Influence of Associated Cations on Chloride Ingress into Concrete Structures

Abstract

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.