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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.
Current capabilities for full-scale field testing are highly resource intensive. Reliable small-scale experiments are an effective alternative. Characterization of the dynamic response and damage of RC elements to scaled blast loads was investigated in scaled-down field experiments. Spatially resolved information on the dynamic structural response using distributed fiber optic acoustic sensing (DAS) and acceleration as well as blast loading by piezoelectric pressure sensors.
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.
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.
Bei der Betonage von Abdichtbauwerken können Temperaturen bis 110 °C und hohe Drücke bis 5 MPa erreicht werden. Mittels Technikumsversuchen wurde nachgewiesen, dass Mikroakustik- und Ultraschallsensoren zum Einbau in Demonstrationsbauwerke geeignet sind.
Die Untersuchungen wurden bei der BAM (Bundesanstalt für Materialforschung und -prüfung) in Berlin durchgeführt. Es ist vorgesehen, die Sensoren in Morsleben am Demonstrationsbauwerk im Anhydrit einzusetzen.
Currently, mandatory requirements and recommendations for the detection of irregularities in laser beam welded joints are based on classic micrographs as set out in the standard ISO 13919-1:2019. Compared to classic micrographs, computed tomography enables a non-destructive, three-dimensional and material-independent mode of operation, which delivers much more profound results. Even in building material testing, methods with limited informative value can be checked and supplemented by CT examinations.
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.
Dredging sediment refers to materials removed from the bottom of a water body during dredging operations. Mainly the dreading mud contains clay, silt, sand, water, and alkalis. This work incorporated dredging mud into the calcium sulfoaluminate cement at replacement levels of 0%, 10%, 30%, and 50% by weight. Pastes were evaluated after 1d, 28d, and 90d- hydration through mechanical strengths and the reaction rate by isothermal conduction calorimetry. XRD and MIP characterized the reaction products. The findings showed that small replacements (10% and 30%) increased early strength with higher ettringite formation in the system at 1d of curing. However, the evolution of mechanical strength was lower than the reference (0% replacement) over time. The results showed that in low replacement dosages, the dredging mud act as a nucleation site for the hydration of calcium sulfoaluminate phases.
Thermal runaway investigations were performed by subjecting single and double NMC pouch cells to thermal abuse condition inside an air-tight reactor vessel with an internal volume of 100 dm³. The study was divided into two series. The findings revealed the thermal runaway-induced explosion in the cells results in a rate of temperature increase greater than 10 K/s. The highest gaseous production was achieved at a range of 90 – 100% SOC and higher battery capacities 0.79 L/Wh (Series 1, 10 Ah cell) and 0.87 L/Wh (Series 2, 32 Ah cell). The investigation showed between 25 m³ and 84 m³ of explosible gas mixture could be released from electric vehicles of nominal useable electrical energy from 32 kWh up to 108 kWh at thermal runaway. It was also found that, the release of these explosible gases could undergo a secondary explosion.
Understanding the fundamentals of bioreceptivity enables the developement of functionalized materials. Concrete as the most used building material worldwide is of special interest as microbially greened panels may represent an alternative to classic façade greening with plants. This project includes extensive outdoor experiments, in which eight differently structured concrete panels are weathered under different conditions, aiming to grow a stable biofilm of photosynthetic eukaryotic organisms. Documentation and data analysis of this experiment will be demonstrated using an example of one of the surfaces.
In the maritime context of offshore operation, corrosion, in combination with the materials used, poses a particular challenge to ensure safe operation over long indefinite periods and to minimise susceptibility to failure. Until today, only a few corrosion protection systems have proven themselves for the interaction of efficiency, installation, and maintenance in the offshore sector. In addition, available corrosion test methods sometimes have major deficits about conclusions of the durability. Therefore, there is more research and development needed.
The flagship project H2Mare of the Federal Ministry of Education and Research aims to enable the production of green hydrogen and PtX products at high seas. Research is being driven forward by the partners in four individual projects, where BAM is involved in two.
In PtX-Wind, major kinds of corrosion attacks at offshore constructions are characterized and investigated, and suitable corrosion protection measures determined. In TransferWind, attention focusses on transferring scientific results into standardization.
This poster at the H2Mare Conference 2023 presents an overview of the investigation methods and contribution of the department “Corrosion and Corrosion Protection”.
Algal biofilm façades are an alternative to traditional green façades which can help to improve biodiversity and air quality within cities. They present a low maintenance approach in which subaerial algae are grown directly on concrete substrates. The intrinsic bioreceptivity of the substrate is a critical factor in successful facade colonisation. Existing research has identified several environmental and material properties which influence concrete bioreceptivity, however a consensus has yet to be made on which properties are most influential and how the interaction between properties may promote algal biofilm growth under specific conditions.
