Designation: D 3282 93 (Reapproved 2004)e1Standard Practice forClassication of Soils and Soil-Aggregate Mixtures forHighway Construction Purposes1This standard is issued under the xed designation D 3282; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEAdded keywords editorially in May 2004.1. Scope1.1This practice covers a procedure for classifying mineraland organomineral soils into seven groups based on laboratorydeterminationof particle-size distribution, liquidlimit, andplasticityindex. It maybeusedwhenapreciseengineeringclassication is required, especially for highway constructionpurposes. Evaluationofsoilswithineachgroupismadebymeans of a group index, which is a value calculated from anempirical formula.NOTE 1The group classication, including the group index, should beusefulindeterminingtherelativequalityofthesoilmaterialforuseinearthwork structures, particularly embankments, subgrades, subbases, andbases. However, for the detailed design of important structures, additionaldata concerning strength or performance characteristics of the soil undereld conditions will usually be required.1.2 Thisstandarddoesnot purport toaddressall of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.3This practice offers a set of instructions for performingone or more specic operations. This practice cannot replaceeducationorexperienceandshouldbeusedinconjunctionwith professional judgment. Not all aspects of this practice maybe applicable in all circumstances. This practice is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this practice be applied without consideration of aprojectsmanyuniqueaspects. ThewordStandardinthetitle of this document means only that the document has beenapproved through the ASTM consensus process.2. Referenced Documents2.1ASTM Standards:2D 420Guide to Site Characterization for Engineering, De-sign, and Construction PurposesD 421Practice for DryPreparationof Soil Samples forParticle-SizeAnalysis and Determination of Soil Con-stantsD 422Test Method for Particle-Size Analysis of SoilsD 653Terminology Relating to Soil, Rock, and ContainedFluidsD 1140Test Methods for Amount of Material in Soils FinerThan the No. 200 (75-m) SieveD 1452Practice for Soil Investigation and Sampling byAuger BoringsD 1586Test MethodforPenetrationTest andSplit-BarrelSampling of SoilsD 1587PracticeforThin-WalledTubeSamplingof Soilsfor Geotechnical PurposesD 2217PracticeforWet Preparationof Soil SamplesforParticle-SizeAnalysis and Determination of Soil Con-stantsD 4318TestMethodsforLiquidLimit,PlasticLimit,andPlasticity Index of Soils2.2 AASHTO Document:3M 145The Classication of Soils and Soil Aggregate Mix-tures for Highway Construction Purposes3. Terminology3.1Denitions of Terms Specic to This Standard:1This standard is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.07 on Identication andClassication of Soils.Current edition approved May 1, 2004. Published May 2004. Originallyapproved in 1973. Last previous edition approved in 1997 as D 3282 93 (1997)e1.2Forreferenced ASTMstandards, visitthe ASTMwebsite, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3AvailablefromAmericanAssociationof StateHighwayandTransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---3.1.1The following terms are frequently used in this prac-tice. These terms differ slightly from those given in Terminol-ogyD 653, but areusedheretomaintainconsistencywithcommon highway usage.3.1.2bouldersrock fragments, usually rounded by weath-eringor abrasion, that will beretainedona3-in. (75-mm)sieve.3.1.3coarse sandparticles of rock or soil that will pass aNo. 10(2-mm)sieveandberetainedonaNo. 