Concrete can sweat if no vapor barrier was put down before it was laid. Its normal for concrete to do so. Some contractors use it some don't if you decide to put carpet or laminate or even a hardwood down first check to see if your concrete is sweating.
You can check by taking a tissue and pressing it down in several locations around the room. Some areas will do it more then others and its best to check after heavy rain. if you feel any dampness I used vinyl gloves so I knew it wasn't transfer from my palms chances are you concrete is sweating. This can cause mildew under carpet. You can still do it but you will need a sealant or vapor barrier for the type of product you decide to use to prevent the moisture from becoming an issue.
Every time we now put down concrete we use a vapor barrier and now no more damp sneaks thru.