Preferred orientation of calcium aluminosilicate hydrate induced by confined compression. (November 2018)

• Record Type: Journal Article
• Authors: Geng, Guoqing; Vasin, Roman Nikolayevich; Li, Jiaqi; Qomi, Mohammad Javad Abdolhosseini; Yan, Jinyuan; Wenk, Hans-Rudolf; Monteiro, Paulo J.M.
• Is Part Of: Cement and concrete research. Volume 113(2018)
• Page Start: 186
• Page End: 196
• Publication Date: 2018-11
• Subjects: Calcium aluminosilicate hydrate -- Texture formation -- High pressure X-ray diffraction -- Deviatoric stress -- Elastic moduli; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2018.09.002
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: The existing macroscale models of the calcium (alumino)silicate hydrate (C-(A-)S-H), the main binder of concrete, assume that the nanocrystallites maintain random orientation under any loading conditions. However, using synchrotron-radiation-based XRD, we report the development of preferred orientation of nanocrystalline C-A-S-H, from random at ambient pressure to strongly oriented under uniaxial compression with lateral confinement. The c -axes of the nanocrystals tend to align with the primary load. This preferred orientation is preserved after removing of external loading. The texture, quantified using a standard Gaussian fiber orientation distribution function (ODF), was used to calculate the averaged bulk elastic tensor of oriented C-(A-)S-H. It changes from isotropic (without texture) to transversely isotropic (with texture). Our results provide direct evidence of the reorientation of nanocrystalline C-(A-)S-H as a mesoscale mechanism to the irreversible deformation of cement-based material. The implications of these results for modeling the mechanical property of C-(A-)S-H at the macroscale are discussed.