Modelling of Chloride Diffusion into Surface-biodeposited concrete

Chloride diffusuion is regarded as the dominant chloride transport process in concrete and the main cause of the corrosion of steel in concrete structures exposed to chloride-rich environments. Surface biodeposition can be applied to both new and existing concrete structures to restrain this deterioration. To gain comprehensive overview to the protective mechanism of surface biodeposition, a theoretical study of chloride diffusion through surface-biodeposited concrete is required. This paper proposes a physical model for surface biodeposited concrete, and develops a theoretical model to predict chloride diffusion of surface-biodeposited concrete structures. The model describes movement and retention of moisture and chloride by means of balance equations and diffusion laws. The influences of biodeposition and substrate properties on chloride diffusion are studied by a finite difference model. Results indicate that chloride diffusion is controlled by both the biodeposition and the substrate.