1、Designation: C42/C42M 16 American Association StateHighway and Transportation Officials StandardAASHTO No.: T24Standard Test Method forObtaining and Testing Drilled Cores and Sawed Beams ofConcrete1This standard is issued under the fixed designation C42/C42M; the number immediately following the des
2、ignation 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.This standard has been approved for use b
3、y agencies of the U.S. Department of Defense.1. Scope*1.1 This test method covers obtaining, preparing, and test-ing cores drilled from concrete for length or compressivestrength or splitting tensile strength determinations. This testmethod is not applicable to cores from shotcrete.NOTE 1Test Method
4、 C1604/C1604M is applicable for obtaining,preparing, and testing cores from shotcrete.NOTE 2Appendix X1 provides recommendations for obtaining andtesting sawed beams for flexural performance.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The va
5、lues 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 The text of this standard references notes and footnotesthat provide explanatory material. T
6、hese notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.1.4 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safe
7、ty andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C39/C39M Test Method for Compressive Strength of Cylin-drical Concrete SpecimensC78/C78M Test Method for Flexural Strength of Concrete(Using Simple Beam with Third-
8、Point Loading)C174/C174M Test Method for Measuring Thickness of Con-crete Elements Using Drilled Concrete CoresC496/C496M Test Method for Splitting Tensile Strength ofCylindrical Concrete SpecimensC617/C617M Practice for Capping Cylindrical ConcreteSpecimensC642 Test Method for Density, Absorption,
9、and Voids inHardened ConcreteC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC823/C823M Practice for Examination and Sampling ofHardened Concrete in ConstructionsC1231/C1231M Practice for Use of Unbonded Caps inDetermination of Compressive Strength
10、 of Hardened Cy-lindrical Concrete SpecimensC1542/C1542M Test Method for Measuring Length of Con-crete CoresC1604/C1604M Test Method for Obtaining and TestingDrilled Cores of Shotcrete3. Significance and Use3.1 This test method provides standardized procedures forobtaining and testing specimens to d
11、etermine the compressive,splitting tensile, and flexural strength of in-place concrete.3.2 Generally, test specimens are obtained when doubtexists about the in-place concrete quality due either to lowstrength test results during construction or signs of distress inthe structure. Another use of this
12、method is to provide strengthinformation on older structures.3.3 Concrete strength is affected by the location of theconcrete in a structural element, with the concrete at the bottomtending to be stronger than the concrete at the top. Corestrength is also affected by core orientation relative to the
13、horizontal plane of the concrete as placed, with strengthtending to be lower when measured parallel to the horizontal1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.61 on Testing for Strength.Cur
14、rent edition approved Oct. 1, 2016. Published October 2016. Originallyapproved in 1921. Last previous edition approved in 2013 as C42/C42M 13. DOI:10.1520/C0042_C0042M-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Ann
15、ual 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 States1plane.3Thes
16、e factors shall be considered in planning thelocations for obtaining concrete samples and in comparingstrength test results.3.4 The strength of concrete measured by tests of cores isaffected by the amount and distribution of moisture in thespecimen at the time of test. There is no standard procedure
17、 tocondition a specimen that will ensure that, at the time of test,it will be in the identical moisture condition as concrete in thestructure. The moisture conditioning procedures in this testmethod are intended to provide reproducible moisture condi-tions that minimize within-laboratory and between
18、-laboratoryvariations and to reduce the effects of moisture introducedduring specimen preparation.3.5 The measured compressive strength of a core willgenerally be less than that of a corresponding properly moldedand cured standard cylinder tested at the same age. For a givenconcrete, however, there
19、is no unique relationship between thestrengths of these two types of specimens (see Note 3). Therelationship is affected by many factors such as the strengthlevel of the concrete, the in-place temperature and moisturehistories, the degree of consolidation, batch-to-batchvariability, the strength-gai
