Aqueous chemistry and thermodynamic modelling of CaO–SiO<sub>2</sub>–H<sub>2</sub>O gels

Atkinson, A.; Hearne, J. A.; Knights, C.F.

doi:10.1039/dt9890002371

Cited by 39 publications

(24 citation statements)

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“…Therefore it is hard to say which one is better. However, the models proposed by (Atkinson et al, 1989), (Kersten, 1996), (Kulik and Kersten, 2001) and (Carey and Lichtner, 2006) are applicable over a wider range of C/S ratio than those of others.…”

Section: Carbonation Of Calcium Silicate Hydrates (C-s-h) 31mentioning

confidence: 99%

“…Several possible values are reported in the literature. (Atkinson et al, 1989) used two non-ideal solid solutions to describe the behavior of C-S-H, based on experimental data from (Greenberg and Chang, 1965). For C/S≤0.8, end-members were chosen as S -nC·S·mH (amorphous silica -"tobermorite") and for C/S>0.8, end-members were chosen as nC·S·mH -CH ("tobermorite" -portlandite), where n = 0.833 and m = 0.917.…”

Section: Carbonation Of Calcium Silicate Hydrates (C-s-h) 31mentioning

confidence: 99%

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Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Shen

2013

International Journal of Greenhouse Gas Control

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RésuméUn modèle de transport réactif est proposé pour simuler la réactivité des matériaux à base de ciment en contact avec une saumure saturée en CO 2 et/ou le CO 2 supercritique (CO 2 sc) dans les conditions de stockage géologique du CO 2 . Un code a été développé pour résoudre simultanément le transport et la chimie par une approche globale couplée, compte tenu de l'effet de la température et de la pression.La variabilité des propriétés du CO 2 sc avec la pression et la température, telles que la solubilité dans l'eau, la densité et la viscosité sont pris en compte. On suppose que tous les processus chimiques sont en équilibre thermodynamique. Les réactions de dissolution et de précipitation de la portlandite (CH) et Ce modèle est en mesure de simuler les processus de carbonatation des matériaux à base de ciment, dans des conditions à la fois saturés et insaturés, dans une large plage de concentration de CO 2 , de température et de pression. Plusieurs expériences, rapportées dans la littérature, sont simulées en utilisant divers types de conditions aux limites: (i) solutions saturées ou non en CO 2 et carbonate de calcium, (ii) gas supercritique de CO 2 . Les prédictions sont comparées avec les observations expérimentales. Certains II phénomènes observés expérimentalement peuvent être également expliqués par le modèle. Mots-clés:Carbonatation, CO 2 supercritique, Transports, Ciment, C-S-H, Décalcification, Pression, Température, Stockage du CO 2 . AbstractA reactive transport model is proposed to simulate the reactivity of cement based material in contact with CO 2 -saturated brine and supercritical CO 2 (scCO 2 ) under CO 2 geological storage conditions. This code is developed to solve simultaneously transport and chemistry by a global coupled approach, considering the effect of temperature and pressure.The variability of scCO 2 properties with pressure and temperature, such as solubility in water, density and viscosity are taken into account. It is assumed that all chemical processes are in thermodynamical equilibrium. Dissolution and precipitation reactions for portlandite (CH) and calcite (CC) are described by mass action laws and threshold of ion activity products in order to account for complete dissolved minerals. A chemical kinetics for the dissolution and precipitation of CH and CC is introduced to facilitate numerical convergence. One properly chosen variable is able to capture the precipitation and dissolution of the relevant phase. A generalization of the mass action law is developed and applied to calcium silicate hydrates (C-S-H) to take into account the continuous variation (decrease) of the Ca/Si ratio during the dissolution reaction of C-S-H. The changes in porosity and microstructure induced by the precipitation and dissolution reactions are also taken into account.Couplings between transport equations and chemical reactions are treated thanks to five mass balance equations written for each atom (Ca, Si, C, K, Cl) as well as one equation for charge balance and one for the total mass. Ion tran...

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Section: Carbonation Of Calcium Silicate Hydrates (C-s-h) 31mentioning

confidence: 99%

Section: Carbonation Of Calcium Silicate Hydrates (C-s-h) 31mentioning

confidence: 99%

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Shen

2013

International Journal of Greenhouse Gas Control

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“…The predictions indicate that the main influence of aluminum was to promote formation of a hydrogarnet solid solution of general composition C,Al,,S,. Atkinson et al (1991a) completed solubility studies at 80'C of gels for the CaO-Si0,-H,O system to derive their thermodynamic properties. Detailed descriptions of the experimental methods, including synthesis of materials and phase characterization, were provided.…”

