Development of Simulation Model of Chloride Ion Transportation in Cracked Concrete

Ema Kato, Yoshitaka Kato and Taketo Uomoto

Journal of Advanced Concrete Technology, 3(1) 85-94, 2005

Chloride-induced deterioration is the most important deterioration phenomenon in reinforced concrete structures under marine environments. When a crack occurs in cover concrete, it may initiate and accelerate corrosion of steel reinforcement embedded in concrete. The performance of reinforced concrete structure may subsequently decrease even in the early stage of its service life. In this paper, for making clear the mechanism of chloride-induced deterioration, chloride ion transportation in cracked concrete was experimentally investigated and a simulation model for chloride ion transportation in cracked concrete was proposed. The zone having a crack was treated as the exposed surface of concrete in the proposed model of which chloride transportation was assumed to be governed by the density of chloride ion solutions in the crack. In addition, effects of crack width and an apparent diffusion coefficient through the crack on chloride ion transportation were numerically investigated and the applicability of the proposed model was discussed.

Today several proposals for the introduction of durability design in practice of concrete construction exist. Chloride penetration is calculated on the basis of laboratory measurements on un-cracked concrete in most cases. In reality most concrete elements are cracked by mechanical load or by shrinkage. Durability design which does not take cracks into consideration will not lead to conservative predictions. Results of this paper may serve as a basis for more realistic durability design. In this sense the paper describes pioneering work. (Prof. F. H. Wittmann, Aedificat Institute)