1、Designation:C42/C42M11 Designation: C42/C42M 12American 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 immedia
2、tely following 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 b
3、een approved 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.NOTE 1Appendix X1 provides recommendations for obtaining and
4、 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 standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from t
5、hetwo systems may result in non-conformance with the standard.1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of the standard.1.4 This standard doe
6、s not purport to address the safety concerns, if any, associated with its use. It is the responsibility of theuser of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitationsprior to use.2. Referenced Documents2.1 ASTM Standards:2C3
7、9/C39M Test Method for Compressive Strength of Cylindrical Concrete SpecimensC7878/C78M Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)C174/C174M Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete CoresC496/C496M Test Method for
8、 Splitting Tensile Strength of Cylindrical Concrete SpecimensC617617/C617M Practice for Capping Cylindrical Concrete SpecimensC642 Test Method for Density, Absorption, and Voids in Hardened ConcreteC670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsC
9、823823/C823M Practice for Examination and Sampling of Hardened Concrete in ConstructionsC1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened ConcreteCylindersC1542/C1542M Test Method for Measuring Length of Concrete Cores2.2 ACI Standards:318Building Co
10、de Requirements for Structural Concrete3. Significance and Use3.1 This test method provides standardized procedures for obtaining and testing specimens to determine the compressive,splitting tensile, and flexural strength of in-place concrete.3.2 Generally, test specimens are obtained when doubt exi
11、sts about the in-place concrete quality due either to low strength testresults during construction or signs of distress in the structure. Another use of this method is to provide strength information onolder structures.1This test method is under the jurisdiction of ASTM Committee C09 on Concrete and
12、 Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 onTesting for Strength.Current edition approved Aug. 15, 2011. Published September 2011. Originally approved in 1921. Last previous edition approved in 2010 as C42/C42M10a. DOI:10.1520/C0042_C0042M-11.Current edition approv
13、ed Feb. 1, 2012. Published March 2012. Originally approved in 1921. Last previous edition approved in 2011 as C42/C42M11. DOI:10.1520/C0042_C0042M-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Sta
14、ndardsvolume information, refer to the standards Document Summary page on the ASTM website.1This 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 may not be technically possib
15、le 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 the end of this standard.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.3 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 at the top. Core strength i
17、s 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.3These factors shall beconsidered in planning the locations for obtaining concrete samples and in comparing strength test re
18、sults.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 identical moisture condition as
19、 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 preparation.3.5There is no un
20、iversal relationship between the compressive strength of a core and the corresponding compressive strengthof standard-cured molded cylinders. The relationship is affected by many factors such as the strength level of the concrete, thein-place temperature and moisture history, and the strength gain c
21、haracteristics of the concrete. Historically, it has been assumedthat core strengths are generally 85% of the corresponding standard-cured cylinder strengths, but this is not applicable to allsituations. The acceptance criteria for core strength are to be established by the specifier of the tests.AC
22、I 318 provides core strengthacceptance criteria for new construction.3.63.5 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 relationshi
23、p between the strengths ofthese two types of specimens (see Note 2). 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 t
24、he concrete, the condition of the coring apparatus, and the care used in removing cores.NOTE 2A procedure is available for estimating the equivalent cylinder strength from a measured core strength.4NOTE 3In the absence of core strength requirements of an applicable building code or of other contract
25、ual or legal documents that may govern theproject, the specifier 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 318,5which are used to evaluate cores taken to investigate low st
26、rength test results of standard-cured cylinder duringconstruction. According to ACI 318, the concrete represented by the cores is considered structurally adequate if the average strength of three cores is atleast 85 % of the specified strength and no single core strength is less than 75 % of the spe
27、cified strength.3.6 The “specifier of the tests” referenced in this test method is the individual responsible for analysis or review and acceptanceof core test results.NOTE 4For investigation of low strength test results, ACI 318 defines the specifier of the tests as the licensed design professional
28、.3.7 The apparent compressive strength of concrete 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 d
29、iamond impregnated bits attached to a core barrel.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. Sampl
30、ing5.1 General:5.1.1 Samples of hardened concrete 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 2Note 5 and Note 3Note 6). When pre
31、paring strength test specimens from samples of hardened concrete, samples that have beendamaged during removal shall not be used unless the damaged portion(s) are removed and the lengths of resulting test specimenssatisfy the minimum length-diameter ratio requirement in 7.2. Samples of defective or
32、damaged concrete that cannot be tested shallbe reported along with the reason that prohibits use of the sample for preparing strength test specimens.NOTE2Practice C823 5Practice C823/C823M provides guidance on the development of a sampling plan for concrete in constructions.3Available from American
33、Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094, http:/www.concrete.org.3Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” Concrete International, Vol. 23, No. 11, November 2001, pp. 59-68.4Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” C
34、oncrete International, Vol. 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.5Gaynor, R.D., “Effect of Horizontal Reinforcing Steel o
35、n the Strength of Molded Cylinders,” Problems and Practices in Journal of the American Concrete Institute,Proceedings, Vol. 62, No. 7, July 1965, pp. 837-8405“Building Code Requirements for Structural Concrete and Commentary,” ACI 318, American Concrete Institute, 36 P.O. Box 9094, Farmington Hills,
36、 MI 48333,www.concrete.org.C42/C42M 122NOTE3It 6It is not possible to specify a minimum age when concrete is strong enough to withstand damage during removal, because the strengthat any age depends on the curing history and strength grade of the concrete. If time permits, the concrete should not be
37、removed before it is 14 days old.If this is not practical, removal of concrete can proceed if the cut surfaces do not display erosion of the mortar and the exposed coarse aggregate particlesare embedded firmly in the mortar. In-place test methods may be used to estimate the level of strength develop
38、ment prior to attempting removal ofconcrete samples.5.1.2 Except as provided in 5.1.3, cores containing embedded reinforcement, excluding 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 requ
39、irements of 7.1 and 7.2 and that is free of embeddedreinforcement or other metal, the specifier of the tests is permitted to allow testing of cores with embedded metal (see Note 4Note7). If a core tested for strength contains embedded metal, the size, shape, and location of the metal within the core
40、 shall bedocumented in the test report.NOTE4The 7The presence of steel reinforcement, other than fibers, or other embedded metal in a core can affect the measured strength.6,7Thereare insufficient data to derive reliable correction factors that can be applied to the measured strength to account for
41、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 permit a core to be tested for strength if bar reinforcement, or
42、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. away from formed joints or obvious edges of a unit of deposit
43、 (see Note 58). 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 specimen drilled perpendicular to a vertical surface, orperpendicula
44、r 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 specifier of thetests. Record the date core was drilled. If known, r
45、ecord the date when concrete was placed.NOTE5The 8The intent is to avoid drilling cores in non-representative concrete that may exist near formed joints or the boundary of a unit ofplacement.5.3 Slab RemovalRemove a slab sufficiently large to secure the desired test specimens without the inclusion o
46、f 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 diameter of at least94 mm 3.70 in. when the lengths of such c
47、ores 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 directed by specifier of tests.6.2 For cores that are not intende
48、d 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 Except as provided in 7.1.2, the diameter of core specimen
49、s 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 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.NOTE6The 9The compressive strengths of nominal 50-mm 2-in. diameter cores are
