TY - CONF A1 - Henning, Ricky A1 - Sturm, Patrick A1 - Kühne, Hans-Carsten A1 - Keßler, S. A1 - Gluth, Gregor T1 - Untersuchungen zur Wärmeentwicklung von hybriden Zementen N2 - Die Hauptfunktion von Verschlussbauwerken für End- und Zwischenlager von radioaktiven Abfällen besteht in der Erhaltung der geologischen Barriere. Vor allem soll ein potenzieller Stofftransport durch eine möglichst geringe Permeabilität des Bauwerks verhindert bzw. auf vernachlässigbare Werte herabgesetzt werden. Die in-situ-Permeabilität des Verschlussbauwerks steht dabei in direktem Zusammenhang mit dessen Poren- und Makrostruktur, welche bei Bauwerken auf Basis von Beton insbesondere durch Schwind-verformungen und durch thermisch induzierte Rissbildung infolge der Reaktionswärmeentwicklung des Bindemittels gestört werden kann. Die Betone müssen daher neben einer hohen chemischen Langzeitstabilität auch eine geringe bzw. langsame Wärmeentwicklung während der Erhärtungsreaktionen aufweisen. Als hybride Zemente werden Mischungen aus Portlandzement, Betonzusatzstoffen und einem alkalischen Aktivator bezeichnet. Dabei können u. a. Alkalisulfate, Alkalicarbonate, Alkalisilicate und Alkalihydroxide als Aktivatoren zum Einsatz kommen. Aufgrund ihrer hohen chemischen Stabilität im salinaren Milieu sind Betone aus solchen Zementen potenziell besonders gut als Verfüllmaterial für End- und Zwischenlager im Steinsalz geeignet. In der vorliegenden Studie wurden daher hybride Zemente hinsichtlich ihrer Wärmeentwicklung in einem isothermen Kalorimeter sowie hinsichtlich Phasenbestand und Festigkeiten untersucht. Hybride Zementleime wurden auf Basis von Portlandklinker, Hüttensandmehl, Flugasche und Natriumsulfat hergestellt und die Zusammensetzungen systematisch variiert, um den Einfluss der Komponenten auf Wärmeentwicklung, Phasenbestand und mechanische Eigenschaften der Leime zu untersuchen; zusätzlich wurden zu Vergleichszwecken ein Zementleim auf Basis der Betonrezeptur M2 sowie eine alkalisch aktivierte Flugasche untersucht. T2 - 2. Tage der Standortauswahl CY - Online meeting DA - 11.02.2021 KW - Hybride Zemente KW - Hydratationswärme KW - Kalorimetrie PY - 2021 SP - 137 EP - 139 AN - OPUS4-52216 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinrich, Thomas A1 - Traulsen, Christoph Hans-Henning A1 - Darlatt, Erik A1 - Richter, S. A1 - Poppenberg, J. A1 - Traulsen, N.L. A1 - Linder, I. A1 - Lippitz, Andreas A1 - Dietrich, Paul A1 - Dib, B. A1 - Unger, Wolfgang A1 - Schalley, C.A. T1 - The versatility of 'Click' reactions at surfaces: Molecular recognition at interfaces N2 - In order to investigate molecular recognition on surfaces, an azide-functionalized monolayer was deposited on gold. The monolayer was characterized by X-ray photoelectron spectroscopy (XPS) and angle-resolved near-edge X-ray absorption fine structure (NEXAFS) experiments and the decomposition of the azide upon irradiation with X-ray beams was investigated. Subsequently, various alkyne-functionalized host and guest molecules were attached to the azide by 1,3-dipolar cycloaddition. These modified surfaces and their host–guest chemistry were analysed by XPS and angle-resolved NEXAFS. The reversibility of guest binding was shown for one example as a proof of principle. KW - 'Click' reaction KW - Azide-terminated surfaces KW - SAMs KW - Host guest molecules KW - Molecular recognition at interfaces PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-306463 DO - https://doi.org/10.1039/C4RA01730G SN - 2046-2069 VL - 4 IS - 34 SP - 17694 EP - 17702 PB - RSC Publishing CY - London AN - OPUS4-30646 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Henning, Ricky A1 - Sturm, Patrick A1 - Geddes, D.A. A1 - Keßler, S. A1 - Walkley, B. A1 - Gluth, Gregor T1 - The influence of curing temperature on the strength and phase assemblage of hybrid cements based on GGBFS/FA blends N2 - Hybrid cements are composites made of Portland cement or Portland clinker and one or more supplementary cementitious materials like slag, fly ash or metakaolin, activated with an alkali salt. To date, their hydration mechanism and the phase formation at various temperatures is insufficiently understood, partly due to the large variability of the raw materials used. In the present study, three hybrid cements based on ground granulated blast furnace slag, fly ash, Portland clinker and sodium sulfate, and an alkali-activated slag/fly ash blend were cured at 10 and 21.5°C, and subsequently analyzed by XRD, 27Al MAS NMR, and TGA. The compressive strength of the hybrid cements was higher by up to 27% after 91-day curing at 10°C, compared to curing at 21.5°C. The experimental results as well as thermodynamic modeling indicate that the differences in compressive strength were related to a different phase assemblage, mainly differing amounts of strätlingite and C-N-A-S-H, and the