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The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values.
To combat climate change the share of renewable energy production must increase drastically. Offshore energy production – offshore wind and power-to-X – are crucial to achieving climate targets. However, the impact of these offshore constructions – wind turbines and production platforms – on the marine environment remains unclear in many aspects. Potential sources of chemical emissions are corrosion protection systems, remobilization of contaminants from old sediments during construction, the brine of desalination plants and increased shipping for maintenance and transportation. In order to minimize the environmental impact of renewable energies, close monitoring is essential. The goal of this project is the development of a monitoring concept for an offshore power-to-X production platform.
Maritime exposure poses particular challenges for corrosion
protection in plant construction. In addition to the right choice
of materials, special design features that can have an impact
on corrosion resistance must also be taken into account to
ensure long-lasting corrosion protection. In practice, structural
crevice arrangements are unavoidable, and therefore the
crevice corrosion resistances of stainless steels are of
particular importance. These and other influences are being
investigated in this joint project.
While alkali-activated binders offer certain advantages over traditional Portland cement binders, particu¬larly in terms of resistance against chemical attacks and potentially environmental footprint, their degra¬dation mechanisms remain incompletely understood at present, specifically carbonation. Thus, this study investigates the impact of natural and accelerated carbonation (1% and 4% CO2) on three different compositions of alkali-activated concretes: 100% calcined clay (C100) binder, 100% ground blast furnace slag (S100) binder, and a 40% calcined clay and 60% blast furnace slag blend (C40S60). C100 concretes exhibit faster carbonation kinetics, with five times greater natural carbonation depths than S100. This difference diminishes under accelerated carbonation, showing a 1.5 times difference for 1% CO2 and complete carbonation for 4% CO2 at 90 days. The results thus confirm that accelerated carbonation testing of low-Ca alkali-activated concretes yields results that are not representative of natural carbonation. The C40S60 sample demonstrates a carbonation profile similar to a CEM I concrete, i.e., a high carbonation resistance. Microstructure analysis indicates the formation of three polymorphs of calcium carbonate for S100 (calcite, vaterite, and aragonite), with a higher CO2 concentration favouring aragonite over vaterite. C100 exhibits no calcium carbonates; instead, sodium carbonates form, including trona for 4% CO2 and natrite for both accelerated tests. C40S60 shows calcium and sodium carbonates, although to a lesser extent, containing predominantly calcite and minor signals of natrite. Suitable compositions, like C40S60, prove as effective during natural or accelerated carbonation tests as conventional Portland cement concrete.
3D concrete printing is an innovative new construction technology offering the potential to enable an efficient production of individual structures with less consumption of resources. The technology will mainly shape the future construction philosophy, automate the build process and help reaching the climate goals in civil engineering. From the design of a structure to the printed component, many individual steps based on different software are required which must be repeated for each new or changed structure. First, the geometry of the structure is created in a CAD program. Second, the print path is defined in a slicer software creating the machine code for the printer (G-Code). Finally, the structure can be printed. Furthermore, a numerical model of the printed structure is necessary for process optimization and control. In that way the number of test prints can be reduced, costs can be saved, and the component behavior can be predicted. For those purposes, an automated workflow allowing to run all steps or individual steps without interacting with each individual software program is required. Furthermore, changes in parameters or the exchange of parts (using a different design or different printer) must be possible in a simple manner. In the presented work, such an automated workflow based on the example of a parametrized wall element for extrusion-based concrete printing is developed. The investigated wall structure is parametrized using the global geometry parameters: height, width, thickness, radius, kind of infill structure (honey-comb, zig-zag) and number of repeated infills. All above mentioned steps are implemented via python interfaces using pydoit as workflow tool. General interfaces with prescribed input and output files are defined allowing adaptations for different software and tools. The described workflow is tested by performing a test series investigating the influence of the in-fill structure on the mechanical properties of the test walls.
Interlaboratory studies are common tools for collecting comparable data to implement standards for new materials or testing technologies. In the case of construction materials, these studies form the basis for recommendations and design codes. Depending on the study, the amount of data collected can be enormous, making manual handling and evaluation difficult. On the other hand, the importance of the FAIR (findable, accessible, interoperable, and reusable) principles for scientific data management, published by Wilkinson et al. in 2016, is constantly growing and changing the view on data usage.
The benefits of using data management tools such as data stores/repositories or electronic laboratory notebooks are many. Data is stored in a structured and accessible way (at least within a group) and data loss due to staff turnover is reduced. Tools usually support data publishing and analysis interfaces. In this way, data can be reused years later to generate new knowledge with future insights. On the other hand, there are many challenges in setting up a data repository, such as selecting suitable software tools, defining the data structure, enabling data access, and understanding by others and
ensuring maintenance, among others.
This talk discusses the advantages and challenges of setting up and applying a data repository using the interlaboratory study on the mechanical properties of printed concrete structures carried out in RILEM TC 304-ADC as example. First, the definition of a suitable data structure including all information is discussed. The tool-dependent upload process is then described. Here, the data
management system openBIS (open source software developed by ETH Zurich) is used. Since in most cases an open compute platform allowing access from different organisations is not possible or available due to data protection and maintenance issues, tool-independent export options are discussed and compared. Finally, the different query and analysis possibilities are demonstrated.
