TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario A1 - Hünger, Maximilian A1 - Krey, Juliane A1 - Mühlstädt, Mike T1 - Surface coating of siliceous parts of aggregate grains by alumina containing SCM' in alkaline solutions T2 - ICAAR, 15th International Conference on Alkali Aggregate Reaction, July 03-07, 2016, Sao Paulo, Brazil, abstracts N2 - It is well known that SCMs containing alumina can prevent the damaging alkali silica reaction in concrete. This paper deals with the direct interactions between aggregate grain surfaces (quartzitic rock material Q1) and the dissolved amounts of SCMs (metakaolin, aluminum hydroxide). Investigations have confirmed that the presence of such SCMs can strongly decrease the silica release from aggregates in comparison to solubility experiments without SCM addition. The reason for this effect is the formation of a thin alumina containing layer (some nanometers thick) on the grain surfaces. The existence of this layer could be determined by XPS. Only this method provides data of the strongly increased alumina concentration in a thin surface area and also of the layer thickness in dependence on reaction parameters. Dissolution experiments of grains coated with such layer demonstrate the effectiveness of this process and can give a further contribution for understanding the preventing mechanisms of SCMs. KW - Alumina containing SCMs KW - alumina silicate layer KW - XPS method KW - inhibition KW - surface coating Y1 - 2016 SP - S. 42 PB - ICAAR ER - TY - CHAP A1 - Gröschke, Andreas A1 - Uhlmann, Wilfried A1 - Hünger, Klaus-Jürgen A1 - Wiehe, Wolfgang A1 - Beckmann, T. T1 - Spezielle Untersuchungen zur Mineralogie in ungesättigten Kippenmassiven T2 - Vortragsband des 4. GBL-Kolloquiums vom 26. - 28. November 1997 in Cottbus, Ergebnisse und Empfehlungen Y1 - 1998 SN - 3-510-95822-5 SP - 57 EP - 63 PB - Schweizerbart CY - Stuttgart ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Hübert, Cornelia A1 - Scholz, Yvonne T1 - Drum prüfe, was sich ewig bindet … - zur Verträglichkeit der Betonausgangsstoffe T2 - BFT Betonwerk + Fertigteil-Technik Y1 - 2009 SN - 1865-6528 SN - 0373-4331 VL - 75 IS - 3 SP - 46 EP - 55 ER - TY - GEN A1 - Bachmann, Robert A1 - Hünger, Klaus-Jürgen T1 - BTU-SP-Schnelltest zur Beurteilung der Alkaliempfindlichkeit von Gesteinskörnungen : die Entwicklung eines direkten Prüfverfahrens T2 - Beton Y1 - 2009 SN - 0005-9846 VL - 59 IS - 4 SP - 138 EP - 143 ER - TY - GEN A1 - Hünger, Klaus-Jürgen T1 - Der BTU-SP-Test: Direktes Prüfverfahren zur Bewertung der Alkali-Empfindlichkeit von Gesteinskörnungen T2 - Straße und Autobahn Y1 - 2010 SN - 0039-2162 VL - 61 IS - 3 SP - 143 EP - 147 ER - TY - GEN A1 - Krakow, Lutz A1 - Hünger, Klaus-Jürgen A1 - Brigzinsky, Maria T1 - Projekt ALEKOM – Aschegebundenes Ton-/Lehmfeinkornsystem T2 - Ceramic forum international : cfi, Berichte der Deutschen Keramischen Gesellschaft Y1 - 2010 SN - 0173-9913 VL - 87 SP - D8 EP - D10 ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Hill, Steffen T1 - Direct assessment of the alkali sensitivity of precambrian greywackes T2 - Cement International Y1 - 2005 SN - 1610-6199 VL - 3 IS - 1 SP - 104 EP - 119 ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Hill, Steffen T1 - Chemischer Schnelltest zur praxiskonformen Prüfung der Alkaliempfindlichkeit von Gesteinskörnungen für Beton T2 - BFT Betonwerk + Fertigteil-Technik Y1 - 2005 SN - 0373-4331 VL - 71 IS - 7 SP - 36 EP - 47 ER - TY - GEN A1 - Hill, Steffen A1 - Hünger, Klaus-Jürgen T1 - Alkaliempfindlichkeit Lausitzer Grauwacken - neue Perspektiven hinsichtlich eines direkten Prüfverfahrens T2 - Forum der Forschung Y1 - 2004 SN - 0947-6989 VL - 8 IS - 17 SP - 122 EP - 127 ER - TY - THES A1 - Hünger, Klaus-Jürgen T1 - Zum Reaktionsmechanismus präkambrischer Grauwacken aus der Lausitz bei ihrer Verwendung als Gesteinskörnung im Beton Y1 - 2005 SN - 3-8322-4670-3 PB - Shaker-Verlag CY - Aachen ER - TY - GEN A1 - Hünger, Klaus-Jürgen T1 - The Contribution of Quartz and the Role of Aluminum for Understanding the AAR with Greywackes T2 - Cement and concrete research Y1 - 2007 SN - 0008-8846 VL - 37 IS - 8 SP - 1193 EP - 1205 ER - TY - GEN A1 - Bachmann, Robert A1 - Hünger, Klaus-Jürgen A1 - Scholz, Yvonne T1 - Entwicklung eines direkten Prüfverfahrens zur Alkaliempfindlichkeitsbeurteilung von Gesteinskörnungen : der BTU-SP-Schnelltest T2 - Forum der Forschung Y1 - 2007 SN - 0947-6989 IS - 20 SP - 73 EP - 78 ER - TY - CHAP A1 - Scholz, Yvonne A1 - Hübert, Cornelia A1 - Hünger, Klaus-Jürgen T1 - The influence of supplementary cementing materials on the dissolution of aggregates in alkaline solutions T2 - ICAAR, 15th International Conference on Alkali Aggregate Reaction, July 03-07, 2016, Sao Paulo, Brazil, abstracts N2 - Starting from expansion measurements on concrete prisms, produced with two different alkali reactive aggregates, the influence of two aluminium containing SCMs on the expansion of concrete prisms and on the solubility of the aggregates in an alkaline solution were investigated. The solubility of aggregates in an alkaline solution reflects the alkali reactivity of the corresponding aggregate. Initially, the solubility experiments with the aggregates and SCMs were made separately and then in mixtures of each aggregate and SCM. In a further step, the SCMs were stored in KOH solutions containing Ca(OH)2. The concentrations of SiO2 and Al2O3 were determined to investigate the effect of calcium on the solving processes of SCMs. The combination of concrete expansion test and dissolution experiments of two alkali reactive aggregates and two aluminium containing SCMs allows first conclusions about the influence of such SCMs on the reactivity of aggregates. KW - alkali silica reaction KW - supplementary cementing materials (SCM) KW - solubility of aggregate KW - solubility of SCM Y1 - 2016 SP - S. 43 PB - ICAAR ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Hübert, Cornelia A1 - Scholz, Yvonne A1 - Kronemann, Jens T1 - Changes of pore