7 Bauwerkssicherheit
Filtern
Dokumenttyp
- Posterpräsentation (96) (entfernen)
Referierte Publikation
- nein (96)
Schlagworte
- Corrosion (11)
- Stainless steel (7)
- KorroPad (6)
- Corrosion resistance (5)
- Heat treatment (5)
- Corrosion Testing (4)
- Corrosion testing (4)
- EPR (4)
- Flame retardancy (4)
- Monitoring (4)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (96)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (31)
- 7.6 Korrosion und Korrosionsschutz (18)
- 7.1 Baustoffe (17)
- 7.4 Baustofftechnologie (13)
- 8 Zerstörungsfreie Prüfung (13)
- 7.2 Ingenieurbau (10)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (6)
- 8.5 Röntgenbildgebung (6)
- 6 Materialchemie (5)
Resistance to carbonation and chloride migration are critical durability properties in cementitious construction materials. The ingress of CO2 and chlorides can lead to concrete deterioration and reinforcement corrosion, underscoring the importance of ensuring high resistance to these durability-reducing factors. Traditional methods, such as determinating the carbonation coefficient using standard procedures, are time-consuming and resource-intensive. These tests typically require 42 days of preconditioning, followed by 70 days before the final results can be determined using a phenolphthalein test, for a total duration of 112 days. In addition, some test chambers can only accommodate four samples at a time.
In this study, we investigate whether 1H NMR relaxometry can effectively predict not only the carbonation resistance, KAC,3%, but also the chloride migration coefficient, DRCM, and the compressive strength, fc, of concrete, providing a method that could potentially streamline and accelerate the material development process by directing us quickly to potentially well-suited formulations. We performed measurements on non-carbonated fully saturated concrete and mortar samples at 28, 56, and 92 days using the NMR tomograph at BAM (8.9 MHz). Notably, the NMR measurements taken at 28 days showed no significant differences, suggesting that this timeframe is sufficient for meaningful results. The samples analyzed were drill cores, each 70 mm in diameter and approximately 120 mm in height. The NMR features we focused on included the initial amplitude E0, the x and y values of the dominant T2 relaxation time, and the logarithmic mean of the T2 relaxation time distribution. Another key feature was the surface relaxivity, which was determined by comparing the NMR curves with results from mercury intrusion porosimetry. We examined the correlation of these NMR features with the aforementioned durability properties, which were determined in a laboratory on sister samples using standard procedures. No chloride migration tests were performed on the mortar samples, and the carbonation procedure was carried out unter atmospheric conditions.
The preliminary results show that the correlation factors for the NMR features with the carbonation coefficients of concrete were particularly remarkable. The strongest correlations were observed for the dominant relaxation time and the logarithmic mean, with values approaching 1. The preliminary results also indicate that there are high correlations between the compressive strength and amplitude-related features. In contrast, no strong correlations are observed for the DRCM. Although the results related to the mortar samples are still being analyzed, these initial correlations suggest that 1H NMR relaxometry could be a valuable tool for early assessment of material properties. Furthermore, the rapid and non-destructive nature of NMR measurements, requiring only a few minutes per sample, suggests that this technique has the potential to significantly accelerate the process of evaluating durability properties in cementitious materials. This capability also paves the way for the use of NMR features as input for AI-driven predictive models.
Optimization Framework for Powder Bed 3D Printed Concrete Structures under Various Constraints
(2024)
The fusion of 3D printing with concrete has transformed large scale construction, accelerating creative design possibilities. In recent years, multiple printing techniques have been developed and are still under investigation. The powder bed technique enables overhang constructions, thereby increasing design flexibility. To maximize the advantages of those printing techniques, a holistic approach is required taking topology optimization through finite element analysis into account. The challenge is to consider a range of constraints, from material to geometrical to manufacturing.
The current research focuses on the development of a holistic approach to large-scale 3D powder bed printed concrete structure optimization, navigating the in-tricacies of constraints, leveraging the advantages of powder-based printers, and integrating essential information from material tests. A workflow starting from geometry input and ending with printing instructions is derived, minimizing user interaction, and offering fast and reliable results for different structures. Starting from a geometric model of the global design with the required load cases, the geometry is optimized with respect to reduce the mass and thus CO2 emissions. Thereby, the topology optimization includes various constraints: stress con-straints (mitigating tension and limit compressive stress using Drucker-Prager based models), geometric constraints (preserving specific surfaces from optimi-zation), and manufacturing constraints (controlling member size and avoiding trapped powder). Different objective functions, like minimizing compliance or mass are considered in this study. The process receives input from upstream ma-terial tests, offering insights into strength, stiffness and possible anisotropy. This integration of material testing enhances the accuracy and reliability of the opti-mization, aligning the design with real-world behavior of 3D printed concrete. An important aspect of the workflow is the segmentation of the optimized global structure into substructures, aligning with the size limitations of the 3D powder-bed printer. As final output of the developed workflow, printer specific fabrica-tion instructions are generated for each substructure. The developed optimization framework is demonstrated in the design of a multiperson shading element.
