Detail of GB/T 21839-2019

Introduction of GB/T 21839-2019

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative. This standard is developed in accordance with the rules given in GB/T 1.1-2009. This standard replaces GB/T 21839-2008 Steel for prestressed concrete - Test methods. In addition to a number of editorial changes, the following technical changes have been made with respect to GB/T 21839-2008: ——The normative references are modified (see Clause 2; Clause 2 of Edition 2008); ——Some symbols are modified and added (see Clause 3; Clause 3 of Edition 2008); ——The general provisions concerning test pieces are modified (see Clause 4; Clause 4 of Edition 2008); ——Tensile test is modified; requirements for tensile test pieces are added, parameters A and Z are added for the measurement in tensile test, artificial method is added for the measurement of Agt according to GB/T 228.1; measurement of modulus of elasticity (E) is refined (see 5.3.2); ——Judgment of the bend test result is modified (see 6.4; 6.4 of Edition 2008); ——Equipment for reverse bend test is added (see 7.2); ——Adhesion test of coating is added (see Clause 9); ——Relevant technical requirements of extensometer are modified (see Clause 5 and Annex C; Clause 5 and Annex A of Edition 2008); ——Safety warning for chemical reagents is added at the part of stress corrosion test solution (see 12.3.5); ——Requirements for length of indentation are added (see 15.3.2.4); ——Testing of the content of anti-corrosive grease is added (see Clause 18); ——Measurement of sheath thickness is added (see Clause 19); ——Test for uniformity of coating is added (see Clause 20); ——Test for quality of zinc coating is added (see Clause 21). This standard has been redrafted and modified in relation to ISO 15630-3:2010 Steel for the reinforcement and prestressing of concrete - Test methods - Part 3: Prestressing steel. Many structural adjustments have been made with respect to ISO 15630-3:2010, and a comparison table between this standard and ISO 15630-3:2010 in clause/subclause number is listed in Annex A. This standard includes technical differences with respect to ISO 15630-3:2010. The clauses and subclauses concerned are identified by a vertical single line (|) located in the blank on its external margin of the page. These technical differences and their causes are listed in Annex B. In addition, the following editorial changes have been made in this standard: ——“Annex A (informative) Comparison between this standard and ISO 15630-3:2010 in clause/subclause number” is added; ——“Annex B (Informative) Technical differences and their causes between this standard and ISO 15630-3: 2010” is added. ——“Annex C (Informative) Methods for tensile test of strand for prestressing concrete” is added. This standard was proposed by China Iron and Steel Industry Association. This standard is under the jurisdiction of the National Technical Committee on Iron and Steel of Standardization Administration of China (SAC/TC 183). The previous edition of this standard is as follows: —GB/T 21839-2008. Test methods of steel for prestressing concrete 1 Scope This standard specifies the methods concerning tensile test, bend test, reverse bend test, torsion test, adhesion test of winding and coating, isothermal relaxation test, axial force fatigue test, stress corrosion test in a solution of thiocyanate, deflected tensile test, determination of chemical composition, measurement of the geometrical dimension, determination of the relative rib area, determination of deviation from nominal weight per metre, testing of the content of anti-corrosive grease, measurement of sheath thickness, test for uniformity of coating and test for quality of galvanized coating, etc. of steel for prestressing concrete. This standard is applicable to the determination of properties related prestressing steel wire, prestressing steel rod, prestressing steel bar, prestressing steel strand and other products. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 228.1 Metallic materials - Tensile testing - Part 1: Method of test at room temperature (GB/T 228.1-2010, ISO 6892-1:2009, MOD) GB/T 230.1 Metallic materials - Rockwell hardness test - Part 1: Test method (GB/T 230.1-2018, ISO 6508-1:2016, MOD) GB/T 232 Metallic materials - Bend test (GB/T 232-2010, ISO 7438:2005, MOD) GB/T 238 Metallic materials - Wire - Reverse bend test (GB/T 238-2013, ISO 7801:1984, MOD) GB/T 239.1 Metallic materials - Wire - Part 1: Simple torsion test (GB/T 239.1-2012, ISO 7800:2003, MOD) GB/T 1839 Test method for gravimetric determination of the mass per unit area of galvanized coatings on steel products (GB/T 1839-2008, ISO 1460:1992, MOD) GB/T 2972 Test method for uniformity of zinc coating on zinc-coated steel wire by the copper sulphate dip (GB/T 2972-2016, ISO 7989-2:2007, NEQ) GB/T 2975 Steel and steel products - Location and preparation of samples and test pieces for mechanical testing (GB/T 2975-2018, ISO 377:2017, MOD) GB/T 2976 Metallic materials - Wire - Wrapping test (GB/T 2976-2004, ISO 7802:1983, IDT) GB/T 3505 Geometrical product specifications (GPS) - Surface texture: Profile method - Terms definitions and surface texture parameters (GB/T 3505-2009, ISO 4287:1997, IDT) GB/T 4336 Carbon and low-alloy steel - Determination of multi-element contents - Spark discharge atomic emission spectrometric method (routine method) GB/T 12160 Calibration of extensometers used in uniaxial testing (GB/T 12160-2002, ISO 9513:1999, IDT) GB/T 16825.1 Verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Verification and calibration of the force-measuring system (GB/T 16825.1-2008, ISO 7500-1:2004, IDT) 3 Symbols and definitions For the purposes of this document, the symbols given in Table 1 apply. Table 1 Symbols and their description Symbol Unit Description Reference am mm Rib height at the mid-point 15.3, 16.2 amax mm Maximum depth of indentation or height of rib 15.3 as,i mm Average height of a rib in unit length ∆l 16.2 a1/4 mm Rib height at the quarter-point 15.3, 16.2 a3/4 mm Rib height at the three-quarters point 15.3, 16.2 A % Percentage elongation after fracture 5.3.1 Agt % Percentage total elongation at maximum force 5 At % Total elongation at break 5.3.1 b mm Width of transversal rib 15.3.1.6 c mm Rib or indentation spacing 15.3 C mm Groove width of the mandrel used for the deflected tensile test 13.3.4 d mm Nominal diameter of the rod, wire or strand 11.2, 11.4.6, 12.3.4 da mm Nominal diameter of the mandrel used for the deflected tensile test 13.3.4 db mm Diameter with 2 gauge cylinders in the groove of the mandrel used for the deflected tensile test 13.3.4 de mm Diameter of the gauge cylinder used for the deflected tensile test 13.3.4 dg mm Diameter of guide hole 7.3 di mm Inner diameter of the groove of the mandrel used for the deflected tensile test 13.3.4 D % Average coefficient of reduction of the maximum force in the deflected tensile test 13.2, 13.4 Dc mm Inner diameter of the cell in the stress corrosion test 12.3.4 Di % Individual percentage of reduction of the maximum force in the deflected tensile test 13.4 e mm Average gap between two adjacent ribs or indentation rows 15.3.1.4, 15.3.2.4 E GPa Modulus of elasticity 5.3 f HZ Frequency of force cycles in the axial force fatigue test 11.1, 11.4.2 fR — Relative rib area 16 Fa,i N Individual breaking force in the deflected tensile test 13.4 Fm N Maximum force 5.3 N Mean value of the maximum force 10.2, 12.2, 13.2 Fp0.1 N 0.1% proof force 5.3 Fp0.2 N 0.2% proof force 5.3 Fr N Force range in the axial force fatigue test 11.1, 11.3, 11.4.2 Frt N Residual force in the test piece at time t in the relaxation test 10.1 ΔFrt N Force loss in the test piece at time t in the relaxation test 10.1 FR mm2 Area of longitudinal section of one transverse rib 16.2 Fup N Upper force in the axial force fatigue test 11.1, 11.3, 11.4.2 F0 N Initial force in the stress relaxation test and the stress corrosion test 10.1, 10.3, 10.4, 12.4.2 G mm Depth of the groove of the mandrel used for the deflected tensile test 13.3.4 h mm Distance from the top of cylindrical supports to the bottom of the guide 7.2 hb mm Bow height of the plane of prestressing steel 15.3.4 Lt mm Length of the test piece in the stress corrosion test 12.2 L0 mm Original gauge length in the isothermal relaxation test Length of the test piece in contact