associated differences of the volume of hydration products. While the strätlingite was amorphous to X-rays, it could be identified by 27Al MAS NMR spectroscopy, TGA and thermodynamic modeling. The microstructural properties of the hybrid cements and the alkali-activated slag/fly ash blend as well as the compatibility between thermodynamic modeling results and experimental data as a function of curing temperature and time are discussed. KW - Hybrid cements KW - Strätlingite KW - Thermodynamic modelling KW - Hydration PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-557767 DO - https://doi.org/10.3389/fmats.2022.982568 SN - 2296-8016 VL - 9 SP - 1 EP - 16 PB - Frontiers AN - OPUS4-55776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Henning, Ricky A1 - Sturm, Patrick A1 - Keßler, S. A1 - Gluth, Gregor ED - Lothenbach, B. ED - Wieland, E. ED - Altmaier, M. T1 - Influence of salt aggregate on the degradation of hybrid alkaline cement (HAC) concretes in magnesium chloride-rich saline solution simulating evaporite rock N2 - Concretes produced from salt aggregate and hybrid alkaline cements, an alkali-activated slag/fly ash blend, or a Portland cement were exposed to a magnesium chloride-rich saline solution ([Mg2+] = 3.6 m, [Cl−] = 8.3 m), representing a solution formed after contact of surface water with evaporite rock (rock salt) in a nuclear waste repository. The hydration and deterioration of the concretes were studied with X-ray diffraction, thermogravimetric analysis, pH mapping and permeability measurements. The results show that calcium silicate hydrate (C-S-H) or sodium-substituted calcium aluminium silicate hydrate (C-N-A-S-H) and Friedel's salt were the major reaction products in the concretes prior to exposure to the saline solution. During exposure to the saline solution, increasing amounts of C-S-H/C-N-A-S-H dissolved, and gypsum and a secondary AFm phase formed. The durability of the concretes improved with increasing amounts of Portland clinker in the cements, due to the associated differences in permeability and chemical resistance. Nevertheless, a massive increase of permeability occurred for all concretes, likely caused by crack formation due to the formation of gypsum from anhydrite in the salt aggregate. Thus, the behavior of the concretes differed from, and was more complex than, the behavior of plain cement pastes. T2 - Joint 6th International Workshop on Mechanisms and Modelling of Waste/Cement Interactions (JCCW 2023) CY - Prague, Czech Republic DA - 20.11.2023 KW - Nuclear waste repository KW - Evaporite rock KW - Magnesium chloride brine KW - Concrete KW - Hybrid alkaline cement PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-599928 DO - https://doi.org/10.1016/j.apgeochem.2024.106027 SN - 0883-2927 SN - 1872-9134 VL - 168 SP - 1 EP - 14 PB - Elsevier AN - OPUS4-59992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Y. A1 - Lu, X. A1 - Cho, J.I.S. A1 - Rasha, L. A1 - Whiteley, M. A1 - Neville, T. P. A1 - Ziesche, R. A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Manke, I. A1 - Zhang, X. A1 - Shearing, P. R. A1 - Brett, D. J. L. T1 - Multi-length scale characterization of compression on metal foam flow-field based fuel cells using X-ray computed tomography and neutron radiography N2 - The mechanical compression of metal foam flow-field based polymer electrolyte fuel cells (PEFCs) is critical in determining the interfacial contact resistance with gas diffusion layers (GDLs), reactant flow and water management. The distinct scale between the pore structure of metal foams and the entire flow-field warrant a multilength scale characterization that combines ex-situ tests of compressed metal foam samples and in-operando analysis of operating PEFCs using X-ray computed tomography (CT) and neutron radiography. An optimal ‘medium’ compression was found to deliver a peak power density of 853 mW/cm². The X-ray CT data indicates that the compression process significantly decreases the mean pore size and narrows the pore size distribution of metal foams. Simulation results suggest compressing metal foam increases the pressure drop and gas velocity, improving the convective liquid water removal. This is in agreement with the neutron imaging results that demonstrates an increase in the mass of accumulated liquid water with minimum compression compared to the medium and maximum compression cases. The results show that a balance between Ohmic resistance, water removal capacity and parasitic power is imperative for the optimal performance of metal foam based PEFCs. KW - Fuel cell KW - Compression effect KW - Metal foam microstructure KW - Neutron radiography KW - X-ray CT PY - 2021 DO - https://doi.org/10.1016/j.enconman.2020.113785 VL - 239 SP - 10 EP - 113785 PB - Elsevier Ltd. AN - OPUS4-53842 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -