TY - CONF A1 - Stelzner, Ludwig A1 - Powierza, Bartosz A1 - Weise, Frank A1 - Oesch, Tyler A1 - Dlugosch, R. A1 - Meng, Birgit T1 - Analysis of moisture transport in unilateral-heated dense high-strength concrete N2 - Unilateral thermal exposure of concrete building components induces moisture transport processes that have a significant influence on the spalling behaviour of dense high-strength concrete (HSC). These transport processes are based on evaporation and condensation mechanisms of liquid and gaseous water in the pores as well as the chemically bound water within the concrete. The low permeability of HSC and the formation of a saturated zone within building components (also known as a moisture clog) leads to high water-vapour pressures, which contributes to explosive spalling. The formation of these pressures has already been verified by means of pore-pressure measurement techniques. In addition, the redistribution of the moisture within concrete specimens subject to unilateral thermal exposure has been demonstrated on fractured surfaces. Investigations by means of the nuclear magnetic resonance (NMR) relaxometry technique and neutron radiography have shown one-dimensional changes in moisture distribution during thermal exposure. However, none of these methods has been able to depict the moisture distribution in three dimensions (3D), so the link between pore size, concrete micro-structure and moisture content is missing. The research project presented in this paper aims to fill this gap by developing a new multi-level test methodology to characterise non-destructively the temporal course of spatial moisture distribution during unilateral thermal exposure. The procedure used during this programme included the collection of X-ray 3D-computed tomography (CT) measurements using a miniaturised specimen subjected to in-situ thermal exposure and the comparison of those CT results with the results of one-dimensional NMR-relaxometry before and after the heating process. In the first step, a mobile heating device was developed, built and tested. To simulate a unilaterally-heated construction component, a cylindrical specimen made of HSC (Ø = 40 mm, L = 100 mm) was cast into an impermeable glass ceramic shell. The ceramic shell ensured a one-dimensional moisture flux and limited the thermal expansion of the concrete. An additional high-temperature wool (HTW) insulating shell ensured a one-dimensional heat flux. The heating device, which operated using infrared radiation (IR), allowed the unilateral heating of the specimens up to 300 °C using variable heating regimes. In the second step, the mobile heating device was integrated into the CT-scanner, which enabled the collection of measurements before, during and after heating. By subtraction of successive 3D-CT images, X-ray attenuation differences could be resolved three-dimensionally in the specimen and interpreted as changes in the moisture content. Initial results show that this test methodology can monitor the 3D changes of moisture content inside the specimen during thermal exposure. It enables the researcher to visualise areas with moisture accumulation as well as dehydrated areas inside the specimen. Comparative one-dimensional NMR-relaxometry measurements confirm the results of the CT image analysis. T2 - 5th International Workshop on Concrete Spalling due to Fire Exposure CY - Boras, Sweden DA - 12.10.2017 KW - Spalling KW - Fire KW - Moisture clog KW - Moisture transport KW - HPC KW - HSC KW - X-ray CT KW - NMR KW - NDT PY - 2017 SN - 0284-5172 SP - 227 EP - 239 AN - OPUS4-42983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stelzner, Ludwig A1 - Powierza, Bartosz T1 - Thermisch induzierter Feuchtetransport in HPC T1 - Thermally induced Moisture Transport in structure density High-performance Concrete N2 - Die Entwicklung von leistungsfähigen Fließmitteln in den letzten Jahrzehnten ermöglicht die Herstellung von Beton mit sehr geringem w/z-Wert, bei gleichzeitig guter Verarbeitbar-keit. Die Reduzierung des w/z-Wertes geht dabei mit einer Erhöhung der Festigkeit und einer Verdichtung der Gefü-gestruktur einher. Aufgrund der hohen Druckfestigkeit finden diese Hochleistungsbetone vermehrten Einsatz im Hoch-, Brücken-, und Tunnelbau. Unter Brandbeanspruchung neigen diese Hochleistungsbetone allerdings zu explosionsartigen Abplatzungen. Diese werden nach derzeitigem Stand auf thermomechanische und thermohydraulische Prozesse zurückgeführt. Letztere beruhen auf der Generierung hoher Wasserdampfdrücke in einseitig brandbeanspruchten Beton-bauteilen, die zum einen auf die geringe Permeabilität des Hochleistungsbetons und zum anderen auf die Bildung einer wassergesättigten Zone, der sogenannten „moisture clog“ zurückzuführen sind. Dabei spielen Verdampfungs- und Kondensationsvorgänge sowie der vorhandene Temperatur-gradient eine