Ettringite surface chemistry: Interplay of electrostatic and ion specificity

Mędala, Marta; Labbez, Christophe; Pochard, Isabelle; Nonat, André

doi:10.1016/j.jcis.2010.11.031

Cited by 26 publications

(8 citation statements)

References 32 publications

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“…This new simulation algorithm has been applied to the simulation of the charged solid/liquid interfaces of calcium silicate hydrate 25,28 and clay particles. 26,[29][30][31][32] The simulations show good agreement with experimental data. In particular, they show the overcharging process with divalent ions 30 which is a well-known phenomenon that can only be explained by moving beyond typical mean-field theories.…”

Section: Introductionsupporting

confidence: 67%

A semi-grand canonical Monte Carlo simulation model for ion binding to ionizable surfaces: Proton binding of carboxylated latex particles as a case study

Madurga

Rey-Castro²,

Pastor³

et al. 2011

The Journal of Chemical Physics

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In this paper, we present a computer simulation study of the ion binding process at an ionizable surface using a semi-grand canonical Monte Carlo method that models the surface as a discrete distribution of charged and neutral functional groups in equilibrium with explicit ions modelled in the context of the primitive model. The parameters of the simulation model were tuned and checked by comparison with experimental titrations of carboxylated latex particles in the presence of different ionic strengths of monovalent ions. The titration of these particles was analysed by calculating the degree of dissociation of the latex functional groups vs. pH curves at different background salt concentrations. As the charge of the titrated surface changes during the simulation, a procedure to keep the electroneutrality of the system is required. Here, two approaches are used with the choice depending on the ion selected to maintain electroneutrality: counterion or coion procedures. We compare and discuss the difference between the procedures. The simulations also provided a microscopic description of the electrostatic double layer (EDL) structure as a function of pH and ionic strength. The results allow us to quantify the effect of the size of the background salt ions and of the surface functional groups on the degree of dissociation. The non-homogeneous structure of the EDL was revealed by plotting the counterion density profiles around charged and neutral surface functional groups.

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Section: Introductionsupporting

confidence: 67%

A semi-grand canonical Monte Carlo simulation model for ion binding to ionizable surfaces: Proton binding of carboxylated latex particles as a case study

Madurga

Rey-Castro²,

Pastor³

et al. 2011

The Journal of Chemical Physics

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“…This interpretation is consistent with the reported C 3 A dissolution-inhibiting action of PNS 13,32 because the adsorption of macromolecules such as PNS would facilitate the blocking of reactive surface sites. The zeta potential results would then suggest that the adsorption of PNS onto solid reaction products is also likely, particularly onto phases such as ettringite 34 and AFm 44 that specifically complex SO 4 2− (the latter of which precipitates here, see section 3.2), because the chemistry of SO 4 2− and −SO 3 − functional groups in PNS is similar. 45 Existing research shows that PNS alters the chemistry and morphology of ettringite, 33,46 consistent with this interpretation.…”

Section: Resultsmentioning

confidence: 93%

“…The positions of the features in the RSFs for the C3A samples ( Figure 4C although this assignment cannot be made due to the preliminary nature of the analysis presented here. Additional work, e.g., molecular simulations 34 and/or an extension of this Ca EXAFS analysis through use of model adsorbate molecular structures and a better understanding of the chemistry of partially-dissolved C3A is necessary to better determine the cause of this difference.…”

Section: Ca K-edge Xasmentioning

confidence: 99%

“…S and Ca K-edge XAS and zeta potential results are also obtained and discussed for key solid phases in the C3A-CaSO4-H2O system, which have generally not yet been comprehensively analysed. 15,33,34,35 Morphological information of partially-dissolved C3A…”

Section: Introductionmentioning

confidence: 99%

“…This analysis represents a first attempt at simultaneously characterizing S and Ca K -edge XAS data of C 3 A dissolution in aqueous CaSO 4 solutions, which is important to understanding and developing model molecular structures for S and Ca adsorbates on calcium aluminate hydrates. S and Ca K -edge XAS and zeta potential results are also obtained and discussed for key solid phases in the C 3 A-CaSO 4 -H 2 O system, which have generally not yet been comprehensively analyzed. ,− Morphological information on partially dissolved C 3 A particles is obtained by scanning electron microscopy (SEM) and complementary X-ray ptychographic imaging at the Advanced Light Source (ALS) . This article aims to unify these results to provide an advanced description of the surface chemistry of partially dissolved C 3 A and insight into the rate-controlling mechanism of C 3 A dissolution in PC-relevant aqueous solutions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Role of Adsorption Phenomena in Cubic Tricalcium Aluminate Dissolution

et al. 2016

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The workability of fresh Portland cement (PC) concrete critically depends on the reaction of the cubic tricalcium aluminate (CA) phase in Ca- and S-rich pH >12 aqueous solution, yet its rate-controlling mechanism is poorly understood. In this article, the role of adsorption phenomena in CA dissolution in aqueous Ca-, S-, and polynaphthalene sulfonate (PNS)-containing solutions is analyzed. The zeta potential and pH results are consistent with the isoelectric point of CA occurring at pH ∼12 and do not show an inversion of its electric double layer potential as a function of S or Ca concentration, and PNS adsorbs onto CA, reducing its zeta potential to negative values at pH >12. The S and Ca K-edge X-ray absorption spectroscopy (XAS) data obtained do not indicate the structural incorporation or specific adsorption of SO on the partially dissolved CA solids analyzed. Together with supporting X-ray ptychography and scanning electron microscopy results, a model for CA dissolution inhibition in hydrated PC systems is proposed whereby the formation of an Al-rich leached layer and the complexation of Ca-S ion pairs onto this leached layer provide the key inhibiting effect(s). This model reconciles the results obtained here with the existing literature, including the inhibiting action of macromolecules such as PNS and polyphosphonic acids upon CA dissolution. Therefore, this article advances the understanding of the rate-controlling mechanism in hydrated CA and thus PC systems, which is important to better controlling the workability of fresh PC concrete.

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