1、Designation: C42/C42M 12C42/C42M 13 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 follow
2、ing 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.This standard has been approve
3、d for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers obtaining, preparing, and testing cores drilled from concrete for length or compressive strength orsplitting tensile strength determinations. This test method is not applicable to cores from shotcrete.NOTE 1Test
4、Method C1604/C1604M is applicable for obtaining, preparing, and testing cores from shotcrete.NOTE 2Appendix X1 provides recommendations for obtaining and testing sawed beams for flexural performance.1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standar
5、d. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.1.3 The text of this standard references notes and footnotes that provide explanatory
6、 material. These notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of the standard.1.4 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of theuser of this standard to establish ap
7、propriate safety and health practices and determine the applicability of regulatory limitationsprior to use.2. Referenced Documents2.1 ASTM Standards:2C39/C39M Test Method for Compressive Strength of Cylindrical Concrete SpecimensC78/C78M Test Method for Flexural Strength of Concrete (Using Simple B
8、eam with Third-Point Loading)C174/C174M Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete CoresC496/C496M Test Method for Splitting Tensile Strength of Cylindrical Concrete SpecimensC617/C617M Practice for Capping Cylindrical Concrete SpecimensC642 Test Method for Densi
9、ty, Absorption, and Voids in Hardened ConcreteC670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsC823/C823M Practice for Examination and Sampling of Hardened Concrete in ConstructionsC1231/C1231M Practice for Use of Unbonded Caps in Determination of
10、Compressive Strength of Hardened Concrete CylindersC1542/C1542M Test Method for Measuring Length of Concrete CoresC1604/C1604M Test Method for Obtaining and Testing Drilled Cores of Shotcrete3. Significance and Use3.1 This test method provides standardized procedures for obtaining and testing specim
11、ens to determine the compressive,splitting tensile, and flexural strength of in-place concrete.3.2 Generally, test specimens are obtained when doubt exists about the in-place concrete quality due either to low strength testresults during construction or signs of distress in the structure. Another us
12、e of this method is to provide strength information onolder structures.1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 onTesting for Strength.Current edition approved Feb. 1, 2012Jan. 1, 20
13、13. Published March 2012February 2013. Originally approved in 1921. Last previous edition approved in 20112012 asC42/C42M11.12. DOI: 10.1520/C0042_C0042M-12.10.1520/C0042_C0042M-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org
14、. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit m
15、ay not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at t
16、he end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3 Concrete strength is affected by the location of the concrete in a structural element, with the concrete at the bottom tendingto be stronger than the concrete
17、at the top. Core strength is also affected by core orientation relative to the horizontal plane of theconcrete as placed, with strength tending to be lower when measured parallel to the horizontal plane.3 These factors shall beconsidered in planning the locations for obtaining concrete samples and i
18、n comparing strength test results.3.4 The strength of concrete measured by tests of cores is affected by the amount and distribution of moisture in the specimenat the time of test. There is no standard procedure to condition a specimen that will ensure that, at the time of test, it will be inthe ide
19、ntical moisture condition as concrete in the structure. The moisture conditioning procedures in this test method are intendedto provide reproducible moisture conditions that minimize within-laboratory and between-laboratory variations and to reduce theeffects of moisture introduced during specimen p
20、reparation.3.5 The measured compressive strength of a core will generally be less than that of a corresponding properly molded and curedstandard cylinder tested at the same age. For a given concrete, however, there is no unique relationship between the strengths ofthese two types of specimens (see N
21、ote 23). The relationship is affected by many factors such as the strength level of the concrete,the in-place temperature and moisture histories, the degree of consolidation, batch-to-batch variability, the strength-gaincharacteristics of the concrete, the condition of the coring apparatus, and the
22、care used in removing cores.NOTE 3A procedure is available for estimating the equivalent cylinder strength from a measured core strength.4NOTE 4In the absence of core strength requirements of an applicable building code or of other contractual or legal documents that may govern theproject, the speci
23、fier of tests should establish in the project specifications the acceptance criteria for core strengths. An example of acceptance criteria forcore strength is provided in ACI 318,5 which are used to evaluate cores taken to investigate low strength test results of standard-cured cylinder duringconstr
24、uction. According to ACI 318, the concrete represented by the cores is considered structurally adequate if the average strength of three cores is atleast 85 % 85 % of the specified strength and no single core strength is less than 75 % 75 % of the specified strength.3.6 The “specifier of the tests”
25、referenced in this test method is the individual responsible for analysis or review and acceptanceof core test results.NOTE 5For investigation of low strength test results, ACI 318 defines the specifier of the tests as the licensed design professional.3.7 The apparent compressive strength of concret
26、e as measured by a core is affected by the length-diameter ratio (L/D) of thecore as tested and this must be considered in preparing core specimens and evaluating test results.4. Apparatus4.1 Core Drill, for obtaining cylindrical core specimens with diamond impregnated bits attached to a core barrel
27、.4.2 Saw, for trimming ends of cores. The saw shall have a diamond or silicon-carbide cutting edge and shall be capable ofcutting cores without introducing cracks or dislodging aggregate particles.4.3 Balance, accurate to at least 5 g 0.01 lb.5. Sampling5.1 General:5.1.1 Samples of hardened concrete
