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 -