Chloride binding and its effects on microstructure of cement-based materials

When chloride ions are introduced into cement-based materials, some of chloride ions interact with the hydration products, and some of chloride ions absorb to the hydration products or pore wall. The former is called chloride chemical binding, and the latter is called chloride physical adsorption, they are collectively referred to the chloride binding. The formation of Friedel's salt is the main chemical binding, physical adsorption is mainly controlled by C-S-H gel. There are some other factors influencing chloride binding. Some supplementary cement materials (i.e., fly ash, slag and silica fume) also affect chloride binding notably. Due to the chloride binding, it is expected that there should be microstructural changes in cement-based materials. By knowing the chloride binding and the change of microstructure when chloride ions are introduced into cement-base materials well, we could provide a scientific basis for the service life design and prediction of reinforced concrete structures.