Papers by Keyword: Stray Current

Abstract: In recent years, more and more attention has been paid to the effect of stray current on the properties of cement-base materials in subway engineering. In the actual service process, reinforced cement-based systems suffer from various erosive conditions, the degradation mechanisms in reinforced cement-based systems due to the combined effects of stray current and environmental multi-factors have been a serious problem in civil engineering for many years. This paper reviews the research achievements on the properties of cement-based materials under the multi-factor coupling conditions such as stray current and soft water, chloride ion, sulfate, stress, freezing and thawing cycle and so on. Furthermore, the improvement of cement-based materials on stray current resistance is also generalized in it. Prospects of cement-based materials for durability under environment multi-factor coupling actions are also presented.

Abstract: Stray current is one of the crucial factors affecting safety running for train. It is the first Rail Transit Line for Lanzhou. According to the local geological data, line direction, crossing Yellow River, building conditions, some measurements were put forward to restrict the stray current leakage in Lanzhou Rail Transit Line 1. Especially, it is very important to prevent the water permeating into the soil connecting to the railway. Corresponding protection scheme was laid down in this paper. The protection scheme in this study has very important role in the safe operation, system improvement and maintenance process for Lanzhou Rail Transit Line 1.

Abstract: When unprotected structures are nearby to CP systems, interference problems between unprotected and protected structures may be occurred. The stray current interference can accelerate the corrosion of nearby structures. During a recent few decades the protection technologies against stray current induced corrosion have been significantly improved and a number of techniques have been developed. However, there is very limited information in marine environments. In this study, cathodic protection systems installed both the ICCP with Ti-mesh anode and the SACP with zinc anode has been adopted to verify the current influence through laboratory experiment. CP potential and current have been investigated, moreover, 4 hour depolarization test has been involved to reveal the effectiveness of cathodic protection.

Abstract: The corrosion behavior of typical grounding materials Zn and Cu in Shanbei soil solution was studied by immersion test technique, galvanic corrosion current measurement and simulated stray current test. The results showed that Zn was seriously corroded with the corrosion product of ZnCO₃, while Cu was slightly corroded with the main rust of Cu₂(OH)₂CO₃ and copper oxides. The corrosion of Zn was accelerated and Cu was protected when coupled them together. Stray current can significantly increase the corrosion process of both Zn and Cu.

Abstract: Stray current flows through the buried metallic pipeline which exposed to electrochemical corrosion attack. The distribution of stray current is studied by Finite Element Method analysis model, the results indicate that stray current increase gradually along the buried metallic pipeline, reaching to a maximum value in an intermediary point, and then decreases gradually, has a regular bilateral symmetry. The distribution model of stray current is discussed by the inducted electric field theory.

Abstract: The measurement of pipeline to ground potential is the most common method to evaluate protection condition of buried pipeline. For the old pipeline, pipeline to ground potential measured with surface reference electrode method or reference electrode method close to pipeline usually is not the real protection potential of buried pipeline due to presence of an IR drop and/or stray current interference. A portable real protection potential measurement system combining the polarized probe with the portable surface data acquisition unit is developed, the polarized probe can measure the real protection potential by eliminating IR drop and/or stray current interference, meanwhile portable surface data acquisition unit can automatically record protection potential. The on-site application of the system show that the system can quickly and accurately measure the protective potential of buried pipeline, reduce human measurement error, and really reflect the cathodic protection condition of pipeline.

Abstract: Corresponding prevention strategies can be put forward by learning the stray current distribution in the metro rebar. In the paper, the stray current intensity of the rebar in the ballast of the power supply area and the 24-hour polarization potential of the rebar in the ballast are obtained through the test of vertical resistance, track-current drainage net resistance and track-earth resistance, and the polarization potential test in the tunnel ballast of metro system in service. The daily leak of the stray current of the rebar in the ballast is also obtained based on the relationship between the polarization potential and current intensity. The test result shows that the vertical resistance of the track has quite good consistency while the track-current drainage net resistance and track-earth resistance have relatively great discreteness. The polarization potential peak of the rebar in the ballast is over 500mV and the 24-hour equivalent and average current intensity of the rebar in the ballast can rise up to 0.26~0.43A/dm².

Abstract: In this article, simulation tests of chloride binding were made under the condition of sodium chloride as an internal admixture while loaded with stray current externally. Through the potential titration method, free chloride ion concentration Cf 、 total chloride ion concentration Ct and chloride binding rate RCl were determined. The results show that: With the increase of the strength and action time of the stray current, the number of internal free chloride ions in the cement paste increases while that of the corresponding bound chloride ions reduces significantly, leading to the decrease of chloride binding rate. The relationship between chloride binding rate and the two can be shown as follows respectively:RCl=50.754e(-I/28.258)+42.532、RCl=63.427 e(-T/8.238)+27.325.

Abstract: According to the service environment of light rail transit and subway structures, in this paper experiments on the corrosion characteristics of reinforced concrete under single corrosion environment of stray current, single corrosion environment of chloride ions and joint corrosion environment of stray current and chloride ions were respectively carried out. Loading direct current electric field was used to simulate the stray current. The experimental results showed that, the corrosion growth process of the rebar in reinforced concrete under single environment of chloride ions was slow and stable, while that under single environment of stray current being separated two stages, i.e., rapidly increasing stage and stably varying stage. In addition, the rebar of reinforced concrete in stray current alone environment was corroded faster than that in chloride ion alone environment did; when stray current and chloride ion coexist, the stray current speeded up the chloride ion transportation, which gave rise to the increase of the corrosion rate of the rebar of reinforced concrete; the corrosion degree of the rebar depended on the chloride ion concentration, stray current strength and test time. The stronger the stray current strength, the longer the stray current corrosion period and the heavier the chloride ion concentration, the more the corrosion products of the rebar and thus the more serious the reinforced concrete deterioration.

Abstract: This paper analyzes the cause of stray current of subway tracks, classifies the stray current, and explains the hazards. Based on this, the paper also summarizes the advantages and disadvantages of traditional monitoring technologies and current monitoring technologies, and applies the current CIPS detection technology to make simulation in the laboratory. The simulation result well reflects the distribution of stray current on the rail.