In this study, at first, mechanism of chloride ion diffusion was investigated based on the long term marine exposure test. Next, equations to calculate characteristic values were derived based on the actualities of Dap, the apparent diffusion coefficients obtained from specimens and real structures.
The characteristic values are used for prediction of corrosion start time. The main findings are shown in the following;
(1) Resistance for chloride ion penetration improved with increase of replacement level of ground granulated blast-furnace slag. Alternatively, penetration front was stationary even with lapse of time.
(2) It was recognized that Dap showed steady state after about 5 years of exposure duration.
(3) Dap of real structures were about 0.1 ~ 1.6 cm2/year for ordinary Portland cement and about 0.1 ~ 0.8 cm2/year for blast furnace slag cement type B.
(4) Dk, characteristic values of diffusion coefficient used for prediction of corrosion start time, are proposed as follows.(※Please refer to the attached document.)

Key Words: exposure test, investigation of real structures, concrete, chloride ion, apparent diffusion coefficient, characteristic value of diffusion coefficient