TY - CONF A1 - Nikoonasab, Ali A1 - Müller, Thoralf A1 - Licht, M. A1 - Raupach, M. A1 - Gluth, Gregor ED - Rogge, Andreas ED - Meng, Birgit T1 - Sulfides in the pore solutions of GGBFS-containing concretes - Influence on the corrosion of reinforcing steel N2 - Steel corrosion in sulfide-containing solutions is a challenge in various environments, such as reinforced concrete structures. In concrete, sulfides are introduced by ground granulated blast-furnace slag (GGBFS), used in standard cements and alkali-activated materials (AAMs), affecting steel corrosion. This study examined steel in synthetic GGBFS-containing cement pore solutions using electrochemical techniques. Compared to Portland cement solutions, steel in sulfide-containing solutions exhibits lower open circuit potentials and polarisation resistances. Thus, Portland cement concrete corrosion assessment standards are unsuitable for GGBFScontaining concrete. T2 - 11. Jahrestagung des DAfStb mit 63. Forschungskolloquium der BAM Green Intelligent Building CY - Berlin, Germany DA - 16.10.2024 KW - Corrosion KW - Reinforcing steel PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-612963 SN - 978-3-9818564-7-7 SP - 55 EP - 59 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-61296 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nikoonasab, Ali A1 - Licht, M. A1 - Weiler, L. A1 - Achenbach, R. A1 - Raupach, M. A1 - Gluth, Gregor T1 - Pore Solution composition of GGBFS-containing cement pastes N2 - Ground Granulated Blast-Furnace Slag (GGBFS), a by-product of the iron-making process, has gained significant attention as a supplementary cementitious material and has become increasingly popular in recent years due to its remarkable properties. GGBFS can significantly reduce the environmental impact of cement production when it comes to building concrete structures. GGBFS can either be blended with ordinary Portland cement (OPC) (up to a 90% replacement), or it can be used in the production of alkali-activated materials (AAMs). However, a comprehensive understanding of the pore solution composition is necessary for understanding various aspects of cementitious materials and their durability, including corrosion behavior, passivation of steel, and resistance to deteriorative processes. In the present work, the pore solutions of seven different GGBFS-containing cements (alkali-activated slag, alkali-activated slag/fly ash blends, a hybrid alkaline cement, CEM III/C, and CEM III/B) were extracted and analysed by inductively coupled plasma-optical emission spectroscopy, ion chromatography, pH, redox potential, and conductivity measurements. For comparison, a Portland cement pore solution was analysed similarly. The Concentrations of reduced sulfur were noteworthy in all GGBFS-containing cements, particularly in alkali-activated cements, where concentrations were notably higher compared to standard cements. The redox potentials of the pore solutions were primarily dictated by the concentrations of reduced sulfur, although other factors may contribute. Additionally, sulfur species in the pore solutions had an impact on pH, electrical conductivity, and other properties pertinent to the corrosion of reinforcements. T2 - RILEM Spring Convention 2024 & Conference on Advanced Construction Materials and Processes for a Carbon Neutral Society CY - Milan, Italy DA - 10.04.2024 KW - GGBFS KW - AAM KW - Sulfide KW - Pore solution composition KW - Redox potential PY - 2024 AN - OPUS4-59960 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Licht, M. A1 - Nikoonasab, Ali A1 - Gluth, Gregor A1 - Raupach, M. ED - Claßen, M. ED - Hegger, J. ED - Matschei, T. ED - Raupach, M. T1 - Alkali-aktivierte Hüttensandbetone – CO2-reduzierte Bindemittel mit hohem Korrosionsschutzpotential N2 - Durch den Ersatz von Portlandzement können alkali-aktivierte Bindemittel einen bedeutenden Beitrag zur Verringerung der durch die Zementklinkerherstellung verursachten CO2-Emissionen leisten. Für die Verwendung von alkali-aktivierten Bindemitteln in Stahlbetonkonstruktionen, die Chloriden oder Carbonatisierung ausgesetzt sind, ist die Fähigkeit des Stahls, den passiven Zustand zu erreichen und aufrechtzuerhalten, von großer Bedeutung. Die Prozesse der Deckschichtbildung von Stahl in alkali-aktivierten Materialien unterscheiden sich jedoch zum Teil grundlegend von denen in Portlandzementen. Alkali-aktivierte Hüttensandbetone weisen gute technische Eigenschaften auf, bisher fehlen jedoch grundlegende Kenntnisse bzgl. ihrer schützenden Wirkung bei korrosiven Angriffen. Dies ist vor allem auf ihre sulfidhaltige Porenlösung zurückzuführen, welche die elektrochemischen Eigenschaften der Stahloberfläche beeinflusst und die Verwendung herkömmlicher Bewertungsmaßstäbe erschwert. Es werden erste Ergebnisse eines DFG-Forschungsprojektes vorgestellt, in dem das Passivierungsverhalten von Stahl in alkali-aktivierten Hüttensandmörteln unterschiedlicher Zusammensetzungen sowie in Mörteln auf Basis hüttensandhaltiger Normzemente untersucht wird. Über einen Zeitraum von mindestens 28 Tagen werden an Zylinderprüfkörpern im 3-Elektroden-Aufbau das Ruhepotential sowie die Polarisationswiderstände der Stahlelektroden ermittelt. T2 - 10. DAfStb-Jahrestagung mit 62. Forschungskolloquium CY - Aachen, Germany DA - 26.09.2023 KW - Bewehrung KW - Stahlkorrosion KW - Hüttensandmehl KW - Sulfid PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-593775 DO - https://doi.org/10.18154/RWTH-2023-06676 SP - 233 EP - 238 PB - RWTH Aachen CY - Aachen AN - OPUS4-59377 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nikoonasab, Ali A1 - Licht, M. A1 - Weiler, L. A1 - Achenbach, R. A1 - Raupach, M. A1 - Gluth, Gregor T1 - Pore solution compositions and redox potentials of ground granulated blast furnace slag-containing cement pastes N2 - The pore solutions of hardened ground granulated blast furnace slag (GGBFS)-containing cements differ from the pore solutions of other cements with effects on reinforcement corrosion, application of electrochemical methods and immobilisation of radioactive waste. In the present study, the pore solutions of seven different GGBFS-containing cements (alkali-activated slag, alkali-activated slag/fly ash blends, hybrid alkaline cement (HAC), CEM III/C and CEM III/B) were extracted and their elemental and sulfate concentration, pH, redox potential and conductivity were determined; a Portland cement (CEM I) pore solution was analysed analogously. The silicon and aluminium concentrations of the alkali-activated cements increased with fly ash fraction, reaching values up to 5 mM and 10 mM, respectively, and thus were considerably higher than those of the standard cements. The redox potentials of the pore solutions of the GGBFS-containing cements were in the range from −100 mV to –500 mV vs Ag/AgCl, that is considerably lower than that of the Portland cement (8–20 mV vs Ag/AgCl), with the value depending on the GGBFS fraction and whether the cements were alkali-activated or not. These results indicate that the effects of reduced sulfur species from GGBFS in cements are more pronounced in alkali-activated materials, including HAC, and increase with GGBFS fraction. KW - Alkali-activated materials KW - Ground granulated blast furnace slag KW - Sulfide KW - Redox potential KW - Pore solution PY - 2026 DO - https://doi.org/10.1680/jadcr.25.00041 SN - 1751-7605 SN - 0951-7197 VL - 38 IS - 4 SP - 238 EP - 249 PB - Emerald CY - Leeds AN - OPUS4-64619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -