PSI - Issue 64

Alexander Shuvalov et al. / Procedia Structural Integrity 64 (2024) 445–455 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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with ultrasonic control. Figure 6 shows an example of data obtained after processing of raw radarograms.

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Fig 8. a - 3D visualization of cumulative amplitudes, b - scheme of cumulative amplitudes, c – photofixation, d – typical GPR profile layout

The density of GPR survey profiles allowed to compile processed radarograms into maps of cumulative amplitudes for depth ranges from 0.1 m to 0.5 m for each of the column's studied planes. The core idea of this approach is as follows: the more homogeneous the studied medium, the fewer reflections there will be, and the lower the cumulative amplitudes will be. Relatively low values of normalized cumulative amplitudes on plotted maps (supplemented by analysis of processed radarograms) suggest homogeneity of concrete and the absence of significant (as far as the method's resolution allows to judge) defects in the section of columns. To confirm the results of NDT (both ultrasonic and GPR) surveys, cylindrical core samples of 55 mm diameter were extracted at the most unfavorable areas. On visual inspection of the specimens for defective areas, no anomalies in the form of pores or caverns were recorded in the depth of the cross-section. The view of the extracted samples is presented in Figure 9.

Fig.9. Photofixation of control samples

The density of concrete was also measured from the selected samples in order to indirectly determine the increased porosity of the concrete. The density range of the concrete samples ranges from 2,348 to 2,584 kilograms per cubic meter, which corresponds to heavy concrete according to GOST 26633-2015. Based on the results of visual inspection of selected cores, defects in the form of local pores and cavities were