Study On Multi-factor Computational Models Of Surface Chloride Concentration For Concrete Exposed To Marine Environment

Surface chloride concentration of concrete exposed to marine environment is one of the most important quantitative indices for corrosive chloride environmental action,which is affected by various important factors such as environmental conditions,material parameters and exposure time.However,current computational models for surface chloride concentration of concrete in marine environment can't comprehensively reflect the above important influential factors,which restricts the development of durability analysis and design of reinforcement concrete structures exposed to marine environment.Hence,this dissertation focuses on the study on computational models of surface chloride concentration of concrete exposed to marine environment.Firstly,the transport process of chloride ion within concrete and the formation mechanism of surface chloride concentration were explored.Then the influences of environmental conditions,material parameters and exposure time on the surface chloride concentration of concrete in marine atmosphere,splash/tidal and submerged zones were investigated respectively.Furthermore,multi-factor computational models of surface chloride concentration for concrete in different marine environment were developed by means of two-stage the nonlinear regression analysis of tested data from natural exposure experiments.Meanwhile,different values of marine environmental action in terms of surface chloride concentration of concrete were proposed,which provides the quantitative boundary conditions for durability analysis and design of reinforcement concrete structures exposed to marine environment.The main contents of this dissertation include:(1)The transportation process and accumulation law of chloride ions within air and then into the bulk concrete were explored first.Then a multi-factor computational model of the surface chloride concentration for concrete exposed to marine atmosphere zone was developed based on a large amount of field data.Both environmental conditions and material parameters including the distance from the sea,wind speed,water-to-binder ratio,binder type and exposure time were considered in the proposed model.The accuracy and applicability of the proposed model were validated by comparing with current computational models and field investigation data.(2)Based on the statistical and regression analysis of the collected field data from different natural field tests,the transport mechanism and accumulation law of chloride ion within concrete exposed to the marine tidal and splash zones were analyzed.A multi-factor computational model of the surface chloride concentration for concrete structure exposed to the marine tidal and splash zones was developed by taking into account the influences of water-to-binder ratio,type of binding materials,and time-dependent behavior.The accuracy and applicability of the proposed model were demonstrated by comparing with the results of current empirical prediction models and field investigation data.(3)Effects of various influential factors including environmental chloride ion concentration,water-to-binder ratio,and exposure time on the surface chloride concentration of concrete exposed to marine submerged zone were investigated.Then a multi-factor computational model of surface chloride concentration for concrete exposed to marine submerged zone which takes into account the effects of the above influential factors was developed by using the multivariate nonlinear regression analysis.Finally,the accuracy and applicability of the proposed model were validated by comparing with the current empirical models,the tested data from natural exposure experiments and the field data of existing marine concrete structures.(4)In order to overcome the disadvantages of current durability design methods of concrete structures,which cannot take into account the influence of marine environmental action quantitative,different values of marine environmental action in terms of surface chloride concentration of concrete were proposed based on the multi-factor computational models of surface chloride concentration for concrete structures exposed to marine atmosphere,splash/tidal and submerged zones.The proposed models of marine environmental action provide the quantitative boundary conditions for durability analysis and design.The efficiency and applicability of the proposed models were validated based on the durability design of reinforcement concrete structures for seaport engineering in Guangxi Beibu Gulf.