wichtige Rolle. Die Interaktion des Feuchtetra-nsportes mit den Gefügeveränderungen während der thermi-schen Beanspruchung soll im Rahmen weiterer Versuche eingehend untersucht werden. Zur Analyse des Feuchtetransports während der thermischen Beanspruchung wurden miniaturisierte Prüfkörper aus Hoch-leistungsbeton hergestellt, die mit Hilfe eines elektrischen Heizelements einseitig erwärmt wurden. Zur Sicherstellung eines eindimensionalen Wärme- und Feuchtetransportes ist der Betonprüfkörper mit einer speziellen Glaskeramik und einer Hochtemperaturwolle ummantelt. Simultan zur Erwär-mung werden eine Reihe röntgentomographischer Aufnah-men durchgeführt. Durch Differenzbildung aufeinanderfol-gender Aufnahmen können Dichteveränderungen lokal und zeitlich aufgelöst werden. Diese lassen Rückschlüsse auf Än-derungen der Feuchteverteilung im Prüfkörper während der Erwärmung zu. Parallel dazu werden Untersuchungen mittels NMR-Relaxometrie (nuclear magnetic resonance) vor und nach der thermischen Beanspruchung durchgeführt. Diese Prüfmethodologie ermöglicht es erstmals, die Veränderungen der Feuchteverteilung infolge thermischer Beanspruchung im Hochleistungsbeton von den Gelporen bis hin zu vorhande-nen Verdichtungsporen abzubilden. So zeigen erste Ergebnis-se, dass die gewählten Untersuchungsmethoden Veränderun-gen der Feuchteverteilung im Prüfkörper räumlich und zeitlich auflösen können. KW - Abplatzen KW - Spalling KW - Brand KW - Feuchtetransport KW - Hochleistungsbeton KW - Röntgen-3D-Computertomographie KW - NMR KW - Fire KW - Moisture clog KW - Moisture transport KW - HPC KW - HSC KW - X-ray CT PY - 2017 U6 - https://doi.org/10.1002/best.201700022 SN - 0005-9900 SN - 1437-1006 VL - 112 IS - 7 SP - 486 EP - 486 PB - Ernst & Sohn CY - Berlin AN - OPUS4-41826 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stelzner, Ludwig A1 - Powierza, Bartosz A1 - Weise, Frank A1 - Oesch, Tyler A1 - Dlugosch, R. A1 - Meng, Birgit T1 - Analysis of moisture transport in unilateral-heated dense high-strength concrete N2 - Unilateral thermal exposure of concrete building components induces moisture transport processes that have a significant influence on the spalling behaviour of dense high-strength concrete (HSC). These transport processes are based on evaporation and condensation mechanisms of liquid and gaseous water in the pores as well as the chemically bound water within the concrete. The low permeability of HSC and the formation of a saturated zone within building components (also known as a moisture clog) leads to high water-vapour pressures, which contributes to explosive spalling. The formation of these pressures has already been verified by means of pore-pressure measurement techniques. In addition, the redistribution of the moisture within concrete specimens subject to unilateral thermal exposure has been demonstrated on fractured surfaces. Investigations by means of the nuclear magnetic resonance (NMR) relaxometry technique and neutron radiography have shown one-dimensional changes in moisture distribution during thermal exposure. However, none of these methods has been able to depict the moisture distribution in three dimensions (3D), so the link between pore size, concrete micro-structure and moisture content is missing. The research project presented in this paper aims to fill this gap by developing a new multi-level test methodology to characterise non-destructively the temporal course of spatial moisture distribution during unilateral thermal exposure. The procedure used during this programme included the collection of X-ray 3D-computed tomography (CT) measurements using a miniaturised specimen subjected to in-situ thermal exposure and the comparison of those CT results with the results of one-dimensional NMR-relaxometry before and after the heating process. In the first step, a mobile heating device was developed, built and tested. To simulate a unilaterally-heated construction component, a cylindrical specimen made of HSC (Ø = 40 mm, L = 100 mm) was cast into an impermeable glass ceramic shell. The ceramic shell ensured a one-dimensional moisture flux and limited the thermal expansion of the concrete. An additional high-temperature wool (HTW) insulating shell ensured a one-dimensional heat flux. The heating device, which operated using infrared radiation (IR), allowed the unilateral heating of the specimens up to 300 °C using variable heating regimes. In the second step, the mobile heating device was integrated into the CT-scanner, which enabled the collection of measurements before, during and after heating. By subtraction of successive 3D-CT images, X-ray attenuation differences could be resolved three-dimensionally in the specimen and interpreted as changes in the moisture content. Initial results show that this test methodology can monitor the 3D changes of moisture content inside