1、Designation: C42/C42M 10American 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 desi
2、gnation 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 by
3、 agencies of the 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.NOTE 1Appendix X1 provides recommendations for obtaining andtesting sawed beams fo
4、r flexural performance.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
5、in non-conformancewith the standard.1.3 The text of this standard references notes and footnotesthat provide explanatory material. These 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
6、 safetyconcerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C39/C39M Test Method for Compres
7、sive Strength of Cy-lindrical Concrete SpecimensC78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C174/C174M Test Method for Measuring Thickness ofConcrete Elements Using Drilled Concrete CoresC496/C496M Test Method for Splitting Tensile Strength ofCylindri
8、cal Concrete SpecimensC617 Practice for Capping Cylindrical Concrete SpecimensC642 Test Method for Density, Absorption, and Voids inHardened ConcreteC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC823 Practice for Examination and Sampling of Harde
9、nedConcrete in ConstructionsC1231/C1231M Practice for Use of Unbonded Caps inDetermination of Compressive Strength of Hardened Con-crete Cylinders2.2 ACI Standards:3318 Building Code Requirements for Structural Concrete3. Significance and Use3.1 This test method provides standardized procedures foro
10、btaining and testing specimens to determine 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 in
11、the structure. Another use of this 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
12、by core orientation relative to thehorizontal plane of the concrete as placed, with strengthtending to be lower when measured parallel to the horizontalplane.4These factors shall be considered in planning thelocations for obtaining concrete samples and in comparingstrength test results.3.4 The stren
13、gth 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 tocondition a specimen that will ensure that, at the time of test,it will be in the identical moisture condition as concrete in the1This
14、 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.Current edition approved June 15, 2010. Published July 2010. Originallyapproved in 1921. Last previous edition approved in 20
15、04 as C42/C42M04. DOI:10.1520/C0042_C0042M-10.2For 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.3Available from
16、 American Concrete Institute (ACI), P.O. Box 9094, FarmingtonHills, MI 48333-9094, http:/www.concrete.org.4Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” ConcreteInternational, Vol. 23, No. 11, November 2001, pp. 59-68.1*A Summary of Changes section appears at the end of this sta
17、ndard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.structure. The moisture conditioning procedures in this testmethod are intended to provide reproducible moisture condi-tions that minimize within-laboratory and between-laboratoryv
18、ariations and to reduce the effects of moisture introducedduring specimen preparation.3.5 There is no universal relationship between the compres-sive strength of a core and the corresponding compressivestrength of standard-cured molded cylinders. The relationshipis affected by many factors such as t
19、he strength level of theconcrete, the in-place temperature and moisture history, and thestrength gain characteristics of the concrete. Historically, it hasbeen assumed that core strengths are generally 85 % of thecorresponding standard-cured cylinder strengths, but this is notapplicable to all situa
20、tions. The acceptance criteria for corestrength are to be established by the specifier of the tests. ACI318 provides core strength acceptance criteria for new con-struction.4. Apparatus4.1 Core Drill, for obtaining cylindrical core specimenswith diamond impregnated bits attached to a core barrel.4.2
21、 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.5. Sampling5.1 General:5.1.1 Samples of hardened concrete for use in the prepara-tion of strength test spec
22、imens 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 2 and Note 3). When preparing strength testspecimens from samples of hardened concrete, samples thathave been damaged during removal
23、shall not be used unless thedamaged portion(s) are removed and the resulting test speci-men is of suitable length (see 7.2). Samples of defective ordamaged concrete that cannot be tested shall be reported alongwith the reason that prohibits use of the sample for preparingstrength test specimens.NOTE
24、 2Practice C823 provides guidance on the development of asampling plan for concrete in constructions.NOTE 3It is not possible to specify a minimum age when concrete isstrong enough to withstand damage during removal, because the strengthat any age depends on the curing history and strength grade of
25、theconcrete. If time permits, the concrete should not be removed before it is14 days old. If this is not practical, removal of concrete can proceed if thecut surfaces do not display erosion of the mortar and the exposed coarseaggregate particles are embedded firmly in the mortar. In-place testmethod
26、s may be used to estimate the level of strength development priorto attempting removal of concrete samples.5.1.2 Specimens containing embedded reinforcement shallnot be used for determining compressive, splitting tensile, orflexural strength.5.2 Core DrillingWhen a core will be tested to measureconc
27、rete strength, the core specimen shall be drilled perpen-dicular to the surface and not near formed joints or obviousedges of a unit of deposit. Record and report the approximateangle between the longitudinal axis of the drilled core and thehorizontal plane of the concrete as placed. A specimen dril
28、ledperpendicular to a vertical surface, or perpendicular to asurface with a batter, shall be taken from near the middle of aunit of deposit when possible. When obtained for purposesother than determination of strength, drill cores in accordancewith the instructions provided by the specifier.5.3 Slab
