ASTM_D_7625_-_22.pdf

Designation:D762522Standard Test Method forLaboratory Determination of Abrasiveness of Rock Usingthe CERCHAR Abrasiveness Index Method1This standard is issued under the fixed designation D7625;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.Scope*1.1 This test method covers the determination of the abra-siveness of rock by the CERCHAR Abrasiveness Index(CAI)method.The test method consists of measuring the wear on thetip of steel stylus with a cone shape and known RockwellHardness,caused by scratching against a freshly broken or sawcut rock surface for a prescribed 10 mm distance using one ofthe two test apparatus.1.2 This test method is intended for freshly broken rocksurfaces;however,saw cut surfaces are covered for when asatisfactory rock surface cannot be obtained.1.3 The Rockwell Hardness(HR)of the stylus can have aprofound effect on the results.The focus of this test method isan HRC value of 55 for every test(1,2).2However,there aresituations where styli with different Rockwell Hardness can beused.Therefore,this test method includes discussions on styluswith different Rockwell Hardness.1.3.1 The Rockwell hardness(HR)value is based on theindentation hardness of a material.The Rockwell test,E18,measures the depth of penetration of an indenter under a largeload(major load)compared to the penetration made by apreload(minor load).(3)There are different scales,denoted bya single letter(Ato F),that use different loads or indenters.Theresult is a dimensionless number noted as HRA,HRB,HRC,etc.,where the last letter is the respective Rockwell scale whichin this test method is the scale C,which is for hardensteel.1.4 Basically,the CERCHAR test is a measurement of therelative different hardness of stylus tip and rock specimensurface.The stylus tip is made of steel having a knownRockwell Hardness.Experiments have shown that CAI variesinversely with stylus hardness.Test results with the same steeltype stylus but with different hardness need to be normalized tostandard stylus hardness(2).1.5 The scratch distance shall be limited to 10 mm.Ingeneral,85%of the stylus wear occurs during the first 2 mmof scratchs length.The remaining 15%of the stylus wearoccurs during the last 8 mm of the scratchs length.Therefore,minor variation in the scratchs length from test to test doesntsignificantly affect the total stylus wear and the resulting CAIwhen variation in scratch length is kept between 60.5 mm inlength(3).1.6 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.6.1 The procedures used to specify how data are collected/recorded or calculated,in this standard are regarded as theindustry standard.In addition,they are representative of thesignificant digits that generally should be retained.The proce-dures used do not consider material variation,purpose forobtaining the data,special purpose studies,or any consider-ations 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.1.7 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.1.8 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved Oct.1,2022.Published October 2022.Originallyapproved in 2010.Last previous edition approved in 2010 as D7625 10,whichwas withdrawn June 2019 and reinstated in October 2022.DOI:10.1520/D7625-22.2The bold numbers in parenthesis refer to a list of references at the end of thisstandard.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDe