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chloride content and pH value in the pore solution of concrete under carbonation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第1期14卷 71-78页

作者： Xiao-mei WAN Folker H. WITTMANN Tie-jun ZHAO Hong FAN Aedificat Institute Freiburg Freiburg D-79100 Germany School of Civil Engineering Qingdao Technological University

chloride content and the pH value of the pore solution in the neighborhood of steel reinforcement are decisive pa- rameters for initiation and rate of corrosion. The pore solution of cement mortar and hardened cement paste has been expressed from the pore space by high pressure in the investigation. The influence of the water-cement ratio, age, and addition of chloride to the fresh mix on chloride content in the pore solution has been determined by ion chromatography. At the same time the pH value of the pore solution has been determined. The dissolved chloride content decreases with increase in the water-cement ratio. The amount of bound chloride increases with time, but it decreases with decreasing content of dissolved chloride in the pore solution. A significant influence of carbonation on the dissolved chloride content of the pore solution has been observed. With complete carbonation, the dissolved chloride content in cement mortar and hardened cement paste increases by a factor between 2 and 12. The bound chloride decreases by 27%--54%. As expected, the pH value decreases from around 13.2 to as low as 8.0 due to car- bonation. It can be concluded that carbonation not only lowers the pH value but liberates bound chloride. This is one obvious reason why the combined action of chloride penetration and carbonation accelerates steel corrosion and shortens the service life of reinforced concrete structures.

关键词： chloride Pore solution Carbonation pH value

chloride ion ingress distribution within an alternate wetting-drying marine environment area

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Science China(Technological Sciences) 2012年第4期55卷 970-976页

作者： XU Chen LI ZhiYuan JIN WeiLiang ZHANG Yi YAO ChangJian Department of Civil Engineering Zhejiang UniversityHangzhou 310058China

Concrete structures in an alternate wetting-drying area often suffer from severe chloride ion ingress more than those in other areas. Field tests of marine structures were conducted, and chloride concentration is found to reach a maximum value at a certain elevation. The surface concentration and diffusion coefficient of chloride ions at different elevations exhibit Gaussian unimodal curve distributions. Using the chloride ion unsaturated permeability model, the distribution regularity mechanism is analyzed. Finally, an improved indoor accelerated simulation experiment is proposed to simulate the rules governing chloride ion ingress into concrete structures in an alternate wetting-drying area.

关键词： concrete durability chloride

chloride Diffusivity Analysis of Existing Concrete Based on Fick's Second Law

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Journal of Wuhan University of Technology(Materials Science) 2010年第1期25卷 142-146页

作者：张俊芝 College of Architecture&Civil Engineering Zhejiang University of Technology

According to the existing concrete core samples obtained in site, chloride concentration and porosity of existing normal hydraulic concrete were measured, and chloride diffusivity in existing hydraulic concrete was studied. By Fick’s second law, the chloride diffusion coefficients in the steady diffusion area were calculated. The chloride diffusion of different mix proportion concrete was tested, and chloride diffusion coefficients and porosities of freshly concrete were measured, moreover, the relationship between diffusion coefficient and porosity was analyzed. The results show that the varying law of chloride diffusion coefficient with exposure time of existing concrete can be predicted in a better way by Fick’s second law and water-cement ratios or porosity of concrete and chloride concentration in existing concrete.

关键词： existing concrete Fick’s second diffusion law chloride diffusion coefficient

chloride Binding Isotherm from Migration and Diffusion Tests

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Journal of Wuhan University of Technology(Materials Science) 2013年第3期28卷 548-556页

作者：元强 DENG Dehua SHI Caijun De Schutter Geert School of Civil Engineering Central South University College of Civil Engineering Hunan University Magnel Laboratory for Concrete Research Department of Structural Engineering Ghent University

chloride binding is often described by chloride binding isotherm, which is closely related to the service life of concrete structures in chloride environments. Many methods have been proposed to determine chloride binding isotherm. Compared to other methods, chloride binding isotherms obtained directly from non- steady-state diffusion tests seem closer to the reality. We studied the chloride binding isotherm from both non- steady-state electrical-accelerated migration and diffusion tests at different temperatures. Twelve concrete mixes with different supplementary cementing materials and water-to-binder ratios of 0.35, 0.48 and 0.6 were cast for study. The specimens after diffusion （or migration） tests were sliced layer by layer, and acid-soluble and free chloride contents of each layer were measured. A chloride binding isotherm was obtained from one specimen. Experimental results indicated that electrical voltage had a slight effect on the chloride binding isotherm of concrete. Temperature had a positive effect on chloride binding. The higher the water-to-binder ratio was, the higher the chloride binding was.

关键词： chloride binding isotherm concrete supplementary cementing materials

chloride transference during electrochemical chloride extraction process

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Science China(Technological Sciences) 2010年第6期53卷 1466-1470页

作者： YAO Wu & ZHAO Zheng Key Laboratory of Advanced Civil Engineering Materials (Tongji University),Ministry of Education of China,Shanghai 200092,China 1. Key Laboratory of Advanced Civil Engineering Materials (Tongji University) Ministry of Education of China Shanghai 200092 China

Chemical titration method and lab-made chloride probes were jointly adopted to investigate the effects of water-to-cement (W/C) ratio and the impressed current density on chloride transport for cement-based materials during electrochemical chloride extraction (ECE) *** dissolution of bound chlorides and the effect of current density on dissolution were *** variations of chloride concentration at different depths and the chloride transference process were *** results show that W/C ratios adopted have slight influence on chloride extraction,while chloride extraction efficiency is mainly determined by the impressed current *** ECE process a portion of bound chloride ions dissolved and the amount of bound chlorides released is directly proportional to current density.

