Microbiologically induced concrete corrosion: A case study from a combined sewer network

Abstract

In this study, a strongly deteriorated concrete-based sewer system was investigated by using a multi proxy approach based on gaseous, hydro-geochemical, microbiological, mineralogical and mechanical analyses. Therefore, gas, liquid, and solid samples were taken throughout the entire sewer system. Long term measurements of gaseous hydrogen sulfide (H 2 S) within the sewer atmosphere yielded concentrations up to 367 ppm. Interstitial fluids, extracted from deteriorated concrete by squeezing, contained sulfate (SO 4 2− ) concentrations of up to 104 g l −1 at strong acidic conditions (0.7 N pH N 3.1) and are close to the saturation state of gypsum. This sulfuric acid attack is indicative for a well-established biofilm containing sulfide oxidizing bacteria (SOB), which was analyzed to consist mainly of Acidithiobacillus thiooxidans. The micro-structure of the attacked concrete displays a progressing alteration zone, which is caused by microbially induced concrete corrosion (MICC), with a suggested pH gradient from about 13 to b 1, from the intact inner concrete zone to the outermost heavily deteriorated concrete. Calcium sulfate minerals such as gypsum (CaSO 4 · 2H 2 O), bassanite (CaSO 4 · 1/2H 2 O) and anhydrite (CaSO 4 ) are abundant in the altered concrete, which were formed from the dissolution of the cement phases and Ca-bearing aggregates. Remarkably high corrosion rates of different precast concrete manholes were quantified to reach values greater than 1 cm yr −1 , despite the fact that C 3 A-free cement, fly ash and a w/c of~0.35 was used.

Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments

“…From a larger specimen a 4x4x8 cm 3 prim was cut before placing it for 12 months in a sewer system, strongly affected by biogenic acid corrosion. A detailed characterization of the exposure system is given elsewhere [26,27]. In brief, prevailing environmental conditions comprised r.h. levels of between 80 and 100% and high concentrations of hydrogen sulfide (H 2 S) (average of 34 ppm; peak levels of 350 ppm) and CO 2 (1000 to 6200 ppm).…”

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

“…In order to visualize the microbial distribution within the deterioration layers fluorescent staining and imaging was performed. A detailed description of the sewer system, including concrete properties, corrosion rates, wastewater chemistry, microbial aspects and interstitial fluid chemistry has been recently described in [8]. A schematic description of the analytical methods applied for the model generation is presented in Fig.…”

“…The cementitious matrix of non-corroded concrete was dominated by Ca and Si rich phases like portlandite (Ca(OH)2) and calcium silicate hydrates (C-S-H phases), framing siliceous and carbonate aggregates. The transition zone (TZ) between non-corroded and strongly affected concrete was characterized by an extreme drop in pH from 13 to below 1 with a reaction front of around 1 mm (for detail on pore fluid chemistry see Grengg et al 2015). 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.…”

“…2.). In fact, described in situ acid production at and close to the corrosion front has to be recognized as one central factor, steering high corrosion rates of about 1 cm yr -1 and associated failure of parts of the sewer system after a service life of 10 years [5,8].…”

Using computational fluid dynamics to describe H2S mass transfer across the water–air interface in sewers

“…A combined attack of the cement stone mineral's chemical dissolution and of expansive mineral formation (e.g. gypsum) can result in corrosion rates up to 1 cm yr -1 or higher, even for concretes developed for such conditions (Grengg et al, 2015).…”