Changes in pore water composition and in total chloride content at different levels of cement paste plates under different storage conditions
✍ Scribed by J. Tritthart
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 522 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0008-8846
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✦ Synopsis
Besides the total chloride content, the CI/OH ratio is a very important factor for the assessment of corrosion risk of reinforcements in concrete. First the changes of the total chloride were investigated at different levels of cement paste plates during about 6 months of exposure to 3% NaCl-solution. Then the changes of the same parameter and of the concentration of chloride and hydroxide ions as well as of the C1/OH ratio in the pore solution were determined during storage for one year: (i)under water; (ii) outdoors (unprotected) and (iii) wrapped in plastic. Under these storage conditions the total chloride content decreased only in the boundary areas but increased in the inner ones as did the a-concentration and the C1/OH-ratio of the pore solution. The decrease of the Cl/OH-ratio was smallest in the samples stored outdoors but about equal in samples immersed in water and wrapped in plastic, although the C1 concentration in the pore solution of the water exposed samples had decreased much more than in those wrapped in plastic. However, the OH concentration was found to be much higher in the boundary zones of the samples which were protected against environmental influences by plastic than in the water exposed ones so that the C1/OH ratio was about the same. l,.Ialr.~hllaiaa It is generally appreciated today that knowing how much total chloride is contained in concrete is not sufficient to assess the corrosion risk of steel reinforcements. Since the passive layer on the steel surface earl be damaged only by chloride ions which are dissolved in the pore water, the chloride concentration of the pore solution is of major interest. However, the C1 concentration in the pore solution alone cannot provide any definite answer, as it is assumed that the higher the concentration of passivating hydroxide ions, the more chloride ions are harmless.