Several mechanisms exist by which concrete floors can be a major moisture source. If the concrete is not thermally insulated from the ground, and if the ground is cold, moisture in the building interior air can condense on the floor. This is a common source of moisture above a well-constructed slab.
Several palliatives are available.
By dehumidification of the interior air, the dew point of that air can be kept below the concrete temperature. Alternatively, the interior surface of the slab can be thermally insulated, with a vapor barrier above the insulation. Depending on the nature of the concrete, water in the earth around the slab can wick inward through the concrete. More likely, if ground water exists at the slab, it will percolate through cracks. If the concrete is in good condition, both of these mechanisms can be controlled by treating the interior of the slab with a waterproofing paint, which properly applied is effective.