Magnesium oxychloride cement

NAP-XPS Probes the Electronic Structure of the Mg–Al–Cl Layered Double Hydroxide upon Controlled Hydration

“…One should note that a metastable gel phase was also reported in that region: 37,38 It is commonly admitted that reactive species (polynuclear Mg complexes) combine with the Cl − and H 2 O to form an amorphous hydrogel in which reduced diffusion rate prevents solid crystallization. 39 The following consistent scheme can be drawn. In a neutral/ alkaline solution (water in excess), the MgAl-Cl-LDH surface is in dynamic equilibrium with Mg 2+ solution (even containing Al species at high pH).…”

“…In this region of the ternary diagram, solid Mg­(OH) 2 and MgCl 2 solution (free pH = 7.5) coexist at thermodynamic equilibrium. One should note that a metastable gel phase was also reported in that region: , It is commonly admitted that reactive species (polynuclear Mg complexes) combine with the Cl – and H 2 O to form an amorphous hydrogel in which reduced diffusion rate prevents solid crystallization …”

Exploring the Potential of Nonclassical Crystallization Pathways to Advance Cementitious Materials

“…The strength primarily arises from the presence of the 5-phase, which has been shown to translate into higher compressive strengths. , In contrast, MOCs where the 3-phase dominates exhibit lower strength and higher water solubility . The 5-phase is metastable and gradually transforms into the most stable 3-phase, which subsequently decomposed into brucite, leading to volume instability in the material . This phase transition is the underlying cause of MOC’s poor water resistance, significantly limiting its application in an engineering context.…”

“… 383 The 5-phase is metastable and gradually transforms into the most stable 3-phase, 376 which subsequently decomposed into brucite, leading to volume instability in the material. 384 This phase transition is the underlying cause of MOC’s poor water resistance, significantly limiting its application in an engineering context.…”

“…Numerous methods have been used to stabilize the 5-phase in MOC, involving the addition of trace amounts of inorganic (e.g., phosphates, gypsum, carbonates) and organic substances (e.g., tartaric acid, ethylene-vinyl acetate, and steric acid-styrene copolymers), with some of those showing promising perspectives. 384 Notably, tartaric and phosphoric acids have been demonstrated to increase the lifespan of the amorphous phase significantly. 385 This extension contributes to improved water resistance by interlocking the 5-phase crystals in the matrix, hindering their decomposition, and reducing the pore volume.…”