The nano-branched structure of cementitious calcium–silicate–hydrate gel

Dolado, Jorge S.; Griebel, Michael; Hamaekers, Jan; Heber, Frederik

doi:10.1039/c0jm04185h

Cited by 69 publications

(57 citation statements)

References 33 publications

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“…Second, the globule disk radius R increases in samples with additives of PCE23-2 and PCE102-6. This means that when adding PCE23-2 and PCE102-6, the microstructure of CÀSÀH becomes more like the continuous extension of branched or interconnected multi-lamellar sheets, as in the models proposed by Dolado et al [17,18] and McDonald et al [19]. In addition, by fitting the SAXS data with IðQ Þ ¼ C p Â Q À4 in the range of 0.23 Å À1 < Q < 0.29 Å À1 , where the contribution from S(Q) is negligible, we found that the Porod constant C p (not shown), which is proportional to the total surface area per volume, has the trend: CÀSÀH > CÀSÀH/PCE102-2 > CÀSÀH/PCE23-6 > CÀSÀH/PCE23-2 > CÀSÀH/PCE102-6.…”

Section: Resultsmentioning

confidence: 86%

Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

Chiang

Fratini

Lim

et al. 2013

Journal of Colloid and Interface Science

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a b s t r a c tThe microstructure of calcium-silicate-hydrate (CÀSÀH) gel, a major hydrated phase of Ordinary Portland Cement, with and without polycarboxylic ether (PCE) additives is investigated by combined analyses of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) data. The results show that these comb-shaped polymers tend to increase the size of the disk-like globules but have little influence on the thickness of the water and calcium silicate layers within the globules. As a result, the fractal packing of the globules becomes more open in the range of a few hundred nanometers, in the sense that the mass fractal dimension diminishes, since the PCE adsorption on the globules increases the repulsive force between and polydispersity of the CÀSÀH units. Moreover, scanning electron microscope (SEM) study of the synthesized CÀSÀH gels in the micrometer range shows that the PCEs depress the formation of fibrils while enhancing the foil-like morphology.

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Section: Resultsmentioning

confidence: 86%

Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

Chiang

Fratini

Lim

et al. 2013

Journal of Colloid and Interface Science

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“…This could provide more insights into the connection between gels and gas-liquid behavior of colloidal systems. We would like to extend our model to study physical systems like Janus particles but also the formation of calcium-silicate-hydrate (CSH) gels formed during cement hydration [88]. In the later case, it could be interesting to mix an aggregation process with the nucleation and growth of the basic building blocks of CSH gels [89].…”

Section: Discussionmentioning

confidence: 99%

Brownian cluster dynamics with short range patchy interactions: Its application to polymers and step-growth polymerization

Prabhu

Babu

Dolado

et al. 2014

The Journal of Chemical Physics

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We present a novel simulation technique derived from Brownian cluster dynamics used so far to study the isotropic colloidal aggregation. It now implements the classical KernFrenkel potential to describe patchy interactions between particles. This technique gives access to static properties, dynamics and kinetics of the system, even far from the equilibrium. Particle thermal motions are modeled using billions of independent small random translations and rotations, constrained by the excluded volume and the connectivity. This algorithm, applied to a single polymer chain leads to correct static and dynamic properties, in the framework where hydrodynamic interactions are ignored. By varying patch angles, various chain flexibilities can be obtained. We have used this new algorithm to model step-growth polymerization under various solvent qualities. The polymerization reaction is modeled by an irreversible aggregation between patches while an isotropic finite square-well potential is superimposed to mimic the solvent quality. In bad solvent conditions, a competition between a phase separation (due to the isotropic interaction) and polymerization (due to patches) occurs. Surprisingly, an arrested network with a very peculiar structure appears. It is made of strands and nodes. Strands gather few stretched chains that dip into entangled globular nodes. These nodes act as reticulation points between the strands. The system is kinetically driven and we observe a trapped arrested structure. That demonstrates one of the strengths of this new simulation technique. It can give valuable insights about mechanisms that could be involved in the formation of stranded gels.

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“…[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%

“…Simulations of actual nanocrystals, aqueous interfaces, surface reactions, selective adsorption of organic modifiers, and assembly of nano-objects thus require classical molecular dynamics simulations and Monte Carlo simulations. 8,10,19,23,24 Such models on the basis of force fields retain all-atomic detail for up to a million atoms and access time scales up to microseconds. Simulation of yet larger systems of micrometersize particles, grinding, sedimentation, and aggregate mechanical properties is feasible using coarse-grain and continuum 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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The nano-branched structure of cementitious calcium–silicate–hydrate gel

Cited by 69 publications

References 33 publications

Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

Brownian cluster dynamics with short range patchy interactions: Its application to polymers and step-growth polymerization

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

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