cement itself isn't really sticky

I'd advise against that. As NT said - you can't use cement itself for adhesive. Use thinset w/a polymer additive. Still singing my song of the best - Mapei Ultra Flex II, a polymer modified mortar for professionals - sold at Lowes. Just bought 50 lbs yesterday. W/never consider using anything other than that for outdoor projects.

One thing that I should have mentioned is that I am doing this onto a bird bath. The old bird bath has some indentations and designs that I am going to have to level out to make it work with the tile.

Can I use thinset to do this?

I believe that you can use the mortor in that way, hopefully the experts will weigh in.

Mixing weldbond and cement sounds like a terrible idea to me.

Rant: I'm so jealous because the neary (25 mi away) Lowes didn't have Mapei!!
I never went back after I found out and now they are closing, ha!
I wonder how I find out if any stores that I might travel by in new england have it?

Kathy

What a bummer, CONCRETE: You can use any thinset, but the additive is very important for adhesion. SHARONS: Yes, thinset w/be a good leveler - smooth it out w/a wet paint brush. I got that idea from NT, and it works beautifully when I apply mortar to my metal lath structures. Be sure and spritz the birdbath b/f applying new concrete (thinset) to old concrete.