The decisive role of acidophilic bacteria in concrete sewer networks: A new model for fast progressing microbial concrete corrosion

Microbial induced acid corrosion from a field perspective - Advances in process understanding and construction material development

“…This reaction front is characterized by dynamic dissolution and precipitation reactions, determined by single mineral stability ranges which could be observed in element distributions and high resolution spot analyses of the mineralogical compositions. Opposed to current hypothesis [9, 10] microorganisms within this system were not limited to the uppermost layers of the deteriorated concrete, but were distributed throughout the entire corrosion front [5]. Acidithiobacillus ferrooxidans was isolated from the deteriorated concrete and could be linked with Fe accumulation zones within the deeper, anoxic to anaerobic corrosion layers, thereby proving H2SO4 production on site at and close to the corrosion front thus strongly affecting corrosion dynamics.…”

“…As presented by Grengg et al (2017) the novel model intertwined biological, mineralogical and hydrochemical factors, which resulted in a dynamic micro-system, dominated by ongoing mineral dissolution and reprecipitation and subordinated microbial distribution, ultimately controlled by pH and aqueous diffusion [5]. Element mappings of Al, Ca, Fe, Mg, S and Si throughout these corrosion fronts revealed a clearly defined element succession path controlled by diffusion of dissolved species and pH (Fig.…”

“…Samples were stabilized using a two-component epoxy resin. Subsequent mineralogical and microbiological analytics were performed as described in detail by Grengg et al (2017). In brief, thick sections containing the up to 4 cm thick corrosion layers were prepared for high resolution light microscopy and EPMA elemental mappings and high resolution spot analyses using micro-XRD.…”

“…Thereby, Fe 3+ , present in iron hydroxides and sulfates, e.g. goethite and lepidocrocite, gets reduced to Fe 2+ during oxidation of reduced sulfur compounds at strongly acidic conditions [5]. Accordingly, the central role of iron regarding bioreceptivity and associated durability of concrete affected by MICC should be emphasized.…”

“…Limited information is found in the literature describing MICC processes drawn from field studies and field observations. This work presents a new conceptual model describing crucial process aspect within advanced MICC, from a field perspective, intertwining analytics of spatial microbial distributions with chemical, mineralogical and (micro)structural related aspects [5]. Gained in depth knowledge of the physicochemical construction material characteristics and their impact regarding biofilm adhesion, development and structure form the basis for continuative development of suitable materials.…”