ABSTRACT
When penetrating into cement-based materials, chloride ions will confront both internal environments, such as discrepancies in pore structure and pore solution composition and saturation, and external environments, such as electric field and pressure gradient. This chapter discusses the influence of ion types, pore structure, interfacial transition zone, chloride binding, and cracking on the transport of chloride in cement-based materials. The chloride diffusion coefficient in concrete and cement paste varies in a wide range, which largely depends on the water/cement (w/c) ratio of the cement-based material. The relationship between the pore diameter and the chloride diffusion coefficient has a similar trend with the relationship between the porosity and the diffusion coefficient. The chloride diffusion coefficient is found to continuously decrease when the volume of aggregates keeps increasing, as shown by the results in the literature. When chloride ion transports through diffusion alone, the chemical gradient is the only driving force.
