A thermodynamic model for blended cements

Atkins, M.; Bennett, D.G.; Dawes, A.C.; Glasser, F. P.; Kindness, Andrew; Read, David

doi:10.1016/0008-8846(92)90093-b

Cited by 53 publications

(49 citation statements)

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“…From the results, strätlingite has shown compatibility with calcite, gypsum, sulfate and carbonate AFm and AFt at temperatures below about 55°C. Strätlin-gite coexistence with AFt (ettringite), has also been predicted in previous thermodynamic models [1,4].…”

Section: Strätlingite-co 3 -Afm Phase Relations: 20-85°cmentioning

confidence: 57%

Strätlingite: compatibility with sulfate and carbonate cement phases

Okoronkwo

Glasser

2015

Mater Struct

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The silicate AFm, strätlingite, has been shown to be stable in high aluminosilicate cement systems but its stability with respect to the anion content of hydrated Portland cement paste is unknown. The stability of strätlingite in the presence of sulfate and carbonate phases relevant to cement systems are reported. Results show that strätlingite persists at the sulfate activity conditioned by gypsum, ettringite and at carbonate activity conditioned by the presence of calcite, carbonate AFm, or carbonate AFt. Structural incorporation of anions such as carbonate or sulfate in strätlingite was not observed in the temperature range 20-85°C.

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Section: Strätlingite-co 3 -Afm Phase Relations: 20-85°cmentioning

confidence: 57%

Strätlingite: compatibility with sulfate and carbonate cement phases

Okoronkwo

Glasser

2015

Mater Struct

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“…The code CEMCHEM predicts the equilibrium phase distribution at 25'C, including mol% of each constituent hydrate phase, as a function of blending proportions based on the starting chemical composition for the OPC and blending agents. The range of applicability of CEMCHEM extends to 9: 1 blast furnace slag-OPC and 2:3 fly ash-OPC Additional objectives of the work of Atkins et al (1992b) and Bennett et al (1992) were to determine new equilibrium constants for cement relevant phases as upgrades to thermodynamic databases and to develop solubility models for cement phases that dissolve incongruently, such as the C-S-H. Atkins et al measured the solubilities using the repeated dispersion/ filtration technique of phases of interest synthesized in pure form. Solubility product (Y,) values were determined for C,AH, and AF,.…”

Section: A2 Studies By E P Glasser and Others At The University Of mentioning

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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“…2) and Atkins et al, 3,4) have not been experimentally confirmed as yet. It is important to confirm the behavior of Al, which is the third main component of cement, during the cement alteration process for understanding of the long-term performance of repository.…”

Section: Original Papermentioning

confidence: 99%

“…Atkins et al 3,4) undertook a more detailed study of cement alteration, taking magnesium and sulfur oxides also into account. Their model covers the thermodynamic stabilities of ettringite, hydrotalcite and gehlenite hydrate (C 2 ASH 8 ) in addition to the above main components.…”

Section: Original Papermentioning

confidence: 99%

Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

Miyamoto

Uehara

Sasoh

et al. 2006

Journal of Nuclear Science and Technology

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Application tests for advanced TEM analysis techniques were carried out to study the cement alteration processes associated with water penetration at high spatial resolution. Prior to TEM analysis, we measured the changes in the penetration coefficient and determined the characteristics of the penetrating water in order to gain a fuller understanding of the overall process. These experiments revealed that the process begins with the preferential dissolution of Ca(OH) 2 . After most of the Ca(OH) 2 is dissolved out, the penetration coefficient increases, while the pH value of the water decreases. It has been demonstrated that scanning transmission electron microscope (STEM) techniques are quite useful for determining local structures and compositions in the cement at sub-micron meter spatial resolution. The preferential dissolution of Ca ions results in refinement of cement grains. When the Ca/Si ratio decreases to 1.05, most grains have a round shape in the sub-micron range. X-ray mapping suggests the formation of 3CaOÁAl 2 O 3 Á xSiO 2 Á(6À2x)H 2 O (x¼0{3). Ettringite has been mostly dissolved out. But Mg ions remain still in form of brucite. When Ca/Si reaches 0.91, the morphology has changed to a mixture of fibers and granules. The fibers have been identified as a mixture of Calcium Silicate Hydrate Gel and silica gel. Quantitative EDX composition analyses have demonstrated that the granules are altered products of hydrogrossular, 3CaOÁAl 2 O 3 Á2SiO 2 Á2H 2 O, which have been predicted by previous theoretical studies. It is also been shown that hydrotalcite with Mg and Al has been also formed. The results thus obtained are in principle in accordance with the process predicted by previously proposed thermodynamic models.

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A thermodynamic model for blended cements

Cited by 53 publications

References 1 publication

Strätlingite: compatibility with sulfate and carbonate cement phases

Strätlingite: compatibility with sulfate and carbonate cement phases

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

Characterization of Cement Alteration Process by Transmission Electron Microscopy with High Spatial Resolution

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