Assessing the Adsorption and Diffusion Behavior of Multicomponent Ions in Saturated Calcium Silicate Hydrate Gel Pores Using Molecular Dynamics

In concrete structures, ion transport is a major factor in the corrosion of steel and the loss of concrete durability. Because the macroscopic and microscopic research levels are not sufficient to explain the essential mechanism of ion transport, this Article simulates the transport behavior of nanoscale ions in saturated C–S–H gel pores using molecular dynamics and then explores the influence of a calcium–silicon ratio and ion type on transport behavior. The adsorption rate of chloride ions on the surface of the C–S–H gel is lower than that of cations due to the effect of the electric double layer. The ratio of calcium to silicon will significantly affect the adsorption capacity of chloride on the surface of C–S–H. C–S–H gel has the strongest adsorption capacity when the ratio of calcium to silicon is 1.2. At the same concentration, calcium salt can promote the adsorption of chloride ions by the C–S–H gel compared with sodium salt. This simulation is consistent with the experimental results of related references. In this study, the mechanism of anion and cation transport in the gel pore was explained from the point of view of molecular dynamics, which has relevant significance for the study of concrete resistance to ion erosion.