TY - CONF A1 - Gluth, Gregor A1 - Rickard, W. ED - Leonelli, C. ED - Romagnoli, M. T1 - Design and characterization of fly ash-based geopolymer concretes for a round-robin durability testing program N2 - Fly ash-based, ambient-cured geopolymer concretes for a round-robin durability testing program were designed and characterized. Optimum activator composition was determined based on the Chemical composition of the amorphous part of the fly ash. Fly ash content, water content, and grading curves of the aggregates were varied for the concretes. Characterization of the concretes involved flow diameter, air void content, density, compressive strength, and permeability. The workability of the concretes was notably sensitive to changes in the mix-design. The majority of strength development in the concretes occurred within the first 28 days of curing; concrete strengths reached up to 86 MPa after 56 days. Two concretes, both with sufficient workability, but significantly different grading curve, water content, strength and permeability were identified to be suitable for the round-robin testing program. T2 - Geopolymers 2015 - The route to eliminate waste and emissions in ceramic and cement manufacturing - Engineering conference international (ECI) CY - Hernstein, Austria DA - 24.05.2015 KW - Fly ash geopolymer concrete KW - Concrete properties KW - Permeability PY - 2015 SN - 978-1-326-37732-8 SP - 67 EP - 70 AN - OPUS4-33106 LA - eng 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 - JOUR A1 - Watolla, Marie-Bernadette A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Rickard, W.D.A. A1 - Krüger, Simone A1 - Schartel, Bernhard T1 - Intumescent geopolymer-bound coatings for fire protection of steel N2 - The passive fire protection of steel structures and other load-bearing components will continue to gain importance in future years. In the present contribution, novel intumescent aluminosilicate (geopolymer-bound) composites are proposed as fire-protective coatings on steel. Steel plates coated with these materials were exposed to the standard temperature-time curve as defined in ISO 834 – 1:1999. The coatings partially foamed during curing and expanded further during thermal exposure, demonstrating their intumescent characteristic.Thermogravimetryandoscillatory rheometry determined that the intumescent behavior is attributed to a transition to a viscous state (loss factor > 1) in the temperature range of major water release, differing from conventional geopolymers. XRD and SEM images showed that the coatings had characteristics of ceramic or glass-ceramic foams after fire resistance testing, suggesting superior performance under challenging conditions. The thickness of the coatings influenced their foaming and intumescent behavior and thus the time for the coated steel plates to reach 500 °C. A number of additives were also studied with the best performance obtained from samples containing sodium tetraborate.Acoating of just 6mmwas able to delay the time it takes for a steel substrate to reach 500 °C to more than 30 minutes. KW - Geopolymers KW - Fire protection KW - Intumescence KW - Coatings KW - Fire resistance PY - 2017 UR - https://www.ceramic-science.com/articles/all-articles.html?article_id=100558 DO - https://doi.org/10.4416/JCST2017-00035 VL - 8 IS - 3 (Topical issue: Geopolymers) SP - 351 EP - 364 PB - Göller Verlag CY - Baden-Baden AN - OPUS4-42139 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 -