Tile over existing concrete shower pan?

I have a shower with a concrete pan, all angled correctly. It doesn't look like it leaks (the bathroom was half demolished when we bought the house).

I want to put tile (probably pebbles on a sheet set in thinset) over the concrete. Is this possible? Any suggestions on this - should I score the concrete for better adhesion, seal it??? I am assuming I will be able to extend the waste by the 3/4 inch or so I will need.

Thanks.

yes, I would hit it with a grinder to make sure it is clean and slightly roughed up. there are also some epoxy "thinsets" which might help seal the concrete to prevent seepage. concrete is porous and will allow water through, so if it was not installed properly, rubber membrane and proper drain which allows water that does get through to drain, you might have water issues.

Looking at it again, the pan to the lowest point where water would hit the (rusty) metal at the edge is barely 3/4" - that's no good as it stands, let alone with a layer of tile on top. Methinks the pan is being replaced...

I would also replace the pan!

Yep, it came out, in lots of pieces. Still debating whether to put my own in with tile, or just go the lowes route...