28、 for use in the preparation of strength test specimens shall not be taken until the concreteis strong enough to permit sample removal without disturbing the bond between the mortar and the coarse aggregate (see Note 56and Note 67). When preparing strength test specimens from samples of hardened conc
29、rete, samples that have been damaged duringremoval shall not be used unless the damaged portion(s) are removed and the lengths of resulting test specimens satisfy theminimum length-diameter ratio requirement in 7.2. Samples of defective or damaged concrete that cannot be tested shall bereported alon
30、g with the reason that prohibits use of the sample for preparing strength test specimens.NOTE 6Practice C823/C823M provides guidance on the development of a sampling plan for concrete in constructions.NOTE 7It is not possible to specify a minimum age when concrete is strong enough to withstand damag
31、e during removal, because the strength atany age depends on the curing history and strength grade of the concrete. If time permits, the concrete should not be removed before it is 14 days old.If this is not practical,practicable, removal of concrete can proceed if the cut surfaces do not display ero
32、sion of the mortar and the exposed coarseaggregate particles are embedded firmly in the mortar. In-place test methods may be used to estimate the level of strength development prior to attemptingremoval of concrete samples.5.1.2 Except as provided in 5.1.3, cores containing embedded reinforcement, e
33、xcluding fibers, or other embedded objects shallnot be used for determining strength of concrete.5.1.3 If it is not possible to prepare a test specimen that meets the requirements of 7.1 and 7.2 and that is free of embeddedreinforcement or other metal, the specifier of the tests is permitted to allo
34、w testing of cores with embedded metal (see Note 78).If a core tested for strength contains embedded metal, the size, shape, and location of the metal within the core shall be documentedin the test report.3 Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” Concrete International, Vo
35、l. 23, No. 11, November 2001, pp. 59-68.4 “Guide for Obtaining Cores and Interpreting Compressive Strength Results,” ACI 214.4R, American Concrete 34 Institute, P.O. Box 9094, Farmington Hills, MI 48333,www.concrete.org.5 “Building Code Requirements for Structural Concrete and Commentary,” ACI 318,
36、American Concrete Institute, 36 P.O. Box 9094, Farmington Hills, MI 48333,www.concrete.org.C42/C42M 132NOTE 8The presence of steel reinforcement, other than fibers, or other embedded metal in a core can affect the measured strength.6,7 There areinsufficient data to derive reliable correction factors
37、 that can be applied to the measured strength to account for embedded reinforcement perpendicularto the core axis. If testing of cores containing embedded reinforcement is permitted, engineering judgment is required to assess the significance of theresults. The specifier of the tests should not perm
38、it a core to be tested for strength if bar reinforcement, or other elongated embedded metal object, isoriented close to parallel to the core axis.5.2 Core DrillingWhen a core will be tested to measure concrete strength, the core shall be drilled perpendicular to the surfaceand at least 150 mm 6 in.
39、away from formed joints or obvious edges of a unit of deposit (see Note 89). This minimum distancedoes not apply to the formed boundaries of structural members. Record the approximate angle between the longitudinal axis ofthe drilled core and the horizontal plane of the concrete as placed. A specime
40、n drilled perpendicular to a vertical surface, orperpendicular to a sloping surface, shall be taken from near the middle of a unit of deposit when possible. If cores are obtainedfor purposes other than determination of strength, drill cores in accordance with the instructions provided by the specifi
41、er of thetests. Record the date core was drilled. If known, record the date when concrete was placed.NOTE 9The intent is to avoid drilling cores in non-representative concrete that may exist near formed joints or the boundary of a unit of placement.5.3 Slab RemovalRemove a slab sufficiently large to
42、 secure the desired test specimens without the inclusion of any concretethat has been cracked, spalled, undercut, or otherwise damaged.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 dia
43、meter of at least94 mm 3.70 in. when the lengths of such cores are stipulated to be measured in accordance with Test Method C174/C174M.When core length for determining the thickness of a member is not required to be measured in accordance with Test MethodC174/C174M, core diameter shall be as directe
44、d by specifier of tests.6.2 For cores that are not intended for determining structural dimensions, measure the longest and shortest lengths on the cutsurface along lines parallel to the core axis. Record the average length to the nearest 5 mm 14 in.7. Cores for Compressive Strength7.1 Diameter7.1.1
45、Except as provided in 7.1.2, the diameter of core specimens for the determination of compressive strength shall be at least94 mm 3.70 in. or at least two times the nominal maximum size of the coarse aggregate, whichever is larger.7.1.2 If limited member thickness makes it impossible to obtain cores
46、with length-diameter ratio (L/D) of at least 1.0 or if cleardistance between reinforcement is limited, core diameters less than 94 mm 3.70 in. are not prohibited. If a core diameter less than94 mm 3.70 in. is used, report the reason.NOTE 10The compressive strengths of nominal 50-mm 2-in. diameter co
47、res are known to be somewhat lower and more variable than those ofnominal 100-mm 4-in. diameter cores. In addition, smaller diameter cores appear to be more sensitive to the effect of the length-diameter ratio.87.2 Length7.2.1 Except as provided in 7.2.2, the preferred length of the capped or ground
48、 specimen is between 1.9 and 2.1 times thediameter. If the ratio of the length to the diameter (L/D) of the core exceeds 2.1, reduce the length of the core so that the ratio ofthe capped or ground specimen is between 1.9 and 2.1. Core specimens with length-diameter ratios equal to or less than 1.75r
49、equire corrections to the measured compressive strength (see 7.9.1). A strength correction factor is not required for L/D greaterthan 1.75.Acore having a maximum length of less than 95 % of its diameter before capping or a length less than its diameter aftercapping, trimming, or end grinding shall not be tested.7.2.2 If the compressive strengths of cores are to be compared with specified strengths based on standard concrete cubes, coresshall be tested with L/D, after end preparation, in the range of 1.00 to 1.05 unless otherwise directed by the spec
