I needed to do some patching on my chimney, so I used a bag of topping that I had stored in a somewhat humid environment for a few months. The bag was hard in places and lumpy when I poured it out, but it mixed right up with no lumps.

Now it doesn't seem to want to set up. The surface can easily be eroded into sand and it's not stone hard. It's what I would expect after only a few hours, but it's had 4 days already.

I guess it must have absorbed some water... Will it ever set up or do I have to take it out and redo?