ASTM A981 A981M-2011 Standard Test Method for Evaluating Bond Strength for 0 600-in [15 24-mm] Diameter Steel Prestressing Strand Grade 270 [1860] Uncoated Used in Prestressed Grou.pdf

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1、Designation: A981/A981M 11Standard Test Method forEvaluating Bond Strength for 0.600-in. 15.24-mm DiameterSteel Prestressing Strand, Grade 270 1860, Uncoated,Used in Prestressed Ground Anchors1This standard is issued under the fixed designation A981/A981M; the number immediately following the design

2、ation indicates the yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes proce

3、dures to establish therelative bond strength of 0.600-in. 15.24-mm diameter, Grade270 1860 steel prestressing strand in cement grout as used inprestressed ground anchors for the purpose of evaluating theeffects of manufacturing practices on bond strength.1.2 The bond strength values obtained are not

4、 intended to beused to design the bond length of ground anchors that dependon field conditions.1.3 This test method is not intended to be used as a bond testfor prestressed concrete applications.1.4 The values stated in either inch-pound or SI units are tobe regarded as standard. Within the text, th

5、e SI units are shownin brackets. The values stated in each system may not be exactequivalents; therefore, each system shall be used independentlyof the other. Combining values from the two systems mayresult in non-conformance with the standard.1.5 This standard does not purport to address all of the

6、safety concerns, if any, associated 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:2A416/A416M Specification for

7、 Steel Strand, UncoatedSeven-Wire for Prestressed ConcreteC150 Specification for Portland CementC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC1019 Test Method for Sampling and Testing GroutE4 Practices f

8、or Force Verification of Testing Machines3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 bond strengthmaximum measured load in a pull teston a 0.600-in. 15.24-mm diameter steel prestressing strandembedded in cement grout.3.1.2 bonded lengththe length of the test strand that is

9、 incontact with the cement grout.4. Apparatus4.1 EquipmentA suitable tensile testing machine or loadframe shall be used. The loading system shall be calibrated inaccordance with Practices E4. The test system shall havesufficient capacity to prevent yielding of its various compo-nents and shall ensur

10、e that the applied tensile load remainsparallel to the axis of the steel prestressing strand duringtesting.4.2 Strand Displacement MeasurementsDisplacements ofthe free end of the steel prestressing strand shall be measuredwith respect to the loaded surface of the test specimen usingsuitable measurem

11、ent devices. Dial gages having the smallestdivision of not more than 0.001 in. 25 m or linear variabledifferential transformers (LVDTs) with equal or superior accu-racy are examples of satisfactory devices.5. Strand Bond Test Specimen5.1 Steel Prestressing StrandStrand shall be 0.600-in.15.24-mm dia

12、meter, Grade 270 1860 and comply withSpecification A416/A416M and shall be cut from standardproduction coils prior to packaging. The surface of the testsamples shall not be wiped or cleaned in order to preserve theiroriginal condition. Minimum recommended sample length is30 in. 750 mm.1This test met

13、hod 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 April 1, 2011. Published May 2011. Originallyapproved in 1997. Last previous edition approved in 2007

14、 as A981 97 (2007).DOI: 10.1520/A0981_A098M-11.2For 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 to the standards Document Summary page onthe ASTM website.1Copyright AST

15、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Test Specimen FabricationThe test specimen shallconsist of the steel prestressing strand embedded in cementgrout and centered inside a steel pipe, 5-in. 125-mm O.D.with a 0.125-in. 3-mm thick wal

16、l, 18-in. 450-mm long witha 6 by 6 by 0.25 in. 150 by 150 by 6 mm base plate weldedto one end of the steel pipe, or otherwise attached with aleakproof connection. Other mold designs, including reusablemolds, shall be permitted, provided that the dimensions andconfinement in regard to circumferential

17、 stress provided for thegrout body are the same. A 0.625-in. 16-mm diameter holeshall be provided in the base plate to allow the strand to passthrough. A 2-in. 50-mm long debonding tube (Note 1) shallbe positioned on the strand above the base plate and the strandshall protrude at least 2 6 0.5 in. 5

18、0 6 10 mm from the topof the grouted steel tube. A typical test specimen is illustratedin Fig. 1.NOTE 1Polyethylene, trademark Styrofoam,3or similar material arecommonly used for this purpose.5.3 Test Specimen PreparationThe untensioned strandsample shall be installed and centered inside the steel p