solution composition under accelerated mortar bar and concrete prism test conditions T2 - ICAAR, 14th International Conference on Alkali Aggregate Reaction, May 20-25, 2012, Austin, TX N2 - Accelerated tests of mortar bars and concrete prism were carried out at temperatures ≥ 40°C in order to reduce the test duration. Because the OH-/SO42- equilibrium is shifted to lower values with increasing temperature and alkali content of the cement, there exists the possibility of side reactions between sulphate ions from the cement and aluminate ions which can come from mineral admixtures and aggregates. Solubility measurements of two types of aggregates in sulphate free KOH solutions indicate that the temperature effect on the silica releasing rate is bigger than the inhibiting effect of the decreasing OH- concentration. To avoid side reactions during aggregate test procedure, expansion measurements should be performed at 40°C in combination with adapted solubility measurements. KW - pore solution KW - temperature KW - mineral admixture KW - solubility of aggregates Y1 - 2012 UR - https://www-docs.b-tu.de/fg-baustoffe/public/050_021811-HUNG.pdf ER - TY - CHAP A1 - Brigzinsky, Maria A1 - Hünger, Klaus-Jürgen T1 - Durable Extruded and Self-Hardening Loam Bricks Based on Fly Ash from Lignite T2 - Proceedings, 23rd Czech Concrete Day 2016 N2 - The basis of the primary energy supply in the Czech Republic is mainly lignite combustion. Power plants are for example Chvaletice, Melnik, Pocerady, Porici, Prunerov, Ledvice, Tusimice, Tisova and Hodonin [1,2]. Accordingly, there is a large amount of fly ash with its latent hydraulic and puzzolanic properties, depending on the composition. In terms of sustainability, such industrial residues offer huge potential for conversation of resources and often connected with it, a CO2-reduction. Especially lime-rich fly ashes offer a variety of possibilities in the high quality production of self-hardening loam-bricks, having an improved durability. Different clays/loams were mixed with fly ashes (10 to 30 wt-%) and homogenized by addition of water. Out of these mixtures, samples were moulded in different dimensions by using an extruding press. After curing under different humidity conditions at room temperature, the samples were tested for their strength and their durability. The investigations showed, that the choice of the starting materials has significant impact to the workability and the development of the strength. Furthermore, there is an optimal amount for the ash in the recipes to prevent a rapid destruction by capillary water absorption. The modified clay bricks could make a decisive contribution to the improvement of weather resistance e.g. in tropical areas with sudden rain showers. KW - Waste materials KW - Fly ash KW - CO2-reduction KW - Resource conservation KW - Durability Y1 - 2016 UR - https://www-docs.b-tu.de/fg-baustoffe/public/P37-Brigzinsky.pdf SN - 978-80-906097-6-1 ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Hübert, Cornelia A1 - Scholz, Yvonne T1 - On the Interactions of Aggregates with Supplementary Cementing Materials for Durable Concrete Structures T2 - Proceedings, 23rd Czech Concrete Day 2016 N2 - Supplementary cementing materials (SCMs) are an important part of modern concrete structures. Their use has many advantages (reduction of the cement amount, improvement of the durability and therefore CO2 reduction). For example certain SCMs added to concrete mixtures can avoid the alkali-silica reaction (ASR). But such materials have a wide range of composition and therefore the mechanisms can be very differently. The knowledge of dissolution processes of aggregates and SCMs separate and together in alkaline solutions can help to understand the damage of concretes caused by ASR and the effects to avoid ASR in more details. Many dissolution experiments were performed in highly alkaline solutions (KOH) under CPT conditions (pH 14, 40°C) using aggregates in original grain sizes and Si and Al containing SCMs in different ratios. Also Calcium hydroxide was added to investigate the influence of calcium ions as a main part of the pore solution. The concentrations of soluble silica and alumina were determined by ICP-OES. Such dissolution experiments, with which an interaction was settled between the aggregate and the SCM via the alkaline solution, arose that under specific conditions the dissolution of aggregates was strongly influenced. Obviously both main constituents of concretes interact with each other. Additionally effects of the dissolved calcium ions must be considered. It was found that the efficiency depends on the amount and chemical composition of the SCMs used and on the reactivity of aggregates. KW - SCMs, Aggregates, ASR inhibition, Dissolution behavior, Alkaline solution Y1 - 2016 UR - https://www-docs.b-tu.de/fg-baustoffe/public/C26-Huenger.pdf SN - 978-80-906097-6-1 ER - TY - CHAP A1 - Bachmann, Robert A1 - Hünger, Klaus-Jürgen T1 - Interactions of chemical and physical parameters of aggregate grains for a better understanding of alkalisilca-reaction T2 - ICAAR, 14th International Conference on Alkali Aggregate Reaction, May 20-25, 2012, Austin, TX N2 - Mortar bar and concrete prism tests are the most commonly used methods for the evaluation of alkali-silica reactivity (ASR). Despite their widespread use, both methods have significant drawbacks. The largest issue is that neither test is a direct measurement of the aggregate. Matrix effects from the mortar or concrete, or variations in the individual non-aggregate materials can influence the outcome. This paper describes fundamental results as the basis for the chemical and physical test method (BTU-SP test) directly carried out at aggregate grains. Additional methods (BET, microscopy) confirm that not only the aluminate from the aggregate controls the silica release but also the pore structure inside of rocks (i.e. voids, cracks) buffer the swelling potential of the formed alkali-silica gel. As a result a