|
Title |
Time Dependent Chloride Transport Evaluation of Concrete Structures Exposed to Marine Environment
|
|
Keywords |
내구성 평가 ; 표면염소이온농도 ; 염소이온 확산계수 ; 임계염소이온농도 durability evaluation ; surface chloride concentration ; chloride diffusion coefficient ; chloride threshold level |
|
Abstract |
This paper presents a model for durability evaluation of concrete structures exposed to marine environment, considering mainly a build-up of surface chloride (Cs) as well as diffusion coefficient (D) and chloride threshold level (Clim). In this study, time dependency of Cs and D were extensively studied for more accurate evaluation of service life of concrete structures. An analytical solution to the Fick's second law was presented for prediction of chloride ingress for time varying Cs. For the time varying Cs, a refined model using a logarithm function for time dependent Cs was proposed by the regression analysis, and averaging integrated values of the D with time over exposed duration were calculated and then used for prediction of the chloride ingress to consider time dependency of D. Durability design was also carried out for railway concrete structures exposed to marine environment to ensure 100 years of service life by using the proposed models along with the standard specification on durability in Korea. The proposed model was verified by the so-called performance-based durability design, which is widely used in Europe. Results show that the standard specification underestimates durability performances of concrete structures exposed to marine environment, so the cover depth design using current durability evaluation in the standard specifications is very much conservative. Therefore, it is found that utilizing proposed models considering time dependent characteristics of Cs and D can evaluate service lift of concrete structures in marine environment more accurately.
|