Mineralogical characterization of the alteration layer of chemically and biologically altered cementitious materials

Author(s): T. Pons, C. Fourdrin, A. Grandclerc, M. Gueguen-Minerbe, M. Tarrida, M. Peyre Lavigne, E. van Hullebusch, T. Chaussadent and Y. Pechaud
Paper category: Proceedings
Book title: Proceedings of the Final Conference of RILEM 253-MCI Microorganisms-Cementitious Materials Interactions Volume I
Editor(s): Alexandra Bertron and Henk Jonkers
ISBN: 978-2-35158-207-7 (Set)
ISBN: 978-2-35158-209-1 (Volume1)
e-ISBN: 978-2-35158-206-0
Publisher: RILEM Publications SARL
Publication year: 2018
Pages: 11-21
Total Pages: 288
Language : English

Abstract: In the context of biocorrosion of concrete sewer pipes, this study aims at characterizing the alteration layers present on different types of cementitious materials (ordinary Portland cement: CEM I, blended Portland cement: CEM III, calcium aluminate cement: CAC). The studied samples resulted from laboratory expositions to H2S under abiotic and biotic conditions from a bio-deterioration test ([H2S] = 30 ppm; T = 30°C; RH = 100%).
For both exposure conditions, cross sections of mortar slices were first chemically characterized using SEM-EDS to obtain elemental mapping. Chemical analysis evidenced an enrichment of Ca and S for CEM I and CEM III samples, suggesting the formation of gypsum at the surface of the alteration layer. For CAC samples, an enrichment of S and Al and in a
minor extent of Ca was observed.
To further investigate the sulphur-bearing phases, μ-Raman maps were performed on the altered areas. For the CEM I and CEM III mortars under the abiotic conditions, the altered layer was composed by the following distribution: (i) at the surface the main phase was hannebachite (CaSO3.1/2H2O), (ii) calcite was observed either in co-precipitation with hannebachite or in a underlying layer. Finally, for the CAC mortar, aluminum hydroxides (AH3) were observed at the surface followed by a co-precipitation of hannebachite and calcite.
Under biotic conditions, gypsum was evidenced as the main sulphur-bearing phase, while hannebachite was not observed in the studied samples (CEM I, CEM III, CAC). Those results highlight the bacterial contribution in the gypsum formation.
Besides, the results obtained, by a deeper description of the phases in presence, are expected to allow an improvement of the understanding of the alteration mechanisms and in turn could be implemented in mechanistic models.

Online publication : 2018
Publication type : full_text
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