1、Designation: A 944 05Standard Test Method forComparing Bond Strength of Steel Reinforcing Bars toConcrete Using Beam-End Specimens1This standard is issued under the fixed designation A 944; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method describes procedures to establish therelative bond strength of steel reinforcing
3、 bars in concrete.1.2 This test method is intended to determine the effects ofsurface preparation or condition (such as bar coatings) on thebond strength of deformed steel reinforcing bars (of sizesranging from No. 10 to No. 36 No. 3 to No. 11) to concrete.1.3 The bond strengths obtained using this
4、test method arenot directly applicable to the design of reinforced concretemembers.NOTE 1The bond strengths obtained using this test method aregenerally higher than obtained in development or splice tests using beamswith the same embedment lengths. The results obtained using this testmethod should o
5、nly be used for comparisons with results for otherreinforcing bars tested using this method.1.4 The values stated in SI units are to be regarded as thestandard. The values given in brackets are for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, asso
6、ciated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 775/A 775M Specification for Epoxy-Coated Steel Rein-fo
7、rcing BarsC 192/C 192M Practice for Making and Curing ConcreteTest Specimens in the LaboratoryE4 Practices for Force Verification of Testing MachinesE 575 Practice for Reporting Data from Structural Tests ofBuilding Constructions, Elements, Connections, and As-semblies3. Terminology3.1 Definitions o
8、f Terms Specific to This Standard:3.1.1 bond strength, nmaximum measured load in atensile bond test of a steel reinforcing bar.3.1.2 bonded length, nthe length of the test bar that is incontact with concrete.3.1.3 concrete cover, nminimum distance between thesurface of the test bar and the top or bo
9、ttom of the testspecimen.3.1.4 embedment length, nthe distance from the surface ofthe concrete test specimen to the installed end of the steelreinforcing bar. This equals the sum of the lead length and thebonded length.3.1.5 lead length, nthe length of the test bar that is not incontact with concret
10、e but is between the surface of the concretetest specimen and the bonded length.3.1.6 relative rib area, nratio of the projected rib areanormal to bar axis to the product of the nominal bar perimeterand the center-to-center rib spacing.3.2 Symbols:Cb= Concrete cover, mm in.db= Nominal diameter of re
11、inforcing bar, mm in.le= Embedment length, mm in.4. Apparatus4.1 EquipmentA schematic of a suitable testing system isshown in Fig. 1. The loading system shall be capable ofmeasuring the forces to an accuracy within 62 % of theapplied load, when calibrated in accordance with Practices E4.The test sys
12、tem shall have sufficient capacity to preventyielding of its various components and shall ensure that theapplied tensile load remains parallel to the axis of the steelreinforcing bar during testing.4.2 Compression Reaction PlateThe compression reac-tion plate shall be placed a minimum clear distance
13、 equal to 0.9lemeasured from the center of the test bar to the edge of thereaction plate.4.3 Bar Displacement MeasurementsDisplacements ofthe loaded and free ends of the steel reinforcing bar shall bemeasured with respect to the loaded and free surfaces, respec-tively, of the concrete using suitable
14、 measurement devices.Dial gages having the smallest division of not more than 25 m1This test method is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel, and Related Alloys and is the direct responsibility of SubcommitteeA01.05 on Steel Reinforcement.Current edition approved Oct.
15、 1, 2005. Published October 2005. Originallyapproved in 1995. Last previous edition approved in 2004 as A 944 99 (2004).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
16、 to the standards Document Summary page onthe ASTM website.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, United States.0.001 in. or linear variable differential transformers (LVDT
17、s)with equal or superior accuracy are examples of satisfactorydevices.5. Test Specimen5.1 Beam-End SpecimenThe test specimen shall consistof the test bar cast in a block of reinforced concrete 600 6 25mm 24 6 1 in. long by db+ 200 6 13 mm db+8612 in.wide by a minimum of db+Cb+le+60mmdb+Cb+le+212in.
