While moisture has always been an issue when installing flooring over a concrete slab, according to Peter Craig with Concrete Construction, the problems with it seem to be more common today. He suggests that it is the speed with which things are done; the concrete simply isn't allowed time to dry properly before any installation is made. There are ways to accelerate the rate at which moisture leaves the concrete slab, which will ensure success when covering the concrete.
Allow the slab sufficient time to dry naturally. According to Plant Services, this takes upwards of 168 days in ideal conditions.
Ventilate the area containing the concrete. Ventilation allows the evaporating moisture an outlet, rather than having it hang in the air and fall back onto the concrete.
Use fans or blowers. Moving air is shown to triple evaporation rates.
Apply heat. According to TWResin Technologies, forced air heat works the most effectively.
Dehumidify the area containing the concrete. Removing excess moisture from the air also draws excess moisture from the concrete slab.