Three types of concrete with compressive strengths of about 45, 80 and 100 MPa are exposed in a loaded state in a closed container and subjected to a sequence of wetting by salt fog and drying. For each concrete, the measurements of chloride content on three prismatic specimens allow us: 1/ to study the profiles of chloride ingress into concrete, 2/ to compare the different results obtained in relation to the loading state of each specimen, and 3/ to calculate the apparent diffusion coefficient Da. The results show the influence of concrete strength and the effect of the load applied on the penetration of chlorides into concrete. A linear relationship is found between the chloride’s apparent diffusion coefficient Da and the concrete strength. There is also a relationship between Da and the loading level. These relationships are established independently of the exposure period.