Knowing the service life of a concrete structure allows the engineer to build cost effectively. The Strategic Develop-ment Council of ACI recognized the need for a consensus model to do this. A consortium under SDC funded this development and now the first generation of the model, Life-365, is available through those companies and organizations that sponsored the work. CCIA will be one of the organizations that sponsor a second consortium to improve the model and develop the necessary data for its future use.

Concrete, itself, is one of the best protective coatings for steel. Reinforced Concrete gains its strength from the strong bond between the steel reinforc-ing and the concrete. If the bond is lost the concrete properties are diminished. When salt is allowed to penetrate concrete, the corrosion protection properties of concrete are lost (see below). Salt gets into concrete when the roads are salted in the winter and when concrete structures are built along the seacoast. Also, some aggregates and admixtures contain salt. Concrete can also loose its protective quality in heavy industrial environments where CO₂ gets into the concrete and reduces the pH.

One of the best ways to control corrosion, when chloride or carbon dioxide penetrate, is to add a corrosion inhibitor while making the concrete. Corrosion inhibitors work with concrete to maintain the protection without the loss of bond.

However, when a corrosion inhibitor is used, the concrete quality must be maintained the same as without the inhibitor. There are other ways to reduce the probability of corrosion that should be considered along with the use of a corrosion inhibitor. The most important of which is to reduce the permeability of the concrete. Lower permeability reduces the amount of salt that can get into the concrete and, of course, this lessens the problem. The permeability can be reduced by the use of a water reducing agent or/and the use of selected pozzolans, such as certain fly ashes, granulated blast furnace slag, blended cement or condensed silica fume. Ensuring that there is at least two inches of concrete cover over the rebars does not reduce the permeability but it does make it more difficult for the salt to get to the steel in the concrete.

If the concrete is kept dry it is difficult for the salt to get in, but this is practically impossible to do. However, curing concrete well reduces the permeability and improves the strength. Thus, careful attention to curing is important.