Control of the M-S-H Crystallization for Building a Green Future
Final Report Abstract
The main objective of the research project was to gain a fundamental understanding of the crystallization of M-S-H in the presence and absence of different polymeric additives. By understanding nucleation and growth of M-S-H, we aimed to pave the way towards developing novel binders that could emulate Portland cements regarding mechanical performance while being less environmentally impactful. First, we analyzed the formation of pure M-S-H to identify the pre- and post-nucleation stages of the crystallization process. We demonstrated a non-classical multistep pathway where a highly complex mixture of defined hydrated magnesium (sodium)-silicate oligomeric species exists in solution before nucleation. Our results suggest that these entities aggregate, yielding an unshaped M-S-H precursor phase (depleted in Mg compared to the final product), which later transforms into a denser M-S-H interconnected network (Mg:Si ratio ca. 1) with a more defined sheet-like structure that still retains its poorly crystalline character. In the second part of the project, we investigated the influence of different organic additives, specifically anionic and non-ionic components of polycarboxylate ethers (PCEs), on M-S-H formation. We found that acrylic acid and methacrylic acid monomers caused a slight delay in M-S-H nucleation, whereas maleic acid and ethylene glycol did not affect the nucleation. Regarding the polymers, we identified a delay in M-S-H nucleation when all anionic polymers were in the media and no effect of polyethylene glycol. Polyacrylic acid caused the most prominent retardation among the anionic polymers. Additionally, we explored two applications of M-S-H: as a waste encapsulation matrix and for CO₂ sequestration. We investigated the immobilization capacity of M-S-H for various metal cations, finding that M-S-H can incorporate up to 30% of the total metal content at early formation stages without significantly delaying nucleation. For the second application, we studied the mechanism and enhancement of CO₂ sequestration by carbonation of M-S-H/Mg(OH)₂. Our findings indicate that the carbonation process typically begins with an amorphous precursor phase, eventually transforming to nesquehonite with distinct crystallinity after prolonged CO₂ exposure. This project has significantly contributed to understanding the fundamental processes occurring during M-S-H formation and how various additives can influence these. The knowledge ained is crucial for developing sustainable cementitious materials with improved properties, potentially leading to a reduction in the CO₂ footprint of the construction industry.
Publications
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Immobilization of (Aqueous) Cations in Low pH M-S-H Cement. Applied Sciences, 11(7), 2968.
Marsiske, Maximilian R.; Debus, Christian; Di Lorenzo, Fulvio; Bernard, Ellina; Churakov, Sergey V. & Ruiz-Agudo, Cristina
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Carbonation of M-S-H/Mg(OH)₂ mixtures for CO₂ sequestration. RILEM Conference 2023, Vancouver
Marsiske, M. R. & Ruiz-Agudo, C.
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Organic Additive's Influence on M-S-H Formation. 16th International Congress on the Chemistry of Cement 2023 (ICCC2023), Bangkok, Thailand, September 18–22, 2023
Ruiz-Agudo, C. R. & Marsiske, M.
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Uncovering the Early Stages of Magnesium Silicate Hydrate Formation: A Nonclassical Multistep Pathway. ACS Applied Engineering Materials, 1(1), 696-707.
Marsiske, Maximilian R.; Köser, Rebecca; Bäumle, Benedikt & Ruiz-Agudo, Cristina
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Insights into the impact of small anionic additives on Mg-silicate hydrate nucleation. The Journal of Chemical Physics, 162(6).
Bastian, Annika; Emminger, Yannick Hermann; Kerdieh, Nour; Bernard, Ellina & Ruiz-Agudo, Cristina
