Study of transport and binding behavior of chloride ions in concrete under single-sided salt-freezing cycle

The transport and binding of chloride ions (Cl-) in concrete inside a salt-freezing (S-F) environment significantly impact concrete durability. The experiment on single-side S-F of concrete examined the variation patterns in compressive strength, mass loss, and Cl- content during the S-F process, alongside an analysis of the microscopic morphology and phase composition of the concrete through microscopic testing. The results indicate that a 10 % concentration of Cl- in the erosion solution exacerbates the coupling effect of the freezing-thawing (F-T) cycle and chloride erosion, leading to more serious S-F damage to concrete. The S-F environment significantly influences the transport and binding of Cl-, with the erosive effect of 10 % and 20 % chloride concentrations enhancing Cl- transport within the concrete, and the binding capacity of the concrete correlates with the extent of S-F damage. Moreover, microanalysis revealed that the S-F cycle action inflicted serious damage on the concrete's structure, hastening carbonation and influencing the chemical binding and physical adsorption process of Cl- within the concrete. The mechanism analysis showed that the impact of S-F cycle on Cl- transport and binding behavior was primarily due to the deterioration of pore structure and the elevated Cl- concentration. The results of this study can serve as a reference for designing the S-F resistance durability of concrete in cold regions.