Even after autoclaving for 2 weeks in the temperature range of 120 to 200 °C, CEM I paste with a water-to-cement ratio of 0.5 still contains some low-crystalline C-S-H. The conversion of low-crystalline C-S-H to crystalline is faster with increasing temperature. The observed low-crystalline and crystalline C-S-H phases (reinhardbraunsite, jaffeite) indicate that the samples have not reached equilibrium yet under these experimental conditions. However, there is a good agreement between experiment and thermodynamic modelling for the other solids indicating that the used datasets are suitable for this application.
The transfer of flame-retardant epoxy resin formulations to composites for structural and lightweight applications in the energy and transport sector can be complex and requires systematic investigation. Here, uncoated and silane-coated ammonium polyphosphate (APP, Si-APP) intumescent compounds are transferred to prepregs using a Bisphenol A diglycidyl ether (DGEBA) resin matrix to 0/90o bidirectional glass fibers with an aerial weight of 600 g/m2. Inorganic silicates (InSi) are added to improve the fire residues of the composites after combustion and the total amount of flame retardants in the resin formulations was 10% by weight. The prepregs' fiber volume content (FVC) is corroborated using in-process measurements and thermogravimetric analysis. This was found to be approximately 60% for the composites containing APP, which is ideal for load-bearing applications with high mechanical strength. However, the Si-APP containing prepregs showed an inconsistent FVC potentially due to interactions with the commercial sizing of the glass fibers. The composites subsequently prepared are analysed for potential filtration effects of the additives via SEM after immobilization in a cured resin and platinum sputtering. The inter-laminar shear strength and the mechanical strength of the composites are compared via three-point bending tests. Additionally, the fire performance of the composites is analysed using cone calorimetry. It was found there was minimal impact of the loading of the flame retardants on the delamination of the composites and the flexural strength. However, the high density of the glass fibers possibly results in a suppression of the mode of action of the flame retardants in the composites. Therefore, the fire residues of the composites are further compared using SEM, and the flame-retardant modes of action upon transfer are investigated.
Fire resistance of fiber-reinforced polymers (FRPs) has been an important area of research for many years since FRPs are mainly used in the transportation and construction sectors. This study presents the fire behavior, and mechanical performance between the flame retarded pure epoxy resin and flame retarded glass-fiber composites before, during, and after a fire event. This enables a deeper understanding of the transferability of flame retardants on composite materials.
The residual post-fire mechanical properties of fiber-reinforced epoxy composites are influenced by their fire residues after burning. This study uses intumescent/low-melting glass flame retardants 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. Minimal effects were found on the pre-fire flexural strengths of the composites due to low loading of the flame retardants. However, when transferred to glass-fiber reinforced composites, the fire residues diminish significantly. Further studies are required to improve theoretical and experimental estimations of the post-fire mechanics of the composites.
This study presents the processability, fire behavior, and mechanical performance between the flame retarded pure epoxy resin and flame retarded glass-fiber-reinforced plastic before, during, and after a fire event. This enables a deeper understanding of the transferability of flame retardants, modes of action, char enhancement, and flame inhibition on composite materials
Bench-scale fire stability testing - Protective layers in carbon fibre reinforced polymer laminates
(2023)
Fire resistance testing of components made of carbon fibre reinforced polymers (CFRP) composites usually demands intermediate-scale or full-scale testing. In this study, a bench-scale test is presented as a practicable and efficient method to assess the improvement in structural integrity of CFRP with different protective interlayers during fire.
Safety is a key parameter for the design and construction of buildings. The most widely used construction material to date is concrete that consists of about 15-20 wt.-% cement, which is responsible for the main concrete properties, i.e., strength and durability. Despite many standards regulating the quality of cement, at present, there exists no viable method to track the cement life cycle “from cradle to grave”. This led to an increasing interest in simple and robust methods for studying the processes and changes occurring during the life cycle of cement. In this context, we explored the applicability of fluorescence measurements which can be performed with relatively inexpensive and miniaturized instrumentation yet require robust optical probes which survive the harsh cement environment. Therefore, we developed a platform of lanthanide-based upconversion nanoparticles (UCNPs), consisting of a NaYF4 matrix doped with Yb3+ and Er3+ with sizes between 20 nm and 55 nm, which show characteristic multi-color emission patterns, composed of narrow bands of varying intensity in the ultraviolet, visible, near-infrared, and short-wave spectral region and examined their potential for cement probing and the non-invasive monitoring of the hydration processes occurring during cement formation.
