Vapor pressures are often blamed for vapor emission problems, but in reality, the actual vapor pressures are so low, that they can only be calculated, not measured. In fact, vapor pressures rarely exceed 0.50 psi and under livable conditions, cannot even achieve pressures exceeding 1.0 psi. Dewpoint may well be the least understood and least appreciated influence in flooring failures. Dewpoint effects can strongly resemble vapor emission, but is largely controlled by a natural hydrological cycle. Dewpoint can occur as the concrete temperature cools.
Moisture begins to condense in and on the concrete surface.
The condensed moisture might not even be visible if the interior section of the concrete is cooler than the surface as the moisture will tend to migrate to the cooler interior. If the surface continues to cool and reaches dewpoint, the concrete surface can literally become saturated with moisture. This has potential devastating effects on many types of adhesives and coatings, even though the majority of the industry is virtually unaware of this phenomenon. The ways alkalinity can damage adhesives and coatings are complex. For example, an adhesive may have excellent resistance to moisture, yet as the pH levels increase, the tendency toward reemulsification may increase exponentially.