Replacing a liner in a 16x32' inground pool

[DIYLINER]

Thanks,

I am planning on adding the 2" foam to the existing hopper bottom
Then add some 8x16 pavers to hold them in place, add sand/small rock to level off.....then compact as much as possible
Then pour a new floor on top of the sand etc..........I'm thinking of only raising the floor less then 12"

2" rigid, 2" sand etc....Then 4" concrete on top of that - would that be enough ?
I'm not sure fo the difference between concrete and cement......just the mix ?
If the vermiculite/sand/cement mix is better then I can go with that, HD has 2 cu ft vermiculite bags for $21

Smoother is better for the liner

Thanks
-Dave