TY - CONF A1 - Gluth, Gregor A1 - Lehmann, Christian A1 - Haase, Oskar A1 - Rübner, Katrin A1 - Kühne, Hans-Carsten ED - Uzoegbo, H.C. ED - Schmidt, Wolfram T1 - Strength development and characterization of the reaction products of a one-part-geopolymer derived from a silica residue and sodium aluminate T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 2013-01-28 KW - Geopolymers KW - Waste materials KW - Sodium aluminate KW - Strength KW - Microstructure PY - 2013 SN - 978-3-9815360-3-4 SP - 253 EP - 259 AN - OPUS4-27758 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gluth, Gregor A1 - Lehmann, Christian A1 - Rübner, Katrin A1 - Kühne, Hans-Carsten T1 - Reaction products and strength development of wastepaper sludge ash and the influence of alkalis N2 - Wastepaper sludge ash (WSA) from a newsprint paper mill was investigated for its mineralogical composition and its reaction products and strength development after activation with water and sodium and potassium hydroxide solutions. The results showed the WSA to consist of calcite, free lime, gehlenite, tricalcium aluminate, belite, talc, quartz and probably a glassy phase. The principle reaction product was monocarboaluminate (CO3–AFm) for the water- as well as for the alkali-activated WSA. Formation of monocarboaluminate and strength gain was more rapid for the alkali-activated WSA until 1 day of curing. However, afterwards reactions proceeded much slower when alkali solutions were used, leading to an about twice as high compressive strength for water-activated WSA mortars after 28 days of curing. The observed behavior is tentatively ascribed to a less uniform microstructure of the alkali-activated WSA. Significant differences between NaOH- and the KOH-activated WSA were not observed. KW - Wastepaper sludge ash KW - Reaction products KW - Monocarboaluminate KW - Strength KW - Alkali-activation PY - 2014 U6 - https://doi.org/10.1016/j.cemconcomp.2013.09.009 SN - 0958-9465 SN - 1873-393X VL - 45 SP - 82 EP - 88 PB - Elsevier CY - Barking, Essex AN - OPUS4-29930 LA - eng 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 T1 - Hydration and strength development of calcite-rich wastepaper sludge ash N2 - In paper recycling large amounts of waste sludge, containing organics as well as inorganic fillers of the recycled paper, are produced. A large fraction of these sludges is incinerated; the ashes generated in this process, often referred to as wastepaper sludge ash (WSA), have the potential to be used as binder material, either alone or as supplementary cementitious material. However, ashes from different paper mills differ in their Chemical and mineralogical composition, thus, the reaction products and the properties of the hardened binders may vary s i gn i fi cantley. In the present study, a calcite-rich WSA was analyzed for reaction products and strength development. The WSA contained, besides calcite, hydraulic phases such as tricalcium aluminate (C3A) and belite (C2S), lime as well as inert phases. When activated with water, the WSA yielded a compressive strength of up to 12.3 MPa and the major hydration product was monocarboaluminate (C4A CO2 IIH2O or C4ACH11). Activation with 2M NaOH or 2M KOH solution caused a more rapid strength gain until one day of curing, but afterwards the strength development slowed down and the strength afiter 28 days was significantly lower than for the water-activated pastes. From TG analyses it is apparent that the higher strength of the alkaliactivated pastes after one day of curing was caused by a more rapid consumption of calcite and associated formation of C4ACH11. At later curing times the amount of calcite did not change substantially and consequently strength development almost ceased. The results demonstrate the complex influence of alkaline conditions on the hydration of WSA and show that the reaction products, which determine the durability properties of the hardened pastes (and materials made from it), of the calcite-rich WSA differ from the products of other WS As, as discussed in the article. T2 - CIC 2014 - Concrete Innovation Conference 2014 CY - Oslo, Norway DA - 11.06.2014 KW - Wastepaper sludge ash (WSA) KW - Alkali-activation KW - Strength KW - Tetracalcium monocarboaluminate PY - 2014 SP - 1 EP - 8 AN - OPUS4-31038 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hu, Nanjie A1 - Hüsken, Götz A1 - Gluth, Gregor A1 - Kühne, Hans-Carsten T1 - The influence of activator composition on the strength, shrinkage and chloride migration resistance of alkali-activated slag mortars N2 - Alkali-activated slag materials are known for their high Chloride penetration resistance. This makes them potentially applicable as repair systems for damaged steel-reinforced concrete structures, which are exposed to chloride attack. For this purpose, the influence of the activator composition, i.e. the SiO2 and Na2O concentration of the alkaline solution on a) the compressive strength, b) shrinkage and mass change and c) the resistance against chloride penetration of four alkali-activated slag mortars (AASM) were studied. An ordinary Portland cement-based mortar was used as the reference sample. Increasing SiO2 and Na2O concentrations increased the strength, shrinkage and mass loss of the AASMs. The resistance of the mortars against chloride penetration was evaluated using the non-steady-state migration coefficient Dnssm obtained from NT BUILD 492. The results indicate that the Dnssm is related to differences in the pore solution of the AASMs rather than to differences in their microstructure. An upcoming study of the authors is going to evaluate this hypothesis by the accelerated chloride penetration (diffusion) test. T2 - 6th International Conference Non-Traditional Cement and Concrete 2017 CY - Brno, Czech Republic DA - 19.06.2017 KW - Alkali-activated slag mortar KW - Strength KW - Shrinkage KW - Chloride migration coefficient PY - 2018 U6 - https://doi.org/10.4028/www.scientific.net/KEM.761.61 SN - 1662-9795 VL - 761 SP - 61 EP - 64 PB - Trans Tech Publications CY - Switzerland AN - OPUS4-43884 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -