Characterization of Cebama low-pH reference concrete and assessment of its alteration with representative waters in radioactive waste repositories

Vehmas, Tapani; Montoya, Vanessa; Alonso, C.; Vašíček, Radek; Rastrick, Emily; Gaboreau, Stéphane; Večerník, Petr; Leivo, Markku; Holt, Erika; Fink, Nicolas; Mouheb, N. Ait; Svoboda, Jiří; Read, David; Červinka, Radek; Vasconcelos, Rita G. W.; Corkhill, Claire L.

doi:10.1016/j.apgeochem.2020.104703

Cited by 12 publications

(8 citation statements)

References 42 publications

(40 reference statements)

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“…Moving on to science outcomes, numerous applications, such as for CWF of heavy elements or for concrete secondary containment walls in deep geological repositories, 49,53–55 require safety assessments relevant for long timelines 38,56 . Yet longitudinal studies of cementitious materials under relevant environmental conditions or without using aging accelerants, for example, wet/dry cycling, CO 2 , O 2 temperature, and humidity, benchmarked against true age cement metrics remain limited 57–59 …”

Section: Resultsmentioning

confidence: 99%

An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

et al. 2021

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The evolution of sulfur chemistry in cements is best known in the bailiwick of failure mechanisms via sulfate attack, but is equally important for its contributions to the reduction capacity of cementitious materials often used for immobilizing nuclear waste streams destined for long‐term storage, for example, cementitious waste forms (CWF). The total reduction capacity of CWFs, encompassing contributions from both S and Fe reductants, and its implications toward radionuclide immobilization is most often studied by destructive wet chemistry methods requiring acid digestion in the presence of Ce(IV) and subsequent titration and colorimetric interpretation. Here, we investigate a similarly analytical but nondestructive alternative, benchtop high resolution wavelength‐dispersive X‐ray fluorescence spectroscopy, most commonly known as X‐ray emission spectroscopy (XES), for probing the bulk sulfur oxidation state distribution. We present here an initial investigation of S XES, including an improved experimental protocol for lab XES of inhomogeneous samples, both as a complement to the Ce(IV) test and for new scientific opportunities that it enables for observing changes in sulfur chemistry. We discuss future improvements and opportunities, including: (1) the practical challenges associated with coordinating XES and Ce(IV) liquid extraction for a more comprehensive perspective on reduction capacity and for a high‐precision evaluation of uncertainties in the Ce(IV) test; and (2) new opportunities, due to the nondestructive nature of XES, for controlled evolution studies aimed at elucidating specific chemical responses of CWFs exposed to invasive gas or liquid species or to accelerated aging by radiative dose or thermal treatment.

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Section: Resultsmentioning

confidence: 99%

An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

et al. 2021

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“…1. Blast furnace slag is formed when iron ore or iron pellets, coke, and flux (limestone or dolomite) are melted together in a blast furnace [87]. 2.…”

Section: Compositions and Specific Co2 Uptake Potentials Of Selected Materialsmentioning

confidence: 99%

The Carbon Dioxide Emissions Reduction Potential of Carbon-Dioxide-Cured Alternative Binder Concrete

Mäkikouri

Vares

Korpijärvi

et al. 2021

RPM

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Climate change has been identified as one of the biggest issues plaguing human life at present. Hence, immense attention is being paid to developing methods that can potentially reduce carbon dioxide emission. With the help of carbon-negative concrete, manufactured from alternative binders and cured with waste carbon dioxide, a major part of the manufacturing industries that emit carbon dioxide can be potentially turned into a carbon sink. In this study, the waste material streams in Finland, suitable for disposing carbon-dioxide-cured concrete, were mapped. Mine tailings, blast furnace and steel slags, recycled concrete, biomass, coal and municipal waste incineration ashes, green liquor dregs, and foundry sands were studied. It was found that there were sufficient amounts of potential secondary raw materials (about 27 Mt/a) for the preparation of Finnish cement and the production of concrete (requirement: approximately 1.4 Mt/a and 11.2 Mt/a, respectively). The total carbon dioxide uptake potential was estimated to be approximately 1.9 Mt/a (vs. emissions from the cement industry in Finland, 0.84 Mt/a). In addition, the carbon footprints of the conventionally manufactured concrete block were compared with the carbon footprint produced by a modeled carbon-dioxide-cured blast furnace slag block. If such novel concrete were used to produce all the concrete-based substances, it would bring down the emission of carbon dioxide from 1.9% to negative 1.3% in Finland.

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“…Examples of siliceous SCMs include blast-furnace slag (BFS), fly ash (FA) and silica fume (SF), which can be used to produce encapsulating grouts for the immobilisation of specific waste streams 2 . Cements and concretes containing SF may also be used to line and plug the vaults of geological disposal facilities 3 , with significant silica addition giving rise to a C–S–H phase with a low Ca content (i.e. a lower Ca/Si ratio) 3 , 4 .…”

Section: Introductionmentioning

confidence: 99%

“…Cements and concretes containing SF may also be used to line and plug the vaults of geological disposal facilities 3 , with significant silica addition giving rise to a C–S–H phase with a low Ca content (i.e. a lower Ca/Si ratio) 3 , 4 . Addition of lime-based powders to Portland cement has been considered in the production of high-pH backfill cement for geological disposal facilities (i.e.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic identification of Ca-bearing uranyl silicates formed in C–S–H systems

Yorkshire

Stennett

Walkley

et al. 2023

Sci Rep

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Portland cement-based grouts used for radioactive waste immobilisation contain a Ca- and Si-rich binder phase, known as calcium–silicate–hydrate (C–S–H). Depending on the blend of cement used, the Ca/Si ratio can vary considerably. A range of C–S–H minerals with Ca/Si ratios from 0.6 to 1.6 were synthesised and contacted with aqueous U(VI) at 0.5 mM and 10 mM concentrations. Solid-state 29Si MAS-NMR spectroscopy was applied to probe the Si coordination environment in U(VI)-contacted C–S–H minerals and, in conjunction with U LIII-edge X-ray absorption spectroscopy analysis, inferences of the fate of U(VI) in these systems were made. At moderate or high Ca/Si ratios, uranophane-type uranyl silicates or Ca-uranates dominated, while at the lowest Ca/Si ratios, the formation of a Ca-bearing uranyl silicate mineral, similar to haiweeite (Ca[(UO2)2Si5O12(OH)2]·3H2O) or Ca-bearing weeksite (Ca2(UO2)2Si6O15·10H2O) was identified. This study highlights the influence of Ca/Si ratio on uranyl sequestration, of interest in the development of post-closure safety models for U-bearing radioactive waste disposal.

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Characterization of Cebama low-pH reference concrete and assessment of its alteration with representative waters in radioactive waste repositories

Cited by 12 publications

References 42 publications

An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

An exploration of benchtop X‐ray emission spectroscopy for precise characterization of the sulfur redox state in cementitious materials

The Carbon Dioxide Emissions Reduction Potential of Carbon-Dioxide-Cured Alternative Binder Concrete

Spectroscopic identification of Ca-bearing uranyl silicates formed in C–S–H systems

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