40(425-m)sieve.3.1.4ne sandparticles of rock or soil that will pass a No.40 (425-m) sieve and be retained on a No. 200 (75-m) sieve.3.1.5gravelparticlesofrockthat will passa3-in. (75-mm) sieve and be retained on a No. 10 (2-mm) sieve.3.1.6silt-clay (combined silt and clay)ne soil and rockparticles that will pass a No. 200 (75-m) sieve.3.1.7siltyne-grained material that has a plasticity indexof 10 or less.3.1.8clayeyne-grained material that has a plasticityindex of 11 or more.4. Signicance and Use4.1Thepracticedescribedclassies soils fromanygeo-graphic location into groups (including group indexes) basedontheresultsofprescribedlaboratoryteststodeterminetheparticle-size characteristics, liquid limit, and plasticity index.4.2The assigning of a group symbol and group index can beused to aid in the evaluation of the signicant properties of thesoil for highway and aireld purposes.4.3The various groupings of this classication systemcorrelateinageneral waywiththeengineeringbehaviorofsoils. Also, in a general way, the engineering behavior of a soilvaries inversely with its group index. Therefore, this practiceprovides a useful rst step in any eld or laboratory investi-gation for geotechnical engineering purposes.5. Apparatus5.1ApparatusforPreparationof SamplesSeePracticesD 421 or D 2217.5.2ApparatusforParticle-SizeAnalysisSeeTest Meth-ods D 1140 and D 422.5.3Apparatus for Liquid Limit and Plastic Limit TestsSeeTest Methods D 4318.6. Sampling6.1Conduct eld investigations and sampling in accordancewith one or more of the following procedures:6.1.1Guide D 420,6.1.2Practice D 1452,6.1.3Test Method D 1586, and6.1.4Practice D 1587.7. Test Sample7.1Test samples shall represent that portionof theeldsample ner than the 3-in. (75-mm) sieve and shall be obtainedas follows:7.1.1Air-dry the eld sample,7.1.2Weigh the eld sample,7.1.3Separate the eld sample into two fractions on a 3-in.(75-mm) sieve,7.1.4Weigh the fraction retained on the 3-in. (75-mm)sieve. Compute the percentage of plus 3-in. material in the eldsample, and note this percentage as auxiliary information, and7.1.5Thoroughlymixthefractionpassingthe3-in. (75-mm) sieve and select the test samples.NOTE 2If visual examination indicates that no boulder size material ispresent, omit 7.1.3 and 7.1.4.7.2Preparethetest sampleinaccordancewithPracticesD 421 or D 2217. Determine the percentage of the sample nerthan a No. 10 (2-mm) sieve.NOTE 3It isrecommendedthat themethodforwet preparationbeused for soils containing organic matter or irreversible mineral colloids.8. Testing Procedure8.1Determine the percentage of the test sample ner than aNo. 200 (75-m) sieve in accordance with Test MethodsD 1140 or D 422.NOTE 4For granular materials, the percentage of the sample ner thana No. 40 (425-m) sieve must also be determined.8.2Determine the liquid limit and the plasticity index of aportion of the test sample passing a No. 40 (425-m) sieve inaccordance with Test Methods D 4318.9. Classication Procedure9.1Using the test data determined in Section 8, classify thesoil into the appropriate group or subgroup, or both, inaccordancewithTable1or Table2. UseFig. 1toclassifysilt-claymaterialsonthebasisof liquidlimit andplasticityindex values.NOTE 5All limiting values are shown as whole numbers. If fractionalnumbers appear on test reports, convert to the nearest whole numbers forthe purpose of classication.9.1.1With the required test data available, proceed from leftto right in Table 1 or Table 2 and the correct classication willbe found by the process of elimination. The rst group from theleft into which the test data will t is the correct classication.NOTE 6Classication of materials in the various groups applies onlyto the fraction passing the 3-in. (75-mm) sieve. Therefore, any specica-tion regarding the use of A-1, A-2, or A-3 materials in construction shouldstate whether boulders (retained on 3-in. sieve) are permitted.10. Description of Classication Groups10.1GranularMaterials, containing35 %orlesspassingthe No. 200 (75-m) sieve:10.1.1Group A-1The typical material of this group is