20、n characteristics of the concrete, thecondition of the coring apparatus, and the care used inremoving cores.NOTE 3Aprocedure is available for estimating the equivalent cylinderstrength from a measured core strength.4NOTE 4In the absence of core strength requirements of an applicablebuilding code or
21、of other contractual or legal documents that may governthe project, the specifier of tests should establish in the project specifica-tions the acceptance criteria for core strengths. An example of acceptancecriteria for core strength is provided in ACI 318,5which are used toevaluate cores taken to i
22、nvestigate low strength test results of standard-cured cylinder during construction. According to ACI 318, the concreterepresented by the cores is considered structurally adequate if the averagestrength of three cores is at least 85 % of the specified strength and nosingle core strength is less than
23、 75 % of the specified strength.3.6 The “specifier of the tests” referenced in this test methodis the individual responsible for analysis or review andacceptance of core test results.NOTE 5For investigation of low strength test results, ACI 318 definesthe specifier of the tests as the licensed desig
24、n professional.3.7 The apparent compressive strength of concrete as mea-sured by a core is affected by the length-diameter ratio (L/D) ofthe core as tested and this must be considered in preparing corespecimens and evaluating test results.4. Apparatus4.1 Core Drill, for obtaining cylindrical core sp
25、ecimenswith diamond impregnated bits attached to a core barrel.4.2 Saw, for trimming ends of cores. The saw shall have adiamond or silicon-carbide cutting edge and shall be capable ofcutting cores without introducing cracks or dislodging aggre-gate particles.4.3 Balance, accurate to at least 5 g 0.0
26、1 lb.5. Sampling5.1 General:5.1.1 Samples of hardened concrete for use in the prepara-tion of strength test specimens shall not be taken until theconcrete is strong enough to permit sample removal withoutdisturbing the bond between the mortar and the coarse aggre-gate (see Note 6 and Note 7). When p
27、reparing strength testspecimens from samples of hardened concrete, samples thathave been damaged during removal shall not be used unless thedamaged portion(s) are removed and the lengths of resultingtest specimens satisfy the minimum length-diameter ratiorequirement in 7.2. Samples of defective or d
28、amaged concretethat cannot be tested shall be reported along with the reasonthat prohibits use of the sample for preparing strength testspecimens.NOTE 6Practice C823/C823M provides guidance on the developmentof a sampling plan for concrete in constructions.NOTE 7It is not possible to specify a minim
29、um age when concrete isstrong enough to withstand damage during removal, because the strengthat any age depends on the curing history and strength grade of theconcrete. If time permits, the concrete should not be removed before it is14 days old. If this is not practicable, removal of concrete can pr
30、oceed ifthe cut surfaces do not display erosion of the mortar and the exposedcoarse aggregate particles are embedded firmly in the mortar. In-place testmethods may be used to estimate the level of strength development priorto attempting removal of concrete samples.5.1.2 Except as provided in 5.1.3,
31、cores containing embed-ded reinforcement, excluding fibers, or other embedded objectsshall not be used for determining strength of concrete.5.1.3 If it is not possible to prepare a test specimen thatmeets the requirements of 7.1 and 7.2 and that is free ofembedded reinforcement or other metal, the s
32、pecifier of thetests is permitted to allow testing of cores with embedded metal(see Note 8). If a core tested for strength contains embeddedmetal, the size, shape, and location of the metal within the coreshall be documented in the test report.NOTE 8The presence of steel reinforcement, other than fi
33、bers, or otherembedded metal in a core can affect the measured strength.6,7There areinsufficient data to derive reliable correction factors that can be applied tothe measured strength to account for embedded reinforcement perpendicu-lar to the core axis. If testing of cores containing embedded reinf
34、orcementis permitted, engineering judgment is required to assess the significance ofthe results. The specifier of the tests should not permit a core to be testedfor strength if bar reinforcement, or other elongated embedded metalobject, is oriented close to parallel to the core axis.5.2 Core Drillin
