ASTM_D_425_-_88_2008.pdf

Designation:D42588(Reapproved 2008)Standard Test Method forCentrifuge Moisture Equivalent of Soils1This standard is issued under the fixed designation D425;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the mois-ture equivalent of soil in the laboratory by means of acentrifuge technique.1.2 This test method is limited to disturbed specimens ofcoarse-grained soils having fines of low plasticity such as SP,SW,SC-SM,or SM soils.The test is limited to soils passing the2.00-mm sieve or that fraction of a soil passing a 2.00-mmsieve.NOTE1Test Method D3152 or Test Method D2325 should be used toevaluate the capillary-moisture relations of fine-grained soils and coarse-grained soils having fines of medium to high plasticity,undisturbed soils,and soils at specific desired units weights.1.3 The test method is temperature-dependent,and consis-tent comparable results can be obtained only if the tests areperformed under a constant-temperature condition.1.4 The values stated in SI units are to be regarded as thestandard.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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil,Rock,and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture)Content of Soil and Rock by MassD2325 Test Method for Capillary-Moisture Relationshipsfor Coarse-and Medium-Textured Soils by Porous-PlateApparatus(Withdrawn 2007)3D3152 Test Method for Capillary-Moisture Relationshipsfor Fine-Textured Soils by Pressure-Membrane Apparatus(Withdrawn 2007)3D4753 Guide for Evaluating,Selecting,and Specifying Bal-ances and Standard Masses for Use in Soil,Rock,andConstruction Materials TestingE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3.Terminology3.1 All definitions are in accordance with TerminologyD653.Terms of particular significance are as follows:3.2 capillary fringe zonethe zone above the free waterelevation in which water is held by capillary action.3.3 centrifuge moisture equivalentthe water content of asoil after it has been saturated with water and then subjected forone hour to a centrifugal force equal to 1000 times that ofgravity.3.4 specific retentionthe ratio of the volume of water thatcannot be drained from a saturated soil under the action offorce of gravity to the total volume of voids.3.5 water-holding capacitythe smallest value to which thewater content of soil or rock can be reduced by gravitydrainage.4.Summary of Test Method4.1 The centrifuge moisture equivalent of soils is deter-mined by initially air-drying the soil,selecting two 5-g testspecimens,thoroughly soaking each test specimen,and thendetermining the water content of each specimen after it hasbeen centrifuged for 1 h at a force equal to 1000 times that ofgravity at a controlled temperature of 20 6 1C.5.Significance and Use5.1 Not all water contained in a saturated soil can beremoved by gravity drainage.The amount of water retainedafter gravity drainage is usually expressed as water holdingcapacity or specific retention.It varies with time,and with the1This 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 Feb.1,2008.Published March 2008.Originallyapproved in 1935.Last previous edition approved in 2001 as D425 88(2001).DOI:10.1520/D0425-88R08.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 particle-size distribution and plasticity of the soil(in general,increasing in value with increasing plasticity index).5.2 In general,the centrifuge moisture equivalent is basedon the theory of applying a centrifugal force great enough toreduce the capillary fringe zone enough that it can be ignoredwithout introducing much error,even in small specimens,andyet not so great as to withdraw a large proportion of the waterthat is held securely above the capillary fringe.For example,ifa soil will hold water 100 mm by capillarity acting againstgravity,the soil will theoretically be able to hold the water only0.1 mm against a cent