the specimen during thermal exposure. It enables the researcher to visualise areas with moisture accumulation as well as dehydrated areas inside the specimen. Comparative one-dimensional NMR-relaxometry measurements confirm the results of the CT image analysis. T2 - 5th International Workshop on Concrete Spalling due to Fire Exposure CY - Boras, Sweden DA - 12.10.2017 KW - Spalling KW - Fire KW - Moisture clog KW - Moisture transport KW - HPC KW - HSC KW - X-ray CT KW - NMR KW - NDT PY - 2017 AN - OPUS4-42972 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Souza, Roberto A1 - Knaust, Christian A1 - Andreini, M. A1 - La Mendola, S. T1 - Probability Distribution Sensitivity on the Thermo-Mechanical FEM of a Concrete Tunnel Exposed to Fire N2 - A probabilistic approach for finite element analysis (FEA) for tunnel linings exposed to the nominal fire is presented. The probabilistic FEA accounted for the uncertainties distributions tied to the conductivity and specific heat as well as of the compressive strength, tensile strength, Young’s modulus, and ultimate strain in compression. To get an understanding on the influence of different probability density functions on the distribution of maximum displacements of the tunnel lining, a sensitivity analysis was performed. Four sets of FEAs were carried out with different probability distributions of the conductivity, the specific heat, and the compressive strength of the concrete, respectively. An experimental design based on a Latin Hypercube Sampling algorithm was performed to define the input parameters which describe each analysis case. A reliability analysis was executed considering a limit state function based on the temperature-dependent ultimate strain. The results show that, depending on the distribution adopted, the standard deviation of the maximum displacements can vary up to 47,4% of the minimum standard deviation. The large standard deviation is associated with the possibility of a greater displacement and, hence, to a structure more vulnerable to fire. T2 - 4th Symposium Structural Fire Engineering Braunschweig CY - Brunswick, Germany DA - 12.09.2017 KW - Probabilistic analysis KW - Fire KW - Concrete KW - Finite elements analysis PY - 2017 SP - 1 EP - 13 AN - OPUS4-42681 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rosignuolo, F. A1 - Chaves Spoglianti de Souza, Roberto A1 - Andreini, M. A1 - La Mendola, S. A1 - Knaust, Christian T1 - A comparison between empirical models and FDS simulation to predict the ceiling gas temperature distribution in a tunnel fire N2 - A comparison between the results obtained from a Computational Fluid Dynamic (CFD) simulation and from the application of an empirical formula for determining the temperature distribution inside a tunnel in case of fire is presented. The temperature is measured and calculated at different distances from the location of the fire and at different time intervals. The fire considered varies with time following a time-heat release rate curve which has a parabolic growing phase, a constant period and a linear decay. The comparison reveals differences in the results. The temperatures calculated with the empirical formula resulted higher than the temperatures obtained by means of the CFD simulation. A list of possible reasons for this limited correspondence is also presented and commented. A proposal for further studies to better define the limitations of both the procedures and to define the influence of each parameter involved is finally presented. T2 - World Tunnel Congress 2017 – Surface challenges – Underground solutions CY - Bergen, Norway DA - 09.06.2017 KW - CFD KW - Fire KW - Tunnel KW - Design Fire PY - 2017 AN - OPUS4-40655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Powierza, Bartosz A1 - Stelzner, Ludwig A1 - Oesch, Tyler A1 - Gollwitzer, Christian A1 - Weise, Frank A1 - Bruno, Giovanni T1 - Water migration in one-side heated concrete: 4D in-situ CT monitoring of the moisture-clog-effect N2 - Explosive spalling due to fire exposure in concrete structures can lead severe damage and, in the worst case, to premature component failure. For this reason, an in situ investigation of water Migration in concrete due to surface heating was undertaken. During these experiments, a miniaturized concrete specimen within a confining and insulating double-hull was subjected to surface heating during simultaneous X-ray computed tomography (CT) scanning. Through the use of subtraction-based Image analysis techniques, it was possible to observe and quantify not only drying within areas of the concrete matrix close to the heated surface, but also the migration of moisture to both pore and matrix regions deeper within the specimen. It was also discovered that the correction of CT images for specimen deformation using DVC and variable detector performance using