Adhesion Dynamics of Ulva -Diatom Biofilms on Mortar Surfaces in Dynamic Marine Environments and Their Mechanistic Roles in Substrate Performance Deterioration

Considering that current research on biocorrosive building materials is predominantly conducted through field exposure in marine environments or static laboratory cultivation, field tests struggle to achieve precise quantification of individual biological species’ effects on concrete. Meanwhile, experimental studies on the impact of cultured marine fouling organisms on concrete remain in the nascent phase of static cultivation. To address these challenges and better simulate the natural marine environment, this study incorporates a wave pump within an incubator to create dynamic flow conditions. We investigate the evolution of biofilm adhesion on mortar surfaces under this dynamic environment and analyze its effects on the structural integrity and durability of the mortar. Experimental results demonstrated that flow conditions enhance the photosynthetic and metabolic activities of the U l v a - diatom biofilm organisms, significantly influencing the pH and dissolved oxygen levels of the water. Furthermore, the adhesion of the U l v a - diatom biofilm in the dynamic environment detrimentally affects the mortar’s mechanical properties: compressive strength decreased by 45.0% and flexural strength decreased by 46.6% over the 360-day period; in contrast, the control group without algae showed a decrease of 34.1% in compressive strength and 39.0% in flexural strength over the same period. Additionally, the calcium carbonate ( CaCO 3 ) content within the mortar exposed to dynamic seawater initially increased but subsequently decreased due to dissolution. These microstructural changes also impacted the mortar’s electrochemical impedance, resulting in a 60.60% decrease in electrical resistance over 360 days; in contrast, the control group exhibited only a 36.49% decrease in electrical resistance over the same 360-day period.