Concrete "leaking" damp when wet weather?

Lotus-eater

Some of you may remember my thread about my garage which had water leaking in through the walls, I have started sorting it out by digging out a french drain down the external walls and it has stopped ingress of water.
But yesterday I noticed after a very damp day that areas of concrete inside the garage that previously were dry, have damp patches all over them.
Is it possible that the concrete has held onto the moisture and is letting it go when the atmosphere is damp, or maybe I just don't notice it when it's dry?
These are predominantly in areas where the water came through the wall before.
I suppose I'm worried that the water from the french drain is going under the garage huge concrete slab and is coming up from underneath. Certainly no DPC built into the slab.

I have a dehumidifier and was thinking of using that for a few days, but I'm not sure if that could dry everything out too quickly?

gmgmgm

I doubt a dehumidifier will ever dry out a concrete wall/floor "too quickly".

Put a fan against the wall/floor for a few hours and see if it goes away.

Lotus-eater

The floor is 10" thick, so I doubt a fan will make any real difference, apart from visual.