with the solution in the stress corrosion test 10.1, 10.3, 10.4, 12.2, 12.3.4, 12.4.5 ΔL0 mm Elongation of the gauge length, L0, under force, F0, in the isothermal stress relaxation test 10.1, 10.3, 10.4 L'0 mm Determined original gauge length of Agt 5.3 L'u mm Determined gauge length after fracture of Agt 5.3 L1 mm Length of the passive side in the deflected tensile test 13.3.2 L2 mm Length of the active side in the deflected tensile test 13.3.2 m, n — Coefficients or numbers 10.4.9, 15.3, 16.2 P mm Lay length of a strand 15.3.3 R mm Corner radius at the base of the groove of the mandrel used for the deflected tensile test 13.3.4 r mm Radius of cylindrical supports 7.2 Ra μm Surface roughness of the mandrel used for the deflected tensile test 13.3.4 Sn mm2 Nominal cross-sectional area of the test piece 5.3.2 ta h Maximum agreed time for the stress corrosion test 12.4.5 tf,i h Individual lifetime to fracture in the stress corrosion test 12.4.5 h Median lifetime to fracture in the stress corrosion test 12.4.6 t0 s Starting time in the isothermal stress relaxation test and in the stress corrosion test 10.4.2, 12.4 V0 mm3 Volume of test solution to fill the test cell in the stress corrosion test 12.4.3 W g/m Weight of unbonded prestressing steel strand per metre 18.3 W1 g/m Weight of steel strand after removing the sheath and anti-corrosive grease from unbonded prestressing steel strand per metre 18.3 W2 g/m Weight of sheath after removing the anti-corrosive grease from unbonded prestressing steel strand per metre 18.3 W3 g/m Weight of anti-corrosive grease in unbonded prestressing steel strand per metre 18.3 Z % Percentage reduction of area 5.3.1 α (°) Angle of deviation in the deflected tensile test 13.3.2 β (°) Transverse rib or indentation angle to the bar or wire axis 15.3 εx — Value of the strain for a force equal to x 5.3.2 ρ % Relaxation 10.4.8 Σei mm Circumference of transverse rib gap 15.3.1.4, 15.3.2.4, 16.2 Note: 1N/mm2=1MPa 4 General provisions concerning test pieces Unless otherwise agreed or specified in the product standard, the test pieces shall be taken from the finished product normally before packaging. Special care should be taken when sampling is made from the packaged product (e.g. coil or bundle), in order to avoid plastic deformation which could change the properties of the samples used to provide the test pieces. Specific complementary provisions concerning the test pieces may be indicated in the relevant clauses of this standard, if applicable. 5 Tensile test 5.1 Test pieces ‎In addition to the general provisions given in Clause 4, the free length of the test piece shall be sufficient for the determination of the percentage total elongation at maximum force (Agt) in accordance with 5.3.1. If the percentage elongation after fracture is determined manually, the test piece shall be marked in accordance with GB/T 228.1. If the percentage total elongation at maximum force (Agt) is determined by the manual method for bar or wire, equidistant marks shall be made on the free length of the test piece (see GB/T 228.1). The distance between the marks shall be 20mm, 10mm or 5mm, depending on the test piece diameter.

Contents of GB/T 21839-2019

Foreword i 1 Scope 2 Normative references 3 Symbols and definitions 4 General provisions concerning test pieces 5 Tensile test 6 Bend test 7 Reverse bend test 8 Torsion test 9 Adhesion test of winding and coating 10 Isothermal relaxation test 11 Axial force fatigue test 12 Stress corrosion test in a solution of thiocyanate 13 Deflected tensile test 14 Chemical analysis 15 Measurement of the geometrical dimension 16 Determination of the relative rib area (fR) 17 Determination of deviation from nominal weight per metre 18 Testing of the content of anti-corrosive grease 19 Measurement of sheath thickness 20 Test for uniformity of coating 21 Test for quality of zinc coating 22 Test report Annex A (Informative) Comparison between this standard and ISO 15630-3: 2010 in clause/subclause number Annex B (Informative) Technical differences and their causes between this standard and ISO 15630-3: Annex C (Informative) Methods for tensile test of strand for prestressing concrete