awell-graded mixture of stone fragments or gravel, coarse sand,ne sand, and a nonplastic or feebly-plastic soil binder.However, this groupalsoincludes stonefragments, gravel,coarse sand, volcanic cinders, etc., without a soil binder.10.1.1.1Subgroup A-1-a includes those materials consistingpredominantlyof stonefragments or gravel, either withorwithout a well-graded binder of ne material.10.1.1.2Subgroup A-1-b includes those materials consistingpredominantlyofcoarsesand,eitherwithorwithoutawell-graded soil binder.D 3282 93 (2004)e12Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---10.1.2Group A-3The typical material of this group is nebeach sand or ne desert-blow sand without silty or clay nes,or with a very small amount of nonplastic silt. This group alsoincludes stream-deposited mixtures of poorly-graded ne sandand limited amounts of coarse sand and gravel.10.1.3GroupA-2Thisgroupincludesawidevarietyofgranular materials which are borderline between the materi-als falling in Groups A-1 and A-3, and the silt-clay materials ofGroups A-4, A-5, A-6, andA-7. It includes all materialscontaining 35 % or less passing a No. 200 (75-m) sieve whichcannot beclassiedinGroups A-1or A-3, duetothenescontent or theplasticityindexes, or both, inexcess of thelimitations for those groups.10.1.3.1Subgroups A-2-4 and A-2-5 include various granu-lar materials containing 35 %or less passing a No. 200(75-m) sieve andwitha minus No. 40(425-m) portionhaving the characteristics of Groups A-4 and A-5, respectively.These groups include such materials as gravel and coarse sandwith silt contents or plasticity indexes in excess of thelimitations of GroupA-1andnesandwithnonplastic-siltcontent in excess of the limitations of Group A-3.10.1.3.2Subgroups A-2-6 and A-2-7 include materials simi-lar to those described under Subgroups A-2-4 andA-2-5,except that theneportioncontainsplasticclayhavingthecharacteristics of the A-6 or A-7 group, respectively.10.2Silt-Clay Materials, containing more than 35 % pass-ing a No. 200 (75-m) sieve:10.2.1Group A-4The typical material of this group is anonplastic or moderately plastic silty soil usually having 75 %or morepassingaNo. 200(75-m) sieve. Thisgroupalsoincludes mixtures of ne silty soil and up to 64 % of sand andgravel retained on a No. 200 sieve.10.2.2GroupA-5Thetypical material of this groupissimilar tothat describedunder GroupA-4, except that it isusuallyofdiatomaceousormicaceouscharacterandmaybehighly elastic as indicated by the high liquid limit.10.2.3Group A-6The typical material of this group is aplastic clay soil usually having 75 % or more passing a No. 200(75-m) sieve. This group also includes mixtures of ne clayeysoil and up to 64 % of sand and gravel retained on a No. 200sieve. Materials of this groupusuallyhaveahighvolumechange between wet and dry states.10.2.4GroupA-7Thetypical material of this groupissimilar to that described under Group A-6, except that it has thehighliquidlimits characteristicof GroupA-5andmaybeelastic as well as subject to high-volume change.TABLE 1Classication of Soils and Soil-Aggregate MixturesGeneral ClassicationGranular Materials(35 % or less passing No. 200)Silt-Clay Materials(More than 35 % passing No. 200)Group Classication A-1 A-3AA-2 A-4 A-5 A-6 A-7Sieve analysis, % passing:No. 10 (2.00 mm) ... ... ... ... ... ... ...No. 40 (425 m) 50 max 51 min ... ... ... ... ...No. 200 (75 m) 25 max 10 max 35 max 36 min 36 min 36 min 36 minCharacteristics of fraction passing No. 40(425 m):Liquid limitPlasticity index...6 max...N.P.BB40 max10 max41 min10 max40 max11 min 41 min11 minGeneral rating as subgrade Excellent to Good Fair to PoorAThe placing of A-3 before A-2 is necessary in the left to right elimination process and does not indicate superiority of A-3 over A-2.BSee Table 2 for values.Reprinted with permission of American Association of State