Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
C, O and S isotopic signatures in concretes which have suffered thaumasite formation and limited thaumasite form of sulfate attack
Thaumasite formation (TF) and limited Thaumasite sulfate attack (TSA) has recently been discovered in sprayed concretes in contact with pyrrhotite-, pyrite- and calcite bearing Alum Shale in Oslo. Several types of calcite occur, including internal Popcorn calcite formed by replacement of both thaumasite and calcium silicate hydrate (CSH). In an attempt to throw further light on the origin of carbonates and sulfates involved, we have used the laser ablasion probe to characterise these secondary minerals with respect to stable isotopes (C, O and S). Mitigation as well as repair may in several cases depend much on correct characterisation and location of the fluids provenance, and stable isotopic characterisation may be an appropriate tool to do so. The preliminary results of this study indicate a complex open system with influence of fluids from several sources. There is a general difference in signatures between ordinary surface carbonation and internal carbonation associated with thaumasite. Calcite deposits within the Alum Shale/concrete contact zone show highly variable isotopic signatures reflecting a composite origin, probably significantly influenced by atmospheric CO2. The sulfur isotopes in thaumasite are much lighter than the Alum Shale constituents. This might possibly be explained by a contribution from atmospheric SO2, or alternatively by sulfide oxidation in Alum Shale assisted by bacterial activity.
C, O and S isotopic signatures in concretes which have suffered thaumasite formation and limited thaumasite form of sulfate attack
Thaumasite formation (TF) and limited Thaumasite sulfate attack (TSA) has recently been discovered in sprayed concretes in contact with pyrrhotite-, pyrite- and calcite bearing Alum Shale in Oslo. Several types of calcite occur, including internal Popcorn calcite formed by replacement of both thaumasite and calcium silicate hydrate (CSH). In an attempt to throw further light on the origin of carbonates and sulfates involved, we have used the laser ablasion probe to characterise these secondary minerals with respect to stable isotopes (C, O and S). Mitigation as well as repair may in several cases depend much on correct characterisation and location of the fluids provenance, and stable isotopic characterisation may be an appropriate tool to do so. The preliminary results of this study indicate a complex open system with influence of fluids from several sources. There is a general difference in signatures between ordinary surface carbonation and internal carbonation associated with thaumasite. Calcite deposits within the Alum Shale/concrete contact zone show highly variable isotopic signatures reflecting a composite origin, probably significantly influenced by atmospheric CO2. The sulfur isotopes in thaumasite are much lighter than the Alum Shale constituents. This might possibly be explained by a contribution from atmospheric SO2, or alternatively by sulfide oxidation in Alum Shale assisted by bacterial activity.
C, O and S isotopic signatures in concretes which have suffered thaumasite formation and limited thaumasite form of sulfate attack
Iden, I.K. (Autor:in) / Hagelia, P. (Autor:in)
2002
10 Seiten, 5 Bilder, 1 Tabelle, 19 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
| British Library Conference Proceedings | 2003
TESTING - Thaumasite form of sulfate attack
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