TY - GEN A1 - Recknagel, Christoph A1 - Goebbels, Jürgen A1 - Meinel, Dietmar ED - Manfred N. Partl, T1 - Identification of the void structure of asphalt materials T2 - International ISAP Symposium on Asphalt Pavements and Environment CY - Zürich, Switzerland DA - 2008-08-18 KW - Inner structure KW - Structure characteristics KW - Void KW - Asphalt KW - Open-pored asphalt PY - 2008 SN - 978-3-905594-51-5 SP - 566 EP - 577 AN - OPUS4-18284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sunder, S. A1 - Jauregui Rozo, Maria A1 - Inasu, S. A1 - Meinel, Dietmar A1 - Schartel, Bernhard A1 - Ruckdäschel, H. T1 - Effect of Ammonium Polyphosphate/Silicate Content on the Postfire Mechanics of Epoxy Glass-Fiber Composites Using Facile Chocolate Bar-Inspired Structures N2 - This study investigates the postfire mechanical properties of epoxy glass-fiber reinforced composites (EP GFRCs) using increasing concentrations of ammonium polyphosphate (APP) and inorganic silicate (InSi) to modify the char and fire residue. A facile chocolate bar-inspired structure was introduced for fire exposure and subsequent flexural testing of the GFRCs. The resin matrix used here was a diglycidyl ether of bisphenol-A (DGEBA) resin, cured with dicyandiamide (DICY), and accelerated by Urone. The microstructures of the degraded composites after three-point bending tests, were evaluated using scanning electron microscopy (SEM) and x-ray computed tomography (XCT) imaging. A previous study showed that increasing the APP and InSi content significantly enhanced flame retardancy, via improved char formation under fire conditions. However, flexural properties and fire resistance were adversely affected after fire exposure, highlighting a trade-off effect. Fiber breakage and delamination of the composites increased upon failure with increasing APP + InSi content in the composite due to unconsolidated char. The experimental values for the postfire flexural mechanics were in good agreement with the two-layer model proposed in literature. This paper presents a preliminary basis for postfire mechanical testing of epoxy composites for use in fire-safe structures, using a combination of standardized testing norms. KW - Flame retardants KW - Post-fire KW - Epoxy KW - Gass fiber composites KW - Prepregs PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-627176 DO - https://doi.org/10.1002/fam.3280 SN - 0308-0501 SN - 1099-1018 VL - 49 IS - 3 SP - 329 EP - 346 PB - Wiley AN - OPUS4-62717 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jauregui Rozo, Maria A1 - Sunder, S. A1 - Inasu, S. A1 - Meinel, Dietmar A1 - Ruckdäschel, H. A1 - Schartel, Bernhard T1 - Weaving Through Fire and Force: Fire Behavior and Fire Stability of Unidirectional, Bidirectional, and Woven Roving Glass-Fiber Composites N2 - This study systematically investigates the transfer of flame retardants (FRs) from epoxy resins to composites. The flame-retardant composites are formulated using bisphenol A diglycidyl ether as the resin and dicyandiamide as the hardener, reinforced with glass fibers (GFs) using various textile architectures: unidirectional (UD), bidirectional (BD), and woven rovings (WR). These composites are evaluated using bench-scale fire stability tests and cone calorimeter experiments to assess critical parameters, including the temperature at failure, time to failure, and fire behavior. Among the tested configurations, UD-GFs demonstrate superior flame retardancy, fire stability, flammability, and mechanical performance, attributed to their higher residue yield, forming a more efficient protective char layer. However, the addition of FRs is limited by their impact on the material's mechanical properties. When the FR content increases to 30 and 50 wt.% of the resin, the composites exhibit a decrease in mechanical performance, adversely affecting both time to failure and temperature at failure. While adding FRs reduces the risk of fire propagation, it does not substantially enhance fire stability or mechanical performance. KW - Fire Resistance KW - Fiber-Reinforced Polymer Composites KW - Fire Stability KW - Glass Fibers KW - Fire Behavior PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-631220 SN - 1438-7492 SN - 1439-2054 VL - 310 IS - 5 SP - 2400432 PB - Wiley VHC-Verlag AN - OPUS4-63122 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weise, Frank A1 - Voland, Katja A1 - Pirskawetz, Stephan A1 - Meinel, Dietmar T1 - Analyse AKR-induzierter Schädigungsprozesse in Beton - Einsatz