| 1. |
- Alhede, Andreas, 1996, et al.
(författare)
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A two-stage study of steel corrosion and internal cracking revealed by multimodal tomography
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618. ; 394
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Tidskriftsartikel (refereegranskat)abstract
- Modeling of corrosion-induced cracking is limited by lacking knowledge on the behavior of corrosion products. In this work, the corrosion and cracking processes were experimentally investigated in 3D at two different stages. The processes were measured at micro-structural scale, applying nondestructive neutron and X-ray computed tomography in two scans at different stages in the corrosion process. A method to evaluate the average volumetric strain of the compressed corrosion layer was proposed and displacements in the concrete matrix were measured. Strain localization revealed cracks not directly visible in the images. Multimodal tomography demonstrated to be an effective method for investigating steel corrosion in reinforced concrete.
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| 2. |
- Alhede, Andreas, 1996, et al.
(författare)
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Monitoring corrosion-induced concrete cracking adjacent to the steel-concrete interface
- 2023
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Ingår i: Materials and Structures/Materiaux et Constructions. - 1359-5997. ; 56:9
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Tidskriftsartikel (refereegranskat)abstract
- Substantial research effort has been devoted on linking corrosion-induced cracking of concrete with the internal corrosion damage level. Still, numerical models of the corrosion and cracking process require internal parameters, that cannot be directly evaluated from experimental data. Therefore, this study provides a novel experimental method for monitoring the effects of steel corrosion adjacent to the steel-concrete interface. This non-destructive method is suited for small-scale laboratory-made specimen, and was designed to provide missing information required for subsequent calibration of numerical models. Hollow steel bars were cast into concrete and subjected to accelerated corrosion using the impressed current technique. The deformations of the hollow steel bars were measured using distributed strain sensing in an optical fibre, attached to the inner surface of the hollow steel bars. After the corrosion period, X-ray Computed Tomography scans were performed to evaluate concrete cracking and corrosion level. The results reveal a non-uniform distribution of strain around the perimeter of the steel, indicating a non-uniform radial stress distribution. The non-uniformity correlated very well with the position of the corrosion-induced cracks; with extension hoop strains in the steel at the location of these cracks and contraction hoop strains in between. Further, the corrosion level varied around the perimeter, with higher values near cracks. The combination of non-destructive monitoring techniques used in this study on small-scale laboratory-made specimens show great potential to reveal new insights on how the corrosion pattern, corrosion-induced cracking of the concrete cover and stress (indirectly measured through the strain in the steel) interact throughout the corrosion process.
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| 3. |
- Alhede, Andreas, 1996
(författare)
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Novel approaches for monitoring effects of steel corrosion in reinforced concrete
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion of steel reinforcement is a common deterioration mechanism in reinforced concrete structures. This deterioration impacts the safety of the structure and may require extensive repair and maintenance work. There is currently no method available for accurately measuring internal corrosion damage non-destructively. Therefore, establishing correlations between outer signs of corrosion, such as crack pattern and width, and the corresponding internal corrosion morphology and level is of significant interest. However, prior research has shown that relying solely on crack width as a performance indicator for corrosion damage is inadequate. Hence, further research is needed to study the corrosion and cracking processes in reinforced concrete to be able to identify and quantify underlying physical processes and factors. To contribute to knowledge in the field, this thesis focuses on novel approaches for non-destructive monitoring of the effects of steel corrosion in small-scale reinforced concrete samples. In this work, time-resolved neutron and X-ray Computed Tomography were applied to link the evolution of material phases to kinematics. Further, two independent studies, one using neutron and the other using X-ray Computed Tomography, were used to quantify corrosion-induced deformations within concrete. These deformations were successfully quantified, and the identified locations of concrete cracking correlated well with the observed strain localisation. Interestingly, the kinematics quantified allowed for the detection of strain localisation in areas where concrete cracks were too small to be visually identified from the image data, indicating the potential for early-stage concrete crack detection. Additionally, an expression for the average volumetric strain in the compressed corrosion layer was derived based on the evolution of material phases within the sample. Further, an experimental setup was designed to monitor corrosion-induced deformations adjacent to the steel-concrete interface using an open-ended steel tube instrumented with an optical fibre for distributed strain sensing. X-ray Computed Tomography allowed for quantitative and qualitative assessment of corrosion level and concrete cracking. The corrosion-induced deformations in the steel tube were found to be non-uniform, indicating a non-uniform distribution of radial stress around the steel. This non-uniformity correlated well with the location of the corrosion-induced cracks, with extension hoop strains observed in the steel tube at the location of these cracks, and contraction hoop strains observed in between them. Corrosion was more severe in bands along the steel, coinciding with the position of the longitudinal cracks. The research conducted in this work demonstrated the potential of non-destructive monitoring of steel corrosion in reinforced concrete. For future research aiming at increasing the fundamental understanding of corrosion-induced concrete cracking, it is essential to integrate advanced experimental techniques with numerical modelling.
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