1、Designation: C 805 02Standard Test Method forRebound Number of Hardened Concrete1This standard is issued under the fixed designation C 805; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pare
2、ntheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 a reboundnumber of h
3、ardened concrete using a spring-driven steelhammer.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pri
4、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 125 Terminology Relating to Concrete and ConcreteAggregates2C 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction
5、Materials2E 18 Test Methods for Rockwell and Rockwell SuperficialHardness of Metallic Materials33. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminology C 125.4. Summary of Test Method4.1 A steel hammer impacts, with a predetermined amountof energy,
6、a steel plunger in contact with a surface of concrete,and the distance that the hammer rebounds is measured.5. Significance and Use5.1 This test method is applicable to assess the in-placeuniformity of concrete, to delineate regions in a structure ofpoor quality or deteriorated concrete, and to esti
7、mate in-placestrength development.5.2 To use this test method to estimate strength requiresestablishing a relationship between strength and reboundnumber. The relationship shall be established for a givenconcrete mixture and given apparatus. The relationship shall beestablished over the range of con
8、crete strength that is ofinterest. To estimate strength during construction, establish therelationship by performing rebound number tests on moldedspecimens and measuring the strength of the same or compan-ion molded specimens. To estimate strength in an existingstructure, establish the relationship
9、 by correlating reboundnumbers measured on the structure with the strengths of corestaken from corresponding locations. See ACI 228.1R4foradditional information on developing the relationship and onusing the relationship to estimate in-place strength.5.3 For a given concrete mixture, the rebound num
10、ber isaffected by factors such as moisture content of the test surface,the method used to obtain the test surface (type of formmaterial or type of finishing), and the depth of carbonation.These factors need to be considered in preparing the strengthrelationship and interpreting test results.5.4 Diff
11、erent hammers of the same nominal design may giverebound numbers differing from 1 to 3 units. Therefore, testsshould be made with the same hammer in order to compareresults. If more than one hammer is to be used, perform tests ona range of typical concrete surfaces so as to determine themagnitude of
12、 the differences to be expected.5.5 This test method is not intended as the basis foracceptance or rejection of concrete because of the inherentuncertainty in the estimated strength.6. Apparatus6.1 Rebound Hammer, consisting of a spring-loaded steelhammer that when released strikes a steel plunger i
13、n contactwith the concrete surface. The spring-loaded hammer musttravel with a consistent and reproducible velocity. The rebound1This test method is under the jurisdiction of ASTM Committee C09 onConcrete and Concrete Aggregates and is the direct responsibility of SubcommitteeC09.64 on Nondestructiv
14、e and In-Place Testing .Current edition approved July 10, 2002. Published August 2002. Originallypublished as C 805 75 T. Last previous edition C 805 97.2Annual Book of ASTM Standards, Vol 04.02.3Annual Book of ASTM Standards, Vol 03.01.4ACI 228.1R-95, “In-Place Methods to Estimate Concrete Strength
15、,” ACIManual of Concrete Practice-Part 2, 2000, American Concrete Institute, 38800Country Club Drive, Farmington Hills, MI 48331.1*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, Unit
16、ed States.distance of the steel hammer from the steel plunger is measuredon a linear scale attached to the frame of the instrument.NOTE 1Several types and sizes of rebound hammers are commer-cially available to accommodate testing of various sizes and types ofconcrete construction.6.2 Abrasive Stone
17、, consisting of medium-grain texturesilicon carbide or equivalent material.6.3 Test Anvil, approximately 150-mm (6-in.) diameter by150-mm (6-in.) high cylinder made of tool steel with an impactarea hardened to 66 6 2 HRC as measured by Test MethodsE 18. An instrument guide is provided to center the
18、reboundhammer over the impact area and keep the instrument perpen-dicular to the surface.6.4 VerificationRebound hammers shall be serviced andverified annually and whenever there is reason to question theirproper operation. Verify the functional operation of a reboundhammer using the test anvil desc
19、ribed in 6.3. During verifica-tion, support the test anvil on a bare concrete floor or slab. Themanufacturer shall report the rebound number to be obtainedby a properly operating instrument when tested on an anvil ofspecified hardness.NOTE 2Typically, a rebound hammer will result in a rebound number
20、of 80 6 2 when tested on the anvil described in 6.3. The test anvil needsto be supported on a rigid base to obtain reliable rebound numbers.Verification on the test anvil does not guarantee that the hammer will yieldrepeatable data at other points on the scale. The hammer can be verifiedat lower reb
21、ound numbers by using blocks of polished stone havinguniform hardness. Some users compare several hammers on concrete orstone surfaces encompassing the usual range of rebound numbers encoun-tered in the field.7. Test Area and Interferences7.1 Selection of Test SurfaceConcrete members to betested sha
22、ll be at least 100 mm (4 in.) thick and fixed within astructure. Smaller specimens must be rigidly supported. Avoidareas exhibiting honeycombing, scaling, or high porosity. Donot compare test results if the form material against which theconcrete was placed is not similar (see Note 3). Troweledsurfa