Die Präsentation gibt einen Überblick über die Arbeiten im German Pilot des EU-Projekts TREEADS. Es werden klein-, mittel- und großskalige Versuche an Waldboden mit einheimischer Vegetation durchgeführt. Begleitend werden numerische Untersuchungen durchgeführt, die eine Variation der Parameter, wie Bodenfeuchte, Temperaturen und Wind über die Experimente hinaus erlauben. Die gemessenen Materialparameter dienen als Input für die numerischen Berechnungen. Die numerischen Modelle werden mit den mittel- und großskaligen Experimenten validiert.
Esta pesquisa avaliou o fenômeno de autocicatrização nas propriedades mecânicas e absorção capilar de concretos estruturais. Foram avaliados dois aditivos cristalizantes em pó, dosados de acordo com o teor recomendado pelos fabricantes. Aditivos cristalizantes aumentam a densidade do gel C-S-H e formam cristais insolúveis, bloqueando fissuras. Três traços de concreto foram produzidos: referência, aditivo-X com 0,8% e aditivo-Y com 2,0% em relação a massa do cimento. Aplicou-se 75% da carga de ruptura aos 3- e 14-dias para gerar microfissuras e comparar com a referência. Posteriormente, a autocicatrização foi avaliada aos 28- e 76-dias. A propriedade de resistência à compressão axial foi determinada aos 28-dias, revelando que os aditivos cristalizantes contribuíram para um aumento médio de 12% desta propriedade. A idade do carregamento dos concretos não apresentou um impacto significativo na resistência à compressão axial, mas apontou resultados significativos entre os tipos de aditivos estudados, conforme ANOVA. As propriedades de absorção de água por capilaridade foram avaliadas aos 28- e 76-dias, indicando uma redução de absorção de água média de 42% devido ao uso dos aditivos cristalizantes. Em conclusão, a incorporação dos aditivos cristalizantes contribuiu de maneira positiva para a autocicatrização dos concretos estudados, indicando uma recuperação parcial das microfissuras.
Chloride binding by the hydrate phases of cementitious materials influences the rate of chloride ingress into these materials and, thus, the time at which chloride reaches the steel reinforcement in concrete structures. A particularly important role in this context is played by layered double hydroxides (LDHs), including AFm phases. Chloride binding isotherms of individual LDH/AFm phases would be required as input for computational models of chloride ingress, but such isotherms are only available for a few AFm phases, and in addition the available data are partly conflicting.
The present study, conducted in the context of RILEM TC 283-CAM ‘Chloride transport in alkali-activated materials’, significantly extends the available database by determining the chloride binding isotherms of LDH/AFm phases (monosulfate, strätlingite, hydrotalcite, and meixnerite), and of alkali-activated slags (AAS) produced with four different activators (Na2SiO3, Na2O∙1.87SiO2, Na2CO3, and Na2SO4), in NaOH/NaCl solutions at various liquid/solid ratios. Selected solids after chloride binding were analysed by X-ray diffraction, and thermodynamic modelling was applied to simulate the phase changes occurring during chloride binding by the AFm phases.
The chloride binding isotherms of LDH/AFm phases depended strongly on the liquid/solid ratio during the experiments, resolving apparent contradictions of the previously available data. The dependency on liquid/solid ratio must be attributed to kinetic restrictions, which are, however, currently poorly understood. Chloride binding by AAS pastes was generally higher than for Portland cement pastes and was only moderately influenced by the employed activator. A steep increase of the chloride binding by AAS occurred at free chloride concentrations above approx. 1.0 M, which is possibly related to chloride binding by the C-(N-)A-S-H gel in the AAS.
Protection against terroristic or accidental scenarios in industrial settings requires suitable designs of structures to resist blast loads. Field testing as well as finite element simulations are among the techniques available to engineers in the understanding of the structural behavior against blast loading.
As blast testing of complex scenarios can be very resource intensive, tests are generally performed for simplified scenarios. Numerical tools can be used to model these scenarios to get better insight into blast loading, structural response, and the resulting damage to the structure. During the next steps, the simplified scenario is successively modified in numerical simulations to incorporate complexities that cannot be covered in blast testing experiments. One of the conditions for this approach to work is that the original simplified numerical simulation is valid. The scopes and challenges encountered in such a validation are the focus of this presentation/article.
A relatively ‘simple’ field test of a horizontal reinforced concrete (RC) slab subjected to blast loading is taken as an example for validation of the performance of numerical tools. The blast test incorporated various measurement techniques to quantify the blast load as well as the behavior of the RC slab. Blast load was measured using flush mounted piezoelectric pressure gauges, whereas acceleration sensors and fiber-optic sensor cables were used to characterize the dynamic behavior of the slab under blast loading. Additionally, damage characteristics were ascertained also using fiber optic sensing. The application of such measurement techniques, along with different numerical software available for the analysis of the scenario in question, demonstrate the scope of our contribution.
When it comes to the challenges, it begins with proper instrumentation of the test specimen followed by the data processing. For numerical modelling, geometric conditions with appropriate boundary constraints, physical conditions such as the configuration of the rebars, as well as material parameters add to this challenge. The issues of choosing appropriate material models and comparison of results with multiple software tools will be discussed. This discussion forms the basis for a coherent approach to technical-safety assessment of blast effects on structures in its broader sense.