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A Study of the Chloride Diffusion Coefficients of HPC (I)
|Contributors: ||NTOU:Department of Harbor and River Engineering|
High performance concrete (HPC);Physicochemical property;Chloride diffusion coefficient
|Issue Date: ||2011-06-29T01:36:56Z
abstract:The main goal of this study is to identify the correct physical models and experimental methods for the accelerated chloride diffusion in concrete. By using the suitable method, the influence of concrete strength and pozollans on chloride diffusivity is examined. The results show that the natural diffusion process in concrete is in term of quasi-steady state and ions' migration due to the electrical field is in term of non-steady state. For the two-chamber accelerated test, the modified equation by adding a sink, which describes the electrochemical reaction; two chloride ions lose two electrons and combine into chloride gas, is first proposed in this study. The results show the diffusion coefficient obtained by using this modified equation is much closer to that obtained from three-chamber accelerated test, and the diffusion coefficient obtained from this modified equation is lower than that obtained from unmodified equation. Furthermore, the sink coefficient is found to be independent on the concrete property under the same electrical field intensity and linear proportional to the electrical field intensity. The three-chamber accelerated test can avoid chloride consumption problem where two-chamber accelerated test cannot do; however, if the modified equation involving the sink is used, similar diffusion coefficients can be obtained for these two experimental methods. Also it is found that the precision of chloride measurement can influence our judgement of using which mathematical model to describe the diffusion phenomenon. Only while the measurement precision is enough, one can find the sink term is obvious. Test results show the chloride diffusion coefficient decreases as the concrete compressive strength increases. Pozzolan replacement can decrease the diffusion coefficient. Comparing to the diffusion coefficient of the similar compressive strength concrete, the blust slag can significantly lower the diffusion coefficient.
|Appears in Collections:||[河海工程學系] 研究計畫|
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