No the wedge must move freely while tightening nut and incasement in concrete will prevent that. Even though wedge won't work the bolt shouldn't pull out but it's waste of money when a regular bolt will work. Why not poke all-thread, plain hex head or carriage head bolts in wet concrete?

A small piece of concrete like that isn't much to secure a post to. What condition is the concrete below? Can you break enough of it up to get a 1/2" anchor bolt or two in before you pour? Then it could all be locked together.

Klem1, thank you. Very good suggestion, maybe I should consider regular bolt with big head, since wedge bolt won't move, I thought I could tighten wedge bolt and open bottom wedge for addition bond.

@ Seaborman, my case is a little bit complex, there was a 2-inch rebar from existing concrete that was supposed to anchor the post. Right now, the rotten bottom could clear ~3 inch room to work, I could cut a little more, but I don't want to saw out rebar that will help bond new concrete base. I also need to flash floor anyway with concrete because the tiles create a "cave" for water pit. I will build a new 'L" shape wood base to attach to this 9-feet post, don't want to replace it as a whole, since it is only one of four, not carry much weight eather...

Thank you