UCNPs of different size and chemical composition were synthesized via a thermal decomposition approach under inert conditions. The tailor-made design of different emission patterns was achieved by tuning particle size and morphology, material composition, and particle surface chemistry in upscaleable syntheses. For cement probing, different types of UCNPs were added to cement and the evolution of the UCNP emission pattern was used to probe in-situ changes of physico-chemical parameters in the cementitious environment during hydration, utilizing a simple and portable custom-designed optical setup. The observed changes in the UCNP emission patterns are characteristic for a given particle size, surface chemistry, and cement composition. In addition to fluorescence measurements, conventional isothermal heat flow calorimetry was used to study the influence of UCNP addition on cement hydration kinetics. Subsequently, both sets of measurements were correlated. Our results underline the potential of our optical approach ad UCNPs for the non-invasive probing of cementitious systems and cement hydration. This can be also exploited for cutting-edge applications of construction materials such as 3D concrete printing.
Das EU Projekt TREEADS „A Holistic Fire Management Ecosystem for Prevention, Detection and Restoration of Environmental
Desasters” beschäftigt sich mit der Erforschung der drei Phasen „Prävention und Bereitschaft“, „Detektion und Reaktion“ und
„Aufforsten und Anpassen“ der Waldbrandverhütung. Im Projekt gibt es acht ausgewiesene Pilotregionen, in denen Deutschland
auch mit einer Pilotregion in Sachsen-Anhalt bzw. in Brandenburg vertreten ist. Unsere Arbeit auf Charakterisierung des Waldbodens und numerische Simulation wird vorgestellt.
Ziel des Projekts HYTEGRA ist die Herstellung leichter Gesteinskörnungen durch hydrothermale Behandlung quarz- und kalkreicher Reststoffe. Als Ausgangsstoffe dienen heterogener Mauerwerkbruch aus Bau- und Abbruchabfällen als SiO2-Träger und Papierasche aus dem Altpapierrecycling als CaO-Träger. Für beide Reststoffe besteht derzeit ein Verwertungsdefizit. Das Verfahren beruht auf der Idee des rohstofflichen Recyclings, d. h. die chemisch-mineralogischen Stoffeigenschaften werden für die hydrothermale Stoffumwandlung genutzt. Bei der Härtung der Hydrothermalgranulate bilden sich Calciumsilicathydrat-Phasen (CSH) aus der Reaktion zwischen Quarzpartikeln und Kalk im Autoklav bei 200 °C und 16 bar Sattdampf.
Corrosion testing in a laboratory container: Corrosion testing with artificial seawater and sediment
(2022)
Electricity generation by offshore wind turbine generators (WTG) is an important pillar of the energy transition. Corrosion processes on WTGs pose a particular challenge with regard to safe operation over longer periods of time due to the highly corrosive conditions in the offshore area. BAM is therefore conducting research to ensure a safe operation of the turbines over their intended service life to protect people and the environment.
In a joint research project, different corrosion-relevant areas of a WTG foundation structure were specifically simulated in test basins within a laboratory container. The aim of the work was, on the one hand, the gravimetric and electrochemical determination of corrosion rates in the different areas of an WTG that are relevant for cathodic corrosion protection (CCP): Underwater and sediment zone as well as the transition area between these two zones. Also, targeted tests were carried out under CCP. In addition, investigations regarding calcareous deposition during CCP were carried out on idealized specimens under laboratory conditions to better assess its influence on the protection process. The investigations were carried out in a laboratory container with different basins, which were filled with sand as sediment and artificial seawater according to ISO 15711and connected via a closed water circuit.
The poster at EURCORR 2022 provides an overview of the investigations and the most important results. It will be evaluated, if a simulation of offshore corrosion conditions is possible to a certain extent in an idealized system with artificial seawater and sediment.
Determination of the corrosion product layer resistance on zinc samples by using gel electrolytes
(2022)
Crash barriers, railings, lamp posts, waste glass containers - these are just a few of the many examples of galvanized surfaces. They withstand wind and weather for decades, which is possible thanks to a protective layer made of corrosion products. When designing the atmospheric durability of galvanized components, a linear corrosion loss is assumed. In the past 30 years, however, the surrounding atmosphere has changed a lot. Due to the restriction of sulfur exhaust air, acid rain completely disappeared in Europe and Germany, which has a direct influence on the type and protective effect of the corrosion products. Under the influence of current atmospheric conditions, zinc layers are significantly more resistant and no longer show any linear corrosion loss. The established test methods cannot correctly map this change in neither short-term nor long-term tests and thus provide incorrect results. In order to solve this problem, a new measurement method was developed at BAM that can assess the protective effect of the formed surface layers in a minimally invasive manner without damaging the sample and in short test times. For this new method, gel electrolytes are used and the so-called corrosion product layer resistance RL, which is made up of various surface resistances, is measured electrochemically. As a single measurement, the surface layer resistance can provide information about the existing corrosion protection, while time-dependent measurements assess the stability of the layer. Thus, it is possible again to evaluate the corrosion protection layer. Furthermore, this method can also be used for field measurements on real components.
