Service life evaluation of marine reinforced concrete structures in coastal soda residue soil subjected to chloride attack

In chloride salt environments, the corrosion of steel reinforcements due to chloride ions intrusion into concrete is the main cause of the durability failure of reinforced concrete structures (RCSs). The chloride content included in coastal soda residue soil (SRS) foundations with a high moisture content has been measured to be 2-3 times that of seawater, which seriously threatens the durability of RCSs built in the SRS environment. Compared with marine tidal environments, the influence of SRS corrosive environment with a high moisture content and high chloride ions content on the chloride ions transport behaviours and the service life for the marine RCSs remains unclear. Therefore, for this paper, an indoor experimental study on chloride ions intrusion into the marine concrete specimens in a coastal SRS environment was carried out. The concentration profiles and transport characteristics of chloride ions within concrete in a real SRS environment with a semi-buried zone (SBZ) and a fully buried zone (FBZ) and in a simulated salt solution (SSS) environment of SRS were revealed. The measured results of chloride transport in concrete specimens exposed to the marine tidal zone (MTZ) were used as the control group to quantify the differences in chloride transport behaviours between concrete buried in the coastal SRS environment and that in the MTZ (marine tidal zone). Chloride transport models of concrete in coastal SRS and MTZ (marine tidal zone) environments were built by means of the Fick's second law of diffusion. Taking a certain marine RCS as an example, the service lives of this structure in coastal SRS and MTZ (marine tidal zone) environments were evaluated via this paper's proposed chloride transport models and then compared. Results indicated that the predicted service life of the RCS in the FBZ (fully buried zone) is the longest, followed by that in the MTZ (marine tidal zone), and that in the SBZ (semi-buried zone) is the shortest. The service lives of the marine RCSs in the FBZ (fully buried zone) and MTZ (marine tidal zone) were approximately 1.37 times and 2.76 times that of the SBZ (semi-buried zone), respectively.