Atomic structure and phase assemblages in novel M-(N)-A-S-H materials. (April 2021)

• Record Type: Journal Article
• Authors: Bedeaux, Matthew; Gevaudan, Juan Pablo; Lama, Bimala; Srubar, Wil V.
• Is Part Of: Cement and concrete research. Volume 142(2021)
• Publication Date: 2021-04
• Subjects: Alkali activated cements -- Layered double hydroxide phases -- Magnesium -- Nuclear magnetic resonance; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2020.106336
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: This paper investigates the atomic structure and phase assemblages in new sodium-stabilized magnesium aluminosilicate hydrate (M-(N)-A-S-H) cementitious binders. Results indicate that in the absence of Ca 2+, Mg 2+ promotes a binder atomic structure of Si-Al tetrahedral sheets and octahedral Mg sheets with hydrated Na + cations likely in the interlayer sites similar to trioctahedral micas (phyllosilicates). NMR studies verify the incorporation of Al in tetrahedral silicate sheets. XRD demonstrates the ability of these regions to nucleate and form zeolites ( i.e., sodalite) as well as the formation of Mg-Al layered double hydroxide (LDH) phases ( i.e., meixnerite), which is expected due to high concentrations of Mg and Al. TGA results indicate that M-(N)-A-S-H possesses chemically bound water and hydroxyl units similar to other Mg binders. These results evince the critical role of Mg to form unique atomic structures and durability-linked phases in low-calcium alkali-activated materials.