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 -