ASTM_A_981_-_A_981M_-_11_2016.pdf

Designation:A981/A981M11(Reapproved 2016)Standard 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 designation 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 procedures 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 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,the 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 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.Referenced Documents2.1 ASTM Standards:2A416/A416M Specification for Low-Relaxation,Seven-Wire Steel Strand 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 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 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 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 ensure 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 measurement 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 diameter,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.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 wall,18-in.450-mm long with1This 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 Sept.1,2016.Published September 2016.Originallyapproved in 1997.Last previous edition approved in 2011 as A981 11.DOI:10.1520/A0981_A098M-11R16.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 a 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 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