Effect of hydroxyl ions on chloride penetration depth measurement using the colorimetric method |
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Authors: | Qiang Yuan Caijun Shi Geert De Schutter Keren Zheng |
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Affiliation: | a School of Civil Engineering and Architecture, Central South University, Hunan, China b College of Civil Engineering, Hunan University, Hunan, China c Magnel Laboratory for Concrete Research, Department of Structural Engineering, Technologiepark-Zwijnaarde 904, B-9052, Ghent (Zwijnaarde), Ghent University, Belgium |
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Abstract: | In this paper, the effect of hydroxyl ions on chloride penetration depth measurement using the colorimetric method was studied. Equivalent silver nitrate solution (i.e. Ag+ = Cl−) was added to the NaCl + NaOH solution with different concentrations, then the amount of precipitated silver chloride and silver oxide were determined by chemical methods, and the color of the precipitated products was examined. Results show that the amount of silver chloride formed decreases linearly as OH− to Cl− ratio (r) increases. Thus, the chloride concentration at color change boundary changes with the pH value of the concrete. AgCl has a white color, while Ag2O has a dark brown color. When the value of r exceeds 4, the color of the mixture looks brown, and color change boundary cannot be easily distinguished. |
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Keywords: | Colorimetric method Chloride ions Silver nitrate Hydroxyl ions |
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