1、Designation: C805/C805M 08C805/C805M 13Standard Test Method forRebound Number of Hardened Concrete1This standard is issued under the fixed designation C805/C805M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers the determination of
3、 a rebound number of hardened concrete using a spring-driven steel hammer.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 ot
4、her. Combining values from thetwo systems may result in non-conformance with the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practic
5、es and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C42/C42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of ConcreteC125 Terminology Relating to Concrete and Concrete AggregatesC670 Practice for Preparing Precisi
6、on and Bias Statements for Test Methods for Construction MaterialsE18 Test Methods for Rockwell Hardness of Metallic Materials3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, refer to Terminology C125.4. Summary of Test Method4.1 A steel hammer impacts, with a p
7、redetermined amount of energy, a steel plunger in contact with a surface of concrete, andthe distance that the hammer rebounds is measured.5. Significance and Use5.1 This test method is applicable to assess the in-place uniformity of concrete, to delineate regions in a structure of poorerquality or
8、deteriorated concrete,variations in concrete quality throughout a structure, and to estimate in-place strength.strength ifa correlation is developed in accordance with 5.4.5.2 For a given concrete mixture, the rebound number is affected by factors such as moisture content of the test surface, the ty
9、peof form material or type of finishing used in construction of the surface to be tested, vertical distance from the bottom of a concreteplacement, and the depth of carbonation. These factors need to be considered in interpreting rebound numbers.5.3 Different instruments of the same nominal design m
10、ay give rebound numbers differing from 1 to 3 units. Therefore, testsshould be made with the same instrument in order to compare results. If more than one instrument is to be used, performcomparative tests on a range of typical concrete surfaces so as to determine the magnitude of the differences to
11、 be expected in thereadings of different instruments.1 This test method is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.64 onNondestructive and In-Place Testing.Current edition approved Aug. 1, 2008Jan. 1, 2013.
12、 Published September 2008January 2013. Originally approved in 1975. Last previous edition approved in 20022008as C805 02.C805 08. DOI: 10.1520/C0805_C0805M-08.10.1520/C0805_C0805M-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.o
13、rg. 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
14、 may 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
15、 the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.4 Relationships between rebound number and concrete strength that are provided by instrument manufacturers shall be usedonly to provide indications of relative
16、 concrete strength at different locations in a structure. To use this test method to estimatestrength, it is necessary to establish a relationship between strength and rebound number for a given concrete mixture and givenapparatus. apparatus (see Note 1). Establish the relationship by correlating re
17、bound numbers measured on the structure with themeasured strengths of cores taken from corresponding locations. locations (see Note 2). At least two replicate cores shall be takenfrom at least six locations with different rebound numbers. Select test locations so that a wide range of rebound numbers
18、 in thestructure is obtained. Obtain, moisture condition, prepare, and test cores in accordance with Test Method C42/C42M. If therebound number if affected by the orientation of the instrument during testing, the strength relationship is applicable for the sameorientation as used to obtain the corre
19、lation date (see Note 3). Locations where strengths are to be estimated using the developedcorrelation shall have similar surface texture and shall have been exposed to similar conditions as the locations where correlationcores were taken. The functionality of the rebound hammer shall have been veri
20、fied in accordance with 6.4 before making thecorrelation measurements.NOTE 1See ACI 228.1R3 for additional information on developing the relationship and on using the relationship to estimate in-place strength.5.3 For a given concrete mixture, the rebound number is affected by factors such as moistu
21、re content of the test surface, themethod used to obtain the test surface (type of form material or type of finishing), vertical distance from the bottom of a concreteplacement, and the depth of carbonation. These factors need to be considered in interpreting rebound numbers.NOTE 2The use of molded
22、test specimens to develop a correlation may not provide a reliable relationship because the surface texture and depth ofcarbonation of molded specimens are not usually representative of the in-place concrete.5.4 Different hammers of the same nominal design may give rebound numbers differing from 1 t
23、o 3 units. Therefore, testsshould be made with the same hammer in order to compare results. If more than one hammer is to be used, perform tests on a rangeof typical concrete surfaces so as to determine the magnitude of the differences to be expected.NOTE 3The use of correction factors to account fo
24、r instrument orientation may reduce the reliability of strength estimates if the correlation isdeveloped for a different orientation than used for testing.5.5 This test method is not suitable as the basis for acceptance or rejection of concrete.6. Apparatus6.1 Rebound Hammer, consisting of a spring-
25、loaded steel hammer that when released strikes a steel plunger in contact with theconcrete surface. The spring-loaded hammer must travel with a consistent and reproducible velocity. The rebound distance of thesteel hammer from the steel plunger is measured on a linear scale attached to the frame of
26、the instrument.NOTE 4Several types and sizes of rebound hammers are commercially available to accommodate testing of various sizes and types of concreteconstruction.6.1.1 The manufacturer shall supply rebound number correction factors for instruments that require such a factor to account forthe orie
27、ntation of the instrument during a test. The correction factor is permitted to be applied automatically by the instrument. Themanufacturer shall keep a record of test data used as the basis for applicable correction factors.6.2 Abrasive Stone, consisting of medium-grain texture silicon carbide or eq
28、uivalent material.6.3 TestVerification Anvil, approximately 150-mm 6-in. diameter by 150-mm 6-in. high cylinder made of tool steel with animpact area hardened to 66 6 2 HRC as measured by Test Methods used to check the operation of the rebound hammer. E18. Aninstrument guide is provided to center th
29、e rebound hammer over the impact area and keep the instrument perpendicular to thesurface.anvil surface. The anvil shall be constructed so that it will result in a rebound number of at least 75 for a properly operatinginstrument (see Note 5). The manufacturer of the rebound hammer shall stipulate th
30、e type of verification anvil to be used and shallprovide the acceptable range of rebound numbers for a properly operating instrument. The anvil manufacturer shall indicate howthe anvil is to be supported for verification tests of the instrument, and shall provide instructions for visual inspection o
31、f the anvilsurface for surface wear.NOTE 5A suitable anvil has included an approximately 150 mm 6 in. diameter by 150 mm 6 in. tall steel cylinder with an impact area hardenedto an HRC hardness value of 64 to 68 as measured by Test Methods E18.6.4 VerificationRebound hammers shall be serviced and ve
32、rified annually and whenever there is reason to question theirproper operation. Verify the functional operation of a rebound hammer using the testverification anvil described in 6.3. Duringverification, support the test anvil on a bare concrete floor or slab. The manufacturer shall report the reboun
33、d number to be obtainedby a properly operating instrument when tested on an anvil of specified hardness.anvil as instructed by the anvil manufacturer.NOTE 6Typically, a rebound hammer will properly operating rebound hammer and a properly designed anvil should result in a rebound number of80 6 2 when
34、 tested on the anvil described in about 80. 6.3. The test anvil needs to be supported on a rigid base as stated by the anvil manufacturer toobtain reliable rebound numbers. Verification on the test anvil does not guarantee that the hammer will yield repeatable data rebound numbers at other3 ACI 228.
