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Author(s): A. Buvignier, M. Peyre Lavigne, C. Patapy, E. Paul and A. Bertron
Paper category: Proceedings
Book title: Proceedings of the Final Conference of RILEM 253-MCI Microorganisms-Cementitious Materials Interactions Volume II
Editor(s): Alexandra Bertron and Henk Jonkers
ISBN: 978-2-35158-207-7 (Set)
ISBN: 978-2-35158-210-7 (Volume 2)
e-ISBN: 978-2-35158-206-0
Publisher: RILEM Publications SARL
Publication year: 2018
Pages: 561-562
Total Pages: 308
Language : English

Abstract: One major process of concrete-based sewer network damage is biodeterioration. By the development of biofilm on the headspace inner surface of the pipes, reduced sulfur compounds are oxidized into sulfate and acid, which lead to leaching of the cementitious material and precipitation of secondary expansive phases [1]. In sewer environment, calcium aluminate cement (CAC) based materials are more resistant than ordinary calcium silcate cement based materials [2,3]. This higher resistance is commonly explained by the content of aluminium inducing a bacteriostatic effect and/or the physico-chemical properties of CAC (neutralisation capacity, porosity, phase stability) [4]. The aim of this study was to understand the role of aluminium in the resistance to biodeterioration of calcium aluminate compared to calcium silicate cement based materials. Binders based on mixture of ordinary Portland cement (OPC) and blast furnace slag (0%, 30%, 50%, 70% and 95% of slag) were compared to CAC pastes on a lab-scale pilot test developed for biodeterioration evaluation (BAC Test) [5,6]. Binder resistance was evaluated by leaching measurements, XRD analysis and SEM observations (degraded depth evaluation). The bacterial populations were identified by biological molecular techniques during the microbial colonisation. At the end, biofilms structures were observed by a specific SEM protocol. No significant difference was observed in terms of bacterial populations and visual observations of biofilm between CAC and OPC/Slag material in favourable bacterial growth condition. The lower neutralisation capacity due to decalcification delayed the acidification (so the intensification of sulfuric acid production) of OPC based materials compared to CAC. Moreover, in reactor, sulfur-oxidizing microorganisms demonstrated a rapid adaptation to high aluminium concentrations, so a significant bacteriostatic effect of aluminium was excluded [7,8]. However, CAC based material had the lowest depth of deterioration and phases leaching. For OPC/Slag material, with increasing slag content, there was an earlier bacterial activity settlement and a lower leaching of the cement matrix and depth of deterioration. The transport phenomena were not limiting deterioration phenomena in our study (in favourable bacterial growth and aggressive deterioration conditions). The deterioration was leaded by the dissolution of the matrix. The key parameter explaining the behaviour of the cement material in the biogenic acid attack was the phase reactivity. More than a bacteriostatic effect of aluminium, the better resistance of CAC based material in the biodeterioration represented in this study wais mainly explain by the stability of the mineralogical phases in the matrix or newly formed from deterioration reactions.

Online publication : 2018
Publication type : full_text
Public price (Euros) : 0.00

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