It has been 24 hours that my perlite/portland cement floor has been curing. I suspect everything is fine but I wanted to check with the community. It does not seem to be hardening at all. It is more like the consistency of thick sand. I was expecting it to set up rock hard like concrete. I mixed 5 parts coarse perlite to 1 part portland cement. I wasn’t too careful, so maybe 5.3 or 4.7 to 1 - but still close. Thoughts?
Sooo…at 24 hours it won’t be completely cured.
A lot depends on how much water you used. If you overwatered it, it will still set up but take longer. (Not saying you did, of course, but it’s a factor.) Multiple posts here emphasize that you need just enough water to allow it to flow into the void.
If on the other hand you used too little water, it wouldn’t be enough to activate the Portland cement. Getting the ratio of dry ingredients approximately correct as you describe is fine.
It is too soon to say whether you have a problem. By tomorrow you should have a firm surface with a little give, and it will still look dark for a while. As it continues to cure it will turn bright gray, but you likely won’t have it uncovered that long.
I covered it with clear plastic. That is the correct thing to do, right? Doesn’t seem much harder after 48 hours. Sort of like firmly packed sand at this point.
Yes, that’s correct on the plastic.
My opinion is that if it doesn’t feel like concrete-hard, you don’t have to worry as long as you got a good proportion of Perlite into the mix.
After you place the frame bricks (and make sure those are firmly in place!), you will be packing sand into the space over the insulation.
The net result will be firmly packed and leveled sand over what amounts to firmly packed and leveled sand. The insulation layer does have the hearth brick over it, which is a widely dispersed load; but it is not a structural load bearing surface.
My advice at this point: leave it covered, move on to your hearth frame, and of course remove the plastic befor you pack with sand.