Brände zerstören immer wieder wichtige Kulturgüter und gefährden nationales Kulturerbe. Das Projekt BRAWA erarbeitet neue Strategien und innovative Technologien, um die Brandsicherheit historischer Gebäude zu erhöhen. Dabei basiert das Konzept auf der Vernetzung von Sensoren, die bereits beim Auftreten bestimmter Gase in der Frühphase der Brandentstehung Alarm auslösen. Durch ein neuartiges Helferkonzept soll eine frühe Branderkennung und -bekämpfung ermöglicht werden.
The internal project "SealWasteSafe" of the Federal Institute for Materials Research and Testing is dedicated to the further improvement in the construction of sealing systems for underground repositories of radioactive waste. Particularly, a multi-sensory concept is developed to ensure quality assurance and continuous long-term monitoring on the engineered barriers. Therefore, beside other measures, the temperature and equilibrium moisture of the construction shall be monitored and respective multi-sensoric monitoring concepts are tested first on the laboratory scale. One focus in this project is on embedded application in alkali-activated mortars (AAM), which results in special requirements for the resistance of the sensors to strongly alkaline environments with up to pH 14. In addition, the ingress of water along cables or at sensor positions is critical for sensors embedded in concrete, as the cable access of the sensor housing is a major weak point. It is therefore advisable to equip wireless high frequent radio frequency identification-based sensors, so called HF RFID sensors (short: RFID), that do not require cable access and thus have a stable and leak-proof sensor housing for long-term monitoring. In this contribution, the results from temperature, moisture and transmitted power monitoring of a AAM and a M2 specimens by means of HF RFID sensor systems are presented.
Molecular orientation has a significant effect on the material properties of polymers. Preferential orientation of the microstructure (polymer chains or crystallites) in a specific direction or plane often enhances the material properties, especially if the high-strength covalent bonds are primarily exposed to loads instead of the weaker van der Waals bonds. However, the orientation-dependent microstructure and its mechanical behavior is in general already well understood by many scientific studies [1-3]. Isotropic materials are frequently required for an intrinsic material characterization without prevailing processing-induced properties, as is the case for Full Notch Creep Test (FNCT) [4] addressing environmental stress cracking (ESC) in high-density polyethylene (PE-HD) [5, 6]. Since ESC is one of the major limiting issues for long-term performance of PE-HD pipes and containers [7], which in contrast have a production-related preferential orientated microstructure due to extrusion or extrusion blow molding, it is important to additionally investigate the ESC resistance of such anisotropic microstructure.
Investigations of the slow crack growth (SCG) with respect to the molecular orientation generally obtain a factor of 1.2 up to 4.7 between crack growth perpendicular to the extrusion direction and crack growth parallel to the extrusion direction 8. Based on FNCT investigations with an aqueous detergent solution as environmental medium, hot pressed sheets with isotropic morphology are compared with extruded sheets from which specimens with different orientation angles are taken. However, the time to failure obtained by FNCT is also significantly influenced by the different cooling conditions under which the final morphology is formed. The tendency of the specimen to fail due to ESC is investigated as a function of environmental medium temperature. For a more detailed analysis of the affecting parameters in the manufacturing process, the ESC resistance is discussed considering the differences in crystallinity as revealed by thermal analysis.
In Germany, the reuse of asphalt has a long tradition. Since the 1980s, the reclaimed
asphalt has been recycled achieving a reuse rate of around 90% and thus a very high
value in the last years. In the future, instead of the amount, the quality of the
reclaimed asphalt will be more important because the recycled asphalt will be reused
again and again. Thus, these asphalt mixes are in the second or even third cycle of
reuse. Concerning this situation, the question arises if asphalt can be reused several
times without any loss in quality. An important factor affecting the asphalt quality is the
binder bitumen. During the production, construction and service life, the ageing of this
binder occurs causing a hardening of the bitumen. To compensate this hardening,
additives for the reclaimed asphalt in terms of rejuvenation agents (rejuvenators) gain
in importance. With these rejuvenators, the physical properties of bitumen can be
modified e.g. the hardness and the stiffness reduced. However, the mechanism of the
rejuvenation agents and the effects of the bitumen chemistry are largely unknown
because the composition of the products varies very strongly. But with growing
knowledge about these mechanisms and effects of the rejuvenation agents, the
chemical composition and thus the physical and ageing behavior of bitumen can be
targeted modified by the use of suitable rejuvenators. In this work, the actual results of
the project Postcarbone road should be presented including investigations about the
chemical and physical mechanisms as well as the efficiency of different rejuvenators.
Further, a model for the cyclic reuse of bitumen should be developed. Based on this
model, the choice of a suitable rejuvenation agent for the considered bitumen or rather
asphalt should be possible. The project Postcarbone road (392670763) is funded by the
German Research Foundation (DFG).
Polyesters with DOPO substituents can be successfully synthesized with 10-[2,5-Bis(2-hydroxyethoxy)phenyl]-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO-HQ-glycolether) and DOPO-substituted dimethyl succinate (PIta). These polyester materials show an effective flame retardancy which can be fine-tuned by the chemical structure of the polyester backbone.
The influence of pressure sensitive adhesive (PSA) tapes as adhesive layers on the burning behaviour of bonded materials has been investigated. Single-sided tapes as an outer connection between construction materials have large influence on flammability, flame spread and fire resistance. In contrast, double sided tapes only take a small impact on the flammability but can drasticly change the burning behaviour in developing fires.
Multifunctional Graphene in Flame Retarded Polybutadiene/ Chloroprene/ Carbon Black Composites
(2021)
Multilayer graphene is investigated as a multifunctional nanofiller to polybutadiene/ chloroprene rubbers (BR/CR) that partially substitutes carbon black (CB) and aluminum trihydroxide (ATH). Loadings of only 3 parts per hundred rubber (phr) MLG replaced 15 phr of CB and/or 3 phr of ATH in BR/CR nanocomposites. Mechanical and fire behavior were investigated, and results point to improved rheological, curing and mechanical properties of MLG-containing rubber composites.
Natural Rubber Nanocomposites via Optimized Latex Premixing and Conventional Technical Processing
(2021)
Creation of highly functional materials and replacement of high amounts of conventional fillers are driving forces for the development of nanocomposites. Besides the type and properties of nanoparticles, their dispersing in the elastomeric matrix and the stability of this dispersion through all processing steps are the
main factors for the resulting performance of the produced material. Therefore, a preparation chain via latex premixing to a highly filled masterbatch, followed by conventional technical processing is to be developed.
Three types of carbon-based particles are characterized as such (SEM, Raman Spectroscopy, BET specific surface area) and in combination with natural rubber, as nanocomposites (TEM. Hardness, Abrasion resistance, Compression set, Cone calorimetry).
All of the studied particles lead to an improvement in the investigated mechanical properties, the extent of reinforcement depends strongly on the specific surface of the particle interacting with the elastomeric matrix in combination with their shape.
A commercially available bio epoxy resin with kenaf fibers and halogen free inorganic and organic flame retardants, respectively, is investigated concerning its thermal stability and fire performance. Particular attention has been paid to the difference of short fibers, fiber mats and woven
materials.
FR additives were incorporated during tanning process. The mode of action of an intumescent system and each component individually, was methodically investigated in a semi-finished leather. Vertical flammability test results showed that the investigated semi-finished leather satisfies the regulations of the Federal Aviation Administration; in addition, afterglow time is strong minimized and forced fire behavior pointed out an important reduction on smoke production.
In the last three decades, the vibrations of many floors and bridges have been measured. The contribution shows some evaluation methods, experimental results and some modelling and theoretical results. Simple evaluation methods have been developed for single and coupled floors. Two coupled beams have been measured in good agreement with the theory. A more complex coupling model has been found for a large wooden floor in a castle consisting of six floor bays which correlates well with the measurements. Damaged and intact poles have been tested by their natural frequencies and damping values, and a fair correlation between the degree of damage and the shift of the frequency. Road bridges have been analysed in detail and some examples are presented. Railway bridges and trains are studied for resonant excitation. The risk of resonance can be estimated in frequency domain by using axle-sequence spectra of the train and the natural frequencies of the bridge. A measurement example shows the amplification, but even stronger the cancellation of the subsequent axle responses. Several high-speed trains and freight trains have been analysed for their potential resonance amplification.
Die Porosität sowie die Porengrößenverteilung (PSD) eines Baustoffs sind wichtige petrophysikalische Eigenschaften, die Transportprozesse im Material beeinflussen und im direkten Zusammenhang mit der Schadensanfälligkeit stehen (Frost-Tau-Schäden, Schäden durch Salzeinträge und sauren Regen). Verfahren zur Ermittlung der Porosität stellen die Quecksilberporosimetrie (MIP), das Prinzip der Tauchwägung nach Archimedes (triple weighing method, TWM) und die Nuklear Magnetische Resonanz (NMR) dar.
Das Hauptziel dieser Arbeit ist der Vergleich der drei Methoden für die Porositätsbestimmung. Als Untersuchungsmaterial wurde Sandstein gewählt. Als Baustoff wird Sandstein trotz einer teilweise geringen Festigkeit, aber aufgrund seiner Farbvielfalt häufig für Kulturbauten, Gehwegmaterial und Fassaden eingesetzt. Sandsteine weisen zudem meist eine hohe effektive Porosität (bis zu ca. 30 %) und teilweise breite Porengrößenspektren auf, wodurch Feuchte- und Ioneneinträge begünstigt werden und zu z. B. langfristigen Verfärbungen an Sandsteinfassaden führen können.
Im Rahmen dieser Arbeit werden die Porositäten von 10 verschiedenen Sandsteinen aus Deutschland und Tschechien bestimmt. Für die Untersuchungen mittels TWM und NMR wurden für jede Sandsteinart zwei zylinderförmige Proben unter Unterdruck mit Leitungswasser aufgesättigt. Beim Vergleich der Verfahren liegt der Fokus insbesondere auf NMR und der verwendeten Gerätetechnik, die mit einer minimalen Echozeit von 50 µs ein Wasserstoffsignal in Sandsteinen aus bis zu ca. 2 nm kleine Poren erfassen kann. Darüber hinaus wird das Auflösungsvermögen von MIP und NMR bezüglich der Poren- bzw. Poreneingangsgrößen diskutiert. Für den Vergleich von NMR und MIP werden an ausgewählten Sandsteinproben ebenfalls die zusätzlich ermittelten PSD in Korrelation zueinander gebracht.
Erste Ergebnisse zeigen eine gute Korrelation von NMR- und TWM-Daten, aber teilweise starke Abweichungen zu den mit MIP bestimmten Porositäten. Ergebnisse zu den PSD zeigen teilweise nahezu identische Kurvenverläufe. Jedoch ist die Abschätzung des Umrechnungsfaktors für die NMR-Daten ohne Hinzuziehen von zusätzlichen Referenzverfahren wie Röntgen-Computer-Tomographie oder Spektral Induzierte Polarisation teilweise sehr schwierig.
Ultra high performance concrete (UHPC) is known for its high compressive strength of more than 150 MPa and its high durability. Thermal treatment at 90°C can accelerate the strength development so that the 28-days-strength can be achieved immediately after the treatment and an additional increase up to 30 % in some cases. The reason for the strength development is an accelerated hydration of the clinker minerals and an intensified pozzolanic reaction leading to a denser microstructure.
In previous research inhomogeneities in form of a zonation after unprotected thermal treatment were observed and analysed in respect to changes in the microstructure. This zonation is defined by a different microstructure in the core compared to the outer zone in the matter of porosity, mineral phase composition and a significant change in the potassium and sulphur concentration of the zones is measurable.
To isolate different transport mechanisms responsible for these element distributions UHPC samples were thermally treated at 90 °C and the microstructure was investigated under dry conditions and after immersion in water to investigate the influence of dehydration during and rehydration after the thermal treatment on the microstructure. Through durability testing via water absorption, water vapour diffusion, permeability testing and sulfuric acid resistance transport mechanisms like diffusion, migration, capillary suction are under investigation in correlation with the microstructure analysis. For the microstructure analysis measurements with µXRF, mercury intrusion porosity, XRD and SEM were conducted.
The full-notch creep test (FNCT) is a common method to evaluate the environmental stress cracking (ESC) behavior of high-density polyethylene (PE-HD) container materials . The test procedure as specified in ISO 16770 provides a comparative measure of the resistance against ESC using the time to failure of specimens mechanically loaded in a well-defined liquid environment. Since the craze-crack damage mechanism underlying the ESC process is associated with brittle failure, the occurrence of globally brittle fracture surfaces is a prerequisite to consider an FNCT measurement as representative for ESC . Therefore, an optical evaluation of FNCT fracture surfaces concerning their brittleness is essential. Due to the experimental setup, an inevitable increase of the true mechanical stress and the associated appearance of small ductile parts on fracture surfaces is induced in any case. Hence, an FNCT experiment is considered as 'valid', if the corresponding fracture surface is predominantly brittle . Based on laser scanning microscopy (LSM) height data of FNCT fracture surfaces , a universal and easy-to-use phenomenological criterion was developed to assess the validity of distinct FNCT experiments. This criterion is supposed to facilitate a quick evaluation of FNCT results in practical routine testing.
Hydrothermale Herstellung von Filter- und Speichermaterialien aus SiO2- und CaO-reichen Reststoffen
(2019)
Jährlich fallen ca. 250 Mio. t mineralische Reststoffe in Deutschland an, die eine vielfältig einsetzbare, sekundäre Rohstoffquelle darstellen. Der Einsatz von Reststoffen führt zur Schonung natürlicher Rohstoffe, zur Reduktion von CO2 Emissionen und zur Einsparung von Deponieraum. Im Projekt HYTEGRA sollen Mauerwerkbruch (SiO2-reich), ein heterogenes Gemisch aus Ziegeln, Beton und
Leichtbeton, Kalksandstein, Porenbeton, Putz und Mörtel, sowie Papierasche (CaO-reich) aus dem Altpapierrecycling rohstofflich wiederverwertet werden. Die Entwicklung von porösen Körnungen über einen hydrothermalen Herstellungsprozess steht dabei im Fokus. In Kooperation mit verschiedenen Industriepartnern sind Anwendungen als Filter- und Speichermaterial geplant.
The advantages of treating prefabricated components made of Ultra-High-Performance Concrete (UCPC) at 90 °C are largely recognized, while hydrothermal treatment at 185 °C and the corresponding saturation pressure of 1.1 MPa, in contrast, is not applied in building practice so far and was studied only by a few researchers.
In the research presented, the parameters pre-storage-time before treatment and dwell time in the autoclave were systematically varied. The results illustrate in which way compressive strength increases with the duration of treatment. Already samples which were only heated up and immediately cooled down show an increase in strength compared to the 28-day reference of about 10 %. After 20 h the maximum increase of about 25 % is reached. Interestingly the compressive strength of samples treated very long hardly decreases. It can be therefore concluded that for the composition investigated the achievable mechanical strength is not severely sensitive regarding the duration of the treatment.
Also, pre-storage times before autoclaving longer than 0.5 days showed no significant impact on strength development. The phase composition measured by XRD exhibits significant changes compared to the reference. The amount of ettringite and portlandite have vanished, the cement clinker phases are substantially decreased and hydroxylellestadite and hydrogarnet are formed as new phases. The increase in strength can be assigned to an improved pozzolanic and hydraulic reaction. Contradictory to literature, there was found no obermorite, a mineral which is known to be susceptible for disintegration at Long autoclaving duration. This explains why no significant strength loss appeared.
Alkali-silica reaction (ASR) is a serious Problem concerning the deterioration of concrete. This leads to significant maintenance and reconstruction costs for concrete infrastructures all over the world. The geographical regions, which play a major role in concrete deterioration, are for example coastal Areas or in general, areas with a high air humidity/salinity due to closeness of rivers or lakes.
These exemplary results show, the application of Raman spectroscopy establishes a valuable approach for characterizing the chemical and structural composition of ASR-products. The results prove the potential to trace the kind of reaction products, developing in dependence on the aggregate and to follow up its local alteration from origin of the gel.
Ausgehend vom sicherheitsbezogenen Aufgabenspektrum der BAM konzentriert sich das Poster auf die messtechnischen Verfahrensgrundlagen und Anwendungsbeispiele aus den Bereichen der experimentellen Bauartprüfung von RAM-Behältern in Fallprüfungen mit Wordt-Case-Szenarien, der Schadensanalyse und der Mitwirkung in F/E-Projekten
Applications of Structural Health Monitoring (SHM) for the design and analysis of Offshore Wind Turbine (OWT) structures has gained much attention within the past few years. Being exposed to repeated cyclic wind and wave loads, OWTs are dynamically sensitive structures and can benefit from monitoring systems to predict time-dependent deterioration. This study focuses on the quantification of the value of SHM information on the maintenance of OWT structures, with emphasis on fatigue of welded joint. By utilizing the decision tree, structural reliability, SHM data, as well as the cost-benefit assessments, a value of information (VoI) analysis can be done to model the fundamental decision of whether the service life of an OWT foundation can be extended beyond the initial design life. The application is demonstrated on a butt weld of a monopile support structure of a 3 MW offshore wind turbine with a hub height of approximately 71m where the prior probability analysis is modelled as a probabilistic fatigue damage model based on S-N approach and designed wind data. The posterior probability of failure of welded joints is updated using the three-year measured oceanographic and one-year strain data. The expected value of SHM information can be found as the difference between the maximum utility obtained in posterior analysis with SHM information and the maximum utility obtained using only prior information. This work can provide insights on how much benefits can be achieved through SHM information, with practical relevance on reliability-based design optimization and fatigue life extension of OWT structures.
