IMPACT OF SULPHATE ON CHLORIDE-INDUCED CORROSION OF STEEL IN CONCRETE

摘要

The aim of the present investigation is to evaluate the effect of admixed chloride, sulphate and chloride-sulphate solutions on the corrosion performance of rebar in concrete, as well as the influence of metakaolin (MK) and red mud (RM) blended concrete. The performance of the rebar was monitored by corrosion current density values using linear polarization resistance technique. The changes in electrical resistivity due to the presence of salts and different binder type reflects the corrosion behavior of rebar. Hence, the present study extended to monitor the variation of electrical resistivity in concrete. In order to achieve the guidelines of ASTM G16-13, the statistical analysis was carried out on the data of corrosion current density. The results indicated that the presence of magnesium sulphate increases the corrosion rate in both OPC and MK blended concrete. However, the analyzed results indicated that the passivity zone increases with conjoint presence of sulphate and chloride ions as internal source, and the risk of the corrosion shifted from moderate to severe and severe state to very high. It implies that once the corrosion initiated, the corrosion rate of rebar is high in concrete admixed with composite solution of chloride-sulphate ions than that of admixed with pure chlorides. The concrete blended with MK performed better as compared to OPC concrete in terms of higher electrical resistivity and lower chloride induced corrosion current density with and without presence of sulphate ions.