Rissbildung in Beton infolge Bewehrungskorrosion

Rissbildungen und Abplatzungen über korrodierender Bewehrung kennzeichnen wichtige Grenzzustände der Dauerhaftigkeit von Stahlbetonbauwerken. Mithilfe eines umfassenden Versuchsprogramms konnte das Verhalten der Betonrandzone unter dem Einfluss korrodierender Bewehrung detailliert untersucht werden. Die systematische Analyse der Schädigungsprozesse ermöglichte die Herleitung eines analytischen Prognosemodells für die korrosionsinduzierte Rissbildung in Stahlbetonbauteilen

A closer look at the corrosion of steel liner embedded in concrete

Containment wall of nuclear power plants is an example of a concrete structure enveloping a steel liner plate. In this research, the situations observed in connection with liner failures were investigated, namely the presence of a piece of wood (foreign matter) and a delamination gap between steel liner and concrete, with the purpose to study and define the corrosion mechanism of the steel liner plate and identify which factors promote or impede the occurrence of corrosion.Specimens were concrete slabs containing a steel plate, an inlay to modify the conditions at the steel surface, and electrodes for electrochemical measurements. The inlays represented “normal” concrete, low-pH concrete, a piece of wood, and a delamination gap between concrete and steel, and the same systems supplemented with chlorides. The results from two-year tests with wetting-drying cycles revealed localized corrosion in steel underneath the piece of wood, close to the inlay perimeter. The attack could be explained mainly by the mechanism of crevice corrosion. In contrast, no corrosion attack of steel liner could be detected in specimens with the delamination gap. The results from the experiments and steel liner characterization are provided in this paper, together with the reasoning behind the proposed degradation mechanism

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

Interpenetrated Magnesium–Tricalcium Phosphate Composite: Manufacture, Characterization and In Vitro Degradation Test

Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test.Magnesium and calcium phosphates composites are promising biomaterials to create biodegradable load-bearing implants for bone regeneration. The present investigation is focused on the design of an interpenetrated magnesium–tricalcium phosphate (Mg–TCP) composite and its evaluation under immersion test. In the study, TCP porous preforms were fabricated by robocasting to have a prefect control of porosity and pore size and later infiltrated with pure commercial Mg through current-assisted metal infiltration (CAMI) technique. The microstructure, composition, distribution of phases and degradation of the composite under physiological simulated conditions were analysed by scanning electron microscopy, elemental chemical analysis and X-ray diffraction. The results revealed that robocast TCP preforms were full infiltrated by magnesium through CAMI, even small pores below 2 lm have been filled with Mg, giving to the composite a good interpenetration. The degradation rate of the Mg–TCP composite displays lower value compared to the one of pure Mg during the first 24 h of immersion test