18、high. A typical test specimen is illustrated in Fig. 2. Thespecimen shall be reinforced by four closed stirrups orientedparallel to the sides of the specimen and two flexural steelreinforcing bars parallel to the test bar, as shown in Fig. 2.Transverse steel reinforcing bars similar to those illustr
19、ated inFig. 2 may be used to aid in fabrication and testing. The test barshall extend from the front surface a distance that is compatiblewith the test system. Two polyvinyl chloride (PVC) pipes shallbe used as bond breakers to control the bonded length of thebar and to avoid a localized cone-type f
20、ailure of the concrete atthe loaded end of the specimen. The free end of the test barshall butt against a hollow steel conduit or other device toprovide access to the free end for measuring slip during thetest. The closed stirrups shall be fabricated from Grade 420Grade 60 No. 10 No. 3 bars for test
21、 bars up to and includingNo. 25 No. 8 and No. 13 No. 4 bars for test bars larger thanNo. 25 No. 8. The two flexural steel reinforcing bars shall beselected so as to provide a total area not less than that of the testbar.NOTE 2The lead length, shown in Fig. 2, is typically between 13 and100 mm 0.5 an
22、d 4 in. This unbonded region is used to prevent acone-type pullout failure at the surface of the concrete. Increases in leadlength generally result in an increase in bond strength.5.2 FabricationThe concrete block shall be fabricatedusing concrete designed to produce a strength at the time of testbe
23、tween 31 and 38 MPa 4500 and 5500 psi. The specimenshall be cast in approximately equal layers not exceeding 250FIG. 1 Schematic of Test ApparatusA944052mm 9 in. in depth. Each layer shall be adequately consoli-dated with an internal vibrator to ensure removal of entrappedair.NOTE 3The nominal maxim
24、um size course aggregate should be lessthan or equal to34 of the minimum clear space between reinforcement orbetween reinforcement and the concrete surface of the beam-end speci-men.NOTE 4The properties of concrete tend to vary, even for concretefrom a single ready-mix truck. Therefore, the order of
25、 casting specimensshould be selected to limit differences in bond strength caused bydifferences in concrete from different portions of the same batch. Forexample, when this test is used to evaluate the effect of epoxy coatings onbond strength, as required by Specification A 775/A 775M, specimenscont
26、aining epoxy-coated bars and uncoated bars should be alternatedduring casting.6. Conditioning6.1 Specimen Conditioning and CuringThe test specimenshall be cured in the forms using a curing compound or aplastic membrane, or both, to prevent rapid evaporation ofwater until the concrete has attained a
27、strength of at least 14MPa 2000 psi. Specimen conditioning and curing shall besuch that the concrete strength shall be between 31 and 38 MPa4500 and 5500 psi at the time of test, unless another concretestrength is required. Standard concrete cylinders shall beprepared in accordance with Practice C 1
28、92 using a represen-tative sample of the concrete used to make the test specimen.The concrete cylinders shall be cured adjacent to and in thesame manner as the test specimen. A minimum of two testcylinders are required.7. Procedure7.1 A tensile load shall be applied to the test bar, asillustrated in
29、 Fig. 1. The loading rate shall be such that failurewill not occur prior to 3 min after starting to load the testspecimens. Data recorded for a test shall include, as a mini-mum, the initial load and displacement readings and themaximum load.NOTE 5The load rate should be between 10 to 33 % of the bo
30、ndstrength per min. At least 10 intermediate displacement and load readingsshould be taken.FIG. 2 Beam-End Test SpecimensA9440538. Report8.1 The report shall include the applicable informationlisted in Practice E 575, and shall specifically include thefollowing:8.1.1 Dates of test and report,8.1.2 T
31、est sponsor and agency,8.1.3 Identification of the bars tested: size, grade, meandeformation height, mean deformation spacing, and, if re-quired, the relative rib area,8.1.4 Description of the steel reinforcing bar surface condi-tion and coating (if used): manufacturer, trade name, andcoating design
32、ation,8.1.5 Description of the fabrication and testing procedures,if these deviated in any way from this test method,8.1.6 Description of the concrete used, including mix de-sign, aggregate type, compressive strength at the time of test(average of a minimum of two cylinders), and age of theconcrete
33、at the time of test,8.1.7 Moisture condition of the concrete at the time of test:saturated surface dry, air dry,8.1.8 Concrete cover, embedment length and lead length ofthe installed reinforcement, in mm in.,8.1.9 Description of the test method, loading procedureused, the displacements measured at e
34、ach load step, and theactual rate of loading,8.1.10 Individual maximum load value (bond strength), in Nlb, for each test specimen,8.1.11 Photographs, sketches, word descriptions, or combi-nations thereof, of the failure modes observed, and8.1.12 Summary of findings.9. Precision and Bias9.1 No statem
35、ent is made on the precision or bias of this testmethod since the test results indicate only whether there isconformance to given criteria and since no generally acceptedmethod for determining precision and bias of this test methodis currently available. General guidelines provided herein forthe spe
36、cimens, instrumentation, and procedures make theresults intractable to calculation of meaningful values bystatistical analysis for precision and bias at this time.10. Keywords10.1 beam-end test; coatings; concrete bond; steel reinforc-ing barsSUMMARY OF CHANGESCommittee A01 has identified the locati
37、on of selected changes to this standard since the last issue (A 944 99(2004) that may impact the use of this standard.(1) Added section 1.3 , Note 1, and Note 4.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this sta
38、ndard. 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 and must be revi
39、ewed 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 of theresponsib
40、le 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 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).A944054
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