Macro crack characterization by linear and nonlinear ultrasound in concrete

International audienceConcrete Non Destructive Characterisation is one of the important stakes to evaluate the life duration in the present and future civil engineering structures. The damaging modes of the structures often imply the phases of the appearance and after growth of the cracks. We have to detect, identify and characterise them. The characterisation result must lead to a diagnosis of the criticality of a crack regarding the integrity of the structure and its ability to full fill its function. The aim of the present study is to determine the nature of a macro-crack (open or close) visible in surface and to give information on its depth. Two approaches are developed. The first one, based on diffuse ultrasound, provides information about the presence and the depth of an opened crack. The last, based on nonlinear ultrasound, gives information about the presence and the depth of a closed crack

Non Destructive characterization of cracks in concrete by ultrasonic auscultation of civil engineering structures

International audienceConcrete Non Destructive Characterisation is one of the important issues to evaluate the life duration in the present and future civil engineering structures. The damaging modes of the structures often imply the phases of the appearance and after growth of the cracks. We have to detect, identify and characterize them. The characterization result must lead to a diagnosis of the criticality of a crack regarding to the integrity of the structure and its ability to fulfill its function. The Non Destructive Evaluation techniques are numerous but the ultrasonic ones are able to give an answer to both the characterization and the follow-up of the defect on site. Yet if this method is potentially relevant to detect and identify the cracks in the concrete, we have today a certain amount of locks to remove in order to offer robust and reproducible industrial solutions. These locks range from research points like the description of the real propagation of linear or non linear ultrasonic waves in a heterogeneous material, to more industrial concepts such as the development of devices designed to be applied in the concrete control. For this purpose, we present our latest works on this topic. We develop an overview of the problem: first, to extract the most important theoretical solutions to analyse an unstopping and closed crack in concrete with an only one face access. Then we suggest a methodology to apply one of these solutions on site. A first step of this work after having chosen a solution is to check the ability of the technique to detect a crack, and its sensitivity to the length, depth and opening of the crack. We have developed an experimental plan based on theoretical concept to compare the linear and non linear survey on a set of specimens composed of concrete beams cracked to different depths. We describe the devices and give the latest results. The non linear technique is able to extract information on the size of the cracks. It is an important step to progress in the methodology. Some points are identified to improve its reproducibility and its applicability on site. That is the next works we are developing

Non linear acoustic applied to the concrete study

International audienceTo characterize concrete, ultrasonic sound is a tool that has been developed to access damage and cracking. Its heterogeneity and the scales of sizes of micro-structural elements are necessary to consider a wide range of tools for characterization. We define the parameters that can be extracted from the wave propagation and vibration conditions into a beam in the laboratory. The scale measures are specified and the importance of each test condition is explained. We focus on nonlinear acoustics which is particularly appropriate for monitoring the developments on the mesoscopic scale. We study the conditions for harmonic generation and modulation, and specify the possibilities of working with energy. The beams in some cases are cracked over a determined length. The findings present the advantages of this technique and the difficulties inherent to their on site implementation

Macro crack characterization by linear and nonlinear ultrasound in concrete

International audienceConcrete Non Destructive Characterisation is one of the important stakes to evaluate the life duration in the present and future civil engineering structures. The damaging modes of the structures often imply the phases of the appearance and after growth of the cracks. We have to detect, identify and characterise them. The characterisation result must lead to a diagnosis of the criticality of a crack regarding the integrity of the structure and its ability to full fill its function. The aim of the present study is to determine the nature of a macro-crack (open or close) visible in surface and to give information on its depth. Two approaches are developed. The first one, based on diffuse ultrasound, provides information about the presence and the depth of an opened crack. The last, based on nonlinear ultrasound, gives information about the presence and the depth of a closed crack

Effect of the presence and size of a localized nonlinear source in concrete

International audienceThe aim of the present letter is to identify the contribution of a macroscopic source of elastic nonlinearity in concrete, a medium which by nature is nonlinear, and belongs to the nonlinear mesoscopic class of materials. The influence of real, localized macro-cracks is characterized with respect to the intrinsic nonlinearity of the material. The influence of the size of the source on the amplitude of the measured nonlinearity is qualitatively demonstrated. A comparison is made between the changes in linear and nonlinear parameters