In order to design mix proportions for an extremely durable concrete with an expected service life of 300 years, the diffusion coefficient of concrete at 28 days (D28) is to be determined. What are the main standards that should be followed to determine D28?
There is no such concrete with 3,000 design life if you are talking about chloride diffusion. Even though you add 8% silica fume with very low chloride diffusion with 75 mm concrete cover, the actual field tests indicates that the rebar corrosion occurs 25 to 30 years in splash zone of jetties in semi-tropical climate.
ASTM C1556 (Standard Test Method for Determining the Apparent Chloride Diffusion Coefficient of Cementitious Mixtures by Bulk Diffusion) might help
There are many opinions that ASTM C1556 does not reflects actual condition because of other ions movement in addition to chloride ions. You can find many papers on this issue.
Dear Adeyemi,
In addition to ASTM Designation C1556, there is another standard with code name NT BUILD 443 which is in use by the Nord countries of Finland, Norway and Sweden. Which one of the above two codes is preferable in the environment of Asian countries like Pakistan and India?
In 1990s, 2 methods of testing concrete durability were used in Nordic countries:
1. An immersion (pure diffusion) test NT Build 443
2. An accelerated (migration) test NT Build 492, the Rapid Chloride Migration (RCM) test.
The immersion test is a true and realistic representation of natural diffusion but it requires 7 weeks of exposure. The 2nd test involves a different transport mechanism of migration but it requires a short execution time and is less laborious.
Both the method have a good linear correlation. Hence it is justified to use the less time consuming and less laborious test of RCM instead of the diffusion test.
Try this article please. Article Calculation of chloride diffusion coefficients in concrete f...
- Badges
- Science topic