Hi - we have an 11 year old polished concrete floor in our house. We did it ourselves after we removed a couple of walls. First we diamond sanded and then we put a polish on the floor. We also contacted a chemist and obtained a green paint so we ended up with green transparent polished concrete. Looked god for a while but now it really needs redoing. The problem was that the polish was never as glossy as we wanted and we think that it was because the concrete was too sandy. I repainted it 6x and even after 6 coats the finish was the same. So we would like to put a thin layer of concrete on our old polished concrete to get a glossy effect. We would also like to put a colour into the new slab so we won't have to get a dye for the gloss.
Would it be possible to put new thin layer onto the concrete?
Thanks for your advise.

I think the odds of a new layer adhering are nil.
The only way to get a glossy coat on concrete is with pigmented wax.
My parents built a house with green concrete floors in 1947. Radiant heat in them too, very advanced for 1947. But they had to wax and polish them (with this huge scary polisher that would spin like crazy if you let go) frequently.