1、Designation: A 981 97 (Reapproved 2007)Standard Test Method forEvaluating Bond Strength for 15.2 mm (0.6 in.) DiameterPrestressing Steel Strand, Grade 270, Uncoated, Used inPrestressed Ground Anchors1This standard is issued under the fixed designation A 981; the number immediately following the desi
2、gnation indicates the year oforiginal adoption or, in the case of revision, 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. Scope1.1 This test method describes pr
3、ocedures to establish therelative bond strength of 15.2 mm (0.6 in.) diameter, Grade 270prestressing steel strand in cement grout as used in prestressedground anchors for the purpose of evaluating the effects ofmanufacturing practices on bond strength.1.2 The bond strength values obtained shall not
4、be used todesign the bond length of ground anchors that depend on fieldconditions.1.3 This test method is not intended to be used as a bond testfor pretensioned concrete applications.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informat
5、iononly.1.5 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Refe
6、renced Documents2.1 ASTM Standards:2A 416/A 416M Specification for Steel Strand, UncoatedSeven-Wire for Prestressed ConcreteC 150 Specification for Portland CementC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and Conc
7、retesC 1019 Test Method for Sampling and Testing GroutE4 Practices for 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 15.2 mm (0.6 in.) diameter prestressing steel strandembedded in ce
8、ment grout.3.1.2 bonded lengththe length of the test strand that is incontact with the cement grout.4. Apparatus4.1 EquipmentA suitable tensile test machine or loadframe shall be used. The loading system shall be calibrated inaccordance with Practices E4. The test system shall havesufficient capacit
9、y to prevent yielding of its various compo-nents and shall ensure that the applied tensile load remainsparallel to the axis of the prestressing steel strand duringtesting.4.2 Strand Displacement MeasurementsDisplacements ofthe free end of the prestressing steel strand shall be measuredwith respect t
10、o the loaded surface of the test specimen usingsuitable measurement devices. Dial gages having the smallestdivision of not more than 25 m (0.001 in.) or linear variabledifferential transformers (LVDTs) with equal or superior accu-racy are examples of satisfactory devices.5. Test Specimen5.1 Prestres
11、sing Steel Strandshall be 15.2 mm (0.6 in.)diameter, Grade 270 and comply with Specification A 416 andshall be cut from standard production coils. The surface of thetest samples shall not be wiped or cleaned in order to preservetheir original condition. Minimum recommended samplelength is 750 mm (30
12、 in.).5.2 Strand Bond Test SpecimenThe test specimen shallconsist of the prestressing steel strand embedded in cementgrout and centered inside a steel pipe, 125 mm (5 in.) O.D. witha 3 mm (0.125 in.) wall, 450 mm (18 in.) long with a 150 by150 by 6 mm (6 by 6 by 0.25 in.) base plate welded, orotherw
13、ise leakproof connected to one end of the steel pipe.Other mold designs, including reusable molds, shall be per-missible, provided that the dimensions and confinement inregard to circumferential stress provided for the grout body arethe same. A hole in the base plate shall allow the strand to passth
14、rough. A 50 mm (2 in.) long debonding tube shall bepositioned on the strand above the base plate and the strand1This 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.C
15、urrent edition approvedSept. 1, 2007. Published September 2007. Originallyapprove din 1997. Last previous edition approved in 2002 as A 981 97 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStand
16、ards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.shall protrude at least 50 6 10 mm (2 6 0.5 in.) from the topof the grouted steel tube. A typica
17、l test specimen is illustratedin Fig.1.5.3 Test Specimen PreparationThe untensioned strandspecimen shall be installed and centered inside the steel pipe 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.
18、1 The grout shall be made solely from fresh portlandcement conforming to Specification C 150, Type I with awater/cement ratio of 0.45. Water shall be potable. The cementshall be added to the water. Mixing of the grout shall continueuntil the grout is free of lumps and undispersed cement. Thegrout th
19、en shall be poured into the steel tube to completely fillit.5.4 Test Specimen ConditioningThe test specimen includ-ing the grout test cubes, shall be cured according to Specifi-cation C511 ata236 1.7C (74 6 3F) temperature andminimum 95 percent relative humidity until the grout strength,as determine
20、d according to Test Method C 1019 on at least two50 by 50 by 50 mm (2 by 2 by 2 in.) test cubes, has reached acompressive strength of 24 to 28 MPa (3500 to 4000 psi). 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 beca
21、use ofgrout bleed or drainage of water, or both, through the inter-stices of the seven-wire strand shall not be more that 13 mm(0.5 in.). Test cylinders with a height loss of more than 13 mm(0.5 in.) shall be discarded and new test cylinders preparedusing a more thorough mixing of the grout or seali
22、ng theinterstices of the seven-wire strand, or both, within the 50 mm(2 in.) wide tape bond breaker zone shown in Fig. 1. However,tests performed successfully on test cylinders shorter than theallowed minimum length, shall be deemed acceptable.6. Pull Test6.1 Pull Test SetupWith the test specimen su
23、pported withits base plate on the table of the test machine or load frame, thefree strand protruding from the base plate shall be gripped bythe jaws of the test machine or load frame with a minimum of300 mm (12 in.) of free strand in between the base plate and thejaws.6.1.1 Adial gage or other suita
24、ble measuring device shall bepositioned to measure the longitudinal displacement at theunloaded end of the test specimen. A suitable test setup isshown in Fig. 2.FIG. 1 Untensioned Strand Specimen FIG. 2 Pull Test SetupA 981 97 (2007)26.2 Pull Test ProcedureTesting shall not commence be-fore the gro
25、ut has reached a compressive strength of 24 MPa(3500 psi), but before reaching a 28 MPa (4000 psi) strength.6.2.1 The pull force shall be applied to the test specimen ata rate of 2.5 mm (0.1 in.) per minute, with a tolerance of 625%, until the displacement at the unloaded end of the strandsample rea
26、ches 0.25 mm (0.01 in.) at which point the forceshall be recorded.NOTE 1Although not required, it is advisable to use a continuousload/displacement recording device. The shape of the load/displacementcurve may yield valuable insight on the bond behavior of the strandsample.7. Report7.1 Report the fo
27、llowing information:7.1.1 Date of test and report,7.1.2 Identification of the prestressing steel strand:7.1.2.1 Strand size and grade,7.1.2.2 Manufacturer of strand,7.1.2.3 Date of strand manufacture,7.1.2.4 Coil or lot number,7.1.3 Any presence of corrosion on the strand tested shall bereported.7.1
28、.4 Description of any deviations from the fabrication ofthe 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 Individual load value (bond strength), in N (lb), f
29、oreach test specimen at a displacement of 0.25 mm (0.01 in.).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 acceptedmethod for determining precision an
30、d 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 time.9. Keywords9.1 bond test; ground anchor
31、s; prestressing steel 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 of the validity of any such patent rights, and the riskof infr
32、ingement 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. Your comments are invited either for revision of this standa
33、rd 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 comments have not received a fair hearing you shouldmake your vie
34、ws 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).A 981 97 (2007)3
