Effectiveness of Polymer-Modified Cement Mortar with Corrosion Inhibitor in Preventing Chloride-Induced Steel Corrosion in Concrete

摘要

In Japan, the polymer-modified cement mortar (PCM) with the corrosion inhibitor has often been used as repair materials for deteriorated reinforced concrete structures due to the chloride-induced steel corrosion. In this study, the reinforced concrete specimens with two levels of chloride content were prepared and exposed to wet and dry cycles in the chamber for a long period to clarify the macro-cell corrosion of steel bar in the concrete. The effectiveness of the type and dosage of corrosion inhibitor, LiNO_2 or Ca (NO_2)_2, in PCM and the degree of chipping around steel bars in repair work in preventing the steel corrosion in concrete were comparatively investigated by means of electro-chemical measurements such as linear polarization resistance and AC impedance methods. From the experimental results, it was found that PCM with both corrosion inhibitors of LiNO_2 and Ca(NO_2)_2 had almost the same effect in preventing the steel corrosion when their NO_2~- molecular ratio to Cl~- was constant, and that the chipping and patching work beyond steel bars was more effective in restoring the passive state of steel bars. Furthermore, both the linear polarization resistance and the AC impedance methods were very useful as a nondestructive inspection method for estimating the corrosion behavior of steel bars in repaired and unrepaired concrete with PCM.