There are five levels of environment exposure of concrete for which durability requirements of concrete depends. These are:
- Mild exposure
- Moderate exposure
- Severe exposure
- Very severe exposure, and
- Extreme exposure.
These are the environments to which the concrete will be exposed during its working life. The durability requirement, like clear cover to reinforcement steel is governed by these exposure conditions. Table below shows exposure conditions of these environments.
Concrete surfaces protected against weather or aggressive conditions, except those situated in coastal area.
Concrete surfaces sheltered from severe rain or freezing whilst wet, Concrete exposed to condensation and rain, Concrete in contact or buried under non-aggressive soil / ground water.
Concrete surfaces exposed to severe rain, alternate wetting and drying or occasional freezing whilst wet or severe condensation.
Concrete completely immersed in sea water, concrete exposed to coastal environment, concrete surfaces exposed to sea water spray, corrosive fumes or severe freeing conditions whilst wet.
Concrete in contact with or buried under aggressive sub-soil / ground water, surface of members in tidal zone, members in direct contact with liquid / solid aggressive chemicals.