35、1R-95,228.1R, “In-Place Methods to Estimate Concrete Strength,” American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333-9094,http:/www.concrete.org.C805/C805M 132points on the scale. The At the users option, the rebound hammer can be verified at lower rebound numbers by using bl
36、ocks of polished stone havinguniform hardness. Some users compare several hammers on concrete or stone surfaces encompassing the usual range of rebound numbers encounteredin the field.7. Test Area and Interferences7.1 Selection of Test SurfaceConcrete members to be tested shall be at least 100 mm 4
37、in. thick and fixed within a structure.Smaller specimens must be rigidly supported.Avoid areas exhibiting honeycombing, scaling, or high porosity. Do not compare testresults if the form material against which the concrete was placed is not similar (see Note 47). Troweled surfaces generally exhibithi
38、gher rebound numbers than screeded or formed finishes. If possible, test structural slabs from the underside to avoid finishedsurfaces.7.2 Preparation of Test SurfaceAtest area shall be at least 150 mm 6 in. in diameter. Heavily textured, soft, or surfaces withloose mortar shall be ground flat with
39、the abrasive stone described in 6.2. Smooth-formed or troweled surfaces do not have to beground prior to testing (see Note 47). Do not compare results from ground and unground surfaces. Remove free surface water, ifpresent, before testing.NOTE 7Where formed surfaces were ground, increases in rebound
40、 number of 2.1 for plywood formed surfaces and 0.4 for high-density plywoodformed surfaces have been noted.4 Dry concrete surfaces give higher rebound numbers than wet surfaces. The presence of surface carbonation can alsoresult in higher rebound numbers.5 In cases of a thick layer of carbonated con
41、crete, it may be necessary to remove the carbonated layer in the test area,using a power grinder, to obtain rebound numbers that are representative of the interior concrete. Data are not available on the relationship betweenrebound number and thickness of carbonated concrete. The user should exercis
42、e professional judgment when testing carbonated concrete.7.3 Do not test frozen concrete.NOTE 8Moist concrete at 0 C 32 F or less may exhibit high rebound values. Concrete should be tested only after it has thawed. The temperaturesof the rebound hammer itself may affect the rebound number. Rebound h
43、ammers at -18 C 0 F may exhibit rebound numbers reduced by as much as2 or 3 units6.7.4 For readings to be compared, the direction of impact, horizontal, downward, upward, or at another angle, must be the sameor established correction factors shall be applied to the readings.7.5 Do not conduct tests
44、directly over reinforcing bars with cover less than 20 mm 0.75 in.NOTE 9The location of reinforcement may be established using reinforcement locators or metal detectors. Follow the manufacturers instructions forproper operation of such devices.8. Procedure8.1 Hold the instrument firmly so that the p
45、lunger is perpendicular to the test surface. Record the orientation of the instrumentwith respect to horizontal to the nearest 45 degree increment. Use a positive angle if the instrument points upward and a negativeangle if it points downward with respect to horizontal during testing (see Note 10).
46、Gradually push the instrument toward the testsurface until the hammer impacts. After impact, maintain pressure on the instrument and, if necessary, depress the button on theside of the instrument to lock the plunger in its retracted position. Read and record the rebound number on the scale to the ne
47、arestwhole number and record the rebound number. Take ten readings from each test area. No two impact tests shall be closer togetherthan The distances between impact points shall be at least 25 mm 1 in., and the distance between impact points and edges of themember shall be at least 50 mm 2 in. Exam
48、ine the impression made on the surface after impact, and if the impact crushes orbreaks through a near-surface air void disregard the reading and take another reading.NOTE 10Digital angle gages are available that can be attached to the body of the instrument to allow quick measurement of the angle w
49、ith respectto horizontal. The recorded orientation would be 0 degrees (horizontal), 645 degrees (inclined), or 690 (vertical). For example, if the instrument pointsvertically down during a test, the angle would be reported as 90 degrees. If the angle is measured to be 55 degrees upward from horizontal, the recordedangle to the nearest 45 degree increment would be +45 degrees.9. Calculation9.1 Discard readings differing from the average of 10 readings by more than 6 units and determine the average of the remainingreadings. If more than
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