Experimental Examination on Chloride Penetration through Micro-Crack in Concrete

摘要

Crack provokes to lose a main performance of watertightness of concrete and leads to accelerate the deterioration of concrete. This brings about reduction of service life of concrete eventually. The background is a good motivation to define a critical crack width to prevent chloride from penetrating through crack in concrete. Since concrete structures have to be proven for a minimum service life, the critical crack width can be regarded as a crucial factor for estimating durability performance and integrity of concrete structures. This study is focused on examining the effect of micro-crack on chloride penetration in concrete and identifying the critical crack width experimentally. Because concrete structures have to meet a minimum service life, crack width must be smaller than the critical crack width. Specimens with different crack width have been subjected to Rapid Chloride Migration testing (RCM). The results of this study show the critical crack width of about 0.013 mm. Cracks smaller than the critical crack width are considered not to have a significant influence on the rate of chloride penetration inwards, while chloride penetration does proceed faster above this critical crack width. Meanwhile, cracked specimens were immersed in artificial seawater for 472 days. The result of this long term experiment indicates critical crack width of 0.04 mm. It is thought that crack healing leads the difference between short and long tern experiment.