Concrete class XD

Corrosion caused by chlorides other than seawater

Chlorides are colorless or colored salts that can be found in different crystalline forms. They are mainly found in de-icing substances, purification facilities, swimming pools, etc. The adverse effect of chlorides at high concentration and sufficient moisture is high as they can lead to corrosion of the reinforcement.

Concrete protects the built-in steel reinforcement through its own highly alkaline nature. High pH values in concrete (usually above 12.5) create a passive and non-corrosion protective oxide film on steel reinforcement. However, the presence of chlorine ions, such as thawing agents or seawater, can penetrate the film and destroy it resulting in rust.

This is an expansive process - the rust expands to 4 times its original volume, causing internal stress and possibly destroying the concrete over the steel reinforcement.


Environment: Moderate humidity.
Example: Concrete surfaces exposed to chlorides dispersed in the air.
Additional classes covered: XC1, XC2, XC3, XF1, XA, XM1


Environment: Under water, rarely dry.
Example: Pools. Concrete exposed to the impact of industrial waters containing chlorides.
Additional classes covered: XC1, XC2, XC3, XS1, XF1, XD1, XA1, XM1


Environment: Cyclical wetting and drying.
Example: Parts of bridges exposed to salts, containing chlorides. Road pavements. Pavements for vehicle parking or driveways.
Additional classes covered: XC1, XC2, XC3, XC4, XS1, XS2, XF1, XF2, XD1, XD2, XA1, XM1, XM2, XM3