Zum zeitabhängigen Verhalten elektrochemischer und morphologischer Kenngrößen bei der chloridinduzierten Korrosion von Stahl in Beton
It is an undeniable fact that the number of chloride induced corrosion damages in reinforced concrete structures has increased considerably during the last decades. In the context of actual scientific efforts regarding the modelling of chloride induced corrosion phenomena of steel in concrete this thesis aims at the analysis of the time dependent behaviour of electro-chemical and morphological parameters of the macro-cell anode being the location of active metal dissolution. As a result of electro-chemical investigations time dependent and statistically firm free corrosion potentials and specific polarisation resistances of the macro cell anode are now available for the modelling of chloride induced corrosion phenomena of steel in concrete with high water and chloride contents. Further investigations into the current-potential-relation of macro cell anodes show a fairly linear devolution up to anodic overpotentials of 140 mV. This information leads to less time consuming calculation procedures in the numerical analyses of chloride induced corrosion phenomena. The combined evaluation of electro-chemical and gravimetric test series shows that the proportion of self corrosion activity can be as high as 50% of the overall corrosion activity. The results confirm that it is absolutely necessary to take self corrosion into account in any future corrosion modelling. Surface analyses by means of a cutting edge 3-D surface scanner shows, that it is possible to quantify the development of depassivated surface areas and maximum pitting depths with high accuracy. Using regression analyses simple mathematical expressions can be derived describing the time dependent behaviour of the surface morphology as a result of ongoing chloride induced corrosion processes. Based on these results a new calculation model is established describing the corrosion related loss of steel volume by means of a modified formula for a cone volume. This formula is based on parameters which can be obtained by onsite inspections of reinforced concrete structures. Furthermore investigations into the minimal residual cross section leads to the development of a time dependent factor which enables the engineer to transform corrosion induced volume losses (e.g. obtained from calculations, morphological or gravimetric investigations) into minimum cross sections of the respective rebar. This factor, for the first time, is based on a significant scientific data base regarding the minimum cross section of corroding steel in concrete with high water and chloride contents.
info:eu-repo/classification/ddc/620, Korrosion, Bewehrung, Morphologie, Elektrochemie, Beton, Stahl, Zeitabhängigkeit, Ingenieurwissenschaften, chloridinduzierte Korrosion, chloride induced corrosion, concrete, reinforcement, morphology, time dependence
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