35、gWhen a core will be tested to measureconcrete strength, the core shall be drilled perpendicular to the3Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” ConcreteInternational, Vol 23, No. 11, November 2001, pp. 5968.4“Guide for Obtaining Cores and Interpreting Compressive Strength
36、Results,”ACI 214.4R, American Concrete Institute, P.O. Box 9094, Farmington Hills, MI48333, www.concrete.org.5“Building Code Requirements for Structural Concrete and Commentary,” ACI318, American Concrete Institute, P.O. Box 9094, Farmington Hills, MI 48333,www.concrete.org.6Gaynor, R. D., “Effect o
37、f Horizontal Reinforcing Steel on the Strength ofMolded Cylinders,” Problems and Practices in Journal of the American ConcreteInstitute, Proceedings, Vol 62, No. 7, July 1965, pp. 837840.7Concrete Society Working Party, “Concrete Core Testing for Strength,”Concrete Society Technical Report No. 11, T
38、he Concrete Society, England, May1976.C42/C42M 162surface and at least 150 mm 6 in. away from formed joints orobvious edges of a unit of deposit (see Note 9). This minimumdistance does not apply to the formed boundaries of structuralmembers. Record the approximate angle between the longitu-dinal axi
39、s of the drilled core and the horizontal plane of theconcrete as placed. A specimen drilled perpendicular to avertical surface, or perpendicular to a sloping surface, shall betaken from near the middle of a unit of deposit when possible.If cores are obtained for purposes other than determination ofs
40、trength, drill cores in accordance with the instructions pro-vided by the specifier of the tests. Record the date core wasdrilled. If known, record the date when concrete was placed.NOTE 9The intent is to avoid drilling cores in non-representativeconcrete that may exist near formed joints or the bou
41、ndary of a unit ofplacement.5.3 Slab RemovalRemove a slab sufficiently large tosecure the desired test specimens without the inclusion of anyconcrete that has been cracked, spalled, undercut, or otherwisedamaged.DRILLED CORES6. Measuring the Length of Drilled Cores6.1 Cores for determining the thick
42、ness of pavements, slabs,walls or other structural elements shall have a diameter of atleast 94 mm 3.70 in. when the lengths of such cores arestipulated to be measured in accordance with Test MethodC174/C174M. When core length for determining the thicknessof a member is not required to be measured i
43、n accordance withTest Method C174/C174M, core diameter shall be as directedby specifier of tests.6.2 For cores that are not intended for determining structuraldimensions, measure the longest and shortest lengths on the cutsurface along lines parallel to the core axis. Record the averagelength to the
44、 nearest 5 mm 14 in.7. Cores for Compressive Strength7.1 Diameter:7.1.1 Except as provided in 7.1.2, the diameter of corespecimens for the determination of compressive strength shallbe at least 94 mm 3.70 in. or at least two times the nominalmaximum size of the coarse aggregate, whichever is larger.
45、7.1.2 If limited member thickness makes it impossible toobtain cores with length-diameter ratio (L/D) of at least 1.0 orif clear distance between reinforcement is limited, core diam-eters less than 94 mm 3.70 in. are not prohibited. If a corediameter less than 94 mm 3.70 in. is used, report the reas
46、on.NOTE 10The compressive strengths of nominal 50-mm 2-in. diam-eter cores are known to be somewhat lower and more variable than thoseof nominal 100-mm 4-in. diameter cores. In addition, smaller diametercores appear to be more sensitive to the effect of the length-diameterratio.87.2 Length7.2.1 Exce
47、pt as provided in 7.2.2, the preferred length of thecapped or ground specimen is between 1.9 and 2.1 times thediameter. If the ratio of the length to the diameter (L/D) of thecore exceeds 2.1, reduce the length of the core so that the ratioof the capped or ground specimen is between 1.9 and 2.1. Cor
48、especimens with length-diameter ratios equal to or less than1.75 require corrections to the measured compressive strength(see 7.9.1). A strength correction factor is not required for L/Dgreater than 1.75.Acore having a maximum length of less than95 % of its diameter before capping or a length less t
49、han itsdiameter after capping, trimming, or end grinding shall not betested.7.2.2 If the compressive strengths of cores are to be com-pared with specified strengths based on standard concretecubes, cores shall be tested with L/D, after end preparation, inthe range of 1.00 to 1.05 unless otherwise directed by thespecifier of the tests. If the strengths of cores with L/D =1 areto be compared with specified concrete cube strength, do notapply the correction factor in 7.9.1.7.3 Moisture ConditioningTest cores after moisture con-ditioning as specified i
