CORROSION RATE OF REINFORCED CONCRETE WITH COMBINED DETERIORATION BY CHLORIDE ATTACK AND ASR

Abstract

Chloride ions destroy the passive film of steel bars in concrete and induce corrosion. Moreover, the alkali-silica reaction (ASR) produces map cracks in concrete through the formation and expansion of a hygroscopic gel around aggregates. Some existing structures simultaneously experience these two types of deteriorations. In this study, the corrosion rate of steel embedded in mortar with this combined deterioration was evaluated. That is, the presence or absence of reactive aggregates and chloride ions was set as experimental parameters, and specimens with single or combined deterioration of chloride attack and ASR were produced. Cracks and rebar corrosion rates were measured and the influences of chloride ions and ASR on rebar corrosion were discussed based on the polarization curves and resistivity. As conclusions, compared with chloride attack alone, concrete with combined deterioration had more oxygen supply through ASR cracks and a faster corrosion rate. Furthermore, the presence of chloride ions facilitated the formation of electric circuits. In contrast, ASR cracks hindered the formation of an electric circuit. Therefore, the mortar resistivity was the lowest in the case of chloride attack alone, the highest in the case of ASR alone, and intermediate in the case of combined deterioration.