Microbial biofilm communities associated with degradation of sprayed concrete in subsea tunnels
microbially induced deterioration
Chalmers, Arkitektur och samhällsbyggnadsteknik, Vatten Miljö Teknik
Microbial attack on subsea sprayed concrete
International RILEM Conference on Microorganisms-Cementitious Materials Interactions,; (2016)p. 63-75
Paper i proceeding
Subsea tunnel reinforced sprayed concrete subjected to deterioration harbours distinct microbial communities
Biofouling,; Vol. 34(2018)p. 1161-1174
Artikel i vetenskaplig tidskrift
Sabina Karačić, Carolina Suarez, Per Hagelia, Frank Persson, Oskar Modin, Britt-Marie Wilén. Using metagenomics to understand sprayed concrete biodeterioration in a subsea road tunnel.
Sabina Karačić, Oskar Modin, Per Hagelia, Frank Persson, and Britt-Marie Wilén. The role of time and surface type on the development of biofilm communities on concrete exposed to seawater (submitted)
In this thesis, it was investigated how microorganisms degrade concrete structures in marine environments, which is a large societal problem with enormous economic impact. In marine and fresh waters, microorganisms such as bacteria, algae and fungi, often grow on surfaces and form thin layers of biofilm. When microorganisms grow they form various acidic compounds. Biofilms growing on concrete can therefore deteriorate and even dissolve the cement, the binding material in the concrete. In the Oslofjord subsea tunnel, microbial activity together with abiotic attack from saline ground water are responsible for degradation of the sprayed concrete used for rock support and for corrosion of the steel fibers used to reinforce the concrete. Difficulties isolating specific microorganisms from the biofilm in order to analyse their effect on concrete biodegradation and separating various biotic and abiotic degradation processes are main reasons for the limited knowledge in this field. In this thesis, molecular methods were used to address these issues.
High throughput amplicon sequencing of 16S rRNA genes together with metagenomics shotgun sequencing revealed that microbial communities at the Oslofjord subsea tunnel concrete were composed of nitrogen converting bacteria, iron-oxidizing bacteria, sulfur oxidizing bacteria, heterotrophic aerobic bacteria, putative manganese-oxidizing bacteria and microorganisms that could not be assigned to any function. Scanning electron microscopy (SEM) together with X-ray power diffraction (XRD) analyses were used to investigate subsea tunnel concrete degradation beneath the biofilms over time. Water chemical analysis and microsensor measurements of oxygen and pH profiles within the biofilm were performed on-site to assess environmental conditions in the biofilms. In parallel, a mesocosm experiment which simulates the condition when cement is exposed to seawater, was performed over a period of 65 weeks to study the role of concrete material properties and fiber reinforcement for biofilm formation and microbial composition.
The results obtained in this thesis help us to understand the complexity of microbial induced concrete deterioration and corrosion of steel fiber reinforcement observed in the subsea tunnels.
The role of microbiol. biofilm communities for degradation of sprayed concr. in subsea tunnels
Statens vegvesen (2011 067932), 2014-10-14 -- 2018-12-31.
Biokemi och molekylärbiologi
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5027
Zoom; ACE Room SB-K373, Chalmers
Opponent: Associate Professor Torben Lund Skovhus, VIA University College, Research Centre for Built Environment, Energy, Water and Climate, Denmark.