innovativer Prüftechniken T1 - Analysis of ASR-induced damage processes in concrete Application of innovative measurement techniques N2 - Zur Beurteilung der Alkaliempfindlichkeit der Gesteinskörnung finden normativ der Betonversuch mit Nebelkammerlagerung bei 40 °C und alternativ der 60 °C-Betonversuch Anwendung. Als Beurteilungskriterium für den Schädigungsprozess wird bei beiden Verfahren die an Betonprismen diskontinuierlich ermittelte Dehnung herangezogen. Auch bei den zusätzlich in der Nebelkammer gelagerten Würfeln beschränkt sich die Schadensanalyse auf eine diskontinuierliche Verfolgung der maximalen Breite der Oberflächenrisse. Im Rahmen des Beitrags wird eine neuartige, bereits erfolgreich erprobte zerstörungsfreie Prüfmethodik vorgestellt. Diese ermöglicht durch eine gleichzeitige kontinuierliche Dehnungs-, Schallemissions- und Ultraschallmessung eine kontinuierliche Verfolgung der inneren Gefügeveränderungen in den Betonprüfkörpern während der AKR-provozierenden Lagerung. Dabei wurden drei zeitlich aufeinanderfolgende Phasen der inneren Gefügeveränderung mit einer Dominanz von Hydratation, Rissbildung sowie vermutlicher Rissverfüllung mit Reaktionsprodukten identifiziert. Die ablaufenden Rissbildungsprozesse wurden zusätzlich mit diskontinuierlich durchgeführten röntgentomografischen Untersuchungen zeitlich und räumlich visualisiert. Die CT-Befunde wurden durch mikroskopische Untersuchungen bestätigt. N2 - The alkali-reactive potential of aggregates is assessed according to the German guidelines by two different test methods. These are the 40 °C fog chamber storage and as an alternative method the 60 °C concrete prism test. In both tests, the discontinuously measured expansion of ASR-generating stored concrete prisms is used as criterion for the internal Damage process. The damage analysis of the cubes additionally stored in the 40 °C fog chamber is also restricted to the discontinuous measurement of the crack width on the cubes surfaces. This paper describes an innovative, already successfully applied, non-destructive measurement methodology. This methodology enables a continuous monitoring of the internal damage processes in ASR-generating stored concrete specimens due to a continuous recording of expansion, acoustic emission and ultrasonic velocity. Thereby, three sequent phases of internal structural changes dominated by hydration, crack formation and filling of the cracks with ASR-gel and/or other reaction products can be detected. The crack formation wastemporally and spatially visualised by discontinuously applied X-ray computed tomography measurements. Microscopic analyses confirm the findings of the X-ray 3D-CT. KW - Beton KW - Frost- und Frost-Tausalz-Prüfung KW - CIF- und CDF-Prüfung KW - Röntgen-3D-CT KW - Photogrammetrie PY - 2012 DO - https://doi.org/10.1002/best.201200049 SN - 0005-9900 SN - 1437-1006 VL - 107 IS - 12 SP - 1 EP - 11 PB - Ernst CY - Berlin AN - OPUS4-27041 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schilling, Markus A1 - Niebergall, Ute A1 - Marschall, Niklas A1 - Meinel, Dietmar A1 - Böhning, Martin T1 - Relation of craze to crack length during slow crack growth phenomena in high‐density polyethylene N2 - The craze‐crack mechanism occurring in high‐density polyethylene (HDPE) causing slow crack growth and environmental stress cracking is investigated in detail with respect to the relation of crack length and the related craze zone. This is essential for the understanding of the resulting features of the formed fracture surface and their interpretation in the context of the transition from crack propagation to ductile shear deformation. It turns out that an already formed craze zone does not inevitably result in formation of a propagating crack, but could also undergo ductile failure. For the examination, the full notch creep test (FNCT) was employed with a subsequent advanced fracture surface analysis that was performed using various imaging techniques: light microscopy, laser scanning microscopy, scanning electron microscopy, and X‐ray micro computed tomography scan. FNCT specimens were progressively damaged for increasing durations under standard test conditions applying Arkopal, the standard surfactant solution, and biodiesel as test media were used to analyze the stepwise growth of cracks and crazes. From considerations based on well‐established fracture mechanics approaches, a theoretical correlation between the length of the actual crack and the length of the preceding craze zone