19、ipe asshown in Fig. 1. A sealing agent shall be applied around thehole in the base plate to prevent leakage of grout from thesample during casting.5.3.1 The grout shall be made solely from fresh portlandcement conforming to Specification C150, Type I with awater/cement ratio of 0.45, by weight. Wate

20、r shall be potable.The cement shall be added to the water. Mixing of the groutshall continue until the grout is free of lumps and undispersedcement. The grout then shall be poured into the steel tube tocompletely fill it. Six 2 by 2 by 2 in. 50 by 50 by 50 mm testcubes shall be cast at the same time

21、 from the same batch ofgrout.5.4 Test Specimen ConditioningThe test specimen includ-ing the grout test cubes, shall be cured according to Specifi-cation C511 ata746 3F 23 6 1.7C temperature andminimum 95 % relative humidity until the grout strength, asdetermined according to Test Method C1019 on at

22、least two 2by 2 by 2 in. 50 by 50 by 50 mm test cubes, has reached acompressive strength of 3500 to 4000 psi 24 to 28 MPa Theseal around the hole in the base plate may be removed once thegrout has set.5.5 The loss in height of the cured test cylinder because ofgrout bleed or drainage of water, or bo

23、th, through the inter-stices of the seven-wire strand shall not be more than 0.5 in.13 mm. Test cylinders with a height loss of more than 0.5 in.13 mm shall be discarded and new test cylinders preparedusing a more thorough mixing of the grout or sealing theinterstices of the seven-wire strand, or bo

24、th, within the 2-in.50-mm wide tape bond-breaker zone shown in Fig. 1.However, tests performed successfully on test cylinders shorterthan the allowed minimum length, shall be deemed acceptable.6. Pull Test6.1 Pull Test SetupWith the test specimen supported withits base plate on the table of the test

25、ing machine or load frame,the free strand protruding from the base plate shall be grippedby the jaws of the testing machine or load frame with aminimum of 12 in. 300 mm of free strand in between the baseplate and the jaws.6.1.1 Adial gage or other suitable measuring device shall bepositioned to meas

26、ure the longitudinal displacement at theunloaded end of the test specimen. A suitable test setup isshown in Fig. 2.6.2 Pull Test ProcedureTesting shall not commence untilthe grout has reached a compressive strength of 3500 psi 24MPa but before reaching a strength of 4000 psi 28 MPa.6.2.1 The pull fo

27、rce shall be applied to the test specimen ata rate of 0.1 in. 2.5 mm per minute, with a tolerance of625 %, until the displacement at the unloaded end of thestrand sample reaches 0.01 in. 0.25 mm at which point theforce shall be recorded.3Styrofoam is a registered trademark of The Dow Chemical Compan

28、y.FIG. 1 Untensioned Strand SpecimenA981/A981M 112NOTE 2Although not required, it is advisable to use a continuousload/displacement recording device. The shape of the load/displacementcurve may provide valuable insight on the bond behavior of the strandsample.7. Report7.1 Report the following inform

29、ation:7.1.1 Date of test and report.7.1.2 Identification of the steel prestressing strand:7.1.2.1 0.600-in. 15.24-mm diameter, Grade 270 1860strand;7.1.2.2 Manufacturer of strand;7.1.2.3 Date of strand manufacture;7.1.2.4 Reel, reelless pack, or lot number.7.1.3 Any presence of corrosion on the stra

30、nd tested shall bereported.7.1.4 Description of any deviations from the fabrication ofthe strand bond test specimen and testing procedures specified.7.1.5 Description of the grout used, including mix design,compressive strength at a time of test (average of a minimumof two cubes), and7.1.6 Individua

31、l load value (bond strength), in pounds N,for each test specimen at a displacement of 0.01 in. 0.25 mm.8. Precision and Bias8.1 No statement 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 a

32、cceptedmethod for determining precision and bias of this test methodis currently available. General guidelines provided herein forthe specimens, instrumentation and procedures make the re-sults intractable to calculation of meaningful values by statis-tical analysis for precision and bias at this ti

33、me.9. Keywords9.1 bond strength test; prestressed ground anchors; steelprestressing strandASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination

34、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 reviewed every five years andif not revised, either reapproved or withdrawn

35、. 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 theresponsible technical committee, which you may attend. If you feel that your com

36、ments 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

37、 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 2 Pull Test SetupA981/A981M 113