Highway and Transportation OfficialsTABLE 2Classication of Soils and Soil-Aggregate MixturesGeneral ClassicationGranular Materials(35 % or less passing No. 200)Silt-Clay Materials(More than 35 % passing No. 200)Group classicationA-1A-3A-2A-4 A-5 A-6A-7A-1-a A-1-b A-2-4 A-2-5 A-2-6 A-2-7A-7-5,A-7-6Sieve analysis, % passing:No. 10 (2.00 mm) 50 max ... ... ... ... ... ... ... ... ... ...No. 40 (425 m) 30 max 50 max 51 min ... ... ... ... ... ... ... ...No. 200 (75 m) 15 max 25 max 10 max 35 max 35 max 35 max 35 max 36 min 36 min 36 min 36 minCharacteristics of fraction passingNo. 40 (425 m):Liquid limitPlasticity index...6 max...N.P.40 max10 max41 min10 max40 max11 min41 min11 min40 max10 max41 min10 max40 max11 min41 min11 minAUsual types of signicant consti-tuent materialsStone Fragments,Gravel and SandFineSandSilty or Clayey Gravel and Sand Silty Soils Clayey SoilsGeneral rating as subgrade Excellent to Good Fair to PoorAPlasticity index of A-7-5 subgroup is equal to or less than LL minus 30. Plasticity index of A-7-6 subgroup is greater than LL minus 30 (see Fig. 1).Reprinted with permission of American Association of State Highway and Transportation Officials.D 3282 93 (2004)e13Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---10.2.4.1Subgroup A-7-5 includes those materials withmoderate plasticity indexes in relation to the liquid limit andwhich may be highly elastic as well as subject to considerablevolume change.10.2.4.2Subgroup A-7-6 includes those materials with highplasticityindexes inrelationtoliquidlimit andwhicharesubject to extremely high volume change.NOTE 7Highlyorganic soils (peat or muck) maybe classiedinGroup A-8. Classication of these materials is based on visual inspectionand is not dependent on the percentage passing the No. 200 (75-m) sieve,liquidlimit, orplasticityindex. Thematerial iscomposedprimarilyofpartiallydecayedorganicmatter,generallyhasabroustexture,adarkbrown or black color, and an odor of decay. These organic materials areunsuitable for use in embankments and subgrades. They are highlycompressible and have low strength.11. Group Index Computation11.1TheclassicationsobtainedfromTable1orTable2may be modied by the addition of a group-index value.Group-indexvaluesshouldalwaysbeshowninparenthesesafter the groupsymbol asA-2-6(3), A-4(5), A-6(12), A-7-5(17), etc.11.1.1Calculate the group index from the following empiri-cal formula:Group index 5 ~F 2 35!@0.2 1 0.005~LL 2 40!# (1)1 0.01~F 2 15!~PI 2 10!where:F = percentage passing No. 200 (75-m) sieve, expressedas a whole number (this percentage is based only onthe material passing the 3-in. (75-mm) sieve),LL = liquid limit, andPI = plasticity index.11.1.2If the calculated group index is negative, report thegroup index as zero (0).11.1.3If thesoil isnonplasticandwhentheliquidlimitcannot be determined, report the group index as zero (0).11.1.4Report the group index to the nearest whole number.11.1.5The group index value may be estimated using Fig. 2by determining the partial group index due to the liquid limitand that due to the plasticity index, then obtaining the total ofthe two partial group indexes.11.1.6Thegroupindexof soils intheA-2-6andA-2-7subgroups shall be calculated using only the PI portion of theformula (or Fig. 2).11.2The following examples illustrate the calculations forthe group index:11.2.1Assume that an A-6 material has 55 % passing a No.200 (75-m) sieve, a liquid limit of 40, and a plasticity indexof 25, then:NOTE 1A-2 soils contain less than 35 % ner than 200 sieve.FIG. 1 Liquid Limit and Plasticity Index Ranges for Silt-Clay MaterialsD 3282 93 (2004)e14Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---Group index 5 ~55 2 35!@0.2 1 0.005~40 2 40!# (2)1 [0.01~55 2 15!~25 2 10!# 5 4.0 1 6.0 5 1011.2.2Assume that an A-7 material has 80 % passing a No.200 (75-m) sieve, a liquid limit of 90, and a plasticity indexof 50, then:Group index 5 ~80 2 35!