Published in:
e-Journal of Nondestructive Testing, 27 (2022) 9
Language:
Without Specification
DOI:
10.58286/27262
ISSN:
1435-4934
Origination:
Footnote:
Description:
Prestressed concrete is present in many civil engineering structures such as dams or containment buildings. Due to aging of the structures (creep, shrinkage, corrosion…) prestressing losses can occur. Thus, it is important to be able to know the stress state in order to ensure structural safety. The current techniques, such as the crossbow-test used for assessing the tension in the prestressing cables, are semi-destructive. However, some structures such as containment buildings cannot withstand intrusive testing. It is thus necessary to use non-destructive techniques to assess the concrete stress in order to monitor the prestressing losses. The aim of this study is to assess the concrete stress variations by electromagnetic techniques. More practically, the study focuses on the impact of compressive stress on the propagation of Ground Penetrating Radar (GPR) waves in concrete.The measurements are done with GPR antennas with a center frequency of 1,5 GHz on concrete specimens under compressive stress. Different GPR measurement configurations (reflection or transmission) are used. Tests are performed on saturated and dry samples and with different orientations of the antennas compared to the loading direction. The signals are analyzed in both time and frequency domain. When the antenna is parallel to the direction of loading, results show that an increase of stress induce a decrease of the magnitude and a time offset of the signal. These outcomes are observed during the loading as well as during the unloading. The results do not depend on the hydric state of the slab. However, they depend on the direction of the wave propagation compared to the loading direction.