Concrete Slab Still Looks Wet

Temperature, humidity, mix ratios...

Have you called the company that poured it? What was their response? Did they send someone out to inspect it?

"A section still looks wet two weeks later"

Have you touched it? Is it in fact still "wet"?

OR

Does it look wet because the company that poured it, seal coated it?

Sometimes water will pool on one section of the concrete. This creates a slicker, darker looking surface. It's dry.

This seems plausible. Couldn't you spray the slab down with water and see if it pools over the "wet spot"?

Sure. Then, once it's wet, they could just brush it and wash it off, making the whole thing a uniform color.

In my experience, these shiny wet looking spots are made up of accumulated particles of concete dust and aren't really adhered to the concrete below.

Of course, if I was putting up a storage shed, and the concrete pad felt hard and dry, I wouldn't put any more thought into it.

Try placing a clear jar or glass upside down over a patch of the concrete and see how much moisture condenses on the inside of the glass when left out in the sun.