An overview of 15 years of French collaborative projects for the characterization of concrete properties by combining NDT methods

Abstract

This communication aims to present the evolution of the activities carried out in France for assessing concrete properties by combining NDT methods. An important effort was done for improving NDT methods, particularly for more suitable on-site applications (for instance use of ultrasonic non-contact or multi-array sensors, development of non-linear acoustic methods). A big database has been progressively built involving many NDT measurements regarding different concrete properties. The combination of NDT methods is explored by data fusion, using the theory of possibilities, for the assessment of compressive strength, moisture content and porosity. This procedure has been improved, reinforced and validated for onsite applications and is being extended to new concrete properties (carbonation depth, mechanical and thermal damages). A specific attention was developed to define and increase the quality and the optimization of the concrete characteristics evaluation. The sensitivity and the variability of NDT measurements were evaluated. The quantification of quality of inversion process and uncertainty of the assessment was also developed. And finally an optimization of number of NDT measurements and their localization on site was proposed.