Recently, the Ministry of Housing and Urban-Rural Development released the latest version of JGJ T23 "Technical Regulations for Testing Concrete Compressive Strength by Rebound Method" for comments, and there are 15 major changes after the revision, and some provisions have changed greatlyThe area of the rebound test area is increased from 004 becomes 009㎡；Rebound test areaThe number of measurement points has changed from 16 to 12 ......
The Ministry of Housing and Urban-Rural Development has new regulations on the rebound law
Changes to the new rules of the rebound law
1.This revision adds the relevant requirements of the H550 rebound hammer, which solves the dilemma that the ordinary concrete meter cannot detect high-strength concrete; Added M225 type rebound hammer with a mass of 1Calibration requirements on 05kg anvil. 3.1.3. M225 rebound tester or H550 type rebound tester should be used in this procedure.
2.The rebound hammer was bounced more than 6,000 times for maintenance (the original specification was 2,000 times).
3.3.1 When the rebound hammer has one of the following conditions, it should be maintained:
1. More than 6,000 rebound shots;
2. The rate value is unqualified;
3 Doubts about the test value. 3.The area of the survey area is modified as:(Original Specification 0.)04㎡）。
4.1.3. When the concrete strength is tested according to a single component, the following provisions shall be met:
5. The area of the survey area should not be greater than 009㎡。4.It is clarified that when testing in batches, it shall not be less than the minimum number of sampling inspections specified in the Technical Standard for On-site Testing of Concrete Structures GB T 50784.
4.1.4. When the concrete strength is tested in batches, the following provisions shall be met:
1. Concrete production technology, strength grade is the same, raw materials, mix ratio, curing conditions are basically the same and similar age of the same kind of components can form an inspection batch.
2. The inspected components should be randomly selected, and the number of sampling should not be less than 30% of the total number of components in the same batch and should not be less than 10 pieces. When the number of sampling components in the inspection batch is greater than 30, it can be appropriately adjusted, but shall not be less than the minimum sampling quantity specified in the "Technical Standard for On-site Testing of Concrete Structures" GB T 50784. 5.The original specification stipulates that "6 core samples with a nominal diameter of 100mm should be taken for coring correction", and this revision adds a provision that "the number of small diameter core samples with a diameter of less than 100 should not be less than 9".
4.1.6. When the test conditions are related to the special strength measurement curve, the regional strength measurement curve and the 62.When the applicable conditions of Article 1 are quite different, or when there is doubt about the rebound test results, the concrete strength conversion value of the measurement area can be corrected by using a drilled core sample or a test block under the same conditions on the component. When the strength of the same inspection batch of concrete is corrected, the number of core specimens with a diameter of 100mm should not be less than 6, the number of core specimens with a small diameter should not be less than 9, and the height-diameter ratio should be 1. The core sample position should be representative and drilled in the survey area, and only one specimen should be processed for each core sample. When the test block under the same condition is corrected, the number of test blocks should not be less than 6, and the side length of the test block should be 150mm.
6.The scope of application of the rebound hammer is specified: "The M225 rebound hammer is used to detect concrete components with strength class C10 C60, and the H550 rebound meter is used to detect concrete components with strength class C60 C80".
4.2.The 1 M225 rebound tester is used to detect concrete elements with strength class C10 C60, and the H550 rebound tester is used to detect concrete components with strength class C60 C80.
7.The readings per survey area are modified to:12 pcs(Original specification.)16 pcs
4.2.3. Each measurement area should read 12 rebound values, and the rebound value reading of each measurement point should be accurate to 1. The measuring points should be evenly distributed within the survey area, and the net distance between the two adjacent measuring points should not be less than 20mm; The distance between the measuring point and the exposed steel bar and embedded parts should not be less than 30mm; The measuring point should not be on a stomata or exposed stone, and the same measuring point should only be hit once.
8.The calculation of the average carbonization depth is refined, and it is clarified that when 6When 0mm, take =60mm。The average carbonization depth value of all survey areas of the member, when d m 6When 0mm, take d m=60mm, accurate to 05mm。
9.When the strength test is carried out on the components with an age of less than one year, when the carbonization depth value exceeds Table 43.3. When the limit value is required, it is advisable to adopt the corresponding carbonization depth value limit in the table.
10.The new specification refines and clarifies the selection of the detection surface, stipulates the selection sequence of the detection surface of non-pumped concrete components, and clarifies that the pouring bottom surface of the concrete should be selected for the pumped concrete of cast-in-situ slabs.
4.4.1. When testing the strength of non-pumped concrete components, the detection surface should be selected in the order of horizontal side, non-horizontal side, and non-horizontal non-side. 4.4.2. When pumping concrete components strength testing, the detection surface should be selected according to the following conditions: 1. For cast-in-situ slab components, the pouring bottom surface of concrete should be selected;
2. For non-cast-in-place slab components, the pouring side of concrete should be selected. 11.The new specification revises the number of rebound measurement points in the survey area and the calculation method, from the original 16 rebound values in each survey area to "12 rebound values, excluding 1 maximum value and 1 minimum value".
5.0.1 When calculating the average rebound value of the survey area, 1 maximum value and 1 minimum value should be excluded from the 12 rebound values of the survey area.
12.The detection range of the compressive strength of the unified strength measurement curve is determined by (10.).0～60.0) MPA is modified to (10.)0～80.0）mpa。
6.2.1 Concrete using a uniform strength measurement curve shall meet the following conditions:
6 The compressive strength is: (10.)0～80.0）mpa。
13.The age of the unified intensity measurement curve was revised from (14 1000) d to (14 1800) d.
6.2.1 Concrete using a uniform strength measurement curve shall meet the following conditions:
5 Naturally conserved and aged: (14 1800) days. 14.The conversion table of the pumping concrete measuring area of the original specification is revised as: the strength conversion table of the pumping concrete bottom facing the upper measuring area and the strength conversion table of the horizontal measuring area on the side of the pumped concrete.
6.2.3 Comply with clause 62.Article 1 stipulates that the strength of the pumping concrete with a compressive strength of (10 80) MPa shall be converted according to the following requirements.
1. For cast-in-situ slab pumped concrete components with a compressive strength of (10 60) MPa, the strength of the measuring area can be converted according to the provisions of Appendix D of these regulations. 2. For non-cast-in-situ slab pumped concrete components with a compressive strength of (10 60) MPa, the strength of the measuring area can be converted according to the provisions of Appendix E of these regulations.
3. For non-cast-in-situ slab pumped concrete components with a compressive strength of (60 80) MPa, the strength of the measuring area can be converted according to the provisions of Appendix F of these regulations. 15.Added "Pumping High-strength Concrete Measurement Area Strength Conversion Table".
Full text of the new regulations of the rebound law
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