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242 results on '"Lothenbach B"'

5. Iron speciation in blast furnace slag cements

Author

Mancini, A, Lothenbach, B, Geng, G, Grolimund, D, Sanchez, DF, Fakra, SC, Dähn, R, Wehrli, B, and Wieland, E

Subjects
Civil Engineering, Engineering, Built Environment and Design, Building, Chemical Engineering, Building & Construction, Civil engineering, Materials engineering
Abstract

Slag-containing pastes and concretes were analysed by element-specific synchrotron-based techniques to determine the speciation of iron on crushed materials through spatially resolved micro-spectroscopic studies. The investigated cement samples were hydrated either in the laboratory, or exposed to river or sea water. Metallic iron, along with minor proportions of iron sulphide and magnetite was detected in the laboratory sample. Iron sulphide, goethite, and siliceous hydrogarnet were discovered in the blended slag cements hydrated in contact with river water for up to 7 years. In contrast, no Fe(0) was observed in blended concretes exposed to sea water. Instead, iron sulphide, iron(II)-hydroxide and -oxide, hematite, magnetite, siliceous hydrogarnet, and goethite were detected as well as ilmenite (FeTiO3) in the aggregates. The strong acceleration of Fe oxidation in samples exposed to sea water and the long-term passivation observed in the other samples indicate comparable processes as those occurring on steel bars.

Published
2021

17. Retention and diffusion of radioactive and toxic species on cementitious systems: Main outcome of the CEBAMA project

Author

Grambow, B., López-García, M., Olmeda, J., Grivé, M., Marty, N.C.M., Grangeon, S., Claret, F., Lange, S., Deissmann, G., Klinkenberg, M., Bosbach, D., Bucur, C., Florea, I., Dobrin, R., Isaacs, M., Read, D., Kittnerová, J., Drtinová, B., Vopálka, D., Cevirim-Papaioannou, N., Ait-Mouheb, N., Gaona, X., Altmaier, M., Nedyalkova, L., Lothenbach, B., Tits, J., Landesman, C., Rasamimanana, S., and Ribet, S.

Published
2020
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22. Effect of ISA and chloride on the uptake of niobium(V) by hardened cement paste and C-S-H phases: quantitative description and mechanistic understanding

Author

Jo, Y., Çevirim-Papaioannou, N., Franke, K., Fuss, M., Pedersen, M., Lothenbach, B., Blochouse, B., Altmaier, M., Gaona, X., Jo, Y., Çevirim-Papaioannou, N., Franke, K., Fuss, M., Pedersen, M., Lothenbach, B., Blochouse, B., Altmaier, M., and Gaona, X.

Abstract

The uptake of niobium by hardened cement paste (HCP) a calcium silicate hydrate (C-S-H) phases was investigated with ⁹³Nb and ⁹⁵Nb (t₁/₂=35.0 days). Structural materials used in nuclear reactors as well as cements contain the naturally occurring isotope ⁹³Nb, while radioactive ⁹⁴Nb with t₁/₂=2×10⁴ years is relevant in the context of nuclear waste disposal. Strong uptake of Nb was observed for both materials, confirming that C-S-H are the main sink of Nb in cement. Isotopic exchange with ⁹³Nb in cement can play a role in the uptake of ⁹⁴Nb under repository conditions. The formation of complexes with isosaccharinic acid (ISA) decreases the Nb uptake, although sorption remains strong up to [ISA]tot=0.1 M. Chloride has a negligible effect on the uptake of Nb up to [NaCl] = 2 M. This work provides a sound basis for the quantitative description and mechanistic understanding of ⁹⁴Nb retention in L/ILW repositories.

Published
2023

23. Data publication: Effect of ISA and chloride on the uptake of niobium(V) by hardened cement paste and C-S-H phases: quantitative description and mechanistic understanding

Author

Jo, Y., Çevirim-Papaioannou, N., Franke, K., Fuss, M., Pedersen, M., Lothenbach, B., Blochouse, B., Altmaier, M., Gaona, X., Jo, Y., Çevirim-Papaioannou, N., Franke, K., Fuss, M., Pedersen, M., Lothenbach, B., Blochouse, B., Altmaier, M., and Gaona, X.

Abstract

This dataset is a report about gamma spectroscopy measurement of the irradiated cyclotron target generated by GammaVision software (ORTEC/AMETEK, Version 8.00.03).

Published
2023

47. Calcium sulfoaluminate sodalite (Ca4Al6O 12SO4) crystal structure evaluation and bulk modulus determination

Author

Hargis, CW, Moon, J, Lothenbach, B, Winnefeld, F, Wenk, HR, and Monteiro, PJM

Subjects
Materials, Materials Engineering, Mechanical Engineering
Abstract

The predominant phase of calcium sulfoaluminate cement, Ca 4(Al6O12)SO4, was investigated using high-pressure synchrotron X-ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al 6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O 12)SO4. The compressibility of Ca4(Al 6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O 12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H 2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate. © 2013 The American Ceramic Society.

Published
2014

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