Section: B2 Studies By a Atkinson And Others At Hanvell Laboratorymentioning

confidence: 99%

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

Krupka¹,

Serne²

1998

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C o p k r o f h b r t r y~m d r t n d v d r u n d h 8~m m r h t h . N R C~~r AbstractThe U.S. Nuclear Regulatory Commission (NRC) is developing a technical position document that provides guidance regarding the performance assessment of low-level radioactive waste (LLW) disposal facilities. This guidance includes considerations associated with the chemical environment of the vault disposal system and the effects this system may have on the release and mobility of radionuclides. Because the disposal system will contain cementitious materials as structural, waste form, andor bacld'ill materials, the geochemical properties of pore waters buffered by reactions with cement will be very different from those waters associated with the local soil and geology. This environment therefore needs to be considered within the source term calculations if credit is taken for solubility limits andor distribution coefficients for -dissolved radionuclide concentrqtions within disposal units. Geochemical modeling may be used to assess potential chemical conditions in concrete vault disposal units and associated effects on aqueous speciation, solubilities, and sorption of radionuclides that are released from the waste form.In support of NRC7s development of this technical position, two literature reviews were done on information related to the chemical environments associated with the interaction of water with cementitious materials. One review was conducted on methods and associated solid-phase assemblages used to model the composition of pore water resulting from reaction with cementitious materials used in a disposal vault. This literature review also included related information on experimental studies of cemendwater systems, natural analogue studies of cement and concrete, and radionuclide solubilities experimentally determined in cement pore fluids.Based on the results of .this review, geochemical modeling was used to demonstrate the calculation of conservative maximum concentrations for dissolved americium, neptunium, nickel, plutonium, radium, strontium, thorium, and uranium with respect to key geochemical input parameters for two ground-water environments associated with the disposal system. These environments include 1) a cement buffered system, wherein the leachate pH is controlled at values above 10 by the effective buffering capacity of the concrete; and 2) a ground-water buffered system, wherein the leachate pH and related solution parameters are dominated by the local ground-water system.Another literature review was completed on the available data for the sorption potential of selected LLW radionuclides onto "fresh" cement/concretewhere the expected pH of the cement pore waters will equal or exceed 10. The review included data for the radionuclides americium, inorganic carbon, chlorine, iodine, lanthanide elements, niobium, nickel, neptunium, plutonium, radium, strontium, technetium, thorium, and uranium. Based on information gleaned from the literature, a database was developed of preferred minimum distribution coeff...

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“…One can also represent the part of a phase diagram that pertains to Table I) into account. The useful thermodynamic data were found in various bibliographical sources: [5] for the CSH minerals, [6] for portlandite, amorphous silica, ettringite, and calcium monosulfoaluminate, [7] for calcite. The choice of thermodynamic data is discussed in [2].…”

Section: Methodsmentioning

confidence: 99%

Use of thermodynamic chemical potential diagrams (µCaO, µCO2) to understand the weathering of cement by a slightly carbonated water

2008

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Cement is a ubiquitous material that may suffer hazardous weathering. The chemical weathering of cement in natural environment is mostly characterized by the leaching of CaO and the addition of CO 2 . The different weathering zones that develop at the expense of the cement may be predicted by the help of chemical potential phase diagrams; these diagrams simulate the behaviour of systems open to some chemical elements. Some components have a so-called inert status, that is to say the system is closed for these components, their amount in the system remains constant; some other components have a mobile status, that is to say these components can be exchanged with the outside of the system, their amount can vary from one sample zone to another. The mobile components are represented in the model by their chemical potentials (linked to their concentrations) that are variable in the external environment. The main features of the weathering of a cement system open to CaO and CO 2 are predicted in a phase diagram with µCaO et µCO 2 as diagram axes. From core to rim, one observes the disappearance of portlandite, ettringite and calcium monosulfoaluminate, the precipitation of calcite and amorphous silica, the modification of the composition of the CSH minerals (hydrated calcium silicates) that see a decrease of their c/s ratio (CaO/SiO 2 ) from the core to the rim of the sample. For the CSH minerals, we have separated their continuous solid solution into three compositions defined by different CaO/SiO 2 ratios and called phases 1, 2 and 3: CaO = 0.8, 1.1, 1.8 respectively for one mole of SiO 2 knowing that H 2 O varies in the three compositions.

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Aqueous chemistry and thermodynamic modelling of CaO–SiO₂–H₂O gels

Cited by 39 publications

References 1 publication

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

Use of thermodynamic chemical potential diagrams (µCaO, µCO2) to understand the weathering of cement by a slightly carbonated water

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Aqueous chemistry and thermodynamic modelling of CaO–SiO2–H2O gels

Cited by 39 publications

References 1 publication

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Reactive transport modeling of CO2 through cementitious materials under CO2 geological storage conditions

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

Use of thermodynamic chemical potential diagrams (µCaO, µCO2) to understand the weathering of cement by a slightly carbonated water

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Aqueous chemistry and thermodynamic modelling of CaO–SiO₂–H₂O gels