Durability of concrete exposed to laboratory-simulated marine microbe-induced corrosion

Laboratory-simulated, microbially induced corrosion was induced to assess concrete durability in seawater. Biotic test group (BTG) specimens with sulphur-oxidizing bacteria (SOB) and abiotic control group (ACG) specimens without SOB were corroded for 8 months in seawater medium containing thiosulphate. Concrete erosion by microorganisms was determined by changes in pH and sulphate ion concentrations. The ACG surfaces were slightly weathered and broken, while the BTG specimens were severely deteriorated, with pitting and material losses along the edge. After 8 months, the pH of the BTG medium decreased from 11.4 to 9.65, and its neutralisation depth was 12.4 mm: approximately 1.75 and 2.3 times, respectively, that of ACG. The ACG specimens had better frost resistance after 100 freeze-thaw cycles. The biofilm was selective for incoming ions and slowed chloride ion penetration, with the BTG specimens having better resistance. Additionally, XRD, SEM, and electrochemical impedance (EIS) analyses showed that the biological sulphuric acid caused concrete dissolution of hydration products and crystalline swelling of sulphate minerals and increased porosity, leading to concrete deterioration.

Automated summary

Laboratory-simulated microbially induced corrosion was conducted to evaluate the durability of concrete in seawater. Sulphur-oxidizing bacteria (SOB) were used in the biotic test group (BTG) specimens, while the abiotic control group (ACG) specimens did not contain SOB. The BTG specimens exhibited severe deterioration with pitting and material losses, while the ACG specimens only showed slight weathering and breakage. The study also found that the biological effects caused concrete dissolution, crystalline swelling, and increased porosity, leading to concrete deterioration.