Formation and Stability of Gismondine-Type Zeolite in Cementitious Systems
Microcrystalline zeolites of the gismondine family are often reported in alkali-activated and blended cement systems. However, little is known about gismondine's compatibility with other cementitious phases to determine stability in long-term phase assemblage. Experimental studies were conducted to investigate the compositional field of gismondine stability in the lime-alumina-silica-hydrate systems, with a particular focus on understanding the compatibility of gismondine with other cement phases such as C-S-H, ettringite, monosulfate, strätlingite, katoite, gypsum, calcite, portlandite, alkali, silica, and aluminosilicate phases. Results show that gismondine-Ca forms readily at ~85°C in high aluminosilicate compositions; and persists in the presence of calcite, gypsum, ettringite, katoite solid solution, low Ca tobermorite-like C-S-H, silica and aluminosilicate phases, at 20-85°C. However, gismondine-Ca reacts with: (a) monosulfate, producing ettringite-thaumasite solid solution; (b) portlandite, forming tobermorite-like C-A-S-H gel and siliceous katoite at > 55°C; (c) aqueous NaOH, generating gismondine-(Na,Ca), a garronite-like zeolite P solid solution; and (d) strätlingite leading to the conversion of strätlingite to gismondine indicating the metastability of strätlingite with respect to gismondine at 55°C. The outcomes are discussed to provide insights into the long-term phase assemblage of relevant cement systems such as lime-calcined clay, alkali-activated materials, and potentially ancient Roman concrete.
M. U. Okoronkwo et al., "Formation and Stability of Gismondine-Type Zeolite in Cementitious Systems," Journal of the American Ceramic Society, vol. 104, no. 3, pp. 1513-1525, Wiley, Mar 2021.
The definitive version is available at https://doi.org/10.1111/jace.17572
Chemical and Biochemical Engineering
Civil, Architectural and Environmental Engineering
Materials Science and Engineering
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01 Mar 2021