Multifactorial Chloride Ingress Model for Reinforced Concrete Structures Subjected to Unsaturated Conditions

The attack of chloride ions is one of the most important factors affecting reinforced concrete (RC) durability. Chloride ingress into concrete is usually studied by assuming constant diffusivity and constant surface chloride concentration. However, these two approximations could badly estimate the chloride concentration in RC structures and then the lifetime assessment. Several factors influence the chloride concentration and ingress mechanisms in the convection area. In this paper, a new multifactorial and multiphase model to account for some effects on chloride surface concentrations in the convection zone is proposed. 136 values have been collected to identify the position and the chloride concentration in the border between the diffusion and convection zones. In addition, a time-dependent multifactorial diffusivity is considered. Diffusivity, which is the key parameter of the mechanical diffusion accounts in this paper for the water/cement ratio, chloride binding, temperature, concrete age, internal humidity, concrete deformation, and damage. The surface chloride model considers environment humidity, temperature, superficial concrete irregularities, and convection area of concrete. Advanced numerical solutions have been carried out to consider space and time dependencies in the model. Results show that the error function-based solutions could underestimate the chloride concentration C for periods < 10 years and for concrete depths > 4.0 cm in comparison with the proposed model.

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