国家重点基础研究发展计划(973计划)项目(2009CB623200)；国家自然科学基金资助项目(51108077)；江苏省自然科学基金资助项目（BK2011612）；江苏省崇启大桥建设项目(CQHT ZG 09002)
Process of the drying and the wetting for concrete were investigated separately. The change of relative humidity(RH) in different depths of concrete with time during the drying and the wetting was monitored. The mass of average evaporation/absorption of water during the drying and the wetting process was also measured, and then the influence of chloride ion on water transportation was considered. The test results show that the drying and wetting regime of concrete can be rationally determined according to the RH and the water evaporation/absorption during the drying and wetting process. The RH and the water evaporation/absorption obtained in the lab can be transferred to assess the effect of drying and wetting on the in site concrete. The evaporation/absorption rate is the highest during the early drying and the wetting process, and subsequently slows down. The degraded depth of concrete is determined by the drying process, therefore the drying time shall be long while the wetting time be short. Water transportation mode shall not be influenced by the chloride ion, while the capillary absorption coefficient and diffusion coefficient of concrete markedly decreases.