TY - CONF A1 - Gluth, Gregor A1 - Mundra, Shishir A1 - Henning, Ricky T1 - Chloride binding by LDH/AFm phases and alkali-activated slag pastes N2 - Chloride binding by the hydrate phases of cementitious materials influences the rate of chloride ingress into these materials and, thus, the time at which chloride reaches the steel reinforcement in concrete structures. A particularly important role in this context is played by layered double hydroxides (LDHs), including AFm phases. Chloride binding isotherms of individual LDH/AFm phases would be required as input for computational models of chloride ingress, but such isotherms are only available for a few AFm phases, and in addition the available data are partly conflicting. The present study, conducted in the context of RILEM TC 283-CAM ‘Chloride transport in alkali-activated materials’, significantly extends the available database by determining the chloride binding isotherms of LDH/AFm phases (monosulfate, strätlingite, hydrotalcite, and meixnerite), and of alkali-activated slags (AAS) produced with four different activators (Na2SiO3, Na2O∙1.87SiO2, Na2CO3, and Na2SO4), in NaOH/NaCl solutions at various liquid/solid ratios. Selected solids after chloride binding were analysed by X-ray diffraction, and thermodynamic modelling was applied to simulate the phase changes occurring during chloride binding by the AFm phases. The chloride binding isotherms of LDH/AFm phases depended strongly on the liquid/solid ratio during the experiments, resolving apparent contradictions of the previously available data. The dependency on liquid/solid ratio must be attributed to kinetic restrictions, which are, however, currently poorly understood. Chloride binding by AAS pastes was generally higher than for Portland cement pastes and was only moderately influenced by the employed activator. A steep increase of the chloride binding by AAS occurred at free chloride concentrations above approx. 1.0 M, which is possibly related to chloride binding by the C-(N-)A-S-H gel in the AAS. T2 - RILEM Spring Convention 2024 & Conference on Advanced Construction Materials and Processes for a Carbon Neutral Society CY - Milan, Italy DA - 07.04.2024 KW - Chloride binding KW - Layered double hydroxides KW - AFm phases KW - Alkali-activated slags KW - Chloride sorption isotherms PY - 2024 AN - OPUS4-59855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -