Durability Improvement of Concrete Structures by Wash-away of Chloride

Concrete structures are subjected to salt carried by air from sea side. This salt accumulates on concrete surfaces causing decreasing of concrete durability and life. At the same time rain washes away this accumulated salt. This processes changes the concentration distribution and the amount of accumulated salt on concrete surfaces. Water can be used in maintenance process to wash away this accumulated salt. Because of the importance of this desorption mechanism in increasing concrete durability and life, a detailed experimental work to understand this phenomenon must be conducted. Many factors are affecting this mechanism like concrete surface finish, attached salt conditions, and water flow conditions. Rough and smooth concrete surface finish were examined to understand the surface finish effect on desorption rate. Two salt contact conditions were tested experimentally; dry and wet. In case of dry contact condition, concrete surface has a moisture percentage around 4.3%, and concrete wall is dry. It was found that salt is washed away mainly due to mechanical movement. Diffusion process occurs in this case, but removed salt amount by diffusion is very little compared to the one by mechanical movement and therefore it can be neglected. In case of wet contact condition, diffusion process is the dominant mechanism, and mechanical movement can be neglected. A comparison between washed away salt amounts for these two mechanisms is presented in this paper. The effect of water flow condition is studied by examining two water flow input methods. In the first method, salt is washed away by water flow. In the second method, salt is washed away by water impact. A comparison between all mentioned conditions and mechanisms is presented in this work to understand the effect of each factor to increase concrete durability and life against chloride attack