Abstract:  The erosion modes of both continuous immersion and wetting-drying cycles were selected to study their effects on the transportation process of sulfate-ion in concrete. The strength grade of concrete was C40, the natural dry mode in room temperature was used. The concentration of sodium sulfate solutions were 800 mg/L, 6000 mg/L and 50 000 mg/L respectively. With the erosion ages of 30 d, 90 d, 180 d, 360 d and 580 d, the samples were made by drilling core, cutting into slices and grinding into powder, and tested by the chemical analysis method. In comparison with continuous immersion, the wetting-drying cycles can generally accelerate the sulfate-ion transportation into concrete in deep, and increase the sulfate  ion content in the same depth of concrete. The sulfate-ions in erosion solution of lower concentration tend to be transported into deep place of concrete where the sulfate-ion content will be increased. The erosion solution of high concentration tends to generate concrete failure from the exterior to the interior, so much more sulfate-ions are gathered in the shallow layer of concrete.

Key words: concrete,  , sulfate erosion , continuous immersion,  , wetting-drying cycle,  , sulfate-ion , transportation