jp0c04563_si_005.mov (1.23 MB)
Silicate Bond Characteristics in Calcium–Silicate–Hydrates Determined by High Pressure Raman Spectroscopy
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posted on 2020-08-07, 21:44 authored by David
W. Gardner, Jiaqi Li, Ali Morshedifard, Saeed Masoumi, Mohammad Javad Abdolhosseini Qomi, Paulo J. M. Monteiro, Roya Maboudian, Carlo CarraroThe
mechanical and thermal properties of the gigatonnes of concrete
produced annually are strongly affected by the anharmonicity of the
chemical bonds in its main binding phase, nanocrystalline calcium−(alumino−)silicate−hydrate
(C−(A−)S−H). Improvements in C−(A−)S−H
design increasingly depend on simulations utilizing a set of effective
interatomic forces known as “CSH-FF”, yet these assumptions
have never been directly examined at the chemical bond level, and
there is no guidance for their improvement. In this work, we use high-pressure
Raman spectroscopy to directly measure bond anharmonicity in a representative
series of C−(A−)S−H samples with varying composition
and two natural model minerals, 14 Å tobermorite and xonotlite.
We find that structural water molecules effectively scatter thermal
energy, providing a heuristic for improving the thermal resistance
of concrete. A comparison of experimental and calculated bond anharmonicities
shows that a stiffer Si–O interaction would improve the transferability
of CSH-FF to the thermal properties of C−(A−)S−H.
High-pressure Raman spectroscopy is suggested to improve the calculations
of C−S−H and to characterize other complex, nanocrystalline
materials.