Influence of Associated Cations on Chloride Ingress into Concrete Structures
Keywords:deicing salts, chloride penetration, coupling effect, durability, concrete
This article presents an experimental study on the effect of different types of chloride-based deicing salts on the rate of chloride penetration into concrete structures. Three different types of deicers commonly used for deicing and anti-icing operations, NaCl, CaCl2, and MgCl2, were selected to investigate the influence of associated cations on the rate of chloride ingress into concrete. The concentration profiles of various ions were measured including Cl-, Na+, K+, Mg2+ and the effect of different cations on the diffusion rate of chloride ion into concrete was systematically studied. The test data were compared to numerical results obtained from a numerical model developed based on the Nernst-Planck equation which considered the ionic coupling effects among ions in chloride solutions and ions in concrete pore solution, Na+, K+, OH-. The test results illustrated that cations in different chloride solutions have significant effects on the penetration rate of chloride ions. This can be summarized in the order of CaCl2 > NaCl > MgCl2 from the fastest to slowest chloride ion penetration. In the case of various salt combinations tested, the diffusion rate of chloride ions can be ranked as NaCl + CaCl2 > CaCl2 + MgCl2 > NaCl + MgCl2. The total chloride concentration obtained from experimental results were compared to the numerical model and a good agreement was observed.
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