Abstract
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.
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