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>Unique Declining Electrochemical Trend of Macro-Cell Half-Cell Potential with Increase in Temperature at Constant High Humidity for Corroding Steel Bars in Repaired Concrete Patches
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Unique Declining Electrochemical Trend of Macro-Cell Half-Cell Potential with Increase in Temperature at Constant High Humidity for Corroding Steel Bars in Repaired Concrete Patches
This paper aims at finding the coupled effect of hot and humid environment on the corroded repairedpatches of chloride contaminated steel reinforced concrete. Chloride induced corrosion under coupledenvironmental effects of high humidity and high temperature often found in gulf marine environmentis a very serious threat for durability of reinforced concrete structures. In the previous research, theauthors experimentally corroborated re-corrosion in the repaired reinforced concrete patches in theform of macro-cells. But, whether this formation of macro-cell is influenced by the coupled effect ofhigh temperature and high relative humidity remained a question and formed the basis of this research.This coupled effect is investigated by laboratory controlled experimentation at varying temperature at30, 40 and 50C and a high ambient relative humidity of 85% in environmental control chambers.Specimens were prepared having total chloride concentration in mixing water 3% and 5 % by mass ofbinder. From the experiment results interesting and novel observations, trends and behaviors have beenidentified. A non-uniform and non-linear corrosion reaction was observed even after the breaking ofpassive layer. Furthermore, a decrease in electrochemical corrosion potential and corrosion mass lossat 50C in comparison to 30 and 40C temperature conditions was seen. This may be due to thereduction of oxygen solubility in the pore solution at high temperature and blockage of concrete poresat high relative humidity. It is expected that a stable oxide layer may have developed under limitingoxygen controlled corrosion reaction. This can form basis for the development of a new technique topassivate steel bar embedded in chloride contaminated concrete and improve the method of repairs.
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