I am a researcher who studies on concrete durability in terms of corrosion effects due to chloride attack. Chloride threshold value has become a predominant factor in predicting the life of the RC structures.
I need to exercise an experiment to find a certain value in order to fit this Threshold value parameter into my model.
Please help me find this.
This is actually a super complicated problem. In academic studies, the chloride threshold is normally defined as [Cl]/[OH]. It is easy to determine the threshold values for different types of steel in solution in the light of electrochemical approaches, as a function of temperature. However, if in concrete, this threshold is more practicable to be determined as a mass percentage of cement or binder material. You can make some reinforced specimens and immersed them in chloride solution, and use electrochemical methods to monitor the evolution of the steel surface status. When a pre-defined status is achieved, break the specimen and test the chloride content in paste surrounding the steel.
I know of a couple of papers by Andrea Sanchez that deal with the Chloride Threshold in concrete, and some of those experiments she did may be what you are looking for.
Thank you Ma. I was also thinking to use an electrochemical method to assess the chloride content. But however, some are practically difficult to set up the apparatus. I was looking for some other methods, may be more than 2 -3 methods which can we yield the threshold value in a high accuracy.
And Joseph, Thanks for your tips too. I will search for some works related to that. If possible, in case you have some related papers please be kind enough to post it up here.
Thank you both of you.
I've attached a paper that may help get you started. I agree with Hongyan, that this is actually a super complicated problem. There is a lot of work that has been done in this area, if you just need some values for modeling it will be much more efficient to use something available in the literature rather than experimentally determining your own.
There is a RILEM committee, TC-CTC, that has worked on this "super-complicated" problem for years and RILEM just started a new committe on this topic. The committees include the real experts on this matter! Check those committees on rilem.net!
There is recent overview of methods and results by Ueli Angst. Search for his paper!
You may find a lot of research works on chloride threshold limit. In many cases, the value is fixed at 0.4% of cement mass, in some cases at 1.2 kg/m3 of concrete. In your model, you may fix a value from the literature. However, it is true that we need more study on this issue. You may find some useful information in the following literature:
Mohammed, T. U., Hamada, H., Hasnat, A., Al Mamun, M. A., (2015). “Corrosion of Steel Bars in Concrete with the Variation of Microstructure of Steel Concrete Interface”, Journal of Advanced Concrete Technology (ACT), Japan Concrete Institute (JCI), Vol. 13, pp. 230-240.
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