A method to determine the structural and damage detection system influencing parameters is proposed based on the value of information analysis. The value of information analysis utilizes the Bayesian pre-posterior decision theory to quantify the value of SHM for the structural integrity management during service life. First the influencing parameters of the structural system such as deterioration type and rate are introduced for the performance of the prior probabilistic system model. Then the damage detection system performance influencing parameters including number of sensors, sensor locations, measurement noise and the Type I error are investigated. The pre-posterior probabilistic model is computed utilizing the Bayes’ theorem to update the prior system model with the damage indication information. Finally, the value of information is quantified as the difference between the maximum utility obtained in pre-posterior and prior analysis based on the decision tree analysis, comprising structural probabilistic models, consequences as well as benefit and costs analysis associated with and without monitoring. With the developed approach, a case study on a statically determinate Pratt truss bridge girder is carried out to validate the method. The analysis shows that the higher the deterioration rate is, the more it is beneficial to do SHM. Furthermore, it shows that more sensors do not necessarily lead to a higher value of information; only specific sensor locations near the highest utilized components lead to a high value of information; measurement noise and the Type I error should be controlled and as small as possible. An optimal sensor employment with highest value of information is found. Moreover, it is found that the proposed method can be a powerful tool to develop optimal service life maintenance strategies - before implementation - for similar bridges and to optimize the damage detection system settings and sensor configuration for minimum expected costs and risks.
A central challenge to ensure the sustainable production and use of nanotechnologies is to understand and effectively control the risks along the industrial innovation value chain. Knowledge about nanotechnology processes and nanosafety issues (hazards, fate, risk...) is growing rapidly but the effective use of this knowledge for risk management by market actors is lagging behind.
EC4SafeNano (European Centre for Risk Management and Safe Innovation in Nanomaterials and Nanotechnologies) promotes a harmonized vision of expertise in risk assessment and management for the public and private sectors to enable the safe development and commercialization of nanotechnology.
EC4SafeNano is operated together by major European risk institutes with the support of numerous associated partners, gathering all stakeholders involved in Nanomaterials and Nanotechnologies (regulators, industry, society, research, service providers...).
In a case study the surface chemical transformations upon 2 different ageing procedures (long-term UV irradiation or swimming pool water) of a representative set of titanium dioxide nanoparticles has been investigated. The materials have been analyzed by various analytical techniques. Each method addresses different aspects of the complex endpoint surface chemistry. The multi technique approach allows evaluation of the capabilities and limitations of the applied methods regarding their suitability to address the endpoint surface chemistry and their sensitivity to identify even small surface chemical transformations.
Results:
- To obtain a comprehensive picture, it is insufficient to concentrate on a single analysis technique.
- By using time-of-flight secondary ion mass spectrometry (ToF-SIMS) in combination with principal component analysis (PCA) it was possible to identify even subtle changes in the surface chemistry of the investigated materials.
- A general trend that was observed for the UV-aged samples is the decrease of organic material on the nanomaterial surface.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 723623.
Behälter aus hochdichtem Polyethylen (PE-HD) werden zur Lagerung und für den Transport von Kraftstoffen eingesetzt. Beim Kontakt beider Medien diffundiert der Kraftstoff in das Polymer, erhöht dessen Volumen und Duktilität und ändert damit das Fließverhalten des Polymers unter Zugbelastung. Zudem weist PE-HD in Luft im verstreckten Bereich das sogenannte strain-whitening (Lichtstreuung) auf, während in Diesel gelagertes PE-HD optisch transparent wird. Zur Untersuchung dieses Phänomens wurden ortsaufgelöste Röntgenrefraktion und –diffraktion (Topographie) eingesetzt. Aus Sicht der molekularen Struktur (Diffraktion) weisen die beiden Probentypen keine Unterschiede auf: im verstreckten Bereich liegt eine „Fasertextur“ der Polymerketten in Belastungsrichtung vor, im unverstreckten Bereich nahezu ideale Isotropie. Die für mikroskopische Strukturen empfindliche Röntgenrefraktion zeigt außerdem für die Probe in Luft im verstreckten Bereich eine ausgeprägte Orientierung von Grenzflächen in Zugrichtung, während die in Diesel gelagerte Probe keine Grenzflächen zeigt. In Analogie zum optischen Verhalten bewirken die ähnlichen Brechungsindizes beider Medien im Röntgenbereich, dass eindiffundierter Diesel als Immersionsflüssigkeit die Brechungseigenschaften herabsetzt.