reaction model describing the interactions of chemical and physical parameters in 4 phases has been developed for an alkalisilica reaction. KW - BTU-SP test KW - 4 phases model KW - silica release KW - open porosity KW - alumino silicate formation Y1 - 2012 UR - https://www-docs.b-tu.de/fg-baustoffe/public/006_021811-BACH.pdf ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Kronemann, Jens A1 - Hübert, Cornelia A1 - Scholz, Yvonne T1 - On the mechanism of ASR inhibition by Si and Al containing SCMs T2 - 13th International Conference on Recent Advances in Concrete Technology and Sustainability Issues, Ottawa, Canada N2 - The use of supplementary cementing materials (SCMs) added to concrete mixtures can avoid the alkali-silica reaction. Such materials have a wide range of composition and therefore the inhibition mechanisms can be very differently. The effectiveness of SCMs which provide silica and alumina into the alkaline solution cannot only be explained by reducing the OH--concentration of the pore solution. From dissolution experiments in potassium hydroxide solutions, an interaction was noted between the aggregate and five SCMs via the alkaline solution. Under specific conditions, no silica is released from the aggregate grains. Mineralogical investigations (XRD, SEM+EDX) of the grain surfaces confirm that quartz is the main source of silica. In the presence of alumina providing SCMs, the quartz dissolution is strongly reduced or even sometimes stopped. On surfaces of grains a very thin layer can be observed which is probably responsible for reduction or stopping of the silica dissolution and therefore for the inhibition of ASR. KW - Alkali-silica reaction KW - alkali reactivity KW - solubility KW - supplementary cementing materials KW - surface layer Y1 - 2015 SN - 978-1-9427272-3-1 SP - 437 EP - 451 PB - American Concrete Institute ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Brigzinsky, Maria T1 - An alternative alumino-silicate binder based on the "just add water method" T2 - ICCM, 10th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete, 2017, Montreal, Kanada N2 - Alumino silicate compounds are important for alternative binders for concretes because of the reduction of CO2 and resource conservation. Such multi-phase systems consist of a solid component, such as e.g. slag, ash, calcined clays and others, and a liquid component, in generally highly concentrated alkaline solutions (water glass or NaOH/KOH). Because of safety and other reasons, such systems exclude large-scale practical applications. The newly developed alternative binder consists of a highly soluble silicate waste material, which is not common in geopolymere production, and a powdered Al-provider. It is called alumino silicate network (ASN) binder. Both components can be mixed dry in different ratios. Only after addition of water, a polymerization process is induced and the formation of amorphous phases, and sometimes zeolites can be observed. Mortar bars were produced and tested for different properties. The best results regarding to workability, strength development and sustainability were obtained with a molar Si/Al ratio of 2:1 in combination with fine-grained rock filler components. Investigations on the hardening process showed, that the mechanical properties varied over a wide range. Strength reserves, a ratio between compressive and tensile strength of approx. 3 and so far good resistance against acid solutions allow the use as a binder in high performance mortar and concrete structures. KW - alternative binders KW - geopolymere KW - alumino silicate structures KW - Si/Al ratio KW - industrial residues Y1 - 2017 UR - https://www-docs.b-tu.de/fg-baustoffe/public/Supp_320_24.pdf PB - RILEM ER - TY - CHAP A1 - Kositz, Mario A1 - Hünger, Klaus-Jürgen T1 - A predicitve model for the assessment of aggregate sensitivity to ASR T2 - ICCM, 10th ACI/RILEM International Conference on Cementitious Materials and Alternative Binders for Sustainable Concrete, 2017, Montreal, Kanada N2 - Different aggregates stored in alkaline solutions have different solubility of silica and alumina. The dissolved silica reacts with water and alkalis to form an alkali silica gel, which can swell. ASR swelling can be reduced or prevented, if enough space is available for the alkali silica gel formation. This “space” is the open porosity, which can also be determined directly at the aggregate grains. Concrete specimens made with different aggregates were produced. They all were stored in a fog chamber at 104°F (40°C) and the ASR swelling was measured for one year. At the same time, the aggregates were stored in 0.1 mol KOH solution at 176°F (80°C) for 56 d only. The solubility of silica and alumina was determined continuously by ICP-OES. The obtained dissolution rates, open porosity and expansion data were compared and a reliable model for predicting the ASR sensitivity of concrete aggregates was derived. KW - alkali silica reaction KW - modeling KW - aggregate reactivity KW - dissolution of silica and alumina KW - dissolution rate KW - open porosity Y1 - 2017 UR - https://www-docs.b-tu.de/fg-baustoffe/public/Supp_320_24.pdf PB - RILEM ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Sander, Ingolf A1 - Zuckow, Natalia T1 - On the Workability of Mortar and Concrete Mixtures containing Calcined Clay Blends T2 - Proceedings 3rd International Conference on Calcined Clays for Sustainable Concrete, 15. - 17. Oktober, Neu Delhi N2 - Calcined Clays can be used in mortar and concretes as a part of a binder (LC3) or as a Supplementary Cementing Material (SCM). The aim here is to sub-stitute fly ash as an additive in concrete recipes. A stable mixture between two regionally available clays, burnt together with a certain ratio of 60 : 40 wt.