calibrated image filters significantly improved the quality of the results. This clearly demonstrates the potential of X-ray CT for evaluation of other rapid-density-change phenomena in concrete and other building materials. T2 - 8th Conference on Industrial Computed Tomography (iCT 2018) CY - Wels, Austria DA - 06.02.2018 KW - In-Situ X-ray CT KW - Digital Volume Correlation KW - Heated concrete KW - Water migration KW - Fire PY - 2019 U6 - https://doi.org/10.1007/s10921-018-0552-7 SN - 1573-4862 SN - 0195-9298 VL - 38 IS - 1 SP - 15, 1 EP - 11 PB - Springer US CY - New York / Heidelberg AN - OPUS4-47147 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Powierza, Bartosz A1 - Stelzner, Ludwig A1 - Oesch, Tyler A1 - Weise, Frank A1 - Bruno, Giovanni T1 - In-situ CT observation of water migration in heated concrete N2 - In order to study damage in concrete exposed to fire, a series of continuous X-ray computed tomography (CT) measurements were performed on a concrete sample heated, in-situ, on one side. The water migration relative to time and 3D space and, in particular, the dynamic condensation and vaporization of water droplets in the pores was quantified. This approach shows significant potential for further investigation of fire-related concrete damage. T2 - 3rd International Conference on Tomography of Materials and Structures CY - Lund, Sweden DA - 26.06.2017 KW - In-situ KW - X-ray CT KW - Heated concrete KW - Pores KW - Water migration KW - Fire PY - 2017 UR - http://meetingorganizer.copernicus.org/ICTMS2017/ICTMS2017-29.pdf AN - OPUS4-43062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Powierza, Bartosz A1 - Stelzner, Ludwig A1 - Oesch, Tyler A1 - Weise, Frank A1 - Bruno, Giovanni T1 - Water Migration in One-Side Heated Concrete: 4D In-Situ CT Monitoring of the Moisture-Clog-Effect N2 - In order to study damage in concrete exposed to fire, a series of continuous X-ray computed tomography (CT) measurements were performed on a concrete sample heated, in-situ, on one side. The water migration relative to time and 3D space and, in particular, the dynamic condensation and vaporization of water droplets in the pores was quantified. This approach shows significant potential for further investigation of fire-related concrete damage. T2 - 8th Conference on Industrial Computed Tomography (iCT 2018) CY - Wels, Austria DA - 06.02.2018 KW - CT KW - X-ray KW - In-Situ KW - Pores KW - Heated Concrete KW - Water Migration KW - Fire PY - 2018 AN - OPUS4-46381 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pirskawetz, Stephan T1 - The burned shield-bearers: a detective story N2 - Severe fires at the Friedrichshain flak bunker in May 1945 destroyed or severely damaged an important part of the collection of the Kaiser-Friedrich-Museum, Berlin, today’s Bode Museum. Fragments of two marble sculptures by Tullio Lombardo, sculptor of the Italian renaissance, have survived and are now stored in the Bode Museum. In preparation for restoration, the condition of the sculptures has been documented in detail in 2010. The study revealed that the fragments are not stable enough to exhibit them in a horizontal nor in an upright position. The intention of a further study in 2012 was to find a correlation between ultrasonic velocity and mechanical properties of burned Carrara marble as a basis for stabilization measures. The results and numerous supplementary experiments show that the current condition of the sculptural fragments can not only be explained by the exposure to fire. KW - Marble sculptures KW - Marble deterioration KW - Fire KW - Ultrasonic velocities KW - Mechanical properties PY - 2018 U6 - https://doi.org/10.1007/s12665-018-7267-z SN - 1866-6280 SN - 1866-6299 VL - 77 IS - 4 SP - Article 130, 1 EP - 12 PB - Springer-Verlag GmbH CY - Berlin Heidelberg AN - OPUS4-44159 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Otremba, Frank A1 - Sklorz, Christian T1 - Testing of pressurized vessels N2 - The results are based on data1. Figure 3 displays temperatures of the tank wall and of the gas phase over testing time. It can be seen that a complete coating strongly delayed the heating of tank wall and gas phase, whereas the partly coated tanks only had a minor influence on temperature development. There was no significant difference between a half coated and a thirdly coated tank measurable. Figure 4 shows the internal pressure of tanks over testing time. Only the fully coated tank enabled a low pressure over 90 min testing time. Hence, a complete coating is necessary to guarantee the fire safety of hazmat tanks and a partly coating is not sufficient. T2 - Annual Conference on Engineering and Information Technology CY - Nagoya - Japan DA - 29.03.2017 KW - Fire KW - Testing KW - Vessels KW - Dangerous goods PY - 2017 AN - OPUS4-39843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -