TY - CONF A1 - Gluth, Gregor T1 - One-part geopolymers and geopolymer-zeolite composites based on silica: factors influencing microstructure and engineering properties N2 - Mixing and curing of geopolymers and related alkali-activated materials without storage and handling of highly alkaline solutions possesses advantages regarding safety and economic viability; one possible approach is to produce these materials from solid silica feedstocks and solid sodium aluminate, and subsequent mixing with water. We present a comparison between geopolymers and geopolymer-zeolite composites synthesized by this route from different silica feedstocks (by-product silica from chlorosilane production, microsilica, rice husk ash) and with different SiO2/Al2O3 ratios, using results from XRD, NMR, SEM, thermal analysis, mechanical and acid resistance testing. The use of rice husk ash favors formation of a fully amorphous geopolymer with high strength. Utilization of the other silica feedstocks leads to formation of geopolymer-zeolite composites, the amount and kind of zeolites depending on the feedstock and the SiO2/Al2O3 ratio. These composites show beneficial dehydration behavior, viz. no distinct dehydration step of thermal strain, with the phase assemblage after heating to 1000 °C controlled by the starting composition. Mortars produced from both, the geopolymers as well as the compo¬sites, exhibit high resistance to sulfuric acid attack, making them promising materials for the construction and the repair of industrial and sewer structures. T2 - 42nd International Conference and Expo on Advanced Ceramics and Composites CY - Daytona Beach, FL, USA DA - 21.01.2018 KW - Alkali-activated materials KW - Geopolymers KW - Acid resistance KW - High-temperature resistance PY - 2018 AN - OPUS4-44145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Geopolymerisation kieselsäurehaltiger Rückstände aus der Reststoffaufbereitung der Chlorosilanproduktion T2 - 18. Internationale Baustofftagung (IBAUSIL) CY - Weimar, Germany DA - 2012-09-12 PY - 2012 AN - OPUS4-26556 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Structure, acid resistance and high-temperature behavior of silica-based one-part AAMs N2 - One-part geopolymers (OPGs) are a sort of alkali-activated materials (AAMs) which production avoids the use of highly-alkaline activator-solutions and contributes to a better acceptance of alternative mineral binders in terms of safety-related and economic aspects. In the present contribution OPGs were synthesized by blending silica sources (two industrial silicas and two biogenic silicas) with sodium aluminate and only water must be added to initiate the hardening, i.e. mixing is performed in the same way as for conventional Portland cements. The OPGs were characterized by XRD, and SEM and the degrees of reaction of the silicas were determined by a chemical dissolution method. The industrial silicas led to the formation of geopolymer-zeolite composites, that contained, besides geopolymeric gel, crystalline tectosilicates (e.g. zeolite A and hydrosodalite) and depending on the starting composition also unreacted silica. The biogenic silicas provided a higher reactivity and avoided the formation of crystallite by-products. The differences in the microstructures caused differences in the mechanical strength of the specimens. The treatment of the OPG composites at moderate elevated temperatures revealed promising behavior on thermal dehydration in terms of shrinkage and residual strength up to 700 °C. Above 700 °C sintering and partial melting occurred, and new phase formation commenced. After exposure to 1000 °C the specimens appeared virtually amorphous or formed stuffed silica structures of nepheline- or carnegieite-type type. The investigations of the OPG based mortars on their resistance against sulfuric acid in accordance with DIN 19573 (Appendix A) revealed very high residual strengths up to 78 % after treatment with H2SO4 (pH 1) for 70d. A mechanism of dissolution of the primary aluminosilicate reaction products of the pastes and the precipitation of a silica gel that protects the remaining aluminosilicates and decelerates further corrosion was found to be the main reason for the good performance under acidic conditions. The addition of CaO-containing feedstocks enhanced hardening, but at a certain content the resistance against sulfuric acid decreased, due to the formation of gypsum on exposure to sulfate. In addition, the mortars exhibited excellent shrinkage behavior as well as good bond to concrete substrates with pull-off strength up to > 3 MPa. The workability of the fresh mortars provided very good manual applicability; automatic applications such as sprayed and spun mortars will require further optimization regarding rheological properties. In summary, the studied OPG are promising materials for the construction and the repair of concrete structures, such as sewers, that are affected by biogenic sulfuric acid corrosion. T2 - Alkali Activated Materials and Geopolymers CY - Tomar, Portugal DA - 27.05.2018 KW - Alkali-activated materials KW - Geopolymers KW - Acid resistance KW - Solid state NMR PY - 2018 AN - OPUS4-45087 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, W. A1 - Gaggl, M. A1 - Gluth, Gregor A1 - Behrendt, F. T1 - Gas separation using porous cement membrane N2 - Gas separation is a key issue in various industrial fields. Hydrogen has the potential for application in clean fuel technologies. Therefore, the separation and purification of hydrogen is an important research subject. CO2 capture and storage have important roles in 'green chemistry'. As an effective clean technology, gas separation using inorganic membranes has attracted much attention in the last several decades. Membrane processes have many applications in the field of gas separation. Cement is one type of inorganic material, with the advantages of a lower cost and a longer lifespan. An experimental setup has been created and improved to measure twenty different cement membranes. The purpose of this work was to investigate the influence of gas molecule properties on the material transport and to explore the influence of operating conditions and membrane composition on separation efficiency. The influences of the above parameters are determined, the best conditions and membrane type are found, it is shown that cementitious material has the ability to separate gas mixtures, and the gas transport mechanism is studied. KW - Gas separation KW - Porous membrane KW - Clean fuel KW - Cement membrane KW - Inorganic membranes PY - 2014 DO - https://doi.org/10.1016/S1001-0742(13)60389-7 SN - 1001-0742 SN - 1878-7320 VL - 26 IS - 1 SP - 140 EP - 146 CY - Beijing, China AN - OPUS4-30039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Design and Characterization of Fly Ash-Based Geopolymer Concretes for a Round Robin Durability Testing Program T2 - Geopolymers: The route to eliminate waste and emissions in ceramic and cement manufacturing CY - Hernstein, Austria DA - 2015-05-24 PY - 2015 AN - OPUS4-33513 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor A1 - Lehmann, Christian A1 - Rübner, Katrin A1 - Kühne, Hans-Carsten ED - Bílek, V. ED - Kersner, Z. T1 - Influence of sodium concentration of the activating solution on the hydration of calcium carbonate-rich wastepaper sludge ash N2 - In paper recycling several types of waste sludges are produced, which contain organics as well as inorganic fillers of the recycled paper, e.g. kaolinite, calcite, talc, or titanium dioxide [1,2]. Part of these sludges is incinerated to recover energy and to reduce the volume of waste to be handled. The ashes generated in this process are commonly referred to as wastepaper sludge ash (WSA). The quantities of WSA produced are large and at present much of it is still landfilled or otherwise handled entailing costs. Depending on the composition of the recycled paper and the conditions during processing and incineration, WSA can have cementitious properties. In the present investigation a CaC03-rich WSA was