Monitoring of corrosion processes in chloride contaminated mortar by X-ray tomography

Corrosion of steel reinforcement in concrete exposed to chloride containing environment, is a serious problem in civil engineering practice. Electrochemical methods, e.g. potential mapping, provide information whether the steel reinforcement is still passive or depassivation has been initiated. By applying such techniques no information on the type of corrosion, its extent and distribution of corrosion products is available. Until now it is impossible to collect such information without destroying specimens after electrochemical testing has taken place. To overcome this problem it was tried to study the steel surface within the mortar specimens by X-ray tomography (CT). Within the scope of these investigations it could be shown for the first time, that X-ray tomography is suitable to make corrosion pits on rebars visible which are embedded in a mortar with a cover thickness of about 20 mm. Furthermore, sections of embedded bars formed by CT measurements were successfully compared to metallographic sections.