Study On Time-dependent Probabilistic Prediction Model And Design Value Of Surface Chloride Concentration Of Concrete In Marine Chloride Environment

Chloride attack induced steel corrosion and concrete cracking is one of the most important causes for durability degradation of concrete structures in marine chloride environment.Since surface chloride concentration is the quantitative index to reflect the corrosive action of marine chloride environment and the important boundary condition for quantitative durability analysis and design of the concrete structure in marine environment,prediction of surface chloride concentration accurately is important for durability analysis and service life prediction of concrete structures.However,surface chloride concentration is affected by material parameters,environmental conditions and exposure time.It also exhibits remarkable time-dependence and randomness.Thus,it is necessary to develop a probabilistic prediction model of surface chloride concentration and to determine design value of surface chloride concentration for different chloride environment,taking into account the influences of material parameters,environmental conditions and exposure time.This thesis focuses on the study of time-dependent probabilistic prediction model and design value of surface chloride concentration for concrete in different chloride environments(including tidal zone,splash zone,atmosphere zone and submerged zone).The main contents of this thesis are as follows:(1)Based on the chloride profile within concrete from natural exposure experiment,the influences of the time-independent,single time-dependent and dual time-dependent chloride diffusion models on the precision of regression analysis of surface chloride concentration of concrete were investigated.The appropriate chloride diffusion model was selected to fit the surface chloride concentration of concrete considering the accuracy and applicability.(2)Based on collected 917 sets tested data(including 328 sets from tidal zone,296 sets from splash zone,228 sets from atmosphere zone,65 sets from submerged zone)of surface chloride concentration from natural marine chloride environment,the influences of water-to-cement ratio,type of cementitious materials,exposure time,wind speed,distance from the sea,chloride concentration in the sea on surface chloride concentration of concrete exposed to different environment(including tidal zone,splash zone,atmosphere zone and submerged zone)were investigated.Then both deterministic prediction model and time-dependent probabilistic prediction model for surface chloride concentration of concrete in different environmental conditions were developed.(3)Based on the developed time-dependent probabilistic model of surface chloride concentration in tidal,splash,atmosphere and submerged zones,the design value of surface chloride concentration with predefined confidence levels were proposed respectively,which provides a quantitative boundary condition for durability analysis and design of concrete structures in marine environment.