The nanomechanical properties of non-crosslinked calcium aluminosilicate hydrate: The influences of tetrahedral Al and curing age. (September 2022)

• Record Type: Journal Article
• Authors: Li, Jiaqi; Zhang, Wenxin; Sanz-Camacho, Paula; Duttine, Mathieu; Gardner, David; Carraro, Carlo; Maboudian, Roya; Huthwelker, Thomas
• Is Part Of: Cement and concrete research. Volume 159(2022)
• Publication Date: 2022-09
• Subjects: C-A-S-H -- C-S-H -- High-pressure X-ray diffraction -- Bulk modulus -- Blended cement; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2022.106900
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: Calcium aluminosilicate hydrate (C-A-S-H) is the binding phase of both blended cement-based and alkali-activated materials. The intrinsic mechanical properties of non-cross-linked C-A-S-H are important while experimentally unvalidated. Here, the properties are for the first time measured using high-pressure X-ray diffraction. The incompressibility and bulk modulus K0 of C-A-S-Hs are correlated to their nanostructure and stability using nuclear magnetic resonance and X-ray absorption spectroscopies. Al coordination in stable C-A-S-H (Al/Si = 0.1) cured for 546 days is purely tetrahedral (Al IV ), while in metastable C-A-S-H (Al/Si = 0.05) cured for only 182 days is both Al IV and pentahedral (Al V ). The stable C-A-S-H is stiffer along the a, b, c-axis with higher K0 relative to C-S-H. Short-curing-induced metastable C-A-S-H (Al/Si = 0.05) shows expanded interlayer and softer c-axis, thus lower K0 than C-S-H and the stable C-A-S-H. Our results highlight the stiffening effect of Al IV incorporation and the negative influences of insufficient curing on the nanomechanical properties of non-cross-linked C-A-S-H at Ca/Si = 1.