Influence of marine microorganisms on the permeability and microstructure of mortar.

This work investigated the inhibition of ions transporting into and out of the mortar by Pseudoalteromonas (strain B18) and Paracoccus marcusii (strain B23). Mortar samples were immersed for 154 days in sterilized seawater, 2216E liquid medium, and 2216E liquid medium containing one of the above strains. Two strains positively decelerated chloride (Cl − ) ions and magnesium (Mg 2+ ) ions in the solutions permeating into the mortar and OH − ions leaching out from the mortar. And strain B23 is stronger than strain B18 in reducing the permeation of Cl − ions and Mg 2+ ions into and the leakage of OH − ions out of the mortar. Micro structural observation revealed that the biofilm with rod-shaped bacteria covered the mortar surface. Some fibrous and colloidal substances were observed between cells. Thus, biofilm formation can lower the ion permeability of mortar samples. And it can enhance the durability of reinforced concrete (RC) structures located in tidal zones. [ABSTRACT FROM AUTHOR]