ASTM_C_805_-_C_805M_-_13a.pdf

Designation:C805/C805M13aStandard Test Method forRebound Number of Hardened Concrete1This standard is issued under the fixed designation C805/C805M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the determination of a reboundnumber of hardened concrete using a spring-driven steelhammer.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 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:2C42/C42M Test Method for Obtaining and Testing DrilledCores and Sawed Beams of ConcreteC125 Terminology Relating to Concrete and Concrete Ag-gregatesC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsE18 Test Methods for Rockwell Hardness of Metallic Ma-terials3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,referto Terminology C125.4.Summary of Test Method4.1 A steel hammer impacts,with a predetermined amountof energy,a metal plunger in contact with a concrete surface.Either the distance that the hammer rebounds is measured orthe hammer speeds before and after impact are measured.Thetest result is reported as a dimensionless rebound number.5.Significance and Use5.1 This test method is applicable to assess the in-placeuniformity of concrete,to delineate variations in concretequality throughout a structure,and to estimate in-place strengthif a correlation is developed in accordance with 5.4.5.2 For a given concrete mixture,the rebound number isaffected by factors such as moisture content of the test surface,the type of form material or type of finishing used in construc-tion of the surface to be tested,vertical distance from thebottom of a concrete placement,and the depth of carbonation.These factors need to be considered in interpreting reboundnumbers.5.3 Different instruments of the same nominal design maygive rebound numbers differing from 1 to 3 units.Therefore,tests should be made with the same instrument in order tocompare results.If more than one instrument is to be used,perform comparative tests on a range of typical concretesurfaces so as to determine the magnitude of the differences tobe expected in the readings of different instruments.5.4 Relationships between rebound number and concretestrength that are provided by instrument manufacturers shall beused only to provide indications of relative concrete strength atdifferent locations in a structure.To use this test method toestimate strength,it is necessary to establish a relationshipbetween strength and rebound number for a given concrete andgiven apparatus(see Note 1).Establish the relationship bycorrelating rebound numbers measured on the structure withthe measured strengths of cores taken from correspondinglocations(see Note 2).At least two replicate cores shall betaken from at least six locations with different reboundnumbers.Select test locations so that a wide range of reboundnumbers in the structure is obtained.Obtain,prepare,and testcores in accordance with Test Method C42/C42M.If therebound number if affected by the orientation of the instrumentduring testing,the strength relationship is applicable for thesame orientation as used to obtain the correlation date(seeNote 3).Locations where strengths are to be estimated usingthe developed correlation shall have similar surface texture andshall have been exposed to similar conditions as the locations1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.64 on Nondestructive and In-Place Testing.Current edition approved Dec.15,2013.Published January 2014.Originallyapproved in 1975.Last previous edition approved in 2013 as C805 13.DOI:10.1520/C0805_C0805M-13a.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.*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 States1 where correlation cores were taken.The functionality of therebound hammer sha