Korrosionsmonitoring in ungerissenem Stahlbeton in der Schädigungsphase – neue Forschungserkenntnisse

Abstract

Bei der Korrosion im Stahlbetonbau besitzt insbesondere die chloridinduzierte Korrosion ein stark ausgeprägtes Schädigungspotenzial durch den lokalen Schädigungscharakter der dabei auftretenden Lochkorrosion, Bild 1. Anders als bei der carbonatisierungsinduzierten Korro sion sind die Auswirkungen der chloridinduzierten Korrosion nach außen meist nicht oder erst spät erkennbar, da nicht zwangsläufi g Abplatzungen stattfi nden. Mögliche Instandsetzungsverfahren sind in Deutschland in der TR IH [1] geregelt. Bei Stahlbetonbauwerken wird für die Instandsetzung häufi g der chloridbelastete Beton abgetragen und mit einem Betonersatz ergänzt (Verfahren 7.2). Lange Bauzeiten und aufwendige Abstützungsmaßnahmen sind dabei meist die Regel. Daneben existieren auch elektrochemische Instandsetzungsverfahren, bei denen auf einen Abtrag des chloridbelasteten Betons verzichtet werden Stichworte Korrosion; Monitoring; Chloride; Instandsetzung; Bewehrungsstahl; Depassivierung Corrosion Monitoring in Reinforced Concrete Structures -New Research ResultsCorrosion of reinforcing steel caused by de-icing salt and carbonation leads to considerable repair costs in middle Europe every year. The use of corrosion monitoring on reinforced concrete structures opens up new possibilities for interpreting whether damage has already occurred and how quickly it is progressing. Thus, the penetration of the depassivation front into a chloride-loaded structure can be determined, or, if corrosion is already taking place, the magnitude of the damage progress can be estimated. By installing appropriate sensors in existing structures, the repair success can be verifi ed after completion of repair work in accordance with procedure 8.3 of TR IH. To date, however, there is no code of practice for corrosion monitoring. In 2018, a leafl et B12 of the DGZfP was published for the fi rst time, which can serve as a guideline. In addition, a broad WIPANO research project called "KoMICS" on open questions on corrosion monitoring has been carried out in Germany over the past three years. The fi ndings of this project will be incorporated into a DAfStb Guidline, which is currently being edited. Relevant fi ndings of the investigated task part of the research project at the Munich University of Applied Sciences HM are presented below. Keywords corrosion; monitoring; chlorides; repair; reinforcing steel; depassivation Bild 1 Chloridinduzierte Korrosion an freigelegter Bewehrung einer Zwischendecke (links) und eines Stützenfußes (rechts) Chloride-induced corrosion on exposed reinforcement of a ceiling slab (left) and a column base (right)

Carbon steel electrodes within chloride induced reinforcement corrosion in cracked concrete: Approximation to deterministic system response

“…The first and probably most important in terms of corrosion determinant is the steel-concrete interface (SCI). [16,17] Without hierarchical judgment the prominence of the SCI is followed by the polarization resistance on the anodic site, macrocell, [18,19] and microcell corrosion processes, [20,21] electrolytic resistance of concrete [22,23] and effects arising in long-term corrosion monitoring. [1,24,25] For some reason, little has been reported about the formation and evolution of driving potential ΔE, [3] although it builds up a major part in macrocell corrosion modeling (see Section 2).…”

“…The first and probably most important in terms of corrosion determinant is the steel‐concrete interface (SCI). [ 16,17 ] Without hierarchical judgment the prominence of the SCI is followed by the polarization resistance on the anodic site, macrocell, [ 18,19 ] and microcell corrosion processes, [ 20,21 ] electrolytic resistance of concrete [ 22,23 ] and effects arising in long‐term corrosion monitoring. [ 1,24,25 ]…”