The moisture content of unprotected concrete that has been in service for some time tends to equalize with that ofthe atmosphere. Where humidity is high or where concrete is exposed to frequent precipitation, the internal moisture content will remain high. Protective systems applied to moisture-laden structures can fail prematurely if moisture movement within and through the structure is not considered . An uncured protective coating can be damaged if moisture moves out of the structure as water vapor during, or just after, the coating is applied. Moisture inside concrete also can be a problem after the coating cures.
Various systems allow moisture vapor transmission at different rates.
The corrosion will continue until the concrete moisture level falls to the point where corrosion activity is no longer supported. Encapsulating concrete can cause coating failure because internal moisture has nowherte to go. This precast concrete slab is coated with a nonbreathable paint. The paint is peeling from the slab bottom due to moisture buildup in the concrete. If the ambient relative humidity is at least this high, corrosion may never cease.