analyzed for reaction products and strength development after hydration with water, 2 M NaOH solution and 8 M NaOH solution. The rationale for activating the WSA with NaOH was to assess the behaviour of the WSA when alkalis are introduced to the System or when the WSA is used as addition in alkali-activated binders. T2 - NTCC2014 - International conference on non-traditional cement and concrete CY - Brno, Czech Republic DA - 16.06.2014 KW - Wastepaper sludge ash KW - Calcium carbonate KW - Alkali-activation KW - Monocarboaluminate KW - AFm KW - Hydrogarnet PY - 2014 SN - 978-80-214-4867-4 SP - 71 EP - 74 PB - Novpress AN - OPUS4-30992 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gluth, Gregor A1 - Zhang, W. A1 - Gaggl, M. A1 - Hillemeier, B. A1 - Behrendt, F. T1 - Multicomponent gas diffusion in hardened cement paste at temperatures up to 350 °C N2 - Diffusional gas transport of a H2/CO2 mixture versus N2 in the pore system of hardened cement pastes was studied at four temperatures up to 350 °C in a Wicke-Kallenbach cell. The pastes possessed separation factors αH2,CO2 from 1.42 to 3.43, i.e. the diffusion of hydrogen took place considerably faster than the diffusion of carbon dioxide. The separation factors depended on the threshold radii of the pastes, smaller threshold radii leading to higher separation factors. The Knudsen numbers of the controlling constrictions of the pore system and the temperature dependence of the effective diffusion coefficients of the gases show that gas transport in these constrictions takes place in the transient regime between Knudsen diffusion and bulk diffusion, smaller constriction widths leading to predominating Knudsen diffusion. It is therefore possible to use cement paste membranes to separate gas components of low molecular weight from higher weight components. KW - Microstructure (B) KW - Mercury porosimetry (B) KW - Diffusion (C) KW - Cement paste (D) KW - Gas separation KW - Pore structure PY - 2012 DO - https://doi.org/10.1016/j.cemconres.2012.02.001 SN - 0008-8846 SN - 1873-3948 VL - 42 IS - 5 SP - 656 EP - 664 PB - Pergamon Press CY - New York, NY AN - OPUS4-25655 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gluth, Gregor A1 - Rickard, W.D.A. A1 - Werner, Steve A1 - Pirskawetz, Stephan T1 - Acoustic emission and microstructural changes in fly ash geopolymer concretes exposed to simulated fire N2 - Two fly ash-based geopolymer concretes with quartz aggregates or with expanded clay (lightweight) aggregates were exposed to the ISO 834-1 standard fire curve in a small-scale fire test set-up. Acoustic emission measurements during fire exposure and subsequent cooling were employed to study spalling events and cracking during the tests. Optical microscopy and additional acoustic measurements were conducted after the testing to better understand the crack propagation in the samples. The testing revealed that neither of the concretes were susceptible to spalling, which is particularly notable for the concrete with quartz aggregates, as it is a high-strength concrete. This behavior is attributed to the relatively high permeability of the concretes and their low amount of chemically bound water. Significant crack formation was detected only around the temperature of the alpha–beta quartz transition (573 °C) and on cooling. Because of aggregate deformations at the quartz transition temperature, deterioration after heating was more significant in the geopolymer concrete with quartz aggregates. Crack formation also occurred in the concrete with expanded clay aggregates, caused by shrinkage of the geopolymer paste on cooling. Acoustic emission measurements proved to be a valuable tool to investigate processes during high temperature exposure. KW - Geopolymers KW - Spalling KW - Concrete KW - Acoustic emission KW - Heat exposure PY - 2016 DO - https://doi.org/10.1617/s11527-016-0857-x SN - 1359-5997 SN - 1871-6873 VL - 49 IS - 12 SP - 5243 EP - 5254 PB - Springer AN - OPUS4-36907 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Simone