Plastic deformation mechanism of calcium-silicate hydrates determined by deviatoric-stress Raman spectroscopy

Journal Article · Sun Aug 15 04:00:00 EDT 2021 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2021.106476· OSTI ID:23206261

Gardner, David W. ^[1]; Li, Jiaqi ^[2]; Kunz, Martin; Zhu, Chenhui ^[3]; Monteiro, Paulo J.M. ^[2]; Maboudian, Roya; Carraro, Carlo ^[1]

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1. Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720 (United States)
2. Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)
3. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

Highlights: • C-(A-)S-H samples under stress were characterized at the bond and grain level. • Small angle scattering showed that 720 MPa reduced grain thickness by 30%. • In-situ Raman showed that cross-linked C-A-S-H slips along its intralayer. • However, in-situ Raman showed that C-S-H slips along the interlayer. • In-situ Raman also showed a growth in CaCO{sub 3}, indicating fracture in both samples. Creep of the cement matrix affects the structural stability of concrete. In Portland cements, the creep is largely controlled by the binding phase calcium-(aluminum-)silicate-hydrate, or C-(A-)S-H. This phase has a lamellar structure and under deviatoric stress aligns its c-axis with the principal stress. However, the limiting resistance to this reorientation is unknown at the nanocrystalline level. Small-angle X-ray scattering shows that the lamellae thickness decreases under 100's MPa deviatoric stress. Deviatoric stress Raman spectroscopy shows that there are two ways that this break-up can occur. If the material's silicate chains are cross-linked, then strain in SiO bonds does not increase above certain stresses, indicating a relaxation adjacent to the SiO bond. If the chains are not cross-linked, then the silicate chains are broken up by rastering against each other, introducing defects. These results show that the plastic deformation of C-(A-)S-H is relevant for Portland cement creep.

• OSTI ID: 23206261
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 146; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM SILICATES
CALCIUM SILICATES
CREEP
CRYSTALS
HYDRATES
NANOSTRUCTURES
PLASTICITY
PORTLAND CEMENT
RAMAN SPECTROSCOPY
SILICON OXIDES
SLIP
SMALL ANGLE SCATTERING
STABILITY
STRESSES
THICKNESS
X-RAY DIFFRACTION