Number of concrete strength tests using the elastic rebound method

Abstract

The article discusses the determination of the required number of experiments when determining the compressive strength of concrete using the elastic rebound method. It is shown that it is not correct to accept a deterministic value for the minimum number of experiments for all grades (classes of concrete). This value depends on the average strength of concrete and the instrument error of the device used. For a given coefficient of variation, with increasing concrete strength, the required number of experiments increases. For the maximum permissible coefficient of variation of concrete strength of 13.5%, calculated dependences of the minimum number of experiments on the average strength of concrete were obtained for the minimum and maximum instrumental errors of the sclerometers used, determined by analyzing the passport data used in Russian organizations involved in the inspection of buildings and structures. The proposed method, which relates the strength of the material of the structure under study and the instrumental error of the device used, can be extended to other methods of determining strength by non-destructive methods and can be the basis of the technical specifications for the creation of devices for non-destructive testing of concrete.

Keywords

• concrete strength
• schmidt hammer
• number of experiments
• instrument error
• confidence interval
• concrete grade
• concrete class