29、 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 thickness of pavements, slabs,walls or ot
30、her structural elements shall have a diameter of atleast 95 mm 3.75 in. when the lengths of such cores arestipulated to be measured in accordance with Test MethodC174/C174M.6.2 For cores that are not intended for determining structuraldimensions, measure the longest and shortest lengths on the cutsu
31、rface along lines parallel to the core axis. Record the averagelength to the nearest 5 mm 14 in.7. Cores for Compressive Strength7.1 DiameterThe diameter of core specimens for thedetermination of compressive strength in load bearing struc-tural members shall be at least 94 mm 3.70 in. For non-loadbe
32、aring structural members or when it is impossible to obtaincores with length-diameter ratio (L/D) greater than or equal to1, core diameters less than 94 mm 3.70 in. are not prohibited(see Note 4). For concrete with nominal maximum aggregatesize greater than or equal to 37.5 mm 112 in., the corediame
33、ters shall be as directed by the specifier of the tests (seeNote 5).NOTE 4The 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
34、 to the effect of the length-diameterratio.5NOTE 5The preferred minimum core diameter is three times thenominal maximum size of the coarse aggregate, but it should be at leasttwo times the nominal maximum size of the coarse aggregate.7.2 LengthThe preferred length of the capped or groundspecimen is
35、between 1.9 and 2.1 times the diameter. If the ratioof the length to the diameter (L/D) of the core exceeds 2.1,reduce the length of the core so that the ratio of the capped orground specimen is between 1.9 and 2.1. Core specimens withlength-diameter ratios equal to or less than 1.75 requirecorrecti
36、ons to the measured compressive strength (see 7.9.1).Astrength correction factor is not required for L/D greater than1.75. A core having a maximum length of less than 95 % of itsdiameter before capping or a length less than its diameter aftercapping or end grinding shall not be tested.5Bartlett, F.M
37、. and MacGregor, J.G., “Effect of Core Diameter on Concrete CoreStrengths,” ACI Materials Journal, Vol. 91, No. 5, September-October 1994, pp.460-470.C42/C42M 1027.3 Moisture ConditioningTest cores after moisture con-ditioning as specified in this test method or as directed by thespecifier of the te
38、sts. The moisture conditioning proceduresspecified in this test method are intended to preserve themoisture of the drilled core and to provide a reproduciblemoisture condition that minimizes the effects of moisturegradients introduced by wetting during drilling and specimenpreparation.7.3.1 After co
39、res have been drilled, wipe off surface drillwater and allow remaining surface moisture to evaporate.When surfaces appear dry, but not later than 1 h after drilling,place cores in separate plastic bags or nonabsorbent containersand seal to prevent moisture loss. Maintain cores at ambienttemperature,
40、 and protect cores from exposure to direct sunlight.Transport the cores to the testing laboratory as soon aspossible. Keep cores in the sealed plastic bags or nonabsorbentcontainers at all times except during end preparation and for amaximum time of2htopermit capping before testing.7.3.2 If water is
41、 used during sawing or grinding of coreends, complete these operations as soon as possible, but nolater than 2 days after drilling of cores unless stipulatedotherwise by the specifier of tests. After completing endpreparation, wipe off surface moisture, allow the surfaces todry, and place the cores
42、in sealed plastic bags or nonabsorbentcontainers. Minimize the duration of exposure to water duringend preparation.7.3.3 Allow the cores to remain in the sealed plastic bags ornonabsorbent containers for at least 5 days after last beingwetted and before testing, unless stipulated otherwise by thespe
43、cifier of tests.NOTE 6The waiting period of at least 5 days is intended to reducemoisture gradients introduced when the core is drilled or wetted duringsawing or grinding.7.3.4 When direction is given to test cores in a moisturecondition other than achieved by conditioning according to7.3.1, 7.3.2,
44、and 7.3.3, report the alternative procedure.7.4 Sawing of EndsThe ends of core specimens to betested in compression shall be flat, and perpendicular to thelongitudinal axis in accordance with Test Method C39/C39M.If necessary, saw the ends of cores that will be capped so thatprior to capping, the fo
45、llowing requirements are met:7.4.1 Projections, if any, shall not extend more than 5 mm0.2 in. above the end surfaces.7.4.2 The end surfaces shall not depart from perpendicular-ity to the longitudinal axis by a slope of more than 1:8d or1:0.3d where d is the average core diameter in mm orinches.7.5
46、DensityWhen required by the specifier of the tests,determine the density by weighing the core before capping anddividing the mass by the volume of the core calculated from theaverage diameter and length. Alternatively, determine thedensity from the mass in air and submerged mass in accordancewith Te
47、st Method C642. After submerged weighing, dry coresin accordance with 7.3.2 and store in sealed plastic bags ornonabsorbent containers for at least 5 days before testing.7.6 CappingIf the ends of the cores do not conform to theperpendicularity and planeness requirements of Test MethodC39/C39M, they
48、shall be sawed or ground to meet thoserequirements or capped in accordance with Practice C617.Ifcores are capped in accordance with Practice C617, thecapping device shall accommodate actual core diameters andproduce caps that are concentric with the core ends. Measurecore lengths to the nearest 2 mm
49、 0.1 in. before capping.Unbonded caps in accordance with Practice C1231/C1231Mare not permitted.7.7 MeasurementBefore testing, measure the length of thecapped or ground specimen to the nearest 2 mm 0.1 in. anduse this length to compute the length-diameter (L/D) ratio.Determine the average diameter by averaging two measure-ments taken at right angles to each other at the mid-height ofthe specimen. Measure core diameters to the nearest 0.2 mm0.01 in. when the difference in core diameters does notexceed 2 % of their average, otherwise measur
