Effect of crack opening on the local diffusion of chloride in cracked mortar samples

The paper presents an experimental study on chloride penetration in cracked mortar specimens. A mechanical expansive core was used to generate cracks of constant width across the thickness of the sample. Sixteen specimens with crack openings ranging from 6 to 325 µm were subjected to a test designed to allow chloride diffusion along the crack path for a period of 14 days. Chloride penetration tests were carried out on mortars at 28 days and 2 years. Relationships between crack opening and chloride–ion diffusion along a crack are presented and discussed. The results show that crack opening significantly affects chloride–ion diffusion along a crack. Overall, chloride diffusion along a crack decreases with crack opening. On the other hand, no chloride diffusion occurs in cracks with an opening of 30 µm or less. This crack-opening threshold agrees with the critical crack opening obtained from a stress-displacement curve of a mortar sample subjected to uniaxial tension. At crack openings greater than the threshold value, chloride diffusion along the crack path depends on mortar age. This result suggests that self-healing could reduce chloride diffusion in cracks.