23、ces generally exhibit higher rebound numbers thanscreeded or formed finishes. If possible, test structural slabsfrom the underside to avoid finished surfaces.7.2 Preparation of Test SurfaceA test area shall be at least150 mm (6 in.) in diameter. Heavily textured, soft, or surfaceswith loose mortar s
24、hall be ground flat with the abrasive stonedescribed in 6.2. Smooth-formed or troweled surfaces do nothave to be ground prior to testing (see Note 3). Do not compareresults from ground and unground surfaces.NOTE 3Where formed surfaces were ground, increases in reboundnumber of 2.1 for plywood formed
25、 surfaces and 0.4 for high-densityplywood formed surfaces have been noted.5Dry concrete surfaces givehigher rebound numbers than wet surfaces. The presence of surfacecarbonation can also result in higher rebound numbers.6The effects ofdrying and surface carbonation can be reduced by thoroughly wetti
26、ng thesurface for 24 h prior to testing. In cases of a thick layer of carbonatedconcrete, it may be necessary to remove the carbonated layer in the testarea, using a power grinder, to obtain rebound numbers that are represen-tative of the interior concrete. Data are not available on the relationship
27、between rebound number and thickness of carbonated concrete. The usermust exercise professional judgment when testing carbonated concrete.7.3 Do not test frozen concrete.NOTE 4Moist concrete at 0 C (32 F) or less may exhibit highrebound values. Concrete should be tested only after it has thawed. The
28、temperatures of the rebound hammer itself may affect the reboundnumber. Rebound hammers at -18 C (0 F) may exhibit rebound numbersreduced by as much as 2 or 37.7.4 For readings to be compared, the direction of impact,horizontal, downward, upward, or at another angle, must be thesame or established c
29、orrection factors shall be applied to thereadings.7.5 Do not conduct tests directly over reinforcing bars withcover less than 20 mm 0.75 in.NOTE 5The location of reinforcement may be established usingreinforcement locators or metal detectors. Follow the manufacturersinstructions for proper operation
30、 of such devices.8. Procedure8.1 Hold the instrument firmly so that the plunger isperpendicular to the test surface. Gradually push the instrumenttoward the test surface until the hammer impacts. After impact,maintain pressure on the instrument and, if necessary, depressthe button on the side of the
31、 instrument to lock the plunger inits retracted position. Read the rebound number on the scale tothe nearest whole number and record the rebound number. Taketen readings from each test area. No two impact tests shall becloser together than 25 mm (1 in.). Examine the impressionmade on the surface aft
32、er impact, and if the impact crushes orbreaks through a near-surface air void disregard the readingand take another reading.9. Calculation9.1 Discard readings differing from the average of 10readings by more than 6 units and determine the average of theremaining readings. If more than 2 readings dif
33、fer from theaverage by 6 units, discard the entire set of readings anddetermine rebound numbers at 10 new locations within the testarea.10. Report10.1 Report the following information for each test area:10.1.1 Date and time of testing.10.1.2 Identification of location tested in the concrete con-stru
34、ction and the type and size of member tested,10.1.2.1 Description of the concrete mixture proportionsincluding type of coarse aggregates if known, and10.1.2.2 Design strength of concrete tested.10.1.3 Description of the test area including:10.1.3.1 Surface characteristics (trowelled, screeded) ofare
35、a,10.1.3.2 If surface was ground and depth of grinding,5Gaynor, R. D., “In-Place Strength of ConcreteA Comparison of Two TestSystems,” and “Appendix to Series 193,” National Ready Mixed Concrete Assn.,TIL No. 272, November 1969.6Zoldners, N. G., “Calibration and Use of Impact Test Hammer,” Proceedin
36、gs,American Concrete Institute, Vol 54, August 1957, pp. 161165.7National Ready Mixed Concrete Assn., TIL No. 260, April 1968.C 805210.1.3.3 Type of form material used for test area,10.1.3.4 Curing conditions of test area,10.1.3.5 Type of exposure to the environment,10.1.4 Hammer identification and
37、serial number,10.1.4.1 Air temperature at the time of testing,10.1.4.2 Orientation of hammer during test,10.1.5 Average rebound number for test area, and10.1.5.1 Remarks regarding discarded readings of test dataor any unusual conditions.11. Precision and Bias11.1 PrecisionThe single-specimen, single
38、-operator, ma-chine, day standard deviation is 2.5 units (1s) as defined inPractice C 670. Therefore, the range of ten readings should notexceed 12.11.2 BiasThe bias of this test method cannot be evaluatedsince the rebound number can only be determined in terms ofthis test method.12. Keywords12.1 co
39、ncrete; in-place strength; nondestructive testing; re-bound hammer; rebound numberSUMMARY OF CHANGESThe following changes to this test method have been incorporated since the last issue, C 80597.(1) Section 3 on Terminology has been added.(2) Nonmandatory language in various sections has beenreplace
40、d with mandatory language. Some nonmandatory lan-guage has been moved into a note or into the Significance andUse section.(3) The hardness of the test anvil has been revised to correct anerror in the previous issue.(4) The verification procedure has been moved to the Appara-tus section and more guid
41、ance has been provided.(5) Section 7.5 has been added to prevent testing directly overreinforcement with shallow cover.(6) Spelling and grammatical errors have been corrected.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentio
42、nedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee an
43、d must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting o
44、f theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box
45、 C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C 8053
