1、Standard Method of Test for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete AASHTO Designation: T 24M/T 24-15 ASTM Designation: C42/C42M-13 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T 24M/T
2、 24-1 AASHTO Standard Method of Test for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete AASHTO Designation: T 24M/T 24-15 ASTM Designation: C42/C42M-13 1. SCOPE 1.1. This test method covers obtaining, preparing, and testing (1) cores drilled from concrete for length or compressive o
3、r splitting tensile strength determinations. This test method is not applicable to cores from shotcrete. Note 1ASTM Test 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
4、flexural performance. 1.2. The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independentl
5、y of the other. Combining values from the two systems may result in nonconformance 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 requirem
6、ents of the standard. 1.4. This standard does not purport to address safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENC
7、ED DOCUMENTS 2.1. AASHTO Standards: R 39, Making and Curing Concrete Test Specimens in the Laboratory T 22, Compressive Strength of Cylindrical Concrete Specimens T 97, Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) T 140, Compressive Strength of Concrete Using Portions o
8、f Beams Broken in Flexure T 148, Measuring Length of Drilled Concrete Cores T 198, Splitting Tensile Strength of Cylindrical Concrete Specimens T 231, Capping Cylindrical Concrete Specimens 2.2. ASTM Standards: C39/C39M, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
9、 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 24M/T 24-2 AASHTO C78/C78M, Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading) C174/174M, Standar
10、d Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete Cores C496/496M, Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens C617/617M, Standard Practice for Capping Cylindrical Concrete Specimens C642, Standard Test Method for Density, Abs
11、orption, and Voids in Hardened Concrete C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials C823/C823M, Standard Practice for Examination and Sampling of Hardened Concrete in Constructions C1231/C1231M, Standard Practice for Use of Unbonded
12、 Caps in Determination of Compressive Strength of Hardened Concrete Cylinders C1542/C1542M, Standard Test Method for Measuring Length of Concrete Cores C1604/C1604M, Standard Test Method for Obtaining and Testing Drilled Cores of Shotcrete 2.3. ACI Standard: ACI 318, Building Code Requirements for S
13、tructural Concrete 3. SIGNIFICANCE AND USE 3.1. This test method provides standardized procedures for obtaining and testing specimens to determine the compressive, splitting tensile, and flexural strength of in-place concrete. Sampling and sample preparation requirements are given to ensure that dim
14、ensional requirements are met and that the specimens are made of intact, sound concrete, and are as free of flaws as the particular structure will allow. 3.2. Generally, test specimens are obtained when doubt exists about the in-place concrete quality due either to too-low strength test results duri
15、ng construction or to signs of distress in the structure. Additionally, this method is used to provide strength information on older structures. 3.3. Concrete strength is affected by the location of the concrete in a structural element, with the concrete at the bottom tending to be stronger than the
16、 concrete at the top. Core strength is also affected by core orientation relative to the horizontal plane of the concrete as placed, with strength tending to be lower when measured parallel to the horizontal plane.1These factors shall be considered in planning the locations for obtaining concrete sa
17、mples and in 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 specimen at the time of test. There is no standard procedure to condition a specimen that will ensure that, at the time of test, it wil
18、l be in the identical moisture condition as concrete in the structure. The moisture conditioning procedures in this test method are intended to provide reproducible moisture conditions that minimize within-laboratory and between-laboratory variations and to reduce the effects of moisture introduced
19、during specimen preparation. 3.5. The measured compressive strength of a core will generally be less than that of a corresponding properly molded and cured standard cylinder tested at the same age. For a given concrete, however, there is no unique relationship between the strength of these two types
20、 of specimens (see Note 3). 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 2015 by the American Association of State Highway and Transportation Officials.All rights
21、reserved. Duplication is a violation of applicable law.TS-3c T 24M/T 24-3 AASHTO variability, the strength-gain characteristics of the concrete, the condition of the coring apparatus, and the care used in removing cores. Note 3A procedure is available for estimating the equivalent cylinder strength
22、from a measured core strength. Note 4In the absence of core strength requirements of an applicable building code or of the other contractual or legal documents that may govern the project, the specifier of the test should establish in the project specifications the acceptance criteria for core stren
23、gth. An example of acceptance criteria core strength is provided in ACI 318, which are used to evaluate cores taken to investigate low strength test results of standard-cured cylinder during construction. According to ACI 318, the concrete represented by the cores is at least 85 percent of the speci
24、fied strength and no single core strength is less than 75 percent of the specified strength. 3.6. The “specifier” of the tests referenced in this test method is the individual responsible for analysis or review and acceptance of the core test results. Note 5For investigation of low strength test res
25、ults, ACI 318 defines the specifier of the test as the licensed design professional. 3.7. The apparent compressive strength of concrete as measured by a core is affected by the length-diameter ratio (L/D) of the core as tested and this must be considered in preparing core specimens and evaluating te
26、st results. 4. APPARATUS 4.1. Core DrillFor obtaining cylindrical core specimens with diamond impregnated bits attached to a core barrel. 4.2. SawFor trimming ends of cores. The saw shall have a diamond or silicon-carbide cutting edge and shall be capable of cutting cores without introducing cracks
