ASTM_G_187_-_12a.pdf

Designation:G18712aStandard Test Method forMeasurement of Soil Resistivity Using the Two-ElectrodeSoil Box Method1This standard is issued under the fixed designation G187;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 equipment and proceduresfor the measurement of soil resistivity,for samples removedfrom the ground,for use in the assessment and control ofcorrosion of buried structures.1.2 Procedures allow for this test method to be used in thefield or in the laboratory.1.3 The test method procedures are for the resistivitymeasurement of soil samples in the saturated condition and inthe as-received condition.1.4 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.Soil resistivity values are reported in ohm-centimeter.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 to determine theapplicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodG57 Test Method for Field Measurement of Soil ResistivityUsing the Wenner Four-Electrode MethodG193 Terminology and Acronyms Relating to Corrosion2.2 UNS Standards:3UNS Designation S30400&S30403UNS Designation S31600&S316033.Terminology3.1 Definitions:3.1.1 Ohms law,nThe relationship between the electro-motive force,the current,and the resistance.Mathematically:current=electromotive force/resistance or I=E/R;where“I”is measured in amperes,“E”in volts,and“R”in ohms.3.1.2 resistivity(soil),nThe electrical resistance betweenopposite faces of a unit cube of material;the reciprocal ofconductivity.3.1.3 saturated soil,nsoil whose entire soil porosity isfilled with water.3.1.4 soil box factor,nA factor which is determined by atwo-electrode soil boxs internal dimensions(cross sectionalarea/distance between electrode plates).The soil box factor ismultiplied by the measured resistance of a substance in the soilbox to obtain that substances resistivity.3.1.5 soil resistance meter,nAn instrument capable ofmeasuring soil resistance.3.1.6 two-electrode soil box,nAnon-conductive containerof known internal dimensions with two end plate electrodes formeasuring a substances resistivity.3.2 The terminology used herein,if not specifically definedotherwise,shall be in accordance with Terminology G193.Definitions provided herein and not given in TerminologyG193 are limited only to this standard.4.Summary of Test Method4.1 The two-electrode soil box method is predicated onmeasuring the resistance between two opposite faces of a boxcontaining a substance or solution.That resistance measure-ment through the substance being tested is then converted toresistivity based on the conversion formula of Eq 1.1This test method is under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and is the direct responsibility of Subcommittee G01.10 onCorrosion in Soils.Current edition approved Nov.1,2012.Published March 2013.Originallyapproved in 2005.Last previous edition approved in 2012 as G18712.DOI:10.1520/G0187-12A.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.3UNS(Unified Numbering System)was developed jointly by ASTM Interna-tional and SAE International.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.2 A voltage is applied to the opposing electrodes and theresulting current is measured.Ohms law reveals the resistance.The resistivity,is then:ohm2 cm!5 AR/d(1)where:A=exposed area of one electrode face,cm2,R=resistance,ohms,andd=distance between electrodes,cm.5.Significance and Use45.1 The resistivity of the surrounding soil environment is afactor in the corrosion of underground structures.High resis-tivity soils are generally not as corrosive as low resistivitysoils.The resistivity of the soil is one of many factors thatinfluence the service life of a buried structure.Soil resistivitymay affect the material selection and the location of a struc-ture.55.2 Soil resistivity is of particular importance and interest inthe corrosion process because it is basic in the analysis ofcorrosion problems and the design of corrective measures.5.3 The test method is focused to provide an accurate,expeditious measurement of soil resistivity to assist in thedetermination of a soils corrosive natu