1、Designation: C 42/C 42M 04American 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 C 42/C 42M; the number immediately following the
2、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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for u
3、se by agencies of the Department of Defense.1. Scope*1.1 This test method covers obtaining, preparing, and test-ing (1) cores drilled from concrete for length or compressivestrength or splitting tensile strength determinations and (2)beams sawed from concrete for flexural strength determina-tions.1.
4、2 The values stated in either inch-pound units or SI unitsshall be regarded separately as standard. SI units are shown inbrackets. The values stated in each system may not be exactequivalents; therefore, each system must be used indepen-dently of the other. Combining values from the two systemsmay r
5、esult in non-conformance with 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 addr
6、ess the 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:2C 39/C 39M Test Method fo
7、r Compressive Strength of Cy-lindrical Concrete SpecimensC78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C 174/C 174M Test Method for Measuring Length ofDrilled Concrete CoresC 496 Test Method for Splitting Tensile Strength of Cylin-drical Concrete Specim
8、ensC 617 Practice for Capping Cylindrical Concrete Speci-mensC 642 Test Method for Density, Absorption, and Voids inHardened ConcreteC 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC 823 Practice for Examination and Sampling of HardenedConcrete in
9、 ConstructionsC 1231/C 1231M Practice for Use of Unbonded Caps inDetermination of Compressive Strength of Hardened Con-crete Cylinders2.2 ACI Standards:318 Building Code Requirements for Structural Concrete33. Significance and Use3.1 This test method provides standardized procedures forobtaining and
10、 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 inthe structur
11、e. 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 by core orie
12、ntation 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 strength of concr
13、ete measured by tests of cores andbeams is affected by the amount and distribution of moisture inthe specimen at the time of test. There is no standard procedureto condition a specimen that will ensure that, at the time of test,1This test method is under the jurisdiction of ASTM Committee C09 onConc
14、rete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.61 on Testing for Strength.Current edition approved July 1, 2004. Published July 2004. Originally approvedin 1921. Last previous edition approved in 2003 as C 42/C 42M 03.2For referenced ASTM standards, visit the ASTM w
15、ebsite, 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 American Concrete Institute (ACI), P.O. Box 9094, FarmingtonHills, MI 48333.4Neville, A., “Co
16、re 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 standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.it
17、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-laboratoryvariations and to reduce the effects of moisture introduced
18、during 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 the strength level of theconcrete, the in-place temperature
19、 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 situations. The acceptance criteria for corestrength are to be
20、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 Saw, for cutting beam specimens to size for flexuralstren
21、gth tests and to trim ends of cores. The saw shall have adiamond or silicon-carbide cutting edge and shall be capable ofcutting specimens that conform to the prescribed dimensions,without excessive heating or shock.5. Sampling5.1 General:5.1.1 Samples of hardened concrete for use in the prepara-tion
22、 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 1 and Note 2). When preparing strength testspecimens from samples of hardened concrete, samples thathave been d
23、amaged during removal 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 preparingstreng
24、th test specimens.NOTE 1Practice C 823 provides guidance on the development of asampling plan for concrete in constructions.NOTE 2It 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
25、 and strength grade of 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 mort
26、ar. In-place testmethods 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 DrillingAcore specimen sha
27、ll 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 drilledperpendicular to a vertical surfa
28、ce, or perpendicular to asurface with a batter, shall be taken from near the middle of aunit of deposit when possible.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 otherwisedamage
29、d.DRILLED CORES6. Measuring the Length of Drilled Cores6.1 Cores for determining the thickness of pavements, slabs,walls or other structural elements shall have a diameter of atleast 3.75 in. 95 mm when the lengths of such cores arestipulated to be measured in accordance with Test MethodC 174/C 174M
