Can't put a photo in original post.... again! Grrrr

Since you have been using it for a while - did you check it after a while? How much has it broken down? If it is solid rather than mushy, I wouldn't be concerned about 'baking' it ay more. If it turns to mush, I am not sure if temps in oven would be sufficient enough to bake it well. IIRC, hundreds of degrees if not over thousand are needed to bake clays. You can always try to bake smaller amount and test it after. Maybe you can try a freeze-thaw test.

Thanks Rina. Yes I've been using it for a while. I've repotted quite a few plants and see the clay still intact. It's just this one pot yesterday that had a tiny sedum rubrotinctum that never really grew. When I tipped the mix out the clay was fallen apart already and all around the roots and mainly at the bottom of the pot.

Yes I did the soak test, leaving it soaking for 3 days. A lot of the small pieces fell apart, but even though I shook the bigger ones several times a day, they all stayed intact. So I just used the bigger pieces.

I didn't do the freeze-thaw test. Maybe I'll try that tomorrow.