A1 - Gluth, Gregor A1 - Watolla, Marie-Bernadette A1 - Morys, Michael A1 - Häßler, Dustin A1 - Schartel, Bernhard T1 - Neue Wege: Reaktive Brandschutzbeschichtungen für Extrembedingungen N2 - Wesentlich für das Sicherheitsniveau und damit die nachhaltige Wettbewerbsfähigkeit des Technologiestandortes Deutschland ist der Brandschutz in Industrieanlagen, in Gebäuden und im Transportwesen. Der vorbeugende bauliche Brandschutz hat u. a. das Ziel, die Brand- und Rauchausbreitung im Brandfall für eine gewisse Zeit zu behindern, damit die erforderlichen Lösch- und Rettungsarbeiten durchgeführt werden können. Dies geschieht u.a. durch Anforderungen an die Feuerwiderstandsfähigkeit brandbeanspruchter Bauteile. Der Feuerwiderstand eines Bauteils ist die Fähigkeit während eines angegebenen Zeitraums in einer genormten Feuerwiderstandsprüfung bezüglich mechanischer Stabilität und/oder thermischer Isolierung nicht zu versagen. Reaktive Brandschutzbeschichtungen erhöhen für viele Bauteile sehr effektiv den Feuerwiderstand. Die Beschichtungen und die Brandprüfungen müssen jedoch an die immer komplexeren Anwendungen und/oder extremeren Anforderungen angepasst und weiterentwickelt werden. Aktuelle Forschungsschwerpunkte liegen dabei in der Entwicklung neuer Materialien (z.B. Geopolymere, keramisierende Beschichtungen, silikonbasierte Beschichtungen) für extreme Brandszenarien (extreme Temperaturen, lange Beanspruchungszeiten) und in der Realisierung komplexer Funktionalitäten (komplexe Geometrien, bewegliche Komponenten) sowie in der Entwicklung neuer Testmethoden (Feuerwiderstand als bench-scale Tests, kostengünstiges Screening, Feuerwiderstand in extremen Brandszenarien). Die Entwicklung geht dabei weg von der präskriptiven Bewertung hin zur leistungsorientierten (performance-based) Bewertung in individuellen Brandszenarien oder von komplexen Bauteilen. Im Rahmen dieser Arbeit werden Lösungsansätze für die neuen Herausforderungen an die reaktiven Brandschutzsysteme unter Extrembedingungen und deren Testmöglichkeiten vorgestellt und diskutiert. Im Mittelpunkt stehen dabei neu entwickelte bench-scale Testmethoden zum Screening von neuen Beschichtungsmaterialien sowie zur Beurteilung spezieller bzw. materialspezifischer Aspekte des Feuerwiderstands unter Extrembedingungen. KW - Reaktive Brandschutzsysteme KW - Brandtest PY - 2016 DO - https://doi.org/10.1002/bate.201600032 SN - 0932-8351 SN - 1437-0999 VL - 93 IS - 8 SP - 531 EP - 542 PB - Ernst & Sohn CY - Berlin AN - OPUS4-37115 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pistol, Klaus A1 - Gluth, Gregor A1 - Rickard, W. T1 - Mechanische Hochtemperatureigenschaften von flugaschebasierten Geopolymerbetonen N2 - Als umweltschonende Alternative zu portlandzementgebundenen Betonen werden derzeit in der Betonindustrie und in der Baustoffforschung Betone mit alkaliaktivierten Bindemitteln, sog. Geopolymerbetone, intensiv erforscht. Die auf industriellen Reststoffen wie Flugasche und Hüttensand basierenden anorganischen Bindemittel weisen bei geeigneter Zusammensetzung einen hohen Widerstand gegenüber aggressiven Salzlösungen und Säuren auf. Als Grundlage für den rechnerischen Nachweis der Tragfähigkeit von brandbeanspruchten Betonbauteilen auf Basis von alkaliaktivierten Bindemitteln werden deshalb an der Bundesanstalt für Materialforschung und -prüfung (BAM) die mechanischen Hochtemperatureigenschaften von flugaschebasierten Geopolymerbetonen systematisch untersucht. Die bis zu 750 °C erhitzten Probekörper mit quarzitischer und leichter Gesteinskörnung zeigen einen Festigkeitsverlust bis ca. 300 °C, der auf entwässerungsbedingte Mikrorissbildung zurückgeführt werden kann. Bei weiter zunehmender Temperatur steigt aufgrund von Sinterungsprozessen ab ca. 500 °C die Festigkeit der untersuchten Geopolymerbetone wieder an. Diese im Vergleich zu herkömmlichem Beton günstigere Materialeigenschaft eröffnet potenziell auch Anwendungsmöglichkeiten in brandschutztechnisch kritischen Infrastrukturbereichen. Die Ergebnisse der thermomechanischen