Concrete Defects Sizing by Means of Ultrasonic Velocity Maps

Abstract

The paper illustrates the results of an experimental test which intends to check the efficacy of ultrasonic testing (UT) in detecting anomalies inside concrete elements. For this purpose, UT has been carried out on a small concrete wall having different defects deliberately settled inside the wall during casting. A grid of several measurements points has been arranged on the wall surfaces and for each point the ultrasonic signal has been acquired after passing through the thickness of the wall and the propagation velocity V has been extracted and analyzed. A graphic representation of V distribution has been implemented by a map where each pixel identifies one measurement point and is representative of its neighborhood. This map highlights areas with different velocity values, and allows to visually detect areas having particularly low velocity. The matching between the low-velocity areas and the artificial defects has been analyzed, and the level of accuracy of the V map in detecting and sizing the concrete inner defects has been discussed with reference to different spacing of the grid points. Finally, some considerations regarding the choice of the most suitable measurements grid have been addressed.

About the Possible Limitations in the Usage of the Non-Destructive Ultrasonic Pulse Velocity Method for Assessment of Cracks in Reinforced Concrete Structures, Subjected to Direct Environmental Exposure

“…Two transducers are used-one transmitter of ultrasonic signals and the other as a receiver of these signals [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. They usually operate in the frequency range of 25-60 kHz.…”

“…It is labor-intensive and expensive. The study is limited to individual points and does not provide information on the quality and damages of the whole structure [3][4][5].…”

“…In recent years, for assessment of reinforced concrete structures, construction quality control, and detecting existing cracks, NDUPVM has gained increasing popularity and interest [3][4][5][6][7][8][9][10][11]21]. It is a highly specialized and complex method that requires careful data collection and expert analysis.…”

Deploying Geometric Dimensioning and Tolerancing in Construction

“…The 2 m straightedge in the British system [25,33,105] and the 10 ft straightedge method in the American system [15,36] are currently regarded as standard methods. In practice, to determine the flatness of concrete and other types of finished floors, the straightedge basis is used in both American and British systems, especially for floors finished by conventional techniques [15,35,[105][106][107][108]. Figure 16 shows the principle behind using a straightedge to determine the flatness of floor surfaces.…”

The Use of Destructive and Non-Destructive Testing in Concrete Strength Assessment for a School Building

“…The integrated use of varying investigation methodologies allows to establish the effectiveness of a knowledge-based approach and generate new ideas for the development of the structure and its strategic role within the city. Concu and Trulli [18] illustrate the results of an experimental test, which intends to check the effectiveness of ultrasonic testing (UT) in detecting anomalies inside concrete elements [19]. For this purpose, UT is carried out on a small concrete wall having different defects deliberately settled inside the wall during casting.…”