Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Development of a new combined corrosion protection system for chloride-contaminated reinforced concrete structures
Due to significant pre-corrosion of the reinforcing bars the efficiency of cathodic corrosion protection by means of a thermally sprayed zinc layer on the concrete surface could only be proved (based on electrochemical measurements) in some cases. It has been shown that for the exposed test specimens as well as the pilot application on a parking deck a sufficient cathodic corrosion protection effect of the reinforcement was only achieved at very high chloride contents (4% related to mass of cement). This is caused by deactivation of the zinc layer at low chloride contents, high concrete resitivities due to drying and a resulting very low driving voltage. Probably, also the pH value at the interface concrete/zinc is no longer in a range where zinc actively corrodes/dissolves. A sufficient protection effect is only possible if a deactivation of the zinc layer could be avoided by very high chloride contents or a significant pre-corrosion of the reinforcement could be excluded. Without pre-corrosion a contact between reinforcement and zinc layer prevents exceeding of critical potential values necessary to initiate corrosion processes. According to DIN EN 12696-1 this state corresponds to cathodic prevention and for building practice it means a situation of local depassivation without large active anodic areas of the reinforcement. For transferring the reseach results to practical applications it has to be considered that in most cases structures do not have a homogeneous chloride distribution and hence at first only small anodes are to be expected.
Development of a new combined corrosion protection system for chloride-contaminated reinforced concrete structures
Due to significant pre-corrosion of the reinforcing bars the efficiency of cathodic corrosion protection by means of a thermally sprayed zinc layer on the concrete surface could only be proved (based on electrochemical measurements) in some cases. It has been shown that for the exposed test specimens as well as the pilot application on a parking deck a sufficient cathodic corrosion protection effect of the reinforcement was only achieved at very high chloride contents (4% related to mass of cement). This is caused by deactivation of the zinc layer at low chloride contents, high concrete resitivities due to drying and a resulting very low driving voltage. Probably, also the pH value at the interface concrete/zinc is no longer in a range where zinc actively corrodes/dissolves. A sufficient protection effect is only possible if a deactivation of the zinc layer could be avoided by very high chloride contents or a significant pre-corrosion of the reinforcement could be excluded. Without pre-corrosion a contact between reinforcement and zinc layer prevents exceeding of critical potential values necessary to initiate corrosion processes. According to DIN EN 12696-1 this state corresponds to cathodic prevention and for building practice it means a situation of local depassivation without large active anodic areas of the reinforcement. For transferring the reseach results to practical applications it has to be considered that in most cases structures do not have a homogeneous chloride distribution and hence at first only small anodes are to be expected.
Development of a new combined corrosion protection system for chloride-contaminated reinforced concrete structures
Mietz, J. (Autor:in) / Burkert, A. (Autor:in) / Eich, G. (Autor:in) / Raupach, M. (Autor:in)
Materials and Corrosion ; 56 ; 104-110
2005
7 Seiten, 12 Bilder, 3 Tabellen, 14 Quellen
Aufsatz (Zeitschrift)
Englisch
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