Nanostructure of Calcium Silicate Hydrates in Cements

Skinner, Lawrie; Chae, Sejung Rosie; Benmore, C. J.; Wenk, Hans‐Rudolf; Monteiro, Paulo J.M.

doi:10.1103/physrevlett.104.195502

Cited by 232 publications

(208 citation statements)

References 17 publications

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“…The use of the reactive potential allows observing the dissociation of water molecules into hydroxyl groups. More details on the preparation of the model and on the multiple validations with respect to experiments can be found elsewhere [11][12][13][14].…”

Section: A Realistic Model Of C-s-hmentioning

confidence: 99%

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Is cement a glassy material?

Bauchy¹,

Qomi²,

Ulm³

et al. 2014

Computational Modelling of Concrete Structures

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The nature of Calcium-Silicate-Hydrate (C-S-H), the binding phase of cement, remains a controversial question. In particular, contrary to the former crystalline model, it was recently proposed that its nanoscale structure was actually amorphous. To elucidate this issue, we analyzed the structure of a realistic simulation of C-S-H, and compared the latter to crystalline tobermorite, a natural analogue to cement, and to an artificial ideal glass. Results clearly support that C-S-H is amorphous. However, its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that its amorphous state mainly arises from its hydration.

show abstract

Section: A Realistic Model Of C-s-hmentioning

confidence: 99%

“…Hence, it is still unclear whether C-S-H should be considered as a crystalline or an amorphous material. Fortunately, a realistic atomistic model of C-S-H has recently been reported [11][12][13][14], thus opening the way to elucidate its nature.…”

Section: Introductionmentioning

confidence: 99%

Is cement a glassy material?

Bauchy¹,

Qomi²,

Ulm³

et al. 2014

Computational Modelling of Concrete Structures

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show abstract

“…5,10 A wide array of characterization techniques has thus been applied to cement phases, for example, X-ray diffraction (XRD), small angle neutron scattering (SANS), in situ imaging by transmission electron microscopy (TEM), atomic force microscopy (AFM) and nanoindentation, zeta potential measurements, nuclear magnetic resonance spectroscopy (NMR), infrared (IR), and Raman spectroscopy. [11][12][13][14][15][16][17][18] In addition, models and simulations have been developed to enhance understanding and materials design. 8,10,[19][20][21][22][23][24][25][26][27][28][29][30] Such approaches include electronic structure calculations, molecular dynamics, Monte Carlo, and continuum methods, as well as multi-scale combinations of methods.…”

Section: Introductionmentioning

confidence: 99%

A force field for tricalcium aluminate to characterize surface properties, initial hydration, and organically modified interfaces in atomic resolution

et al. 2014

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Tricalcium aluminate (C 3 A) is a major phase of Portland cement clinker and some dental root filling cements. An accurate all-atom force field is introduced to examine structural, surface, and hydration properties as well as organic interfaces to overcome challenges using current laboratory instrumentation. Molecular dynamics simulation demonstrates excellent agreement of computed structural, thermal, mechanical, and surface properties with available experimental data. The parameters are integrated into multiple potential energy expressions, including the PCFF, CVFF, CHARMM, AMBER, OPLS, and INTERFACE force fields. This choice enables the simulation of a wide range of inorganic-organic interfaces at the 1 to 100 nm scale at a million times lower computational cost than DFT methods. Molecular models of dry and partially hydrated surfaces are introduced to examine cleavage, agglomeration, and the role of adsorbed organic molecules. Cleavage of crystalline tricalcium aluminate requires approximately 1300 mJ m −2 and superficial hydration introduces an amorphous calcium hydroxide surface layer that reduces the agglomeration energy from approximately 850 mJ m −2 to 500 mJ m −2 , as well as to lower values upon surface displacement. The adsorption of several alcohols and amines was examined to understand their role as grinding aids and as hydration modifiers in cement. The molecules mitigate local electric fields through complexation of calcium ions, hydrogen bonds, and introduction of hydrophobicity upon binding. Molecularly thin layers of about 0.5 nm thickness reduce agglomeration energies to between 100 and 30 mJ m −2 . Molecule-specific trends were found to be similar for tricalcium aluminate and tricalcium silicate. The models allow quantitative predictions and are a starting point to provide fundamental understanding of the role of C 3 A and organic additives in cement. Extensions to impure phases and advanced hydration stages are feasible.

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“…2,[14][15][16] The proposed structures are produced by introducing vacancy defects in drierketten silicate chains of Tobermorite minerals. 17 Here, we use the molecular structure containing 501 atoms proposed by Qomi et al, 2 which is in agreement with a variety of analytical experiments.…”

mentioning

confidence: 99%

The contribution of propagons and diffusons in heat transport through calcium-silicate-hydrates

Zhou

Morshedifard

Lee

et al. 2017

Applied Physics Letters

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Whether it is glass, ceramics, cement, or concrete, minimizing thermal conduction through disordered materials is a determining factor when it comes to reducing the energy consumption of cities. In this work, we explore underlying physical processes involved in thermal conduction through the disordered glue of cement, calcium-silicate-hydrates (CSH). We find that at 300 K, phonon-like propagating modes in accordance with the Boltzmann transport theory, propagons, account for more than 30% of the total thermal conductivity, while diffusons, described via the Allen-Feldman theory, contribute to the remainder. The cumulative thermal conductivity proves to be close to both equilibrium molecular dynamics calculations and experimental values. These findings help us establish different strategies, such as localization schemes (to weaken diffusons) and scattering mechanisms (to constrain propagons), for reduction of thermal conductivity of CSH without sacrificing its mechanical properties.

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Nanostructure of Calcium Silicate Hydrates in Cements

Cited by 232 publications

References 17 publications

Is cement a glassy material?

Is cement a glassy material?

A force field for tricalcium aluminate to characterize surface properties, initial hydration, and organically modified interfaces in atomic resolution

The contribution of propagons and diffusons in heat transport through calcium-silicate-hydrates

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