In general, for evaluating the durability of concrete on exogenous type salt attack, standard values of diffusion coefficient and chloride ion content of concrete surface are used. These standard values are shown in the specification of Architectural Institute of Japan and Japan Society of Civil Engineers, however these are established on the basis of accelerated tests or exposure tests, because of the lack of the reports on the investigated date in actual buildings. Accordingly, using standard values are estimated on the safe side, but it is uneconomical, so cannot be applied hard.
This research is the rearrangement of the survey results which were conducted approximately 60 reinforced concrete buildings in 1985-88 by the Building Research Institute of the Ministry of Construction (Ministry of Land, Infrastructure and Transport) for the purpose of accumulating data on actual structures subject to the salt attacks.
These buildings were constructed before the notification of the regulation on total salt content in 1986, and located less than 2km from the coast. Furthermore, surface finishes of these buildings were sorted to undressed concrete or covered mortar. On these buildings, this research is examined using the distribution of total chloride ion content in concrete.
As the results, in the actual structures, chloride ion content of concrete surface is larger than the standard value of JASS 5 for durability design. On the other hand, the diffusion coefficient of concrete is smaller than the values of the accelerated test or exposure test. Moreover, it clarify that on the covered mortar, the diffusion coefficient is the same level with concrete.
Furthermore, in the actual structures, the peak of chloride ion distributes moves inside from surface in concrete, because of carbonation and so on. In this case, the treatment of the surface layer is not clear in conventional analysis for durability evaluation. In such a distribution of chloride ion, the diffusion coefficient of concrete is expected from analysis in which the provisional surface is set and the wholesome concrete is targeted.
