1、Designation: D5550 06D5550 14Standard Test Method forSpecific Gravity of Soil Solids by Gas Pycnometer1This standard is issued under the fixed designation D5550; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript 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 sizeis
3、 limited by the dimensions of the 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 onsoils. Note that Test Method D854 does not require the specialized test apparatus n
4、eeded by this test method. However, TestMethod D854 may not be used if the specimen contains matter that can readily dissolve in water, whereas this test method doesnot have that limitation.1.3 All measured and calculated values shall conform to the guidelines for significant digits and rounding est
5、ablished in PracticeD6026.1.3.1 For purposes of comparing,comparing a measured or calculated value(s) with specifiesspecified limits, the measured orcalculated 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
6、 are collected/recorded and calculated in this standard are regarded as the industrystandard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do notconsider material variation, purpose for obtaining the data, special purpose studi
7、es, or any considerations for the users 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
8、.4 UnitsThe values stated in acceptable SI units are to be regarded as the standard. The inch-pound units values given inparentheses are for information only.mathematical conversions to inch-pound units, which are provided for information only andare not considered standard.1.4.1 The converted inch-
9、pound units use the gravitational system of units. In this system, the pound (lbf) represents a unit offorce (weight), while the unit for mass is slugs. The converted slug unit is not given, unless dynamic (F = ma) calculations areinvolved.1.5 This standard does not purport to address all of the saf
10、ety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil,
11、 Rock, and Contained FluidsD854 Test Methods for Specific Gravity of Soil Solids by Water PycnometerD2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil an
12、d Rock as Used inEngineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and ConstructionMaterials TestingD6026 Practice for Using Significant Digits in Geotechnical Data1 This test method is under the jurisdiction
13、of ASTM Committee D18 on Soil and Rock and is the direct responsibility of SubcommitteeD18.03 on Texture, Plasticity andDensity Characteristics of Soils.Current edition approved Nov. 1, 2006Dec. 15, 2014. Published December 2006January 2015. Originally approved in 1994. Last previous edition approve
14、d in 20002006as D5550 00. 06. DOI: 10.1520/D5550-06.10.1520/D5550-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM
15、website.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. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult p
16、rior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1
17、9428-2959. United States13. Terminology3.1 Definitions:3.1.1 The definitions of terms used in this test method shall be in accordance with Terminology D653.3.1 Definitions:3.1.1 For common definitions of terms in this standard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Stan
18、dard:3.2.1 specific gravitythe ratio of the mass in air of a given volume of solids to the mass in air of an equal volume of distilledwater at a temperature of 4C (in accordance with Terminology D653).NOTE 1Distilled water at a temperature of 4C has a density of 1.000 g/cm 3. It is recommended that
19、this test method be performed at or near roomtemperature. The temperature at which the soil volume is measured can be reported but is not required by this test method because of the negligible effectof temperature on the volume of soil solids. However, temperature may have a significant effect on pe
20、rformance of the gas pycnometer. Therefore, testingshould be conducted within the specified operating temperature range of the apparatus.4. Summary of Test Method4.1 This test method is used to determine the specific gravity of soil grains using a gas pycnometer. This test method alsocontains equati
21、ons for correcting the initial specific gravity value for dissolved matter within the pore fluid.5. Significance and Use5.1 The specific gravity value is used in many phase relation equations to determine relative volumes of particle, water, and gasmixtures.5.2 The term soil particle typically refer
22、s 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 assalt) must be corrected for the precipitate that forms on the specimen after dr
23、ying. If the precipitate has a specific gravity less thanthe parent soil grains, the uncorrected test result will be too low. If the precipitate has a higher specific gravity, then the uncorrectedtest value will be too high.NOTE 1Not withstanding the statements on precision and bias contained in thi
24、s test method: The precision of this test method The quality of the resultproduced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used.Agencieswhichthat meet the criteria of Practice D3740 are generally considered c
25、apable of competent and objective testing. Users of this test method standard arecautioned that compliance with Practice D3740 does not in itself ensure reliable testing.results. Reliable testing dependsresults depend on severalmanyfactors; Practice D3740 provides a means of evaluating some of those
26、 factors.6. Apparatus6.1 PycnometerThe gas pycnometer shall be one of the commercially available models that determines the volume of a solidby one of two methods. One measures the pressure drop that occurs after a gas at a known pressure is allowed to flow into anotherchamber (typically the first c
27、hamber contains the solid material being tested). The amount of pressure drop is related to the volumeof soil present. The other type of instrument puts a known volume of gas into a chamber containing the specimen. The increasein pressure is related to the volume of the material. Either type of inst
28、rument is acceptable provided that the required accuracy ofthe instrument produces a volume measurement that is 60.2 % of the specimen volume.NOTE 2Commercially available instruments should be checked using materials with known specific gravities to insureensure that they provideacceptable precision
29、 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 specimen has been loaded) and canproduce a digital di