@0.26 0.005~90 2 40!# (3)1 [0.01~80 2 15!~50 2 10!# 5 20.3 1 26.0 5 46.3~report as 46!11.2.3Assume that an A-4 material has 60 % passing a No.200 (75-m) sieve, a liquid limit of 25, and a plasticity indexof 1, thenGroup index 5 ~60 2 35!@0.2 1 0.005~25 2 40!# (4)1 [0.01~60 2 15!~1 2 10!# 5 25 3 ~0.2 2 0.075!1 0.01~45!~29! 5 3.1 2 4.15 21.0 ~report as 0!11.2.4Assumethatan A-2-7materialhas30 %passingaNo. 200(75-m)sieve, aliquidlimitof50, andaplasticityindex of 30, thenGroup index 5 0.01~30 2 15!~30 2 10! (5)5 3.0or 3~note that only the PI portion of theformula was used!12. Discussion of Group Index12.1Theempirical groupindexformuladevisedfor ap-proximate within-group evaluation of the clayey-granularmaterials and the silt-clay materials is based on the follow-ing assumptions:Reprinted with permission of American Association of State Highway and Transportation OfficialsFIG. 2 Group Index ChartD 3282 93 (2004)e15Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---NOTE 8Groupindexvaluesshouldonlybeusedtocomparesoilswithin the same group and not between groups.12.1.1Materials falling within Groups A-1-a, A-1-b, A-2-4,A-2-5, andA-3aresatisfactoryas subgradewhenproperlydrained and compacted under moderate thickness of pavement(base or surface course, or both) of a type suitable for traffic tobecarriedorcanbemadesatisfactorybyadditionsofsmallamounts of natural or articial binders.12.1.2Materials falling within the clayey granularGroups A-2-6 and A-2-7 and the silt-clay Groups A-4, A-5,A-6, andA-7 will range in quality as subgrade fromtheapproximate equivalent of the good A-2-4 and A-2-5 subgradesto fair and poor subgrades requiring a layer of subbase materialor an increased thickness of base course over that required in12.1.1, in order to furnish adequate support for traffic loads.12.1.3Aminimum of 35 % passing a No. 200 (75-m) sieveis assumedtobe critical if plasticityis neglected, but thecritical minimumis only15 %whenaffectedbyplasticityindexes greater than 10.12.1.4Liquidlimits of 40andaboveareassumedtobecritical.12.1.5Plasticity indexes of 10 and above are assumed to becritical.12.2There is no upper limit of group index value obtainedby use of the formula: The adopted critical values of percent-age passing the No. 200 (75-m) sieve, liquid limit, andplasticity index, are based on an evaluation of subgrade,subbase, and base-course materials by several highway orga-nizations that use the tests involved in this classicationsystem.12.3Under average conditions of good drainage and thor-ough compaction, the supporting value of a material assubgrade may be assumed as an inverse ratio to its group index;that is, a group index of 0 indicates a good subgrade materialandagroupindexof 20or greater indicatesaverypoorsubgrade material.13. Keywords13.1airelds; Atterberg limits; classication; clay; embank-ments; gradation; gravel; group index; highway construction;highways; index ranges; sand; silt; soil aggregate mixtures; soilclassication; soil tests; subgroupsAPPENDIX(Nonmandatory Information)X1. RATIONALEX1.1 The 1992 edition differs from the previous edition inthat thetitlewas changedtobetter indicatetheuseof thestandard.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ve years andif not revised, either reapproved or withdrawn. 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Individual reprints(singleormultiplecopies)of thisstandardmaybeobtainedbycontacting ASTMat theaboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTMwebsite(www.astm.org).D 3282 93 (2004)e16Copyright ASTM International Provided by IHS under license with ASTMLicensee=Defense Supply Ctr/5913977001 Not for Resale, 01/16/2008 20:10:18 MST No reproduction or networking permitted without license from IHS--``````,````,,``,,``,,`,,```,`-`-`,,`,,`,`,,`---