Chloride-induced corrosion of steel reinforcements is the main reason for premature deterioration of coastal concrete structures, which can seriously threaten the durability of concrete structures, shorten the structural service life. The interfacial transition zone (ITZ) in the vicinity of aggregate is generally considered as the weakest link in concrete composites due to its larger pores and higher porosity than those of cement pastes resulting in the higher penetration behaviors of chloride ions. For this paper's studies, two methods based on the sieving experiment of coarse aggregate and the numerical model of concrete are proposed to respectively determine the chloride diffusion coefficient of ITZ in concrete. The comparisons of normalized ITZ chloride diffusion coefficients obtained according to the methods of experiment and numerical model are elaborated. Particularly, an empirical model for the prediction of ITZ chloride diffusion coefficient in concrete is established.
Coastal concrete structures, such as wharfs, breakwaters, cross-sea bridges, artificial islands, etc., are considered as the concrete structures chronically exposed to marine aggressive environments (Chari et al. 2018) and hence attacked by large amount of corrosive ions; especially, chloride ions (Balestra et al. 2019; Tadayon et al. 2016). Chloride-induced corrosion of steel reinforcements is the main reason for premature deterioration of coastal concrete structures, which can seriously threaten the bearing capacity and durability of concrete structures, shorten the structural service life, and exacerbate the structural collapses risks (Moradllo et al. 2018). Concrete composites used in coastal structures are composed by three components, i.e., cement paste, aggregate, and interfacial transition zone (ITZ) (Abyaneh et al. 2013). Especially, the ITZ in the vicinity of aggregate is generally considered as the weakest link in concrete composites due to its larger pores and higher porosity than those of cement pastes, therefore, it possesses the higher penetration behaviors of chloride ions compared with that of cement paste (Gao et al. 2014; Li et al. 2017). Some efforts elaborated that the diffusivity of ITZ is much higher (dozens or even hundreds of times) than that of the cement paste (or mortar) (Jiang et al. 2016; Wang et al. 2018b; Yang and Weng 2013; Yang 2005; Yang and Cho 2005), which indicated that the ITZ can significantly affect the transport behaviors and diffusion properties of chloride ions in concrete composites. As a consequence, it is very essential to investigate the chloride diffusivity of ITZ in concrete composites and further explore the determination methods of ITZ chloride diffusion coefficient for coastal concrete structures.
