JGJ/T 23-2011 in English

1 General Provisions

1.0.1 This Specification was formulated for the purpose of unifying the method to test the compressive strength of ordinary concrete by using rebound hammer and of ensuring the testing accuracy.
1.0.2 This Specification is applicable to the testing of the compressive strength of ordinary concrete (hereinafter referred to as "concrete compressive strength") and is not applicable to the testing of concrete compressive strength with obvious difference in surface layer and internal quality or with defects inside.
1.0.3 The personnel conducting the test by using rebound method shall pass through special technical training.
1.0.4 In addition to this Specification, the testing of concrete compressive strength by rebound method still shall comply with those specified in the current relevant standards of the State.

2 Terms and Symbols

2.1 Terms

2.1.1 Test area
One test unit when testing the concrete compressive strength of the member.
2.1.2 Test point
One rebound test point in the test area.
2.1.3 Conversion value of concrete compressive strength of test area
The concrete compressive strength value at the current concrete age of the test area that is obtained through the testing strength curve or strength conversion table of test area and based on the average rebound value and carbonization depth value of test area.
2.1.4 Estimation value of strength for concrete
The concrete compressive strength value in such member of which the guarantee rate is not less than 95% corresponding to the general distribution of strength conversion value.

2.2 Symbols

dm——the average carbonization depth of the test area.
——the conversion value of concrete compressive strength of test area.
fcor, m——the average concrete compressive strength value of core specimen.
fcu, m——the average concrete compressive strength value of test cube under the same conditions.
——the average conversion value of concrete compressive strength of rebound test area corresponding to the drilling core position or test block under the same conditions.
fcor, i——the compressive strength of the ith concrete core specimen.
fcu, i——the compressive strength of the ith cube concrete test specimen.
——the conversion value of concrete compressive strength of the ith test area before being corrected.
——the conversion value of concrete compressive strength of the ith test area after being corrected.
——the minimum value of the conversion value of concrete compressive strength of test area in the member.
fcu, e——the estimation value of strength for concrete of member.
——the average conversion value of concrete compressive strength of test area.
——the standard deviation of the conversion value of concrete compressive strength of test area in the member.
Ri——the rebound value of the ith test point in the test area.
Rm——the average rebound value of test area or test block.
Rmα——the average rebound value of test area when doing non-horizontal testing with rebound hammer.

1 General Provisions
2 Terms and Symbols
2.1 Terms
2.2 Symbols
3 Rebound Hammer
3.1 Technical Requirements
3.2 Verification
3.3 Maintenance
4 Testing Technology
4.1 General Requirements
4.2 Rebound Value Measurement
4.3 Carbonization Depth Measurement
4.4 Testing of Pumped Concrete
5 Calculation of Rebound Value
6 Testing Strength Curve
6.1 General Requirements
6.2 Unified Testing Strength Curve
6.3 Testing Strength Curve for Regions and Special Projects
7 Calculation of Compressive Strength for Concrete
Appendix A Conversion Table of Compressive Strength of Concrete for Test Area
Appendix B Conversion Table of Compressive Strength of Pumped Concrete for Test Area
Appendix C Modified Value of Rebound Value under Non-horizontal Testing
Appendix D Modified Value of Rebound Value of Different Pouring Planes
Appendix E Method of Formulating Testing Strength Curve for Different Regions and Project Types
Appendix F Report for Testing of Concrete Compressive Strength by Rebound Method
Explanation of Wording in this Specification
List of Quoted Standards