-% at 650-680°C, could be produced. Such Metaclays produced in larger amounts were investigated in different mortar and concrete mixtures. The production indicates an important problem with the workability of the fresh concrete mixtures. That`s why different superplastizers were tested. It could be found that especially a mixture between a PCE- based material and a special additive, developed for loam sands provides very good results. The workability increases from less than 200 mm slump on a value of about 300 mm. The combination of calcined clay materials and special developed superplastizer mixtures allows producing concrete with very different properties. It can be a closed system for the production of durable concrete structures. KW - Calcined clay mixtures, Supplementary cementing material, worka-bility, superplastizers mixtures, precast concrete elements Y1 - 2019 UR - https://www-docs.b-tu.de/fg-baustoffe/public/Calcined%20Clay%20blends-Revised%20Paper.pdf VL - I SP - 207 EP - 215 PB - RILEM ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Danneberg, Matti A1 - Herold, Steven A1 - Acker, Jörg T1 - Stress conditions in quartzite and their quantification by Raman spectroscopy T2 - Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete N2 - The silica solubility of aggregates is one of the most important components of the alkali-silica reaction. It is a surface-controlled process that always still requires more detailed studies to better understand the reaction mechanism. Since strained quartz releases more SiO2 into the pore solution, the properties of grains, crystals and their structure can should be directly quantified. In other work, various possibilities were tested for this purpose in order to obtain analyses of the surface and to correlate these with the mortar bar tests, for example. However, a quantifiable direct measurement of quartz crystal states with satisfactory results has not yet been performed. In this thesis polarization and reflected light microscopy in combination with Raman and confocal microscopy is used to obtain quantifiable data by direct measurement of the strained crystals. First measurements show new surprising signals besides the Raman main peak of the quartz. Such signals cannot be found on the whole sample, but only at places where strains are expected, e.g. at contact zones between different quartz crystals or cracks and sometimes inside of quartz grains too. Thus, a method may have been found to quantify the strained state of different quartz crystals in natural quartzite rocks. KW - ASR; quartzite; Raman microscopy; surface analysis Y1 - 2021 SN - 978-972-49-2315-4 SP - 185 EP - 192 PB - LNEC ER - TY - GEN A1 - Kositz, Mario A1 - Hünger, Klaus-Jürgen A1 - Weise, Frank T1 - Regression analysis of ASR expansions and silica dissolution in the presence of NaCl T2 - Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete N2 - The durability of concrete structures due to alkali-silica-reaction (ASR) is usually been assessed by ASR concrete prism tests (CPT). Therefore, the expansion of concrete specimens indicates an alkalisensitivity. In Germany these tests are performed at 40°C or accelerated 60°C. Nevertheless, ASR prism tests are expensive, power and time-consuming. For these reasons, an alternative chemical test ("mod. BTU-test") was developed in the past. The "mod. BTU-test" was correlated with German standard CPT. In this test, the solubility of silica and alumina in the liquid phase is measured by ICP-OES. For special requirements in concrete road construction, stricter test procedures are necessary. The specimens are repeatedly subjected to cyclic alternating storage in NaCl. On the one hand, the presence of NaCl increases the ASR expansion, on the other hand NaCl also changes the dissolution behaviour of silica and alumina. For now is not possible to correlate the solubilities of mod. BTU-test and ASR expansions influenced by NaCl. Therefore, four aggregates with different ASR sensitivities were chosen and ASR concrete prism tests (in addition with NaCl) have been performed. According to the "mod. BTU-test" the solubilities of silica and alumina in presence of different NaCl concentrations were measured. This paper is about the regression analysis of silica and alumina dissolution and ASR expansion tests in presence of NaCl. The regression analysis shows the influence of a quasi-continuous and an interrupted cyclic alternating storage. Additionally the effects of temperature and NaCl concentration are investigated. In the end, a suitable NaCl concentration of the "mod. BTU-test" for dissolution experiments is recommended. The "mod. BTU-Test with NaCl might be a serious and reliable test method for ASR classification for concrete road construction. KW - alkali silica reaction; alkaline solution; alumina & silica dissolution; NaCl; regression analysis Y1 - 2021 SN - 978-972-49-2315-4 SP - 711 EP - 723 PB - LNEC ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario A1 - Danneberg, Matti A1 - Radnik, Jörg T1 - XPS investigations on quartzite surfaces of natural rock samples for proof of Al exposure T2 - 27th Annual Conference of the German Crystallographic Society / Zeitschrift für Kristallographie. Supplement Y1 - 2019 SN - 978-3-11-065403-5 SN - 0930-486X VL - 39 SP - S. 110 PB - De Gruyter CY - Berlin ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Acker, Jörg A1 - Danneberg, Matti A1 - Herold, Steven T1 - Quantification of stress states in quartzite surfaces by using RAMAN spectroscopy T2 - 27th Annual Conference of the German Crystallographic Society / Zeitschrift für Kristallographie. Supplement Y1 - 2019 SN - 978-3-11-065403-5 SN - 0930-486X VL - 39 SP - S. 122 PB - De Gruyter CY - Berlin ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario A1 - Brigzinsky, Maria A1 - Ajami, Fouad T1 - A fast testing method to characterize ashes and ash mixtures using the ultrasonic technique T2 - Recent Advances in Concrete Technology and Sustainability Issues Proceedings Fourteenth International Conference Beijing, China October-November 2018 N2 - Fly ash is a typical mortar constituent in Germany, other European countries and worldwide. If cement alone is used as a binder, then the mortar is