commercially available models that determines the volume of a solid
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Carroll, D., Clay Minerals: A Guide to Their X-Ray Identification, Geological Society of America Special Paper 126, 1970.
Lambe, T. W., Soil Testing for Engineers, Wiley, 1951.
D5550 − 23
by one of two methods. One measures test specimen. Some pycnometers measure the pressure drop that occurs after a gas at a
known pressure is allowed to flow into another chamber (typically the first chamber contains the solid material being tested). The
amount of pressure drop is related to the volume of soil present. The other type of instrument puts Some others place a known
volume of gas into a chamber containing the test specimen. The increase in pressure is related to the volume of the material. Either
type of instrument is acceptable provided that the required accuracy of the instrument produces a volume measurement that is
60.2 % of the specimen volume.test specimen volume. The use of gas pycnometry described in this test method pertains to both
types of pycnometers used for test specimen volume determination, so no further method differentiation and apparatus description
is needed, regardless of which type of pycnometer is used. In addition, the pycnometer chosen will use one or more test specimen
containers of specific dimensions. Refer to manufacturer’s documentation for test specimen container dimensions, as the container
dimensions will limit the size of the test specimen.
NOTE 2—Commercially available instruments should be checked using materials with known specific gravities to ensure that they provide acceptable
precision and accuracy for the range of soil types to be tested. Some instruments require an operator to manually perform the test (that is, physically move
the working components of the apparatus), whereas, other instruments are fully automatic (after the test specimen has been loaded) and can produce a
digital display of the volume and specific gravity value (the test specimen mass has to be input). Some instruments can also send the test results to a
separate printer. Obviously, inherent errors are more possible with one type of equipment than another. Furthermore, some instruments are constructed
differently than others and can therefore produce more accurate and reproducible results.
6.2 Balance—Balance meeting the requirements of Specifications D4753 and readable, without estimation, to at least 0.1 % of the
test specimen mass.
6.3 Compressed Gas System—Typically research grade helium is required by the instruments. A tank capable of storing the
required volume of gas and associated pressure regulator(s) required to deliver the gas at the specified pressure.
NOTE 3—Other inert gas may be substituted for helium; refer to manufacturer’s suggestions. Helium is often used because it obeys the ideal gas law and
is able to penetrate small soil pores. Ordinary air may produce acceptable results for non-reactive test specimens in some instruments, however, that
practice should be discouraged because of the uncertainty introduced into the test results.
6.4 Drying Oven—Thermostatically-controlled oven, capable of maintaining a uniform temperature of 110 6 5°C (230 6 9°F)
throughout the drying chamber.
6.5 Desiccator—A desiccating cabinet or jar with air-tight seal containing silica gel or an anhydrous calcium sulfate desiccant. The
desiccator needs to be capable of providing isolation for the test specimen after drying while cooling to ambient temperature to
limit adsorption of moisture or other vapors. The desiccator does not necessarily need to have features such as inert gas purge or
ESD protection, though if these are present with the selected desiccator no harm to the test specimen should occur while under
storage.
NOTE 4—Indicating desiccant changes color when it is no longer able to absorb moisture. However, indicating desiccant is more expensive than the
non-indicating variety. To save cost, indicating desiccant can be mixed in with the non-indicating type. A ratio of one part indicating desiccant to
approximately four parts non-indicating has proven to be acceptable in many applications.
NOTE 5—Anydrous calcium sulfate can be rejuvenated by heating at 204°C (400°F) for 1 h. Silica gel can be rejuvenated by heating at 149°C (300°F)
for 3 h. Indicating desiccant that still has the capacity to absorb moisture will change color back to or close to the original color after heating.
6.6 Anhydrous Calcium Sulfate—Desiccant used to reduce adsorption of moisture onto dried test specimen while cooling to
ambient temperature. Note that this is a desiccant and will adsorb water from skin, eyes, and lungs, possibly causing irritation of
contacted surfaces. Therefore, follow recommendations given in Safety Data Sheet (SDS) obtained from the supplier.
NOTE 4—Indicating desiccant changes color when it is no longer able to absorb moisture. However, indicating desiccant is more expensive than the
non-indicating variety. To save cost, indicating desiccant can be mixed in with the non-indicating type. A ratio of one part indicating desiccant to
approximately four parts non-indicating has proven to be acceptable in many applications.
NOTE 5—Anhydrous calcium sulfate can be rejuvenated by heating at 204°C (400°F) for 1 h. Silica gel can be rejuvenated by heating at 149°C (300°F)
for 3 h. Indicating desiccant that still has the capacity to absorb moisture will change color back to or close to the original color after heating.
6.7 Vacuum System—A vacuum pump or aspirator may be required by some instruments. Refer to the manufacturer’s
specifications to determine the requirements of the particular apparatus.
D5550 − 23
NOTE 6—Some pycnometers do not require a vacuum system to remove gas from the chambers, but instead, rely on a series of purges with an inert gas
to clear the instrument of reactive gases.
6.8 Mortar and Pestle, used to pulverize some dried soil test specimens.
6.9 Miscellaneous Equipment, test specimen dishes or weighing paper and insulated gloves or tongs.
7. Reagents and Materials
7.1 Research grade Helium unless otherwise specified as being acceptable by the manufacturer.
8. Sampling and Test Specimen
8.1 The test specimen must be oven dried and shall be representative of the total sample. material of interest. Typically a greater
test specimen mass used in the instrument will produce a more accurate measured volume. The sample test specimen container
within the available pycnometers varies in size from 1 to 350 cm . Because of the principles involved with instrument function,
most manufacturers require that a majority of the test specimen cupcontainer be filled with soil to produce acceptably accurate
volume results. Choose a test specimen accordingly so as to fill at least one-half of the bulk volume of the test specimen container.
Soil grains of any size are acceptable to test provided that they are easily placed within and do not protrude from the test specimen
container.
NOTE 7—Using a small sample test specimen container may require the use of a more accurate balance with higher precision to attain the specified
accuracy required by this test method.
9. Calibration
9.1 The calibration of each type of pycnometer is different. The manufacturer’s instructions should be followed. There are
generally two common calibration checks. The first one requires the specimen holder cup test specimen container be checked when
empty. The determined volume should be within manufacturer’s tolerances of zero. Each pycnometer should also be supplied with
an object of known volume (6 manufacturer’s tolerances) that can be placed in the test specimen cup.container. The measured
object’s volume should fall within specifications.
9.2 The zero check should be made at the beginning of testing on a daily basis. The calibration volume check should be performed
after twenty-five soil test specimens are tested. Depending on its configuration, a pycnometer may also require the periodic
checking of an internal chamber volume(s). If any calibration check falls outside the tolerances set forth by the manufacturer, the
problem must be found and rectified before testing on soil test specimens resumes.
NOTE 8—It may be beneficial to have a number of several soil specimens that are used as internal laboratory standards that behave more similarly to test
samplesspecimens than the stainless steel stainless-steel spheres often supplied with the instruments. A number of Several different minerals (or
combinations) can be used periodically to check for accuracy or precision, or both. One easily obtained mineral is quartz with a specific gravity of 2.65.
One additional benefit of calculating actual mineral grain specific gravity values is that it is also an indirect check on the operation of the balance (there
is however an unlikely possibility that compensating errors in both the mass and volume determinations will produce the expected result).
10. Procedure
10.1 Dry Record initial mass of test specimen, M , then dry the test specimen in an oven at 110 6 5°C (230 6 9°F)per
si
recommendations found in Test Method D2216 until a constant mass is obtained.
NOTE 9—Heating may diagenetically alter the structure
...