Impact of a concrete coating on the reinforcement corrosion in cracked concrete

摘要

Cracks in reinforced concrete structures exposed to chlorides can impair significantly the durability. Cracks are a fast pathway for chlorides and corrosion initiation of the reinforcement is more likely. Relevant standards require additional measures to prevent chloride ingress with regard to endangered structures such as parking decks. Additional design principles to ensure the durability of parking decks are given by the German Society for Concrete and Construction Technology (DBV). One principle consists of the application of a crack bridging concrete coating to prevent further chloride and moisture supply once early cracking is completed even though chlorides are already present in the crack. This recommendation is in line with the repair principle W-Cl according to and the procedure 8.3 respectively with the objective to increase the concrete resistivity. In an extensive experimental study is shown that concrete coating prevents corrosion and can even stop macro cell corrosion successfully in the case of short-term chloride exposed bending cracks. The repassivation is based on the increase of the anodic polarization resistance due to oxide layer formation and/or limited supply of chlorides. The concrete resistivity increases as well because of ongoing drying of the concrete but its effect on the macro-cell activity is negligible. It remains to be determined which amount of chlorides can be left in the concrete to exclude on-going reinforcement corrosion reliably.