too expensive and cannot provide all properties. That`s why many companies have special recipes with fly ash, especially hard coal fly ash components, in the mortar. The aim of this project is to substitute such fly ashes by lignite coal fly ashes, which are cheaper, available at every times or have better properties. However this means, that the calcium free or calcium poor ash should be substituted by calcium rich ashes, which are not certificated because of fluctuations. To compensate the fluctuations in the ash compositions, several ashes are mixed. The European standard EN 450, which contains requirements, for example for the chemical composition of ashes, has to be taken into account. Fly ash mortar compound prisms have been produced and the different mechanical and deformation values were determined in comparison to a reference material. The basis for all experiments was the recipe of the company for a special mortar. An ash compound could be developed with the same workability by considering the economic reasons of the company. An important result too is that the fluctuations of the fly ash batches can be controlled by special developed chemical (color test) and physical (Ultrasonic velocity) test methods. Y1 - 2018 UR - https://www-docs.b-tu.de/fg-baustoffe/public/A%20fast%20test%20method%20for%20ashes-huenger.pdf ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Brigzinsky, Maria ED - Ludwig, Horst-Michael ED - Fischer, Hans-Bertram T1 - Zur Entwicklung eines alumosilicatischen Binders auf der Basis industrieller Reststoffe für den Bereich hochaggressiver Beanspruchungen T2 - Tagungsbericht, 20. Internationale Baustofftagung IBAUSIL, 12. - 14. September 2018, Weimar, Teil 1 N2 - Im Rahmen eines AiF-geförderten Forschungsprojektes wurde ein alumosilicatisches Bindersystem entwickelt, welches nur durch die Zugabe von Wasser zu einem Feststoff mit definierten Eigenschaften erhärtet. Ein wesentlicher Grundgedanke bei der Auswahl der Ausgangsstoffe war, industrielle Reststoffe zu verwenden, die verfügbar sind und beispielweise nicht über einen aufwändigen C alcinierprozess hergestellt werden müssen. Diese sollten andererseits aber eine sehr gute Löslichkeit besitzen, damit sich das hoch alkalische Milieu sofort nach Wasserzugabe einstellt und der alumosilicatische Strukturbildungsprozess unmittelbar in Gang gesetzt wird. Unterschiedliche silicatische und aluminatische Ausgangsmaterialien wurden getestet. Es wurde ein Stoffsystem unter Verwendung eines silicatischen Reststoffes aus der Glasproduktion in Kombination mit einer Natriumaluminatkomponente aus der Waschmittelproduktion entwickelt, welches die gestellten Anforderungen gut erfüllt. Dieses Stoffsystem dient gleichzeitig als Modell, an dem der Strukturbildungsprozess, der zur Bildung eines alumosilicatischen Netzwerkes (ASN) führt, z.B. mittels NMR-Untersuchungen untersucht werden kann. Im Unterschied zu den „klassischen“ Geopolymermaterialien Metakaolin, Hüttensand bzw. Flugaschen, ist das für den Strukturbildungsprozess entscheidende Verhältnis zwischen Si und Al in einem breiten Spektrum frei einstellbar und damit auch die mit dem Binder erzielbaren Eigenschaften variierbar. An Mörtel- und Betonprismen wurden zerstörungsfrei und zerstörend Festigkeiten und Formänderungen untersucht und Dauerhaftigkeitskennwerte bestimmt. Hohe mechanische Festigkeiten bis 60 N/mm2 Druckfestigkeit, aber insbesondere der sehr gute Widerstand gegen Säureangriffe machen Mörtel und Betone unter Verwendung des ASN-Binders interessant für Anwendungen im Bereich der Einwirkungen von aggressiven chemischen Reagenzien. Entsprechende Untersuchungen zum Säureangriff wurden durchgeführt und die Veränderungen mikroskopisch und mittels Eigenfrenquenzanalyse (Grindosonic) verfolgt. Y1 - 2018 SN - 978-3-00-059950-7 SP - 371 EP - 382 PB - F.A. Finger-Inst. für Baustoffkunde, Bauhaus-Univ. Weimar CY - Weimar ER - TY - CHAP A1 - Kronemann, Jens A1 - Hünger, Klaus-Jürgen T1 - Aggregate Reactivity and the Efficiency of Supplementary Cementing Materials T2 - 13th International conference on recent advances in concrete technology and sustainability issues N2 - The knowledge of dissolution processes of aggregates and supplementary cementing materials (SCMs) in alkaline solutions can help to describe the expansion of concretes caused by alkali-silica reaction (ASR) and the effects to avoid ASR by using SCMs in more details. Therefore, dissolution experiments in alkaline solutions under different pH values and different temperatures were performed using aggregates in the original grain size and SCMs in different ratios. The concentrations of soluble silica and additionally alumina were determined by ICP-OES. The investigations showed that up to now the “best” conditions to explain the damage behavior of concrete structures are a pH value of 13 (e.g. 0.1 M KOH solution) and a temperature of 80 °C. The evaluation bases on the parameter “excess silica” which is calculated from the dissolved silica and alumina of the aggregates and the SCMs. It was demonstrated that SCMs reduce and sometimes stop the dissolution of aggregates. The efficiency of the SCMs depends on their amount and chemical composition. KW - alkali silica reaction KW - aggregate reactivity KW - dissolution of silica and alumina KW - dissolution rate Y1 - 2015 SN - 978-1-9427272-3-1 SP - 355 EP - 370 PB - American Concrete Institute ER - TY - CHAP A1 - Brigzinsky, Maria A1 - Hünger, Klaus-Jürgen T1 - Extruded lime-rich fly ash-clay mictures for the use in "cold ceramics" bricks T2 - 2nd International Conference on Advances in Cement and Concrete Technology in Africa N2 - There is a huge potential for the resource conservation and for reduction of CO2 emissions by using industrial by-products, as well as natural slags or ashes in a precise and high-class manner. Apart from mineral coal fly ash, which is used and certificated as an additive for concrete, especially lime- rich fly ashes with their latent hydraulic and puzzolanic properties