Prüfungen werden für numerische Bauteilberechnungen als temperaturabhängige Spannungs-Dehnungs-Beziehungen aufbereitet. N2 - At present, concretes based on alkali-activated binders, socalled geopolymer concretes, are investigated intensively in the building materials industry and by the research community as environmentally friendly alternative to Portland cementbased concretes. These inorganic binders, which are based on industrial by-products such as fly ash and ground granulated blast furnace slag, exhibit high resistance against corrosive acids and salts, if properly designed. The mechanical properties of fly ash-based geopolymer concretes at high temperatures are subject of systematic investigations at the Bundesanstalt für Materialforschung und -prüfung (BAM) to create a basis for the structural design of fire exposed concrete members based on alkali-activated binders. The concrete specimens, produced with quartz aggregates or lightweight aggregates and heated to a maximum temperature of 750 °C, exhibited a decrease of compressive strength up to temperatures of ca. 300 °C, attributed to formation of microcracks caused by dehydration. At higher temperatures the compressive strength of the investigated geopolymer concretes recovered partly, due to sintering processes starting from ca. 500 °C. Because of this beneficial property when compared to conventional concretes, geopolymer concretes can potentially be applied in infrastructure facilities where fire resistance is critical. From the results of the thermomechanical tests stress-strain relationships are derived that can be used for the structural design of members made from geopolymer concretes. KW - Geopolymerbeton KW - Hochtemperatureigenschaften KW - Feuerwiderstand KW - Spannung-Dehnungs-Beziehung PY - 2016 DO - https://doi.org/10.1002 / bate.201600038 SN - 0932-8351 SN - 1437-0999 VL - 93 IS - 8 SP - 521 EP - 530 PB - Ernst & Sohn CY - Berlin AN - OPUS4-37114 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Inhalt der Verordnungen für Heizungsanlagen - Überblick N2 - Seit dem 26.09.2015 gelten in Deutschland Anforderungen an die umweltgerechte Gestaltung und die Energiekennzeichnung von Heizgeräten und Verbundanlagen mit Heizgeräten. Der Vortrag stellt die zugrundeliegenden EU-Verordnungen und die sich ergebenden Konsequenzen überblicksmäßig vor. T2 - Kolloquium Marktüberwachung im Bereich Heizungsanlagen CY - Berlin, Germany DA - 06.04.2016 KW - Heizgeräte KW - Verbundanlagen KW - Umweltgerechte Gestaltung KW - Ökodesign KW - Energieverbrauchskennzeichnung PY - 2016 AN - OPUS4-36924 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Influence of sodium concentrations of the activating solution on the hydration of calcium carbonate-rich wastepaper sludge ash T2 - 5th International Conference on Non-Traditional Cement & Concrete CY - Brno, Czech Republic DA - 2014-06-16 PY - 2014 AN - OPUS4-33514 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Structural Investigations n One-Part Geopolymers after Different Drying Regimes T2 - 34th Cement & Concrete Science Conference CY - Sheffield, England DA - 2014-09-14 PY - 2014 AN - OPUS4-33516 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Hydration and strength development of calcite-rich wastepaper sludge ash T2 - Concrete Innovation Conference - CIC 2014 CY - Oslo, Norway DA - 2014-06-11 PY - 2014 AN - OPUS4-33515 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Energieverbrauchskennzeichnung: Aktivitäten von BAM, UBA und dena T2 - Auftaktveranstaltung - Deutsche Akteursplattform Solarthermie-Labeling CY - Frankfurt/Main DA - 2015-07-06 PY - 2015 AN - OPUS4-33701 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor T1 - Inhalt der neuen Verordnungen für Heizungstechnik T2 - Informationsveranstaltung Ökodesign und Energieverbrauchskennzeichnung von Heizgeräten CY - Berlin, Deutschland DA - 2015-09-09 PY - 2015 AN - OPUS4-35244 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, Wolfram A1 - Rübner, Katrin A1 - Schneider, Joachim A1 - von Werder, Julia A1 - Gluth, Gregor T1 - 63. DAfStb-Forschungskolloquium in der BAM - Themenblock 2: Nachhaltigkeitspotentiale N2 - Die Bauindustrie ist für rd. 40 % des weltweiten Energieverbrauchs und der Kohlenstoffemissionen verantwortlich. Mit der technologischen Entwicklung wird der Energiebedarf in Zukunft sinken, während sich das Problem grauer Emission verschärft. Daher ist ein verantwortungsvoller Umgang mit Ressourcen der Schlüssel zur Erreichung der Pariser Klimaziele. Der Einsatz klimaschonender Baustoffe weist dabei ein erhebliches Nachhaltigkeitspotential auf. Recycling, Rückgewinnung, Ressourcenschonung und Kreislaufwirtschaft können zu unersetzlichen Bestandteilen der Bautechnik werden. Im Folgenden werden einige Möglichkeiten vorgestellt, die bei der Dekarbonisierung der Bautechnik zukünftig hohe Potentiale aufweisen. Diese wurden beim 63. Forschungskolloquium des DAfStb an der BAM vorgestellt und Details können dem Tagungsband (DOI 10.26272/opus4-61338) entnommen werden. T2 - 11. Jahrestagung des DAfStb mit 63. Forschungskolloquium der BAM Green Intelligent Building CY - Berlin, Germany DA - 16.10.2024 KW - Bindemittel KW - Klimaschonende Baustoffe KW - Dekarbonisierung PY - 2025 SN - 0005-9846 VL - 75 IS - 4 SP - 131 EP - 134 PB - concrete content UG CY - Schermbeck AN - OPUS4-63068 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mundra, S. A1 - Bernal, S. A. A1 - Criado, M. A1 - Hlaváček, Petr A1 - Ebell, Gino A1 - Reinemann, Steffi A1 - Gluth, Gregor A1 - Provis, J. L. T1 - Steel corrosion in reinforced alkali‐activated materials N2 - The development of alkali‐activated materials (AAMs) as an alternative to Portland cement (PC) has seen significant progress in the past decades. However, there still remains significant uncertainty regarding their long term performance when used in steel‐reinforced structures. The durability of AAMs in such applications depends strongly on the corrosion behaviour of the embedded steel reinforcement, and the experimental data in the literature are limited and in some cases inconsistent. This letter elucidates the role of the chemistry of AAMs on the mechanisms governing passivation and chloride‐induced corrosion of the steel reinforcement, to bring a better understanding of the durability of AAM structures exposed to chloride. The corrosion of the steel reinforcement in AAMs differs significantly from observations in PC; the onset of pitting (or the chloride ‘threshold’ value) depends strongly on the alkalinity, and the redox environment, of these binders. Classifications or standards used to assess the severity of steel corrosion in PC appear not to be directly applicable to AAMs due to important differences in pore solution chemistry and phase assemblage. KW - Corrosion KW - Alkali-activated PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435162 DO - https://doi.org/10.21809/rilemtechlett.2017.39 SN - 2518-0231 VL - 2 SP - 33 EP - 39 PB - RILEM Publications SARL CY - Paris, France AN - OPUS4-43516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Greiser, Sebastian A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Jäger, Christian T1 - 29Si{27Al}, 27Al{29Si} and 27Al{1H} double-resonance NMR spectroscopy study of cementitious sodium aluminosilicate gels (geopolymers) and gel-zeolite composites N2 - The influence of starting materials and synthesis route on the properties and the structure of cementitious sodium aluminosilicate gels is not fully understood, partly due their amorphous nature and the fact that they often contain residual reactants, which can make the results of single-pulse NMR spectroscopy applied to these materials difficult to interpret or ambiguous. To overcome some of these limitations, 29Si{27Al} TRAPDOR NMR as well as 27Al{29Si} and 27Al{1H} REDOR NMR spectroscopy were applied to materials synthesized by the one-part alkali-activation route from three different amorphous silica starting materials, including rice husk ash. The latter led to formation of a fully amorphous sodium aluminosilicate gel (geopolymer), while the materials produced from the other silicas contained amorphous phase and crystalline zeolites. Application of the double-resonance NMR methods allowed to identify hydrous alumina gel domains in the rice husk ash-based material as well as significantly differing amounts of residual silica in the three cured materials. Four-coordinated Al existed not only in the aluminosilicate gel framework but also in a water-rich chemical environment with only a small amount of Si in proximity, likely in the alumina gel or possibly present as extra-framework Al in the aluminosilicate gel. The results demonstrate how the employment of different silica starting materials determines the phase assemblage of one-part alkali-activated materials, which in turn influences their engineering properties such as the resistance against chemically/biologically aggressive media. KW - Alkali-activated materials KW - Solid-state NMR KW - Aluminium hydroxide KW - Rice husk ash PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-469353 DO - https://doi.org/10.1039/C8RA09246J SN - 2046-2069 VL - 8 IS - 70 SP - 40164 EP - 40171 PB - Royal Society of Chemistry (RSC) CY - London AN - OPUS4-46935 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor A1 - Hlavacek, Petr A1 - Reinemann, Steffi A1 - Ebell, Gino A1 - Mietz, Jürgen ED - Alexander, M.G. ED - Beushausen, H. ED - Dehn, F. ED - Moyo, P. T1 - Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars N2 - Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in high- and low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation. T2 - International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2018) CY - Cape Town, South Africa DA - 19.11.2018 KW - Alkali-activated materials KW - Steel corrosion KW - Leaching KW - Carbonation PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-464381 DO - https://doi.org/10.1051/matecconf/201819902025 VL - 199 SP - Article Number 02025 PB - EDP Sciences AN - OPUS4-46438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gluth, Gregor A1 - Grengg, C. A1 - Ukrainczyk, N. A1 - Mittermayr, F. A1 - Dietzel, M. T1 - Acid resistance of alkali-activated materials: Recent advances and research needs N2 - Cementitious materials are frequently applied in environments in which they are exposed to acid attack, e.g., in sewer systems, biogas plants, and agricultural/food-related industries. Alkali-activated materials (AAMs) have repeatedly been shown to exhibit a remarkably high resistance against attack by organic and inorganic acids and, thus, are promising candidates for the construction and the repair of acid-exposed structures. However, the reaction mechanisms and processes affecting the acid resistance of AAMs have just recently begun to be understood in more detail. The present contribution synthesises these advances and outlines potentially fruitful avenues of research. The interaction between AAMs and acids proceeds in a multistep process wherein different aspects of deterioration extend to different depths, complicating the overall determination of acid resistance. Partly due to this indistinct definition of the ‘depth of corrosion’, the effects of the composition of AAMs on their acid resistance cannot be unambiguously identified to date. Important parallels exist between the deterioration of low-Ca AAMs and the weathering/corrosion of minerals and glasses (dissolution-reprecipitation mechanism). Additional research requirements relate to the deterioration mechanism of high-Ca AAMs; how the character of the corroded layer influences the rate of deterioration; the effects of shrinkage and the bond between AAMs and substrates. KW - Alkali-activated materials KW - Acid attack KW - Acid resistance KW - Concrete repair KW - MIC PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-557376 DO - https://doi.org/10.21809/rilemtechlett.2022.157 SN - 2518-0231 VL - 7 SP - 58 EP - 67 PB - RILEM Publications SARL CY - Paris AN - OPUS4-55737 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 - Gluth, Gregor A1 - Ke, X. A1 - Vollpracht, A. A1 - Weiler, L. A1 - Bernal, S. A. A1 - Cyr, M. A1 - Dombrowski-Daube, K. A1 - Geddes, D. A. A1 - Grengg, C. A1 - Le Galliard, C. A1 - Nedeljkovic, M. A1 - Provis, J. L. A1 - Valentini, L. A1 - Walkley, B. T1 - Carbonation rate of alkali-activated concretes and high-volume SCM concretes: a literature data analysis by RILEM TC 281-CCC N2 - The current understanding of the carbonation and the prediction of the carbonation rate of alkali-activated concretes is complicated inter alia by the wide range of binder chemistries used and testing conditions adopted. To overcome some of the limitations of individual studies and to identify general correlations between mix design parameters and carbonation resistance, the RILEM TC 281-CCC ‘Carbonation of Concrete with Supplementary Cementitious Materials’ Working Group 6 compiled and analysed carbonation data for alkali-activated concretes and mortars from the literature. For comparison purposes, data for blended Portland cement-based concretes with a high percentage of SCMs (≥ 66% of the binder) were also included in the database. The analysis indicates that water/CaO ratio and water/binder ratio exert an influence on the carbonation resistance of alkali-activated concretes; however, these parameters are not good indicators of the carbonation resistance when considered individually. A better indicator of the carbonation resistance of alkali-activated concretes under conditions approximating natural carbonation appears to be their water/(CaO + MgOeq + Na2Oeq + K2Oeq) ratio, where the subscript ‘eq’ indicates an equivalent amount based on molar masses. Nevertheless, this ratio can serve as approximate indicator at best, as other parameters also affect the carbonation resistance of alkali-activated concretes. In addition, the analysis of the database points to peculiarities of accelerated tests using elevated CO2 concentrations for low-Ca alkali-activated concretes, indicating that even at the relatively modest concentration of 1% CO2, accelerated testing may lead to inaccurate predictions of the carbonation resistance under natural exposure conditions. KW - Alkali-activated materials KW - Durability KW - Carbonation KW - Accelerated testing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560037 DO - https://doi.org/10.1617/s11527-022-02041-4 VL - 55 IS - 8 SP - 1 EP - 15 PB - Springer Nature AN - OPUS4-56003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Simon, Sebastian A1 - Bertmer, M. A1 - Gluth, Gregor T1 - Sol–gel synthesis and characterization of lithium aluminate (L–A–H) and lithium aluminosilicate (L–A–S–H) gels N2 - Hydrous lithium aluminosilicate (L–A–S–H) and lithium aluminate (L–A–H) gels are candidate precursors for glass-ceramics and ceramics with potential advantages over conventional processing routes. However, their structure before calcination remained largely unknown, despite the importance of precursor structure on the properties of the resulting materials. In the present study, it is demonstrated that L–A–S–H and L–A–H gels with Li/Al ≤ 1 can be produced via an organic steric entrapment route, while higher Li/Al ratios lead to crystallization of gibbsite or nordstrandite. The composition and the structure of the gels was studied by thermogravimetric analysis, X-ray diffraction, 27Al and 29Si magic-angle spinning nuclear magnetic resonance, and Raman spectroscopy. Aluminium was found to be almost exclusively in six-fold coordination in both the L–A–H and the L–A–S–H gels. Silicon in the L–A–S–H gels was mainly in Q4 sites and to a lesser extent in Q3 sites (four-fold coordination with no Si–O–Al bonds). The results thus indicate that silica-rich and aluminium-rich domains formed in these gels. KW - Lithium aluminosilicates KW - Raman spectroscopy KW - Sol-gel PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-558756 DO - https://doi.org/10.1111/ijac.14187 SN - 1546-542X VL - 19 IS - 6 SP - 3179 EP - 3190 PB - Wiley AN - OPUS4-55875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -