1、Designation: D 5550 06Standard Test Method forSpecific Gravity of Soil Solids by Gas Pycnometer1This standard is issued under the fixed designation D 5550; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the specificgravity of soil solids by means of a gas pycnometer. Particlesize is limit
3、ed by the dimensions of the specimen container ofthe particular pycnometer being used.1.2 Test Method D 854 may be used instead of or inconjunction with this test method for performing specificgravity tests on soils. Note that Test Method D 854 does notrequire the specialized test apparatus needed b
4、y this testmethod. However, Test Method D 854 may not be used if thespecimen contains matter that can readily dissolve in water,whereas this test method does not have that limitation.1.3 All measured and calculated values shall conform to theguidelines for significant digits and rounding established
5、 inPractice D 6026.1.3.1 For purposes of comparing, a measured or calculatedvalue(s) with specifies limits, the measured or calculatedvalue(s) shall be rounded to the nearest decimal or significantdigits in the specified limits.1.3.2 The procedures used to specify how data are collected/recorded and
6、 calculated in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that should generally be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations
7、for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analysismethods for engineering design.1.4 The values stated in acce
8、ptable SI units are to beregarded as the standard. The inch-pound units given inparentheses are for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priat
9、e safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 854 Test Methods for Specific Gravity of Soil Solids byWater PycnometerD 3740 Practice for M
10、inimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD 6026 Practice for Using
11、Significant Digits in Geotechni-cal Data3. Terminology3.1 Definitions:3.1.1 The definitions of terms used in this test method shallbe in accordance with Terminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 specific gravitythe ratio of the mass in air of a givenvolume of solids
12、to the mass in air of an equal volume ofdistilled water at a temperature of 4C (in accordance withTerminology D 653).NOTE 1Distilled water at a temperature of 4C has a density of 1.000g/cm3. It is recommended that this test method be performed at or nearroom temperature. The temperature at which the
13、 soil volume is measuredcan be reported but is not required by this test method because of thenegligible effect of temperature on the volume of soil solids. However,temperature may have a significant effect on performance of the gaspycnometer. Therefore, testing should be conducted within the specif
14、iedoperating temperature range of the apparatus.4. Summary of Test Method4.1 This test method is used to determine the specificgravity of soil grains using a gas pycnometer. This test methodalso contains equations for correcting the initial specific gravityvalue for dissolved matter within the pore
15、fluid.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.03 on Texture, Plasticityand Density Characteristics of Soils.Current edition approved Nov. 1, 2006. Published December 2006. Originallyapproved in 1994. Last p
16、revious edition approved in 2000 as D 5550 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of
17、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.5. Significance and Use5.1 The specific gravity value is used in many phase relationequations to determine relative volumes of particl
18、e, water, andgas mixtures.5.2 The term soil particle typically refers to a naturallyoccurring mineral grain that is not readily soluble in water.Therefore, the specific gravity of soils that contain extraneousmatter (such as cement, lime, and the like) or water-solublematerial (such as salt) must be
19、 corrected for the precipitate thatforms on the specimen after drying. If the precipitate has aspecific gravity less than the parent soil grains, the uncorrectedtest result will be too low. If the precipitate has a higherspecific gravity, then the uncorrected test value will be toohigh.NOTE 2Not wit
20、hstanding the statements on precision and bias con-tained in this test method: The precision of this test method is dependenton the competence of the personnel performing it and the suitability of theequipment and facilities used.Agencies which meet the criteria of PracticeD 3740 are generally consi
21、dered capable of competent testing. Users ofthis test method are cautioned that compliance with Practice D 3740 doesnot ensure reliable testing. Reliable testing depends on several factors;Practice D 3740 provides a means of evaluating some of those factors.6. Apparatus6.1 PycnometerThe gas pycnomet
22、er shall be one of thecommercially available models that determines the volume ofa solid by one of two methods. One measures the pressure dropthat occurs after a gas at a known pressure is allowed to flowinto another chamber (typically the first chamber contains thesolid material being tested). The
23、amount of pressure drop isrelated to the volume of soil present. The other type ofinstrument puts a known volume of gas into a chambercontaining the specimen. The increase in pressure is related tothe volume of the material. Either type of instrument isacceptable provided that the required accuracy
24、of the instru-ment produces a volume measurement that is 60.2 % of thespecimen volume.NOTE 3Commercially available instruments should be checked usingmaterials with known specific gravities to insure that they provideacceptable precision and accuracy for the range of soil types to be tested.Some ins
25、truments 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 can produce a digital display of the volume and specific gravity value(the specimen mass
26、has to be input). Some instruments can also send thetest results to a separate printer. Obviously, inherent errors are morepossible with one type of equipment than another. Furthermore, someinstruments are constructed differently than others and can thereforeproduce more accurate and reproducible re
27、sults.6.2 BalanceBalance meeting the requirements of Speci-fications D 4753 and readable, without estimation, to at least0.1 % of the specimen mass.6.3 Compressed Gas SystemTypically research grade he-lium is required by the instruments. A tank capable of storingthe required volume of gas and associ
28、ated pressure regulator(s)required to deliver the gas at the specified pressure.NOTE 4Other inert gas may be substituted for helium; refer tomanufacturers suggestions. Helium is often used because it obeys theideal gas law and is able to penetrate small soil pores. Ordinary air mayproduce acceptable
29、 results for non-reactive specimens in some instru-ments, however, that practice should be discouraged because of theuncertainty introduced into the test results.6.4 Drying OvenThermostatically-controlled oven, ca-pable of maintaining a uniform temperature of 110 6 5C (2306 9F) throughout the drying
30、 chamber.6.5 DesiccatorA desiccating cabinet or jar with air-tightseal containing silica gel or an anhydrous calcium sulfatedesiccant.NOTE 5Anhydrous calcium sulfate is sold under the trade nameDrierite.3NOTE 6Indicating desiccant changes color when it is no longer able toabsorb moisture. However, i
31、ndicating desiccant is more expensive thanthe non-indicating variety. To save cost, indicating desiccant can be mixedin with the non-indicating type. A ratio of one part indicating desiccant toapproximately four parts non-indicating has proven to be acceptable inmany applications.NOTE 7Anydrous calc
32、ium sulfate can be rejuvenated by heating at204C (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 absorbmoisture will change color back to or close to the original color afterheating.6.6 Vacuum SystemA vacuum pump or
33、aspirator may berequired by some instruments. Refer to the manufacturersspecifications to determine the requirements of the particularapparatus.NOTE 8Some pycnometers do not require a vacuum system to removegas from the chambers, but instead, rely on a series of purges with an inertgas to clear the
34、instrument of reactive gases.6.7 Mortar and Pestle, used to pulverize some dried soilspecimens.6.8 Miscellaneous Equipment, specimen dishes or weighingpaper and insulated gloves or tongs.7. Reagents and Materials7.1 Unless otherwise specified as being acceptable by themanufacturer, research grade he
35、lium should be used in con-junction with the instrument.8. Test Specimen8.1 The test specimen must be oven dried and shall berepresentative of the total sample. Typically a greater specimenmass used in the instrument will produce a more accuratemeasured volume. The sample container within the availa
36、blepycnometers varies in size from 1 to 135 cm3. Because of theprinciples involved with instrument function, most manufac-turers require that a majority of the specimen cup be filled withsoil to produce acceptably accurate volume results. Soil grainsof any size are acceptable to test provided that t
37、hey are easilyplaced within and do not protrude from the specimen container.NOTE 9Using a small sample container may require the use of a moreaccurate balance with higher precision to attain the specified accuracyrequired by this test method.9. Calibration9.1 The calibration of each type of pycnomet
38、er is different.The manufacturers instructions should be followed. However,3Drierite is a registered trademark.D5550062all of them have two common calibration checks. The first onerequires the specimen holder cup be checked when empty. Thedetermined volume should be within manufacturers tolerancesof
39、 zero. Each pycnometer should also be supplied with anobject of known volume (6 manufacturers tolerances) thatcan be placed in the specimen cup. The measured objectsvolume should fall within specifications.9.2 The zero check should be made at the beginning oftesting on a daily basis. The calibration
40、 volume check shouldbe performed after twenty-five soil specimens are tested.Depending on its configuration, a pycnometer may also requirethe periodic checking of an internal chamber volume(s). If anycalibration check falls outside the tolerances set forth by themanufacturer, the problem must be fou
41、nd and rectified beforetesting on soil specimens resumes.NOTE 10It may be beneficial to have a number of soil specimens thatare used as internal laboratory standards that behave more similarly to testsamples than the stainless steel spheres often supplied with the instru-ments. A number of different
42、 minerals (or combinations) can be usedperiodically to check for accuracy or precision, or both. One easilyobtained mineral is quartz with a specific gravity of 2.65. One additionalbenefit of calculating actual mineral grain specific gravity values is that itis also an indirect check on the operatio
43、n of the balance (there is howeveran unlikely possibility that compensating errors in both the mass andvolume determinations will produce the expected result).10. Procedure10.1 Dry the specimen in an oven at 110 6 5C (230 6 9F)until a constant mass is obtained.NOTE 11Heating may diagenetically alter
44、 the structure of some clayminerals.4Therefore caution should be exercised if the mineral composi-tion of a clay specimen is going to be determined after drying. It ispossible to dry the specimen at a lower temperature, however the effect onwater content5and hence specific gravity should be investig
45、ated.10.2 Remove the specimen from the oven and grind it intosand size particles using a mortar and pestle.NOTE 12In some instances the specimen may not have to be groundto a finer size, for example, cohesionless coarse grained sand. Multipletests using pulverized and intact specimens can be perform
46、ed and resultscompared. If a difference is obtained, the pulverized procedure ispreferred.10.3 Place the specimen back in the oven until a constantmass is again obtained. Care should be exercised to avoidlosing any soil during the transfer process.10.4 Remove the specimen from the oven and place it
47、intoa desiccator for the minimum time required for it to cool toambient temperature.NOTE 13While in the instrument, the soil specimen should not bewarmer than room temperature because the operation of many pycnom-eters is adversely affected by such a specimen temperature change. But,the specimen sho
48、uld not be exposed to air (even within the desiccator) anylonger than is required to reach thermal equilibrium because of thepotential for some types of minerals to adsorb moisture, which wouldchange the measured mass and volume. A tightfitting metal cover placedover metal specimen containers has be
49、en successfully used to preventmoisture adsorption during the cooling period.10.5 Quickly obtain and record the mass of the specimen,Ms, to the nearest 0.01 grams.10.6 Transfer the soil into the test chamber.10.7 Following the manufacturers instructions, obtain andrecord the volume of the specimen, Vs, to the nearest 0.05 cm3.10.8 After the test is finished, quickly obtain the mass of thespecimen again, Ms2to the nearest 0.01 grams.NOTE 14This step may be omitted at the discretion of the laboratorymanager. However, the comparison of the second ma
