Incorporating cracking of concrete on chloride ingress and service life modeling of concrete structures

Chloride induced reinforcement corrosion is the most common degradation mechanisms for reinforced concrete structures. The service life of concrete structures is normally predicted by estimating the rate of chloride ingress and the necessary time to initiate reinforcement corrosion. Normally, chloride ingress is modeled as a diffusive process in which concrete is considered as a semi-infinite continuous medium. This modelling approach disregards the influence of cracks on the rate of chloride ingress in concrete. However, experimental studies have shown that the influence of cracks on chloride ingress is significant and cannot be neglected. In practice, cracks in concrete may originate due to different mechanisms. Recommendations on crack control in flexural members consider cracks in the range between 0.15 mm (0.006 in.) and 0.3 mm (0.011 in.) to be permissible in deicing and/or seawater exposure; with the same limit for both exposure classes in Europe. The influence of cracks on service life prediction remains to be clarified. This paper presents describes a conceptual approach for incorporating the effect of flexural cracks on the calculation of the time-tocorrosion initiation of steel reinforcement due to chloride-ingress. The proposed approach consists of applying a correction factor to the chloride diffusion coefficient, which is dependent on the surface crack width.