offer a variety of possibilities in the high quality production of small-sized components like bricks. Fine-grain-mixtures from different clays and fly ashes were homogenized and plasticized by the addition of water in an Eirich-mixer. The added amount of ash was varied from 10 to 30 wt%. Out of these mixtures, test items with a sufficient strength for transport were moulded in an extrusion process. The test samples were stored under various humidity conditions (RH= 33, 65 and 88 %) at 20 °C and, subsequently after different times of self-hardening (28, 70 and 105 days), tested on their strength and durability. Compressive strength up to 15 MPa was achieved. In order to reach that result, at least 20 wt% of the clay should be substituted by ash to get an increase in strength compared to the pure clay samples. Further examinations have shown that it is possible to prevent the destruction by capillary water absorption of pure clay/loam specimens by an optimal use of ash in the recipes. Overall, it can be stated that due to the self-hardening potential of these mixtures there is no need for an energy-intensive and highly CO2 emitting combustion process, if the clay is substituted in fine grain mixtures by high lime component fly ashes. KW - Waste materials KW - Fly ash KW - Self-hardening bricks KW - CO2-reduction KW - Resource conservation KW - Enhancing durability Y1 - 2016 SN - 978-3-9817502-3-2 SP - 545 EP - 552 PB - BAM Bundesanstalt für Materialforschung und –prüfung CY - Berlin ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Krakow, Lutz A1 - Brigzinsky, Maria T1 - Asche Ton Komposite - Baukeramik ohne Trocknen und Brennen T2 - Tagungsbericht, IBAUSIL, 18. Internationale Baustofftagung, 12. - 15. September 2012, Weimar Bauhaus-Universität, Teil 2 Y1 - 2013 SN - 978-3-00-034075-8 PB - F.-A.-Finger-Inst. CY - Weimar ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Gerasch, Robert A1 - Sander, Ingolf A1 - Brigzinsky, Maria T1 - On the Reactivity of calcined clays from lower Lusatia for the production of durable Concrete Structures T2 - Calcined Clays for Sustainable Concrete, Proceedings of the 2nd International Conference on Calcined Clays for Sustainable Concrete N2 - Metakaolin used as a SCM in concrete is obviously a very good tool to improve the resistance against acid and alkali attack too. Even if, finally, the mechanisms are not fully understood until now, lower mass loss (acid attack) or lower expansions (ASR) are showing their efficiency. Metakaolin, burnt by using relatively pure natural kaolin clays, contains Al2O3 and SiO2 only with a ratio of approx. one. The question is: Are there any other clays maybe also in mixtures which are suitable for use as an admixture for concrete or even as a binder? This research work has a strong regional reference. Three clays from Lower Lusatia were selected. The clays and a wide range of mixtures too were burnt at different temperatures (between 600 to 700 °C) to find out the “best” results for such materials. The mixing process has also the background to eliminate fluctuations in the compositions of the clays. A continuous working rotary kiln with a continuous supply of clay materials was used for the production of calcined clay samples. Using this equipment, the rate of heating and the duration of stay of the material under almost practical conditions can be varied. Mineralogical compositions, measured before and after heating, confirm the formation of amorphous phases already under relatively low temperature conditions in dependence on the clay mineral species and the mixing relations. Reactivity (activity index and solubility in alkaline solutions) of each sample were determined and mortar bars were produced. In dependence on their reactivity parameters the so produced calcined clay samples influence mechanical and durability properties of concrete structures. The aim of this research project is to produce concrete bars with such calcined clay as a SCM and store them under extreme conditions in some of the Lusatian lakes. KW - Clay mixtures Solubility KW - Meta clays KW - Activity index KW - Solubility KW - Pozzolani behavior KW - Dynamic modulus of elasticity Y1 - 2017 SN - 978-94-024-1206-2 SN - 978-94-024-1207-9 SP - 205 EP - 211 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Yu, Chenjie A1 - Mo, Xiangyin A1 - Deng, Min A1 - Tang, Mingshu A1 - Shen, Jian A1 - Fournier, Benoit A1 - Hünger, Klaus-Jürgen T1 - Behavior characteristic of lithium ion in alkali-aggregate reaction T2 - Journal of Southeast University (Natural Science Edition) T2 - Dongnan-Daxue-xuebao Y1 - 2009 SN - 1001-0505 VL - 39 IS - 1 SP - 127 EP - 130 ER - TY - GEN A1 - Mo, Xingyin A1 - Zhang, Yue A1 - Yu, Chenjie A1 - Deng, Min A1 - Tang, Mingshu A1 - Hünger, Klaus-Jürgen A1 - Fournier, Benoit T1 - Investigation of alkali-silica reaction inhibited by new lithium compound T2 - ACI Materials Journal Y1 - 2010 SN - 0889-325x VL - 1 IS - 107 SP - 37 EP - 41 ER - TY - GEN A1 - Kositz, Mario A1 - Hünger, Klaus-Jürgen T1 - Untersuchungen zur Korrelation von AKR induzierten Dehnungen und der Löslichkeit von Gesteinskörnungen unter Berücksichtigung von NaCl; Teil 1 T2 - Beton : die Fachzeitschrift für Bau + Technik Y1 - 2021 SN - 0005-9846 VL - 71 IS - 3 SP - 60 EP - 65 ER - TY - GEN A1 - Kositz, Mario A1 - Hünger, Klaus-Jürgen T1 - Untersuchungen zur Korrelation von AKR induzierten Dehnungen und der Löslichkeit von Gesteinskörnungen unter Berücksichtigung von NaCl; Teil 2 T2 - Beton : die Fachzeitschrift für Bau + Technik Y1 - 2021 SN - 0005-9846 VL - 71 IS - 4 SP - 120 EP - 124 ER - TY - CHAP A1 - Hünger, Klaus-Jürgen T1 - The Self-inhibition process of certain greywackes T2 - Proceedings of the 12th International Conference on Alkali-Aggregate Reaction in Concrete, October 15 - 19, 2004, Beijing International Convention Center, Beijing, China, Vol. 1 Y1 - 2004 SN - 978-7-5062-7033-5 SP - 125 EP - 134 PB - Internat. Acad. Publ. CY - Beijing ER - TY - CHAP A1 - Scholz, Yvonne A1 - Hünger, Klaus-Jürgen T1 - Untersuchungen zur Vermeidung von Betonschädigungen infolge AKR durch Zugabe spezieller neuartiger Zusatzstoffe T2 - Tagungsbericht, IBAUSIL, 16. Internationale Baustofftagung : 20. - 23. September 2006, Weimar, Bundesrepublik Deutschland, Bd. 2 Y1 - 2006 SN - 3-00-018263-2 SP - 2-0485 EP - 2-0492 PB - F.