Study On The Deposition Of Chloride Ions In The Surface Layer Of Shenzhen Coastal Buildings

There are several ingressive media in the marine atmospheric zone with complex environment. The main ingressive medium is the chloride ion from the wind-blown salt-laden mist. Lots of reinforced concrete structures in this area suffer from durability problems, due to the chloride-induced reinforcement corrosion. Domestic and foreign researches mainly focus on the chloride diffusion in inner concrete, however, the surface, which is the initial condition of transport and boundary condition, has been rarely considered. In this thesis, the chloride deposition on the surface of concrete structures in Shenzhen was studied by laboratory experiment and sampling from existing buildings. Environmental factors significantly influence the chloride deposition on concrete surface. This paper focus on four environmental factors, in terms of distance from coastline, altitude, wind direction, and shelter, ignoring other environmental factors and nature of concrete.The results of field study show that,in the distance of 0 ~ 1 km from coastline, surface chloride content decrease significantly with the increasing distance and it was found that surface chloride content present logarithmic relevant to distance; Surface chloride ion deposition rises with the increasing height above the sea below certain height, then decrease, which present peak function relation;Under otherwise equal conditions, the chloride content of surface concrete against the wind from sea is much higher than that on the lee side; In the same area, surface chloride content of concrete without shelter from the sea is significantly higher than that of concrete with shelter from the sea; The average of surface chloride content varies greatly cross different districts with 0.256% in Nanshan District, 0.239% in Futian District, 0.251% in Baoan District, and 0.358% in Yantian District. A database system of surface chloride deposition content of concrete cross marine atmospheric zone of Shenzhen is built on the basis of approximately one thousand samples from concrete building in Shenzhen to store and query conveniently. Based on environmental factors and different region, sixteen kinds of prediction models were built for different environment conditions. The correlations between measured data and prediction models were assessed by residual analysis, and the validities of models were further verified using practical data. The built models have an important academic monographs and engineering value to the durability design, maintenance and prediction of service life of reinforced concrete structures in coastal salt spray zone.