30、splay of the volume and specific gravity value (the specimen mass has to be input). Some instruments can also send the test resultsto a separate printer. Obviously, inherent errors are more possible with one type of equipment than another. Furthermore, some instruments are constructeddifferently tha
31、n others and can therefore produce more accurate and reproducible results.6.2 BalanceBalance meeting the requirements of Specifications D4753 and readable, without estimation, to at least 0.1 % ofthe specimen mass.6.3 Compressed Gas SystemTypically research grade helium is required by the instrument
32、s. A tank capable of storing therequired volume of gas and associated pressure regulator(s) required to deliver the gas at the specified pressure.NOTE 3Other inert gas may be substituted for helium; refer to manufacturers suggestions. Helium is often used because it obeys the ideal gas lawand is abl
33、e to penetrate small soil pores. Ordinary air may produce acceptable results for non-reactive specimens in some instruments, however, thatpractice should be discouraged because of the uncertainty introduced into the test results.6.4 Drying OvenThermostatically-controlled oven, capable of maintaining
34、 a uniform temperature of 110 6 5C (230 6 9F)throughout the drying chamber.6.5 DesiccatorA desiccating cabinet or jar with air-tight seal containing silica gel or an anhydrous calcium sulfate desiccant.NOTE 5Anhydrous calcium sulfate is sold under the trade name Drierite.3NOTE 4Indicating desiccant
35、changes color when it is no longer able to absorb moisture. However, indicating desiccant is more expensive than thenon-indicating variety. To save cost, indicating desiccant can be mixed in with the non-indicating type. A ratio of one part indicating desiccant toD5550 142approximately four parts no
36、n-indicating has proven to be acceptable in many applications.NOTE 5Anydrous calcium sulfate can be rejuvenated by heating at 204C (400F) for 1 h. Silica gel can be rejuvenated by heating at 149C (300F)for 3 h. Indicating desiccant that still has the capacity to absorb moisture will change color bac
37、k to or close to the original color after heating.6.6 Vacuum SystemA vacuum pump or aspirator may be required by some instruments. Refer to the manufacturersspecifications to determine the requirements of the particular apparatus.NOTE 6Some pycnometers do not require a vacuum system to remove gas fr
38、om the chambers, but instead, rely on a series of purges with an inertgas to clear the instrument of reactive gases.6.7 Mortar and Pestle, used to pulverize some dried soil specimens.6.8 Miscellaneous Equipment, specimen dishes or weighing paper and insulated gloves or tongs.7. Reagents and Material
39、s7.1 Unless Research grade Helium unless otherwise specified as being acceptable by the manufacturer, research grade heliumshould be used in conjunction with the instrument.manufacturer.8. Test Specimen8.1 The test specimen must be oven dried and shall be representative of the total sample.Typically
40、 a greater specimen mass usedin the instrument will produce a more accurate measured volume. The sample container within the available pycnometers variesin size from 1 to 135350 cm3. Because of the principles involved with instrument function, most manufacturers require that amajority of the specime
41、n cup be filled with soil to produce acceptably accurate volume results. Soil grains of any size areacceptable to test provided that they are easily placed within and do not protrude from the specimen container.NOTE 7Using a small sample container may require the use of a more accurate balance with
42、higher precision to attain the specified accuracy requiredby this test method.9. Calibration9.1 The calibration of each type of pycnometer is different. The manufacturers instructions should be followed. However, allof them have There are generally two common calibration checks. The first one requir
43、es the specimen holder cup be checked whenempty. The determined volume should be within manufacturers tolerances of zero. Each pycnometer should also be supplied withan object of known volume (6 manufacturers tolerances) that can be placed in the specimen cup. The measured objects volumeshould fall
44、within specifications.9.2 The zero check should be made at the beginning of testing on a daily basis. The calibration volume check should beperformed after twenty-five soil specimens are tested. Depending on its configuration, a pycnometer may also require the periodicchecking of an internal chamber
45、 volume(s). If any calibration check falls outside the tolerances set forth by the manufacturer, theproblem must be found and rectified before testing on soil specimens resumes.NOTE 8It may be beneficial to have a number of soil specimens that are used as internal laboratory standards that behave mo
46、re similarly to testsamples than the stainless steel spheres often supplied with the instruments. A number of different minerals (or combinations) can be used periodicallyto check for accuracy or precision, or both. One easily obtained mineral is quartz with a specific gravity of 2.65. One additiona
47、l benefit of calculatingactual mineral grain specific gravity values is that it is also an indirect check on the operation of the balance (there is however an unlikely possibilitythat compensating errors in both the mass and volume determinations will produce the expected result).10. Procedure10.1 D
48、ry the specimen in an oven at 110 6 5C (230 6 9F) until a constant mass is obtained.NOTE 9Heating may diagenetically alter the structure of some clay minerals.3 Therefore caution should be exercised if the mineral composition ofa clay specimen is going to be determined after drying. It is possible t
49、o dry the specimen at a lower temperature, howevertemperature. However the effecton water content4 and hence specific gravity should be investigated. In addition, some materials other than clay may be affected by drying at 110C, suchas gypsum, soils containing organics, fly ash containing residual coal, island sands. Test Method D2216 includes recommendations for drying gypsumusing a lower temperature, such as 60C.10.2 Remove the specimen from the oven and grind it into sand size particles using a mortar and pestle.NOTE 10In some instances t
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