-A.-Finger-Inst. CY - Weimar ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Bachmann, Robert A1 - Scholz, Yvonne A1 - Hübert, Cornelia A1 - Mo, X. ED - Broekmans, Maarten A. T. M. ED - Wigum, Børge J. T1 - An accelerated chemical test method for ASR carried out directly at aggregate grains T2 - Conference proceedings, 13th International Conference on Alkali-Aggregate Reaction in Concrete, Trondheim, Norway, 16 - 20 June 2008 Y1 - 2008 SN - 978-82-7385-128-4 SP - 782 EP - 793 CY - Trondheim ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Hübert, Cornelia A1 - Heidemann, D. ED - Broekmans, Maarten A. T. M. ED - Wigum, Børge J. T1 - Formation of Kanemite from Precursors as a Model for ASR Gel Hydration T2 - Conference proceedings, 13th International Conference on Alkali-Aggregate Reaction in Concrete, Trondheim, Norway, 16 - 20 June 2008 Y1 - 2008 SN - 978-82-7385-128-4 SP - 130 EP - 139 CY - Trondheim ER - TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Scholz, Yvonne A1 - Hübert, Cornelia A1 - Kronemann, Jens T1 - Entwicklung und Beurteilung der Wirkung eines speziellen AKR-vermeidenden Zusatzstoffes T2 - 18. Internationale Baustofftagung IBAUSIL, F.A. Finger-Institut für Baustoffkunde, Bauhaus-Universität Weimar, Tagungsbericht, Teil 2 Y1 - 2013 SN - 978-3-00-034075-8 SP - 2-0585 PB - F.-A.-Finger-Inst. CY - Weimar ER - TY - CHAP A1 - Hübert, Cornelia A1 - Hünger, Klaus-Jürgen T1 - Strukturbildung und Eigenschaften von Alumosilicathydraten in Baustoffen T2 - 18. Internationale Baustofftagung IBAUSIL, F.A. Finger-Institut für Baustoffkunde, Bauhaus-Universität Weimar, Tagungsbericht, Teil 2 Y1 - 2013 SN - 978-3-00-034075-8 SP - 2-0310 PB - F.-A.-Finger-Inst. CY - Weimar ER - TY - CHAP A1 - Hünger, Klaus-Jürgen T1 - Zum Reaktionsmechanismus von Grauwacken im Beton T2 - Tagungsbericht, IBAUSIL, 16. Internationale Baustofftagung, 20. - 23. September 2006, Weimar, Bd. 2 Y1 - 2006 SN - 3-00-018263-2 SP - 2-0427 EP - 2-0434 PB - F.-A.-Finger Inst. für Baustoffkunde CY - Weimar ER - TY - GEN A1 - Msinjili, Nsesheye S. A1 - Vogler, Nico A1 - Sturm, Patrick A1 - Neubert, Markus A1 - Schröder, Hans-Jürgen A1 - Kühne, Hans-Carsten A1 - Hünger, Klaus-Jürgen A1 - Gluth, Gregor J. G. T1 - Calcined brick clays and mixed clays as supplementary cementitious materials: Effects on the performance of blended cement mortars T2 - Construction and Building Materials N2 - While calcined clays in general have been credited with a great potential to mitigate CO2 emissions related to cement production and consumption, calcined brick clays are currently understudied in this regard. In the present work, two brick clays, a low-grade kaolinitic clay, and a mixed clay composed of 50% brick clay and 50% low-grade kaolinitic clay were studied regarding transformations on calcination, and strength and durability performance as well as pore structure of mortars made with the blended cements. All calcined clays exhibited pozzolanic reactivity, with the performance of the brick clays inferior to the low-grade kaolinitic clay. However, the mixed clay performed very similar to the low-grade kaolinitic clay, which points to a viable option for optimal use of brick clays in cementitious systems. The carbonation resistance of the blended cement mortars was generally worse than that of the plain Portland cement mortar, as expected, but the former exhibited a significantly improved chloride penetration resistance. The latter improvement was due to pore structure refinement in the blended cement mortars, compared to the Portland cement mortar. KW - Brick clay KW - Illite KW - Calcined clay KW - Blended cement KW - Carbonation KW - Chloride penetration Y1 - 2021 U6 - https://doi.org/10.1016/j.conbuildmat.2020.120990 SN - 0950-0618 VL - 266 ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario T1 - Thermodynamic modeling of silica dissolution kinetics of quartzitic aggregates stored in highly alkaline solution T2 - Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete N2 - Knowledge's on the dissolution behaviour of SiO2-containing aggregates are the basis for understanding damaging processes regarding ASR. Because of many influences, the solubility of aggregates has still needs to be determined by dissolution experiments. This article is about the reliably modeling of silica dissolution of relatively pure SiO2 containing aggregates in alkaline solutions. Therefore, quartz, quartzite, opal sandstone and flint with different silica modifications were chosen. A kinetic model based on the surface area was derived and numerous thermodynamic data from different authors were evaluated. The surface area of the aggregate grains were determined by an adapted BET method. For this measurement, the original grain sizes were used as they are also used so in concrete. These aggregates were stored in 0.1 mol and 1.0 mol KOH solution at 40°C and 80°C respectively. The dissolution experiments too were performed with grains in the original particle sizes. The concentration of silica in the liquid phase was measured by ICP-OES. The model based on a comparison of calculated and experimental determined silica concentrations, because some parameters of the differential equations are still unknown. The model includes the temperature and molarity dependence of the silica dissolution. The model also takes into account the influences of the SiO2 structures and can vary between crystalline and amorphous SiO2 in a wide range. Thermodynamic data suitable for modeling are recommended. In future, these dissolution calculations shall be extended to other non-pure quartzitic aggregates. Instead of time-consuming ASR concrete prism tests the silica dissolution