Monitoring of corrosion processes in chloride contaminated mortar by electrochemical measurements and X‐ray tomography

Abstract

Corrosion of steel reinforcement in concrete exposed to chloride containing environments 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. Particular the corrosion progress is a significant problem. Especially in the case of macrocell corrosion in reinforced concrete structures, the development at the anode cannot be separated into corrosion damage resulting from macrocell corrosion or selfcorrosion. Until now also in laboratory tests it is impossible to collect such information without destroying specimens after electrochemical testing was performed. 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, that X-ray tomography is suitable to make corrosion pits and their development visible which are embedded in a mortar with a cover thickness of about 35 mm. In this publication the time-dependent corrosion damage of reinforced steel is documented by X-ray tomography.

Analysis of long‐term corrosion behavior in mortars containing recycled ladle furnace slag using computerized tomography and SEM

“…In addition to the numerical results for corrosion at the different dosages, the effect of corrosion was visualized in areas surrounding the reinforcements and the fissured concrete by a 3D CT image reconstruction . As an example, in Fig.…”

Investigation of chloride‐induced pitting corrosion of steel in concrete with innovative methods

“…Only the combination of electrochemical investigations and 3D computed tomography makes it possible to realistically describe the corrosion system. Investigations done by Beck et al show clearly that observations of pitting corrosion are possible by means of the CT method. Figure shows the results of charge per hour from electrochemical investigations and from CT data.…”

“…From the superimposed CT data, the corroded volume can be obtained and hence the mass loss for the different examinations of one specimen . This volume information also enables the calculation of the charge from each pre‐damaging step by means of Faraday's law: Δ Q CT , charge per pre‐damaging step determined by CT‐data with V CT volume information (cm 3 ); ρ specific density (g/cm 3 ); M , molar mass (g/mol); z , number of valence electrons (−); F , Faraday constant (1 F = 96 485 As/mol).…”

Morphology of corrosion products of steel in concrete under macro‐cell and self‐corrosion conditions

“…After the pre-damaging and between the following measurements the specimens were stored under constant environmental conditions (20 8C and 85% relative humidity) in a climatic chamber. Every three months the storage were interrupted and electrochemical measurements [13] and investigations by X-ray tomography [14] were performed.…”