was established that could be evidenced and affirmed by FNCT fracture surface analysis. Moreover, the yield strength of a HDPE material exposed to a certain medium as detected by a classic tensile test was found to be the crucial value of true stress to induce the transition from crack propagation due to the craze‐crack mechanism to shear deformation during FNCT measurements. Highlights - Progress of crack formation in high‐density polyethylene is analyzed by different imaging techniques - Determined growth rates depend on distinction between craze zone and crack - The ratio of the present crack to the anteceding craze zone is validated theoretically - The transition from crack propagation to ductile shear deformation is identified - An already formed craze zone may still fail by ductile mechanisms KW - Craze-crack mechanism KW - Environmental stress cracking (ESC) KW - Full notch creep test (FNCT) KW - Laser scanning microscopy (LSM) KW - Slow crack growth (SCG) KW - X-ray computed tomography (CT) PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-601831 DO - https://doi.org/10.1002/pen.26698 SN - 1548-2634 VL - 64 IS - 6 SP - 2387 EP - 2403 PB - Wiley AN - OPUS4-60183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Paetsch, O. A1 - Baum, D. A1 - Prohaska, S. A1 - Ehrig, Karsten A1 - Meinel, Dietmar A1 - Ebell, Gino T1 - 3D corrosion detection in time-dependent CT images of concrete N2 - In civil engineering, the corrosion of steel reinforcements in structural elements of concrete bares a risk of stability-reduction, mainly caused by the exposure to chlorides. 3D computed tomography (CT) reveals the inner structure of concrete and allows one to investigate the corrosion with non-destructive testing methods. To carry out such investigations, specimens with a large artificial crack and an embedded steel rebar have been manufactured. 3D CT images of those specimens were acquired in the original state. Subsequently three cycles of electrochemical pre-damaging together with CT imaging were applied. These time series have been evaluated by means of image processing algorithms to segment and quantify the corrosion products. Visualization of the results supports the understanding of how corrosion propagates into cracks and pores. Furthermore, pitting of structural elements can be seen without dismantling. In this work, several image processing and visualization techniques are presented that have turned out to be particularly effective for the visualization and segmentation of corrosion products. Their combination to a workflow for corrosion analysis is the main contribution of this work. T2 - DIR 2015 - International symposium on digital industrial radiology and computed tomography CY - Ghent, Belgium DA - 22.06.2015 KW - Concrete KW - Corrosion detection KW - 3D computer tomography (CT) imaging KW - Image processing KW - Visualization PY - 2015 SP - 1 EP - 10 AN - OPUS4-33711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Meinel, Dietmar ED - Rogge, A. ED - Meng, B. T1 - Neue Verfahren zur Untersuchung chloridinduzierter Lochkorrosion an Stahl in Beton N2 - Die Kombination elektrochemischer und computertomographischer Untersuchungs-Verfahren bietet die Möglichkeit, elektrochemische Messungen zerstörungsfrei verifizieren und richtig interpretieren zu können. Die Ermittlung der durch Lochkorrosion geschädigten Stahloberflächen ermöglicht es Probekörper zu entwickeln, die ein der Praxis entsprechendes Schadensbild aufweisen. Ein weiterer Vorteil stellt sich in der Minimierung der Probenmatrix dar. Die klassische Versuchsdurchführung erfordert die Zerstörung von Proben nach jeder Vorschädigungsstufe. Dies kann durch den Einsatz der Computertomografie vermieden werden. Die elektrochemischen Messwerte können flächenbezogen ermittelt werden, solange sich die Korrosionserscheinungen vollständig innerhalb des durch die CT abgebildeten Untersuchungsbereiches befinden. T2 - 52. DAfStb-Forschungskolloquium CY - Berlin, Germany DA - 07.11.2011 KW - Betonstahl KW - Korrosion KW - Lochkorrosion KW - Computertomographie PY - 2011 SN - 978-3-9814281-0-0 IS - G6 SP - 262 EP - 271 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-24805 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Paetsch, O. A1 - Baum, D. A1 - Ebell, Gino A1 - Ehrig, Karsten A1 - Heyn, Andreas A1 - Meinel, Dietmar A1 - Prohaska, S. T1 - Korrosionsverfolgung in 3D-computertomographischen Aufnahmen von Stahlbetonproben N2 - Durch die Alkalität des Betons wird Betonstahl