Investigation On The Service Life Prediction Of Marine Concrete With The Effect Of Multiple Environmental Factors

Corrosion of reinforcing steel induced by chlorides is the primary reason for the deterioration of marine concrete structures.Diffusion is regarded as the major mechanism for the transport of chloride ions in concrete.Under service condition,diffusion of chloride in concrete are influenced by factors such as the time-dependency of surface chloride,the binding effect,the environment temperature and so on.However,these factors affect the diffusion of chlorides have been not yet fully considered in the service life prediction models.In this proposal,numerical simulation and theoretical analysis will be employed to analyze the diffusion of chlorides and service life of concrete structure influenced by time-dependency of chloride diffusion coefficient and surface chloride content,binding effect,environmental temperature under single and coupling action.Based on reliability theory,a method of predicting service life of marine concrete will be proposed by combining numerical simulation and diffusion equation.The results show that the above factors have an important influence on the service life prediction of marine concrete structures.The time dependence of chloride diffusion coefficient will make the apparent chloride diffusion coefficient decrease,and with the increase of the attenuation coefficient,the predicted service life will be longer.The time dependence of surface chloride concentration will make the apparent chloride diffusion coefficient first unchanged or decrease and then increase.The prediction of service life by different boundary condition is the longest linear type and the shortest exponential type.The results show that the apparent diffusion coefficients of the three nonlinear adsorption forms are different at the initial stage of diffusion,and the predicted service life of Langmuir adsorption is similar to that of Temkin adsorption,which is longer than that of Freundlich adsorption.Different activation energy values have great influence on the prediction results.The larger the activation energy value is,the higher the temperature sensitivity of chloride diffusion coefficient is,and the greater the influence of temperature on the service life of concrete is.The influence of the time-varying concentration of chloride on service life is the greatest,the timevarying of diffusion coefficient of chloride and the nonlinear adsorption of chloride ions are the second,and the temperature is the least.The results of structural failure probability considering multifactor coupling are different from those of traditional reliability analysis.Taking the Hong Kong Zhuhai Macao Bridge as an example,when the activation energy is determined according to the experimental formula,the service life of linear,power function and exponential boundary conditions is about 1.05,0.81 and 0.59 times of that of traditional methods.When the temperature is 35?,the service life calculated by the experimental formula of activation energy is only one fourth of the fixed value of activation energy.Therefore,in the life prediction of marine concrete structure with long service life,the time-varying form of surface chloride concentration,environmental temperature and activation energy should be carefully selected according to the actual situation of the project...