Preferred orientation of calcium aluminosilicate hydrate compacts: Implications for creep and indentation

Journal Article · Sat May 15 04:00:00 EDT 2021 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2021.106371· OSTI ID:23206337

Li, Jiaqi; Zhang, Wenxin; Monteiro, Paulo J.M. ^[1]

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1. Department of Civil and Environmental Engineering, University of California, Berkeley (United States)

Nano/micro-indentation has been extensively used to examine elastic properties and creep of cement-based materials. However, there have been inconsistencies in the measured elastic moduli and debate on the creep mechanism of calcium (alumino) silicate hydrates (C-(A-)S-H). To bring new insights, we examined the deviatoric stress-induced preferred orientation of calcium aluminosilicate hydrate (C-A-S-H), portlandite, and ettringite compacts, using synchrotron-based X-ray diffraction. Intense preferred orientations were observed in C-A-S-H compacts, and the c-axis of unit cells is highly aligned with the compression direction; weaker c-axis related fiber-type texture formed in portlandite and ettringite. Higher humidity, greater compacting pressure, and/or increased duration of the pressure intensified the C-A-S-H preferred orientation, which is facilitated by gel-pore water lubrication. This pressure-induced time-dependent preferential re-orientation of crystallites can contribute to the creep of cement-based materials, and it may cause overrepresentation of the soft c-axis of C-(A-)S-H unit-cell in nanoindentation experiments and underestimation of Young's modulus.

• OSTI ID: 23206337
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 143; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CEMENTS
COMPRESSION
CREEP
ELASTICITY
FIBERS
GELS
GRAIN ORIENTATION
HUMIDITY
HYDRATES
LUBRICATION
SILICATES
STRESSES
SYNCHROTRONS
TIME DEPENDENCE
WATER
X-RAY DIFFRACTION