rates may be used then to indicate quickly the ASR sensitivity of aggregates. Of course, it will be possible to distinguish between innocuous, medium and highly reactive grains. KW - alkali silica reaction; kinetic modeling; quartzite aggregates; silica dissolution; thermodynamic data Y1 - 2021 SN - 978-972-49-2315-4 SP - 1447 EP - 1458 PB - LNEC ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario A1 - Danneberg, Matti T1 - Influence of alkali supply from outside on the dissolution behavior of aggregates T2 - Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete N2 - Reactive aggregates, humidity and alkalis are necessary for ASR in concrete structures. If alkalis come additionally from outside, the damaging reaction can be strongly accelerated. However, the reasons therefore are not completely understood. Some researchers discuss a direct attack of alkali ions on the Si-O-Si bonds of quartz structures. This paper provides another point of view to understand this phenomenon. Different aggregates (grain size 2-8mm) were stored in a highly alkaline KOH solution. Additionally to this solution, sodium chloride with different concentrations was added. The aggregates were selected on the one hand according to their reaction behavior in concrete structures, on the other hand to their dissolution behavior. Long-term dissolution experiments were performed over several months. The silica, the aluminum and of course the sodium concentrations were determined. It can be expected, that under the influence of sodium the silica concentrations in the alkaline solution raise up. The question here is: What happens with the aluminum concentration at the same time? Very surprisingly was, that Al reaches a maximum after some days and then it decreases. Exactly from this time when the Al concentration decreases the silica concentration raises up extremely. The reason therefore can only be a precipitation process. Obviously, there is a correlation between the aluminum content in the solution and the extreme silica release of aggregates, both affected by alkali ions from outside. Aggregates, which do not release aluminum because of their composition (e.g. quartzite), do not show this behavior. The conclusion is that such aggregates are not so sensitive against alkali attack from outside. KW - aggregate grains; aluminium concentration; deicing salt; dissolution experiments; silica release Y1 - 2021 SN - 978-972-49-2315-4 SP - 63 EP - 72 PB - LNEC ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Kurth, David T1 - Calcined Clays and Geopolymers for stabilization of loam structures for plaster and bricks T2 - Proceedings 3rd International Conferende on Calcined Clays for Sustainable Concrete, 15. - 17 Oktober 2019, Neu Delhi N2 - Loam is a very ecological building material with a great potential. It is found worldwide and completely recyclable. Under dry conditions, loam develops high strength values. However, loam is not moisture-resistant. Permanently acting moisture reduces the strength dramatically. The idea to improve the water resistance of loams is adding materials to the loam with the same basic structure. Therefore, Metakaolin, Calcined Clay, here so called Metaclay and a specially developed Geopolymer were selected. Blends of 4 different loams with different amounts of these additives were produced and tested. Criteria for an evaluation are the dynamical modulus of elasticity and the water resistance. These studies were supplemented by structural investigations using a light and a scanning electron microscope and XRD. The results are very interesting and the effects depends strongly on the kind of loam too. Not all additives lead to an improving of the mechanical properties. Nevertheless, not the samples with the highest mechanical values show the best water resistance behavior. Obviously, a balanced structure between loam and additive particles is necessarily. Such structures are not so dense but enough resistant to water to guarantee the positive property of fast water absorption and delivery of natural loams. The service lives of the loam prisms could be increased from certain minutes to several days. Best results are obtained with geopolymer based materials as an additive. This is not so surprising because both the loam and the geopolymer form alumino silicate structures during hardening. Y1 - 2019 UR - https://www-docs.b-tu.de/fg-baustoffe/public/Loam-Geopolymer-revised%20paper.pdf VL - III SP - 185 EP - 194 PB - RILEM ER - TY - GEN A1 - Mo, Xiangyin A1 - Jing, Yingjie A1 - Hünger, Klaus-Jürgen A1 - Kang, Cairong A1 - Shen, Jian T1 - Characteristics of alkali aggregate reaction T2 - Gui suan yan xue bao T2 - Journal of the Chinese Ceramic Society Y1 - 2008 SN - 0454-5648 VL - 36 IS - 10 SP - 1385 EP - 1389 ER - TY - GEN A1 - Hünger, Klaus-Jürgen A1 - Kositz, Mario A1 - Danneberg, Matti A1 - Radnik, Jörg T1 - Enrichment of aluminium in the near-surface region of natural quarzite rock after aluminium exposure T2 - Surface and Interface Analysis N2 - Alkali–silica reaction (ASR) is an ongoing problem that causes damage to concrete constructions and reduces their durability. Therefore, minimizing this undesired reaction is of great interest for both safety and economic reasons. Additives containing high aluminium content are very effective in reducing the release of silica and enhancing the durability of concrete; however, the mechanism for this effect is still under discussion. In this study, an enrichment of aluminium in the near-surface region was observed for natural quartzite rock after storage in Al (OH)3 and metakaolin as aluminium sources, from which we conclude that the formation of aluminosilicate sheets of a few nanometres inhibits the silica release; this hypothesis is supported by high-resolution spectra of Al 2p, Si 2p and O 1s. KW - alkali–silica reaction KW - quartzite rock KW - X-ray photoelectron spectroscopy Y1 - 2021 U6 - https://doi.org/10.1002/sia.6918 SN - 1096-9918 VL - 53 IS - 3 SP - 385 EP - 391 ER -