Influence of stress variation on radar wave propagation in concrete: Application to the monitoring of nuclear containment building

• Published in: Nuclear engineering and design Vol. 433; p. 113877
• Main Authors: Confais, Aleth, Klysz, Gilles, Balayssac, Jean-Paul, Taillade, Frédéric, Sanahuja, Julien
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2025; Elsevier
• Subjects: Civil Engineering; Compressive stress; Concrete; Electromagnetic Properties; Engineering Sciences; Ground Penetrating Radar; Nuclear containment building; Ground Penetrating Radar; Compressive stress; Concrete; Nuclear containment building; Electromagnetic Properties
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2025.113877

•A compression stress increase delay and decrease the GPR signal.•This interaction depends on the water content and the stress direction.•Tests performed on a mock-up of a containment building confirmed these tests. Containment buildings of nuclear power plants are made of prestressed concrete. Maintaining the tension in prestressing tendons is essential for the safety of these structures. However, steel and concrete can be subject to ageing and pathology (creep, shrinkage, corrosion…), this can lead to prestressing losses. It is then crucial to be able to know the tension state of tendons. Current techniques used to evaluate tension in cables are semi-destructive and are then unusable on containment buildings. This is why it is relevant to develop non-destructive techniques to evaluate potential prestressing losses. Based on the inaccessibility of the cables, this study suggests evaluating concrete stress rather than cable tension. This work particularly focuses on the influence of stress on radar wave propagation in concrete. Tests show that a compressive stress increase on concrete slabs leads to an isotropic delay in the electromagnetic signal and an anisotropic decrease in amplitude, more pronounced in the direction normal to the stress direction. These variations highly depend on concrete hydric state, as it is observed that an increase in stress on a near-saturation or an oven-dried concrete does not induce a signal variation. Finally, in-situ tests performed onto a mock-up of a nuclear containment building built by EDF confirm the sensitivity of radar waves to a variation of concrete stress.