关键词： electrochemical chloride extraction transference bound chloride current density

Damage on lining concrete in highway tunnels under combined sulfate and chloride attack

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Frontiers of Structural and Civil Engineering 2018年第3期12卷 331-340页

作者： Rongrong YIN Chenchen ZHANG Qing WU Baocheng LI He XIE School of Architeture and Civil Engineering Jiangsu University of Science and Technology Zhenjiang 212003 China

The combined effect from sulfate and chloride is one of the important reasons to cause the damage of lining concrete in highway tunnels. To investigate the effect of chloride ions on the corrosion of lining concretes under sulfate attack, ultrasonic detecting, compression test and X-ray Diffraction （XRD） were performed on the concretes to obtain the ultrasonic velocity, corrosion thickness, compression strength and corrosion products. The ultrasonic results, compression strength and XRD patterns confirmed that the existence of chloride certainly depressed the corrosion damage on the lining concretes under sulfate attack, and the depressing effect increased with the content of chloride in the composite solution. The corrosion damage on the concretes experienced three stages independent of the composition of corrosive solution： initial slower enhancement on the strength, stabilization period and linear degradation period. The existence of chloride mainly affected the final degradation stage and obviously decreased the corrosion thickness.

关键词： lining concrete sulfate chloride compression ultrasonic

Effect of Metal Cations on Corrosion Behavior and Surface Structure of Carbon Steel in chloride Ion Atmosphere

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Acta Metallurgica Sinica(English Letters) 2020年第9期33卷 1302-1310页

作者： Yu-Wei Liu Jian Zhang Xiao Lu Miao-Ran Liu Zhen-Yao Wang Environmental Corrosion Center Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Analysis and Testing Center Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of Chinese Academy of Sciences Beijing 100049.China

In order to better understand why the corrosion behavior of carbon steel exposed in Nansha atmospheric environment is very serious, the effect of sodium, potassium and magnesium chlorides deposited on carbon steel surface has been studied under atmosphere conditions by wet/dry accelerated test. The difference of corrosion behavior and surface structure in Na+, K+, and Mg2+ containing atmosphere has been investigated by thickness loss, scanning electron microscope, X-ray diffraction and electrochemical techniques. The results indicate that the thickness loss of carbon steel exposed in different metal cations containing atmospheric environment increases in the order of Na+, K+, Mg2+. The hard metal cation can promote the dissolution of the steel to a certain extent. In Mg2+ containing atmosphere, the relative content of β-FeOOH is rather higher and the protective ability index α */γ * decreases in the order of Na+, K+, Mg2+. The corrosion current density of both bare carbon steel and the rusted carbon steel increases in the order of Na+, K+, Mg2+. The polarization resistance and the charge transfer resistance decreases in the order of Na+, K+, Mg2+.

关键词： Metal cation Carbon steel chloride Atmospheric corrosion

Effect of chloride ion on corrosion behavior of low carbon steel in 0.1 M NaHCO_3 solution with different dissolved oxygen concentrations

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Journal of Materials Science & Technology 2019年第4期35卷 596-603页

作者： Fang Xue Xin Wei Junhua Dong Changgang Wang Wei Ke Institute of Metal Research Chinese Academy of Sciences University of Science and Technology of China

The corrosion behavior of low carbon steel in 0.1 M NaHCO_3+ 0.1 M NaCl solution with different dissolved oxygen concentrations was investigated with gravimetric tests and electrochemical *** show that the corrosion mass loss of steel is remarkably increased with the addition of chloride ion. In the initial stage, the carbon steel tends to active dissolution due to the dissolution effect of chloride ion on the oxide film; as a result, the corrosion potential maintains as low values. With the immersion time going by, the corrosion potential of the steel is promoted as a result of the accumulation of the corrosion products. However, the rust layer is loose and porous due to the deteriorating effect of chloride ion, which decreases the reduction resistance of oxygen. Meanwhile, the porous rust layer could be repaired by the depolarization of oxygen. Under the synergistic effect of chloride ion and oxygen, the corrosion of the steel is accelerated during the repeated process of dissolution and reparation of the oxide film.

关键词： Carbon steel chloride ion Electrochemical measurements Rust characterization Localized corrosion

Passivity breakdown on 436 ferritic stainless steel in solutions containing chloride

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Journal of Materials Science & Technology 2019年第4期35卷 637-643页

作者： Jiaming Wang Shengsheng Qian Yanhui Li Digby D.Macdonald Yiming Jiang Jin Li Department of Materials Science Fudan University Department of Materials Science and Engineering University of California at Berkeley Key Laboratory of Thermo-Fluid Science and Engineering of MOE Xi'an Jiaotong University

Passivity breakdown on 436 ferritic stainless steel(FSS) has been investigated in solutions containing different concentrations of chloride at 25?C and interpreted in terms of the point defect model(PDM). The measured near-normal distributions of passivity breakdown potentials for 436 FSS under experimental conditions are in good agreement with the calculated results according to the PDM. The linear dependence of breakdown potential on the square root of potential scanning rate, which was described by the PDM,provides the estimation of the critical concentration of condensed vacancies at the metal/film interface,which leads to the passivity breakdown. This value is in good agreement with that calculated from the microstructure properties of the alloy substrate and the barrier layer of the passive film. This study demonstrates the validity of the PDM in describing the passivity breakdown on 436 FSS in NaCl solutions.

关键词： 436 ferrite stainless steel Passivity breakdown Point defect model chloride ions