TY - CONF A1 - Hlavacek, Petr A1 - Reinemann, Steffi A1 - Gluth, Gregor A1 - Ebell, Gino A1 - Mietz, Jürgen ED - Serdar, M. ED - Stirmer, N. ED - Provis, J. T1 - Behaviour of reinforced alkali-activated fly ash mortars under leaching conditions N2 - Corrosion of steel reinforcement in concrete is one of the major deterioration mechanisms limiting the service life of reinforced concrete structures. While for conventional (Portland cement-based) concretes a great amount of experience exists in this regard, the factors that determine the onset of reinforcement corrosion in alkali-activated materials are incompletely understood yet. One aspect of corrosion protection is leaching and the accompanying changes of the concrete pore solution. In the present study, alkali-activated fly ash mortars with embedded carbon steel rebars were exposed to de-ionised water for periods up to 330 days, and the electrochemical response of the steel (free corrosion potential, polarisation resistance), the alteration of the mortar (ohmic resistance, mechanical strength, pore size distribution) as well as the pore solution composition were monitored. Although substantial alkali leaching was observed, the pH of the pore solution remained at values sufficient to protect the embedded steel from depassivation. The mortar did not exhibit indications of significant deterioration. Thus, the present results suggest that leaching is not critical for protection of steel reinforcement in alkali-activated fly ash mortars and concretes. T2 - International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) CY - Rovinj, Croatia DA - 20.03.2019 KW - Alkali-activated materials KW - Steel corrosion KW - Leaching PY - 2019 SN - 978-2-35158-223-7 VL - 1 SP - 118 EP - 124 PB - RILEM Publications CY - Paris AN - OPUS4-47585 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Corrosion behavior of galvanized reinforcement in chloride containing mortar and carbonated mortar N2 - Korrosionseigenschaften von feuerverzinktem Betonstahl unterscheiden sich grundlegend von herkömmlichen Betonstahl. In diesem Vortrag sind Beispiele für das Korrosionsverhalten in chloridhaltigen und carbonatisierten Mörteln dargestellt T2 - Intergalva 2018 - 25th International Galvanizing Conference CY - Berlin, Germany DA - 17.06.2018 KW - Corrosion KW - Korrosion KW - Verzinkt KW - Betonstahl PY - 2018 SP - 301 EP - 309 AN - OPUS4-45240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gluth, Gregor A1 - Hlavacek, Petr A1 - Reinemann, Steffi A1 - Ebell, Gino A1 - Mietz, Jürgen ED - Alexander, M.G. ED - Beushausen, H. ED - Dehn, F. ED - Moyo, P. T1 - Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars N2 - Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in high- and low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation. T2 - International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2018) CY - Cape Town, South Africa DA - 19.11.2018 KW - Alkali-activated materials KW - Steel corrosion KW - Leaching KW - Carbonation PY - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-464381 VL - 199 SP - Article Number 02025 PB - EDP Sciences AN - OPUS4-46438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hlavacek, Petr A1 - Gluth, Gregor A1 - Reinemann, Steffi A1 - Ebell, Gino A1 - Kühne, Hans-Carsten A1 - Mietz, Jürgen T1 - Corrosion of steel reinforcement in geopolymer mortars - carbonation resistance, chloride migration, and preliminary corrosion potential data N2 - Alkali-activated materials such as geopolymers are currently receiving a lot of attention because of their potential to be used as binders for concrete with advantageous engineering properties and reduced manufacturing CO2 emissions. Knowledge of the durability of steel in these concretes and related properties of alkali-activated materials is a prerequisite for their application as building materials, if they are to be used for steel reinforced elements. However, to date only limited data exists on this topic. The present contribution focuses on durability-related transport properties of geopolymer-based mortars (as model systems for concrete). We report results of accelerated carbonation, rapid chloride migration (RCM) and air permeability measurements as well as porosity data for fly ash-based geopolymer mortars, including mixes containing ground granulated blast furnace slag (GGBFS). In addition, we report polarization resistance data and corrosion potential vs. time curves for carbon steel bars embedded in two of the fly ash-based geopolymer mortars and a CEM I-based mortar (as reference). Despite comparable total porosities, the carbonation depths, the chloride migration coefficients and the air permeabilities of the mortars differed significantly. In general, the addition of GGBFS to the binders improved the performance (decreased transport coefficients); however, this was not found to be true for the air permeability in all cases. This latter effect can be explained by drying damage of the C-(A-)S-H gel in GGBFS-containing binders. On the other hand, low transport coefficients can also be achieved by optimization of the binder formulation without the addition of GGBFS, which is also reflected in the material’s air permeability. Thus, there exists no simple correlation between air permeability (of harshly dried mortars) and durability-related transport coefficients for the studied alkali-activated materials. The corrosion potential vs. time curves in combination with polarization resistance values reveal that the steel reinforcement in geopolymer mortars assumed a passive state. However, this happened considerably later than for steel in CEM I-based mortars. The free corrosion potential of carbon steel reinforcement in the geopolymer mortars had different values than the free corrosion potential values for the CEM I-based mortar for both the active and the passive state; possible reasons for this behavior are discussed. T2 - EUROCORR 2017 CY - Prague, Czech Republic DA - 03.09.2017 KW - Geopolymers KW - Alkali-activated materials KW - Corrosion KW - Steel reinforcement KW - Concrete PY - 2017 SP - Paper 87351, 1 EP - 7 AN - OPUS4-41870 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Poltavtseva, M. A1 - Mietz, Jürgen ED - Ottosen, L. T1 - Electrochemical investigation of carbon-based conductive coatings for application as anodes in ICCP system of reinforced concrete structures N2 - Carbon-based conductive coatings are complex composites, consisting of an organic or inorganic binder and conductive carbon components, for application as anodes in impressed current cathodic protection systems of reinforced concrete structures. The electrochemical properties of three coatings at different humidity and in saturated calcium hydroxide solution were studied by electrochemical methods, such as electrochemical impedance measurement, measuring of open circuit potential over time and galvanostatic polarization. T2 - International RILEM Conference on Materials, Systems and Structures in Civil Engineering 2016 CY - Lyngby, Denmark DA - 21.08.2016 KW - ICCP KW - Coating KW - Cunductive KW - Corrosion KW - reinforcement KW - Concrete KW - Cathodic protection PY - 2016 SN - 978-2-35158-176-6 SN - 978-2-35158-177-3 VL - Proceedings PRO 111 SP - 43 EP - 46 PB - RILEM Publications S.A.R.L. CY - Paris, France AN - OPUS4-37216 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Hydrogen evolution on galvanized rebar in fresh concrete with different chromate-reduced cements N2 - The reduction of the chromate contents in cements affects the electrochemical reactions of galvanized reinforcing steels in fresh concrete. It is important to investigate the critical conditions in the first hours following the pouring of the concrete. T2 - EUROCORR 2015 - European corrosion congress CY - Graz, Austria DA - 06.09.2015 KW - Hydrogen evolution KW - Concrete KW - Galvanized rebar KW - Reinforcement KW - Chromate PY - 2015 SP - paper 9_703 AN - OPUS4-34619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Mietz, Jürgen A1 - Burkert, Andreas T1 - Investigation of chloride-induced pitting corrosion of steel in concrete by a combination of electrochemical methods with X-ray tomography N2 - Steel in concrete is protected by the alkaline pore water environment and the resulting formation of a protective passive layer against corrosion. Adverse environmental conditions due to carbonation or chloride ingress can destroy the passive layer on the steel surface. Corrosion processes starting in those areas lead to uniform corrosion or local corrosion like pitting corrosion. In comparison to uniform corrosion pitting corrosion is a form of increased local corrosion and thus leads to a progressive reduction in cross-section of the reinforcing steel. The corrosion products are first absorbed by the pores of the concrete matrix, without causing visible external changes at the concrete surface. T2 - EUROCORR 2014 - European corrosion congress CY - Pisa, Italy DA - 08.09.2014 KW - Corrosion KW - Rebar KW - Chloride KW - Pitting corrosion PY - 2014 SN - 978-3-89746-159-8 SP - O-7207, 274-275 AN - OPUS4-31431 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Poltavtseva, Marina A1 - Ebell, Gino A1 - Mietz, Jürgen T1 - Entwicklung und Erprobung einer neuen Prüfmesszelle für elektrochemische Untersuchungen leitfähiger Beschichtungen auf Karbonbasis in Elektrolytlösungen T2 - 15. Sommerkurs Werkstoffe und Fügen am Institut für Werkstoff- und Fügetechnik CY - Magdeburg, Germany DA - 2014-09-12 PY - 2014 SN - 978-3-940961-85-3 SP - 207 EP - 214 AN - OPUS4-31474 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ebell, Gino A1 - Poltavtseva, Marina A1 - Mietz, Jürgen T1 - Electrochemical investigation of carbon-based conductive coatings for application as anodes in ICCP system of reinforced concrete structures N2 - Carbon‐based conductive coatings are complex composites, consisting of an organic or inorganic binder and conductive carbon components, for application as anodes in impressed current cathodic protection systems of reinforced concrete structures. The electrochemical properties of three coatings at different humidity and in saturated calcium hydroxide solution were studied by electrochemical methods, such as electrochemical impedance measurement, measuring of open circuit potential over time and galvanostatic polarization. The dissolved organic and inorganic carbons in electrolyte solution were quantified by using a photometric method. The structures of the coatings were investigated before and after the electrochemical tests by microscopy and scanning electron microscope/EDX analysis. The results of the electrochemical impedance measurements show that the tested coatings all have a relatively low resistance, which is between 100 and 200V. The binder and the surface porosity influence the degradation behavior of those coatings. Especially the organic binder reacts with the strong alkaline medium under dissolving of organic carbon. T2 - EUROCORR 2014 - European corrosion congress CY - Pisa, Italy DA - 08.09.2014 KW - Cathodic protection KW - Concrete KW - ICCP PY - 2014 SN - 978-3-89746-159-8 SP - O-7489, 481 EP - O-7489, 481 AN - OPUS4-31430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Burkert, Andreas A1 - Fischer, Joachim A1 - Mietz, Jürgen A1 - Lehmann, Jens A1 - Ebell, Gino T1 - Neues DGZfP - Merkblatt der elektrochemischen Potentialfeldmessung zur Detektion von Bewehrungsstahlkorrosion T2 - Tagung Korrosionsschutz der Stähle im Kontakt mit Beton - Neue Entwicklungen und Forschungsergebnisse CY - Stuttgart-Vaihingen, Deutschland DA - 2010-10-07 KW - Verfahrensbeschreibung KW - Messraster KW - Einflussgrößen KW - Fehlerquellen KW - Prüfprotokoll KW - Nachweisgrenzen PY - 2010 SN - 978-3-935406-43-7 SP - 149 EP - 156 CY - Frankfurt/M. AN - OPUS4-22197 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -