Influences of crack width on macrocell corrosion of steel reinforcement in concrete beams immersed in seawater

摘要

This paper presents the results of an investigation of the macrocell effect between steel reinforcement sections in uncracked concrete which are in electrical continuity with a section that intersects a concrete crack. Six concrete beam specimens were investigated. Each beam specimen contained four separate steel rebars in uncracked concrete in line with another short rebar intersecting a crack. The width of the concrete crack was 0, 0.1, 0.2, 0.4, 0.8 or 3mm for the six beams respectively. The beam specimens were immersed in a seawater tank and the macrocell current between the electrically connected five steel rebars in each specimen was monitored with a Zero-Resistance Ammeter. The macrocell current between the steel rebars in concrete was found to drop significantly over the first few weeks of immersion. The crack width was found to have insignificant influences on the macrocell current to the rebar section in the crack zone. A gradual development of more anodic surface over the rebar sections next to that at the crack was observed in the experiment. This was indicated by the current flowing into the rebar section becoming greater than that flowing out of it, in other words, oxidation was happening on the rebar section. The corrosion rate due to the macrocell effect was evaluated for the rebar sections intersecting the cracks of different widths.