Chloride induced corrosion of steel in concrete exposed in a marine environment
Paper in proceedings, 2007
This paper presents the results from the measurement of chloride penetration and reinforcement corrosion in concrete slabs after over 13 years exposure in the marine environment. In the beginning of 1990’s over 40 reinforced concrete slabs with different types of binder and water-binder ratios were exposed in a marine environment at Swedish west coast. In this study a new rapid technique was used for non-destructive measurement of corrosion. Based on the results from the non-destructive measurement, the actual corrosion of steel bars in five concrete slabs was visually examined and the chloride profiles in the penetrating direction as well as at the cover level were measured. The results show that the visible corrosions normally occurred about 10-20 cm under the seawater level, where the oxygen may be sufficiently available for initiating the corrosion. It is also found that chloride may easily penetrate through a poor interface between concrete and mortar spacer and initiate an early corrosion. As a conclusion, although the chloride level 1% by mass of binder may not be the same as the conventionally defined threshold value, it can be taken as the critical level for significant on-going corrosion that is visible by destructive visual examination, despite of types of binder.