JGJ/T 23-1992 Technical specification for testing the compressive strength of concrete by rebound method JGJ/T23-92 JGJ/T23-1992 Standard download decompression password: www.bzxz.net

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Industry Standard of the People's Republic of China
Technical Specification for Inspection of Concrete Compressive Strength by Rebound Method
1994 North
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Industry Standard of the People's Republic of China
Technical Specification for Inspection of Concrete Compressive Strength by Rebound Method JGJ/T23-92
Editor: Shaanxi Provincial Architectural Science Research and Design Institute Approval Department: Ministry of Construction of the People's Republic of China Implementation Date October 1, 1993
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Notice on the Release of the Industry Standard "Technical Specification for Testing Concrete Compressive Strength by Rebound Method"
Jianbiao [1993] No. 385
According to the requirements of the former Ministry of Urban and Rural Construction and Environmental Protection (88) Chengbiao No. 141, the "Technical Specification for Testing Concrete Compressive Strength by Rebound Method" edited by Shaanxi Provincial Building Science Research and Design Institute has been reviewed and approved as an industry standard, numbered JGJ/T23-92, and will be implemented from October 1, 1993.
This specification is managed by the China Academy of Building Research, the Ministry of Construction's construction engineering standards and technology management unit. Its specific interpretation and other work are the responsibility of Shaanxi Provincial Building Science Research and Design Institute. It is organized and published by the Ministry of Construction's Standards and Norms Research Institute. Ministry of Construction of the People's Republic of China
May 18, 1993
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Main Symbols
2 Rebound Hammer
2.1 Technical Requirements
Testing Technology
General Provisions
0000000
Rebound Value Measurement?
Carbonization Depth Measurement
Rebound Value Calculation
Strength Measurement Curve
General Provisions
Uniform Strength Measurement Curve
Regional and Special Strength Measurement Curve
Calculation of Concrete Strength
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Test report
Method for formulating special strength test curve
Correction value of rebound value in non-horizontal state testCorrection value of rebound value of different casting surfaces
Conversion table of concrete strength in test area
Original record table of rebound method test
Calculation table of concrete strength of components
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(15)
：(18)
(19)
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Appendix H Explanation of terms used in this code
Additional instructions
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Main Symbols
Rebound value
Rebound value of the ith measuring point
Average rebound value of the measuring area or test piece
Average rebound value of the measuring area when the rebound hammer is testing in a non-horizontal directionAverage rebound value of the measuring area when the rebound hammer is testing the concrete casting surface in a horizontal direction
Average rebound value of the measuring area when the rebound hammer is testing the concrete casting bottom surface in a horizontal direction
Correction value of the rebound value when the rebound hammer is testing the concrete casting surfaceCorrection value of the rebound value when the rebound hammer is testing the concrete casting bottom surface in a non-horizontal directionCarbonation depth
Carbonation depth value of the first measurement
Measurement Average carbonation depth value of the area
Compressive strength value
Conversion value of concrete strength in the measurement area
Average value of the conversion value of concrete strength in the measurement area foa,minThe smallest conversion value of concrete strength in the measurement area Sta in the component
Standard deviation of the conversion value of concrete strength in the measurement area of ​​the same batch of components Engineering Construction Standard Full Text Information System
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feasEstimated value of concrete strength of component
Correction coefficient
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1 General Principles
, This code is formulated to unify the method of using rebound hammer to test the compressive strength of ordinary concrete and ensure the detection accuracy.
1.0.2 This code is applicable to the detection of the compressive strength of ordinary concrete (hereinafter referred to as concrete strength) in engineering structures.
The inspection and assessment of concrete strength shall be carried out in accordance with the current national standards "Concrete Structure Engineering Construction and Acceptance Code" and "Concrete Strength Inspection and Assessment Standard". When there is doubt about the concrete strength in the structure, it can be tested in accordance with this procedure, and the test results can be used as a basis for handling the quality of concrete.
This procedure is not applicable to the inspection of concrete components with obvious differences in surface and internal quality or internal defects.
1.0.3 All personnel who use rebound hammers for engineering inspections shall pass professional training recognized by the competent authorities and hold corresponding qualification certificates. 1.0.4 In addition to complying with this procedure, the use of the rebound method to detect and estimate concrete strength shall also comply with the provisions of the relevant current national standards. Engineering Construction Standard Full Text Information System
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2 Rebound Hammer
2.1 Technical Requirements
2.1.1 The instrument for measuring the rebound value shall be a concrete rebound hammer with a pointer direct reading indication system. Rebound hammers of the same impact energy using other indication systems are also allowed to be used if they have been identified and approved, have stable performance and have reliable methods for verifying the accuracy of the indication.
2 The rebound hammer must have a product certificate from the manufacturer and a calibration certificate from the calibration unit.
2.1.3Qualified rebound hammers shall meet the following standard conditions: (1) When the hammer is unhooked during horizontal impact, the standard energy of the rebound hammer shall be 2.2J;
(2) When the hammer collides with the impact rod, the impact spring shall be in a free state, and the starting point of the hammer shall correspond to the "0" on the pointer scale; (3) On a steel anvil with a Rockwell hardness HRC of 60±2, the calibration value of the rebound hammer shall be 80±2.
2.1.4 The ambient temperature when the rebound hammer is used shall be -4℃ to +40℃. 2.2 Calibration
2.2.1 The rebound hammer shall be sent to the calibration unit for calibration in any of the following cases: (1) before the new rebound hammer is put into use;
(2) the calibration validity period has expired (valid for half a year); (3) the cumulative number of impacts exceeds 6,000 times;
(4) the calibration value of the steel anvil fails to meet the standard after routine maintenance; (5) it suffers from severe impact or other damage.
