Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete

Abstract

The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions.

Evolution characteristics and mechanism of concrete performance under water pressure environment: A comprehensive review

“…In fact, in addition to its own diffusion, chloride ions can also be transported by convection with increasing water pressure. [140][141][142][143] Besides, the direction of chloride ion convection is consistent with its diffusion direction. 144 Zhang et al 141 found that chloride ion migration in concrete is affected by diffusion, capillary suction, and water pressure.…”

“…However, these are only studied with saturation as the basic variable. In fact, in addition to its own diffusion, chloride ions can also be transported by convection with increasing water pressure 140–143 . Besides, the direction of chloride ion convection is consistent with its diffusion direction 144 .…”

“…Reference [142] also indicated that when water pressure gradually increased, the transport mode of chloride ions changed from capillary absorption to permeation. In this regard, some scholars 140,143,145,146 studied the permeation behavior of chloride ions under water pressure, and all showed that the permeation depth of chloride ions gradually increased with the increase of water pressure and the enhancement of water pressure duration. Zhao et al 145 found that compared with natural immersion, the effect of water pressure enabled chloride ions to continuously accumulate at a certain depth from the concrete surface, thus making the chloride ion content within a certain range, indicating that water pressure can deepen the migration of chloride ion.…”

Corrosion Behavior of Reinforcing Steel in the Immersed Tube Tunnel (ITT) under Submarine Environment

“…An analysis of seawater samples obtained along the South China coast revealed a chloride ion concentration of 16.5 g/L; thus, the corrosion medium used in this study was based on sodium chloride at 10 times the concentration of simulated seawater, i.e., a chloride ion concentration of 165 g/L. To simulate the effect of the seawater pressure on chloride ion transport in the ITTs, the model was placed in a special corrosion vessel, and a pressurized device was used to maintain 6.5 atmospheres of pressure inside the vessel (comparable to the seawater pressure in the ITT of the Hong Kong-Zhuhai-Macao Bridge located at 40 m underwater) [36], as shown in Figure 2.…”

Evaluation of Chloride-Ion Diffusion Characteristics of Wave Power Marine Concrete Structures

“…They have low durability owing to the following reasons: stress on concrete caused by sea waves, accelerated corrosion of steel due to dry and wet conditions, physical erosion due to the freezing expansion of water in concrete, chloride attack caused by the corrosion and expansion of reinforcing bars due to the diffusion of salts such as sulfates, and carbonation due to low concrete pH caused by carbon dioxide in the air. Chloride attack is the principal cause of deterioration because it decreases the strength of structures and leads to cracks owing to the corrosion of reinforcing bars [ 7 , 8 , 9 , 10 , 11 , 12 ].…”