Chloride permeability of distressed concrete

Concrete structures such as concrete pavements, bridge decks, and structures in/near marine environments are subjected to a combination of chloride and load. The chloride penetrates the concrete by means of diffusion of the chloride ions through surface cracks or the interconnected pores in the concrete. The interaction between chloride diffusion and microcracks in the structures affects the durability of these structures. Limited information is available on the influence of these factors on chloride ion penetration into concrete. The impact of damage upon chloride diffusion process through concrete was carried by an experiment in the present study. The damage of specimens evaluated by ultrasound pulse velocity clearly showed correlation with chloride permeability of distressed concrete in this experiment.;Prismatic concrete specimens (4" x 4" x 6") were induced microcracks by mechanical uniaxial compression. Five loading levels: 40%, 70%, 90%, 100% of the ultimate strength, and 90% of the ultimate strength after the peak were loaded on specimens and salt ponding test was carried out to determined microcrack affected chloride diffusion coefficients. Two directions of chloride ingress, parallel and perpendicular to casting and loading direction, were set for the evaluation of anisotropic chloride permeability. The damage of specimens was evaluated by elastic stiffness degradation and ultrasound pulse velocity.;The damage evaluated by ultrasound pulse velocity showed linearity to the chloride permeability of distressed concrete the direction parallel to casting and loading. The chloride permeability of the direction perpendicular showed logarithmic relation to the ultrasonic damage evaluation. The direction of ultrasonic measurement to evaluate the damage should be parallel to the chloride ingress for the relevance of chloride permeability. The chloride permeability in each series tends to be isotropic below 70% of the ultimate strength. The anisotropic chloride permeability was observed above 90% of the ultimate strength and above 5% of damage.