27、or dislodging aggregate particles. 4.3. BalanceAccurate to at least 5 g 0.01 lb. 5. SAMPLING 5.1. General: 5.1.1. Samples of hardened concrete for use in the preparation of strength test specimens shall not be taken until the concrete is strong enough to permit sample removal without disturbing the
28、bond between the mortar and the coarse aggregate (see Note 5 and Note 6). When preparing strength test specimens from samples of hardened concrete, samples that have been damaged during removal shall not be used unless the damaged portion(s) are removed and the length of the resulting satisfy the mi
29、nimum length-diameter ratio requirement in 7.2. Samples of defective or damaged concrete that cannot be tested shall be reported along with the reason that prohibits use of the sample for preparing strength test specimen. Note 6ASTM C823/C823M provides guidance on the development of a sampling plan
30、for concrete in constructions. Note 7It is not possible to specify a minimum age when concrete is strong enough to withstand damage during removal, because the strength at any age depends on the curing history and strength grade of the concrete. If time permits, the concrete should not be removed be
31、fore 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 particles are embedded firmly in the mortar. In-place test methods may be used to estimate the level of strength development pri
32、or to attempting removal of concrete samples. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 24M/T 24-4 AASHTO 5.1.2. Except as provided in 5.1.3, cores containing embedded reinforcement, exclud
33、ing fibers, or other embedded objects shall not 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 Sections 7.1 and 7.2 and that is free of embedded reinforcement or other metal, the specifier of the tests is permitted
34、 to allow testing for cores with embedded metal (see Note 8). If a core tested for strength contains embedded metal, the size, shape, and location of the metal within the core shall be documented in the test report. Note 8The presence of steel reinforcement, other than fibers, or other embedded meta
35、l in a core can affect the measured strength. There are insufficient data to derive reliable correction factors that can be applied to the measured strength to account for embedded reinforcement perpendicular to the core axis. If testing of cores containing embedded reinforcement is permitted, engin
36、eering judgment is required to assess the significance of the result. The specifier of the test should not permit a core to be tested for strength if the bar reinforcement, or other elongated embedded metal object, is oriented close to parallel to the core axis. 5.2. Core DrillingWhen a core will be
37、 tested to measure concrete strength, the core shall be drilled perpendicular to the surface and at least 150 mm 6 in. away from formed joints or obvious edges of a concrete pour (see Note 9). This minimum distance does not apply to the formed boundaries of structural members. Record the approximate
38、 angle between the longitudinal axis of the drilled core and the horizontal plane of the concrete as placed. A specimen drilled perpendicular to a vertical surface, or perpendicular to a sloping surface, shall be taken from near the middle of a concrete pour when possible. If cores are obtained for
39、purposes other than determination of strength, drill cores in accordance with the instructions provided by the specifier of the tests. Record the date core was drilled. If known, record the date when concrete was placed. Note 9The intent is to avoid drilling cores in nonrepresentative concrete that
40、may exist near formed joints or the boundary of a concrete pour. 5.3. Slab RemovalRemove a slab sufficiently large to secure the desired test specimens without the inclusion of any concrete that has been cracked, spalled, undercut, or otherwise damaged. DRILLED CORES 6. MEASURING THE LENGTH OF DRILL
41、ED CORE 6.1. Cores for determining the thickness of pavements, slabs, walls or other structural elements shall have a diameter of at least 94 mm 3.70 in when the lengths of such cores are stipulated to be measured in accordance with T 148. When core length for determining the thickness of a member i
42、s not required to be measured in accordance with T 148, core diameter shall be as directed by specifier of test. 6.2. For cores that are not intended for determining structural dimensions, measure the longest and shortest lengths on the cut surface along lines parallel to the core axis. Record the a
43、verage length to the nearest 5 mm 0.25 in. 7. CORES FOR COMPRESSIVE STRENGTH 7.1. Diameter: 7.1.1. Except as provided in Section 7.1.2, the diameter of core specimen for determination of compressive strength shall be at least 94 mm 3.70 in. or at least two times the nominal maximum size of the coars
44、e aggregates, whichever is larger. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 24M/T 24-5 AASHTO 7.1.2. If limited member thickness makes it impossible to obtain cores with length-diameter ra
45、tion (L/D) of at least 1.0 or if clear distance between reinforcement is limited, core diameter less than 94 mm 3.70 in. is not prohibited. If a core diameter less than 94 mm 3.70 in. is used, report the reason. Note 10The compressive strengths of nominal 50-mm 2-in. diameter cores are known to be s
46、omewhat lower and more variable than those of nominal 100-mm 4-in. diameter cores. In addition, small diameter cores appear to be more sensitive to the effect of the length-to-diameter ratio.27.2. Length: 7.2.1. Except as provided in Section 7.2.2, the preferred length of the capped or ground specim
47、en is between 1.9 and 2.1 times the diameter. If the ratio of the length to the diameter (L/D) of the core exceeds 2.1, reduce the length of the cores so that the ratio of the capped or ground specimen is between 1.9 and 2.1. Core specimens with length-diameter ratios equal to or less than 1.75 requ
48、ire corrections to the measured compressive strength (see Section 7.9.1). A strength correction factor is not required for L/D greater than 1.75. A core having a maximum length less than its diameter after capping, trimming, or end grinding shall not be tested. 7.2.2. If the compressive strength of
49、the cores are to be compared with specified strength based on the standard concrete cubes, cores shall be tested with L/D, after end preparation, in the range of 1.00 to 1.05 unless otherwise directed by the specifier of the tests. If the strength of the cores with L/D = 1 are to be compared with specified concrete cube strength, do not apply the correction factor in Section 7.9.1. 7.3. Moisture ConditioningTest cores after moisture conditioning as specified in this test method or as directed by the specifier of
