Steel beam in concrete ceiling - how to plaster?

One more time: the ceilings are NOT to be plastered. They will only be filled, sanded, and painted directly. We do not want any plaster.

I have now solved the whole thing with epoxy resin and threw sand on it. That was a good basis for the plasterer to neatly fill the steel beam flush with the ceiling. It has also already been sanded and painted. Looks perfect. I also hope it will last. But I spoke with a building inspector who also gave me the tip with the resin. He says the solution will hold up...

Okay, then I hope that the transition from steel to concrete with the thin layer thickness without reinforcement mesh does not crack.