Evaluation of concrete strength by means of ultrasonic waves: A method for the selection of coring position

• We propose a new method to select the eligible positions where to extract the cores.
• We compare the implications of a random choice and the proposed guided choice.
• The risk to have cases of correlation curves not representative is reduced.

The evaluation of the concrete properties in a structure has a fundamental importance for safety and structural integrity assessments. An adequate knowledge of the structural concrete performances can be obtained from a large number of cores where performing destructive tests. Non-destructive ultrasonic waves test can be performed before other kind of tests, allowing to improve the assessment of the structural concrete performances and to extend the results to the same kind of elements of the structure, not directly investigated by destructive tests. The aim of this work is to test a new method to identify a good practice to select the position of testing points on which extract the cores starting from an analysis of a preliminary campaign of non-destructive measurements. In this way it is possible to reduce risk of errors of the compressive strength evaluation by a different approach from those used nowadays. The data obtained from an experimental campaign with both non-destructive and destructive tests on 75 concrete columns were considered to validate the new method. The implications of a completely random choice and the guided choice, using the method proposed, were analysed with an iterative and exhaustive approach. European Standard (EN 13791) was followed for in situ measurements and preliminary data analysis.