30、.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 nearest14 in. 5 mm.7. Cores for Compressive Strength7.1 DiameterThe diameter of core specimens
31、for thedetermination of compressive strength in load bearing struc-tural members shall be at least 3.70 in. 94 mm. For non-loadbearing structural members or when it is impossible to obtaincores with length-diameter ratio (L/D) greater than or equal to1, core diameters less than 3.70 in. 94 mm are no
32、t prohibited(see Note 3). For concrete with nominal maximum aggregatesize greater than or equal to 112 in. 37.5 mm, the corediameters shall be as directed by the specifier of the tests (seeNote 4).NOTE 3The compressive strengths of nominal 2-in. 50-mm diam-eter cores are known to be somewhat lower a
33、nd more variable than thoseof nominal 4-in. 100-mm diameter cores. In addition, smaller diametercores appear to be more sensitive to the effect of the length-diameterratio.5NOTE 4The preferred minimum core diameter is three times thenominal maximum size of the coarse aggregate, but it should be at l
34、easttwo times the nominal maximum size of the coarse aggregate.7.2 LengthThe preferred length of the capped or groundspecimen is 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 capp
35、ed orground specimen is between 1.9 and 2.1. Core specimens withlength-diameter ratios equal to or less than 1.75 requirecorrections 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 %
36、 of itsdiameter before capping or a length less than its diameter aftercapping or end grinding shall not be tested.7.3 Moisture ConditioningTest cores after moisture con-ditioning as specified in this test method or as directed by the5Bartlett, F.M. and MacGregor, J.G., “Effect of Core Diameter on C
37、oncrete CoreStrengths,” ACI Materials Journal, Vol. 91, No. 5, September-October 1994, pp.460-470.C 42/C 42M 042specifier of the tests. The moisture conditioning proceduresspecified in this test method are intended to preserve themoisture of the drilled core and to provide a reproduciblemoisture con
38、dition that minimizes the effects of moisturegradients introduced by wetting during drilling and specimenpreparation.7.3.1 After cores 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,plac
39、e cores in separate plastic bags or nonabsorbent containersand seal to prevent moisture loss. Maintain cores at ambienttemperature, 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 nonabsorbe
40、ntcontainers at all times except during end preparation and for amaximum time of2htopermit capping before testing.7.3.2 If water is 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
41、 the specifier of tests. After completing endpreparation, wipe off surface moisture, allow the surfaces todry, and place the cores 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
42、bags ornonabsorbent containers for at least 5 days after last beingwetted and before testing, unless stipulated otherwise by thespecifier of tests.NOTE 5The waiting period of at least 5 days is intended to reducemoisture gradients introduced when the core is drilled or wetted duringsawing or grindin
43、g.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, 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 a
44、xis in accordance with Test Method C 39/C 39M.If necessary, saw the ends of cores that will be capped so thatprior to capping, the following requirements are met:7.4.1 Projections, if any, shall not extend more than 0.2 in.5 mm above the end surfaces.7.4.2 The end surfaces shall not depart from perp
45、endicular-ity to the longitudinal axis by a slope of more than 1:8d or1:0.3d where d is the average core diameter in inches ormm.7.5 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
46、from theaverage diameter and length. Alternatively, determine thedensity from the mass in air and submerged mass in accordancewith Test Method C 642. After submerged weighing, dry coresin accordance with 7.3.2 and store in sealed plastic bags ornonabsorbent containers for at least 5 days before test
47、ing.7.6 CappingIf the ends of the cores do not conform to theperpendicularity and planeness requirements of Test MethodC 39/C 39M, they shall be sawed or ground to meet thoserequirements or capped in accordance with Practice C 617. Ifcores are capped in accordance with Practice C 617, thecapping dev
48、ice shall accommodate actual core diameters andproduce caps that are concentric with the core ends. Measurecore lengths to the nearest 0.1 in. 2 mm before capping.Unbonded caps in accordance with Practice C 1231/C 1231Mare not permitted.7.7 MeasurementBefore testing, measure the length of thecapped
49、or ground specimen to the nearest 0.1 in. 2 mm 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 0.01 in.0.2 mm when the difference in core diameters does notexceed 2 % of their average, otherwise measure to the nearest0.1 in. 2 mm. Do not test cores if the difference between thelargest and smallest diameter exceeds 5 % of their average.7.8 TestingTest the spec
