Abstract
As with the leakage of stray current in the surrounding medium, the chloride transport in concrete is influenced by the stray current and loading of the subway structure. This paper presents the results of the experimental study on the chloride transport properties of concrete under the combined action of stray current and sustained compressive loading. First, an experiment was setup to explore the chloride transport in the subway structure as the concrete specimen embedded with steel under test current and study the influence of the existence of steel on the chloride transport profiles in concrete under stray current. Then, to investigate the combined effect of stray current and loading on the chloride transport properties, an improved experiment was designed with stray current and sustained compressive loading. The chloride transport profiles were measured, respectively, subjected to different stray currents and compressive stress levels. The experimental results indicated that stray current and sustained compressive loading have a significant influence on the chloride transport properties of concrete, and the loading threshold existed as the turning point of the chloride transport rate. Based on the experimental data and migration theory, the prediction model of chloride transport in concrete under stray current and sustained compressive loading was established and verified by the experimental measurements, and the steel corrosion-induced cover cracking was studied, and the comparison indicated that the numerical results were consistent with the experimental results.
Highlights
During the operation of subways, the insulation between the rail and the track bed is reduced, and the protective measures become invalid over time. us, the leakage of stray current to the surrounding medium is increased in the subway structures, especially for the DC power supply system [1, 2]
Several reviews described Friedel’s salt will be formed and precipitated in macropores when the chloride penetrates into the cement, reducing the number of macropores and changing the pore structure and distribution [7,8,9]. e bound chlorides in concrete could be released under the electric field, which significantly increased the concentration of the free chlorides [10, 11], and the external electric field accelerated the dissolution of Ca2+ in the pore solution of concrete [12]. e consequence of this chemical change was the decrease in Advances in Materials Science and Engineering
Considering the corrosion characteristics of the subway structure, two experiments were conducted in this study to investigate the effects of stray current and sustained compressive loading on the chloride transport in concrete
Summary
During the operation of subways, the insulation between the rail and the track bed is reduced, and the protective measures become invalid over time. us, the leakage of stray current to the surrounding medium is increased in the subway structures, especially for the DC (direct current) power supply system [1, 2]. The chloride transport in concrete may be affected by stray current, which causes the steel corrosion in advance [3, 4], resulting in durability failure of the subway structure. The compressive loading on the structure may cause the occurrence and development of cracks in concrete, which affect the chloride transport in concrete. Erefore, to evaluate the durability of the subway structures accurately, it is essential to consider the coupling effect of stray current and external loading on chloride transport in concrete. It was found that the transport properties of chloride in concrete depend largely on the transport channels (pore structure and micro cracks) [6]. Several reviews described Friedel’s salt will be formed and precipitated in macropores when the chloride penetrates into the cement, reducing the number of macropores and changing the pore structure and distribution [7,8,9]. e bound chlorides in concrete could be released under the electric field, which significantly increased the concentration of the free chlorides [10, 11], and the external electric field accelerated the dissolution of Ca2+ in the pore solution of concrete [12]. e consequence of this chemical change was the decrease in Advances in Materials Science and Engineering
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