dauerhaft vor Korrosion geschützt. Infolge von Chlorideintrag kann dieser Schutz nicht länger aufrechterhalten werden und führt zu Lochkorrosion. Die zerstörungsfreie Prüfung von Stahlbetonproben mit 3D-CT bietet die Möglichkeit, eine Probe mehrfach gezielt vorzuschädigen und den Korrosionsfortschritt zu untersuchen. Zur Quanti-fizierung des Schädigungsgrades müssen die bei dieser Untersuchung anfallenden großen Bilddaten mit Bildverarbeitungsmethoden ausgewertet werden. Ein wesent-licher Schritt dabei ist die Segmentierung der Bilddaten, bei der zwischen Kor-rosionsprodukt (Rost), Betonstahl (BSt), Beton, Rissen, Poren und Umgebung unterschieden werden muss. Diese Segmentierung bildet die Grundlage für sta-tistische Untersuchungen des Schädigungsfortschritts. Hierbei sind die Änderung der BSt-Geometrie, die Zunahme von Korrosionsprodukten und deren Veränderung über die Zeit sowie ihrer räumlichen Verteilung in der Probe von Interesse. Auf-grund der Größe der CT-Bilddaten ist eine manuelle Segmentierung nicht durch-führbar, so dass automatische Verfahren unabdingbar sind. Dabei ist insbesondere die Segmentierung der Korrosionsprodukte in den Bilddaten ein schwieriges Problem. Allein aufgrund der Grauwerte ist eine Zuordnung nahezu unmöglich, denn die Grauwerte von Beton und Korrosionsprodukt unterscheiden sich kaum. Eine formbasierte Suche ist nicht offensichtlich, da die Korrosionsprodukte in Beton diffuse Formen haben. Allerdings lässt sich Vorwissen über die Ausbreitung der Korrosionsprodukte nutzen. Sie bilden sich in räumlicher Nähe des BSt (in Bereichen vorheriger Volumenabnahme des BSt), entlang von Rissen sowie in Porenräumen, die direkt am BSt und in dessen Nahbereich liegen. Davon ausgehend wird vor der Korrosionsprodukterkennung zunächst eine BSt-Volumen-, Riss- und Porenerken-nung durchgeführt. Dieser in der Arbeit näher beschriebene Schritt erlaubt es, halb-automatisch Startpunkte (Seed Points) für die Korrosionsprodukterkennung zu finden. Weiterhin werden verschiedene in der Bildverarbeitung bekannte Algorithmen auf ihre Eignung untersucht werden. T2 - DGZfP-Jahrestagung 2014 CY - Potsdam, Germany DA - 26.05.2014 KW - Korrosion KW - Corrosion KW - CT KW - Computertomographie KW - 3D KW - Stahlbeton KW - Betonstahl KW - Bewehrung KW - Lochkorrosion PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-325080 UR - http://jt2014.dgzfp.de/portals/jt2014/BB/di1c3.pdf SN - 978-3-940283-61-0 IS - DGZfP-BB 148 SP - Di.1.C.3, 1 EP - 10 PB - Deutsche Gesellschaft für Zerstörungsfreie Prüfung (DGZfP) AN - OPUS4-32508 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meinel, Dietmar T1 - Classic Materials Testing in the Light of CT N2 - 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. T2 - 13th International Conference on Industrial Computed Tomography (iCT2024) CY - Wels, Austria DA - 06.02.2024 KW - Computed Tomography KW - Additive Manufacturing KW - Machine-Learning Segmentation KW - Air Void System PY - 2024 AN - OPUS4-59568 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Fischer, Joachim A1 - Lehmann, Jens A1 - Müller, Thoralf A1 - Meinel, Dietmar A1 - Paetsch, O. T1 - Investigation of chloride-induced pitting corrosion of steel in concrete with innovative methods N2 - The combination of electrochemical and 3D computed tomography (CT) investigations offers the possibility of verifying electrochemical measurements non-destructively. Determining the steel surfaces damaged by pitting corrosion allows developing specimens having damage pattern corresponding to practice. Corrosion phenomena like decoupled pitting corrosion cannot be verified by electrochemical measurements only, but with the combination of those two kinds of investigations it is possible. Another advantage is the minimization of the number of samples. The classical experimental procedure requires the destruction of samples after each damage step.This can be avoided by the use of 3D computed tomography. As long as the corrosion phenomena are completely within the examination zone shown by the 3D computed tomography, the electrochemical measurements can be calculated on an area basis to get the specific corrosion rate or polarization resistance. KW - Corrosion KW - Concrete KW - 3D x-ray KW - Corrosion rate PY - 2016 DO - https://doi.org/10.1002/maco.201608969 SN - 1521-4176 SN - 0947-5117 SN - 0043-2822 VL - 67 IS - 6 SP - 583 EP - 590 PB - Wiley-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-36341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -