Life Prediction Of Concrete Structures Eroded By Chloride Based On Gamma Process

The stochastic process modeling method can be used to predict the life of reinforced concrete(RC)structures exposed to chloride erosion.At present,there are few studies on the life prediction model of RC structures by chlorine-salt erosion from the perspective of random process.In this paper,the two-dimensional diffusion model of chloride ions in RC structures corroded by chloride salts is discussed,and the chloride ion concentration generated by the twodimensional diffusion model is used as the degradation data to predict the initial rust time of steel bars in RC structures corroded by chloride salts.Combined with the calculation characteristics of Gamma process,A prediction model for the initial rust time of steel bars in chlorine-salt corroded structures was established considering the two-dimensional diffusion of chloride ions.Finally,the life prediction of chlorine-corroded RC structures is made by the existing model of rust expansion and cracking.The main research content of this paper can be roughly divided into the following points:(1)Several methods for life prediction of RC structures by chloride erosion are introduced.Based on the durability failure criterion of chlorine-salt corroded RC structures,three durability failure stages of chlorine-salt corroded RC structures are discussed.Respectively,the time period T1 of reinforcement corrosion in the structure caused by chloride ion diffusion,the time period T2 of rust expansion stress between reinforcement and concrete caused by the continuous increase of corrosion products,and the time period T3 of external concrete protective layer cracking and falling off caused by rust expansion stress.(2)By discussing various external factors affecting chloride ion diffusion,the analytical model and numerical model of chloride ion diffusion considering multiple factors are established.In order to verify the applicability of the model,the model was used to calculate the chloride ion concentration values of two engineering examples at different protective layer thicknesses in a given period of time,and compared with the measured data,the applicability of the model was verified.(3)The concentration of chloride ions was simulated by the above numerical model considering the effects of multiple factors.The maximum likelihood method was used to estimate the parameters of Gamma process.The prediction model of the initial rust time of RC structure corroded by chlorine salt was established by estimating the parameters obtained.The prediction model of initial rust time based on Gamma process and that based on Monte Carlo method is compared and analyzed.It is proved that Gamma process is reasonable to predict the initial rust time of RC structure corroded by chlorine salt.(4)The relationship between three stages of durability degradation of chlorine-corroded RC structures was studied.Combined with the above prediction model of derusting time based on Gamma process,the life of chlorine-corroded RC structures was predicted.