Modelling of aged reinforced concrete structures for design extension conditions (CONFIT)

The CONFIT project uses a multi-disciplinary approach to investigate the various physical and chemical degradation mechanisms and how they affect the mechanical load bearing capacity of concrete in long term operation. Reinforced concrete structures are, indeed, of safety relevance in nuclear power plants due to the containment function of the reactor building and load bearing functions of the control building and shielding functions of specific concrete structures.

During the project, it was investigated how various external chemical and physical stressors affect the mechanical concrete properties as a material (Ferreira, M. and Fülöp, L., 2020) and in particular how corrosion of the reinforcement affects the load bearing capacity of a concrete structure (Calonius, et al., 2023b) and how this can be numerically simulated (Calonius, et al. 2021). For the simulation of full-scale loading scenarios on reinforced concrete structures involving physically, chemically or mechanically deteriorated concrete, specific material models for concrete were developed during the project. One of the advantages of such advanced concrete models is the ability to respond to anisotropic behaviour, which is inherent in damaged concrete (Vilppo, et al., 2021).

Since the calibration of the model parameters requires measurements of anisotropy in concrete under controlled multiaxial loading, a specific method using ultrasonic wave velocity measurement was developed (Calonius et al., 2022c). This method enables the computation of the damaged stiffness matrix components from the ultrasonic pressure and shear wave velocity measurements on the concrete sample in different directions.

As a result, the project has generated important findings in the domain of nuclear safety, some of which present novelty value of academic importance.