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2.2.2 The rebound hammer calibration agency shall be established in a unit recognized by the competent authority. The calibration unit shall calibrate the rebound hammer in accordance with the metrological calibration regulations. 2.2.3 The rebound hammer shall be calibrated on the steel station before and after the engineering inspection. 2.2.4 The calibration test of the rebound hammer should be carried out at room temperature of 20±5℃. During calibration, the steel sticker should be placed firmly and flat on a concrete entity with high rigidity. When the rebound hammer strikes downward, the stable rebound values ​​of three consecutive strikes are averaged, and the striking rod should be rotated four times, each time by about 90°. The calibration average value of each rotation of the striking rod should meet the requirement of 80±2.
2.3 Maintenance
2.3.1 Routine maintenance should be performed on the rebound hammer in any of the following situations: (1) The strikes exceed 2000 times;
(2) When there is doubt about the test value;Www.bzxZ.net
(3) The calibration value on the steel anvil is unqualified.
Regular maintenance should meet the following requirements:
(1) Remove the movement after unhooking the hammer, then remove the firing rod (take out the buffer spring inside) and the three-piece (firing hammer, firing spring and spring seat); (2) Clean the various parts of the movement, especially the inner hole and impact surface of the center guide rod, firing hammer and firing rod. After cleaning, apply a thin layer of No. 20 engine oil on the center guide rod: other parts should not be oiled;
(3) Clean the inner wall of the casing, remove the scale, and check the pointer. The friction should be 0.5~0.8N;
(4) The zero adjustment screw on the tail cover that has been positioned and tightened shall not be rotated;(5) Parts shall not be made or replaced;
(6) After maintenance, the calibration test shall be carried out in accordance with the requirements of Article 2.2.4 of this regulation. 2.3.3 After the use of the rebound hammer, the impact rod shall be extended out of the casing, and the dirt and dust on the impact rod (including the front spherical surface, the scale surface and the casing) shall be cleaned. When the rebound hammer is not in use, the impact rod shall be pressed into the instrument. The button can only be pressed and the movement locked after the impact. Put the rebound hammer into the sleeve and place it flat in a dry and cool place. Engineering Construction Standard Full Text Information System
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3 Testing Technology
3. 1 General Provisions
3.1.1 When testing the concrete strength of a structure or component, the following information should be available: (1) Project name and the names of the design, construction and construction units; (2) Name, dimensions, quantity and concrete strength grade of the structure or component; (3) Cement type, grade, stability and factory name; Sand and stone type and particle size; Admixture or admixture type and dosage; Concrete mix ratio, etc.; (4) Material measurement during construction, formwork, pouring, curing and molding date, etc.
(5) Necessary design drawings and construction records; (6) Reason for testing.
3.1.2 The following two methods can be used to test the concrete strength of a structure or component. Their scope of application and number of components should comply with the following provisions: (1) Single test: Applicable to the testing of a single structure or component; (2) Batch test: Applicable to similar components with the same production process conditions, the same concrete strength grade, basically the same raw materials, mix ratio, molding process, and curing conditions, and similar age. For components tested in batches, the number of random inspections shall not be less than the same 30% of the total number of batch components and the number of measurement areas shall not be less than 100. When sampling components, the relevant parties shall reach a consensus to ensure that the selected components are representative. 3.1.3 The measurement area of ​​each component shall meet the following requirements: (1) For components with a length of not less than 3m, the number of measurement areas shall not be less than 10. For components with a length of less than 3m and a height of less than 0.6m, the number of measurement areas may be appropriately reduced, but shall not be less than 5;
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(2) The distance between two adjacent measuring areas should be controlled within 2m, and the distance between the measuring area and the edge of the component should not be greater than 0.5m;
(3) The measuring area should be selected so that the rebound hammer is in a horizontal direction to detect the side of the concrete pouring. When this requirement cannot be met, the rebound hammer can be placed in a non-horizontal direction to detect the side, surface or bottom of the concrete pouring;(4) The measuring area should be selected on two symmetrical measurable surfaces of the component, or on one measurable surface. The surface should be evenly distributed. The measurement area must be arranged at the stress-bearing and weak parts of the component, and should avoid embedded parts;
(5) The area of ​​the measurement area should be controlled within 0.04m2;(6) The test surface should be the original concrete surface, and should be clean and flat. There should be no loose layer, floating slurry, oil stains, honeycombs, or rough surfaces. If necessary, the loose layer and debris can be removed with a grinding wheel, and there should be no residual powder or debris;(7) Thin-walled and small components that vibrate when struck should be supported and fixed.
3.1.4 The measurement area of ​​the structure or component should be clearly marked with numbers. If necessary, the measurement area layout diagram and appearance quality should be described on the record paper. 3.1.5 When the test conditions are significantly different from the applicable conditions of the strength curve, the same condition test piece or drilled concrete core sample can be used for correction. The number of test pieces should be no less than 3. When calculating, the concrete strength conversion value of the test area should be multiplied by the correction factor. The correction factor can be calculated according to formula 3.1.5-1 or 3.1.5-2: m
fani/fa
fcon/fa,
where n is the correction factor, accurate to 0.01
(3.1.5-1)
(3.1.5-2)
feul, foor are the compressive strength values ​​of the ith concrete cube specimen (side length is 150mm) or core specimen (p100×100mm), accurate to 0.1MPa;
fou,—corresponds to the rebound value and carbonation depth value of the ith specimen, which are given by the attached Engineering Construction Standard Full-text Information System
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