It's normal if the concrete temperature reaches a temperature below dew point temperature. You outdoor side walk of concrete may have the same symptoms on a cool morning when the surface cools below dew point temperature. After you remove that plastic that shouldn't have ever been there, it's time to do some concrete surface temperature and dew point temperature monitoring to know which direction to take.
EDIT EDIT : We have concrete floors plus basement concrete ( carpeted ) with sheet vinyl and carpet ( ground floor ) without those problems in 37 years. Nothing under concrete except original soil.
EDIT EDIT : We have concrete floors plus basement concrete ( carpeted ) with sheet vinyl and carpet ( ground floor ) without those problems in 37 years. Nothing under concrete except original soil.