Germany has set itself the task to become a world leader in the field of green hydrogen technologies and is promoting the transition to a hydrogen economy. The H2Mare flagship project is exploring the offshore production of green hydrogen and other power-to-X products. One of the most important goals is the safe and cost-efficient operation of offshore infrastructures, where a service life of at least 25 years is aimed. However, the corrosive environment towards metallic materials presents challenges in marine areas. The atmosphere at one location could be affected by the distance to the sea level and does not have the same corrosivity for all exposed kinds of materials. The creation of an atmosphere corrosion atlas for marine environments by weathering campaigns aims to close this gap. Operators of offshore structures can use the data to estimate the corrosivity of the atmosphere on the construction site. This allows planning to be optimized in terms of platform safety as well as maintenance costs.
ISO 9223 standard for the classification of corrosivity in atmospheres is based on the mass loss of standard samples. We are concerned with the question of which corrosivity categories for Fe-sheets can be found at an offshore wind turbine and where they are comparable with our offshore locations.
The preliminary results indicate that the extreme corrosivity of class CX is only given in splash water-affected exposure, which is not a real atmospheric exposure condition. The results of the exposure at the SP show that the corrosivity category changes into C4, only a few meters above the splash water zone. Compared to the marine environments at Helgoland or OSS-Platform, the corrosivity is higher. The offshore environment is not as corrosive as originally expected, no atmospheric corrosion attack could be determined that would form the corrosivity category C5.
Extrusion based 3D concrete printing (3DCP) is a growing technology because of its high potential for automating construction and the new possibilities of de-sign. In conventional construction methods, a sample is taken to be representative for one material batch. However, in 3DCP continuous mixing is used which re-sults in variations during the mixing process. Therefore, one sample is not repre-sentative for the entire structure. This leads to the necessity of continuous and re-al-time process monitoring.
At the Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin, a test rig is developed to allow for comprehensive monitoring of the printing process. For this purpose, sensors for torque, temperature, pressure and moisture are in-stalled into the pipe. A laser scanner is installed at the nozzle to acquire infor-mation about the geometry of the extruded material.
This study focuses on the variations of pressure and temperature which are caused by changes in the material due to the ongoing mixing process. Preliminary results indicate that changes in the material properties cause changes in the sensor signals as well. These changes can be observed in various sensors with a delay, caused by material which is carried downstream. In the following, the data is ana-lysed to investigate if the changing material and the so caused change in pressure can be used to calculate volume flow.
The residual post-fire mechanical properties of fiber-reinforced epoxy (EP) composites are influenced by their fire residues after burning. This study uses intumescent/low-melting glass flame retardants (FRs) to tailor fire residues in epoxy resin. Processibility of prepregs, and their quality are analysed for transfer of the flame-retardant epoxy resins to layered glass-fiber reinforced composites (GFRCs). Minimal effects were found on the pre-fire flexural strengths of the composites due to low loading of the FRs. However, when transferred to GFRCS, the fire residues diminish significantly. Process, testing, and material adaptations are required to improve theoretical and experimental estimations of the post-fire mechanics of the composites.
The global plastic industry relies on fossil-based materials, presenting environmental challenges. A sustainable polymer namely poly(limonene carbonate) (PLimC), made of limonene and CO2 as two monomers from non-food sources, shows advances in various applications where additives such as flame retardants (FRs) are crucial to comply with fire safety measures.
The variety of FRs is wide, and therefore the approach involved conducting a comparative study of four different halogen-free flame retardant systems that are conventionally used in polycarbonates and polyolefins to understand which FR enhances the flame resistance of PLimC most effectively. The primary task of the project is to conduct experimental evaluations to analyze the thermal properties, flammability, and fire behavior of each system. This data will offer valuable insights towards the advancement of safer and more sustainable materials.
Aspects of corrosion protection in the maritime sector– Focus of Current research of BAM for H2Mare
(2024)
Germany has set itself the task of becoming a world leader in the field of green hydrogen technologies and is promoting the transition to a hydrogen economy. The H2Mare flagship project is exploring the offshore production of green hydrogen and other power-to-X products. One of the most important goals is the safe and cost-efficient operation of offshore infrastructures, where a service life of at least 25 years is aimed at. However, the corrosive environment towards metallic materials presents challenges in marine areas. The atmosphere at one location could be affected by the distance to the sea level and does not have the same corrosivity for all exposed kinds of materials. The research of the durabilitty of different materials and corrosion protection systems by weathering campaigns and laboratory experiments aims to close this gap of knowledge. BAM‘s mandate is to make the data available to the responsible operators through standardisation to ensure safety and cost efficiency.
The development of standards that include simulation models is often based on heuristics that include experimental data that is used to calibrate and validate the simulation models. However, these data and the corresponding calibration procedures are usually not part of the publicly accessible documentation making it very difficult to identify gaps in the current standard or extend it to new innovative solutions. The poster shows an adapted procedure that integrates the complete process into a database and a workflow to be published alongside the standard.